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2e91f69afa
linux/fs/dcache.c
Joel Granados 78eb4ea25c sysctl: treewide: constify the ctl_table argument of proc_handlers 
const qualify the struct ctl_table argument in the proc_handler function
signatures. This is a prerequisite to moving the static ctl_table
structs into .rodata data which will ensure that proc_handler function
pointers cannot be modified.

This patch has been generated by the following coccinelle script:

```
  virtual patch

  @r1@
  identifier ctl, write, buffer, lenp, ppos;
  identifier func !~ "appldata_(timer|interval)_handler|sched_(rt|rr)_handler|rds_tcp_skbuf_handler|proc_sctp_do_(hmac_alg|rto_min|rto_max|udp_port|alpha_beta|auth|probe_interval)";
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

  @r2@
  identifier func, ctl, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int write, void *buffer, size_t *lenp, loff_t *ppos)
  { ... }

  @r3@
  identifier func;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int , void *, size_t *, loff_t *);

  @r4@
  identifier func, ctl;
  @@

  int func(
  - struct ctl_table *ctl
  + const struct ctl_table *ctl
    ,int , void *, size_t *, loff_t *);

  @r5@
  identifier func, write, buffer, lenp, ppos;
  @@

  int func(
  - struct ctl_table *
  + const struct ctl_table *
    ,int write, void *buffer, size_t *lenp, loff_t *ppos);

```

* Code formatting was adjusted in xfs_sysctl.c to comply with code
  conventions. The xfs_stats_clear_proc_handler,
  xfs_panic_mask_proc_handler and xfs_deprecated_dointvec_minmax where
  adjusted.

* The ctl_table argument in proc_watchdog_common was const qualified.
  This is called from a proc_handler itself and is calling back into
  another proc_handler, making it necessary to change it as part of the
  proc_handler migration.

Co-developed-by: Thomas Weißschuh <linux@weissschuh.net>
Signed-off-by: Thomas Weißschuh <linux@weissschuh.net>
Co-developed-by: Joel Granados <j.granados@samsung.com>
Signed-off-by: Joel Granados <j.granados@samsung.com>
2024-07-24 20:59:29 +02:00

3230 lines
85 KiB
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// SPDX-License-Identifier: GPL-2.0-only
/*
* fs/dcache.c
*
* Complete reimplementation
* (C) 1997 Thomas Schoebel-Theuer,
* with heavy changes by Linus Torvalds
*/
/*
* Notes on the allocation strategy:
*
* The dcache is a master of the icache - whenever a dcache entry
* exists, the inode will always exist. "iput()" is done either when
* the dcache entry is deleted or garbage collected.
*/
#include <linux/ratelimit.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/fscrypt.h>
#include <linux/fsnotify.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/cache.h>
#include <linux/export.h>
#include <linux/security.h>
#include <linux/seqlock.h>
#include <linux/memblock.h>
#include <linux/bit_spinlock.h>
#include <linux/rculist_bl.h>
#include <linux/list_lru.h>
#include "internal.h"
#include "mount.h"
#include <asm/runtime-const.h>
/*
* Usage:
* dcache->d_inode->i_lock protects:
* - i_dentry, d_u.d_alias, d_inode of aliases
* dcache_hash_bucket lock protects:
* - the dcache hash table
* s_roots bl list spinlock protects:
* - the s_roots list (see __d_drop)
* dentry->d_sb->s_dentry_lru_lock protects:
* - the dcache lru lists and counters
* d_lock protects:
* - d_flags
* - d_name
* - d_lru
* - d_count
* - d_unhashed()
* - d_parent and d_chilren
* - childrens' d_sib and d_parent
* - d_u.d_alias, d_inode
*
* Ordering:
* dentry->d_inode->i_lock
* dentry->d_lock
* dentry->d_sb->s_dentry_lru_lock
* dcache_hash_bucket lock
* s_roots lock
*
* If there is an ancestor relationship:
* dentry->d_parent->...->d_parent->d_lock
* ...
* dentry->d_parent->d_lock
* dentry->d_lock
*
* If no ancestor relationship:
* arbitrary, since it's serialized on rename_lock
*/
int sysctl_vfs_cache_pressure __read_mostly = 100;
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
EXPORT_SYMBOL(rename_lock);
static struct kmem_cache *dentry_cache __ro_after_init;
const struct qstr empty_name = QSTR_INIT("", 0);
EXPORT_SYMBOL(empty_name);
const struct qstr slash_name = QSTR_INIT("/", 1);
EXPORT_SYMBOL(slash_name);
const struct qstr dotdot_name = QSTR_INIT("..", 2);
EXPORT_SYMBOL(dotdot_name);
/*
* This is the single most critical data structure when it comes
* to the dcache: the hashtable for lookups. Somebody should try
* to make this good - I've just made it work.
*
* This hash-function tries to avoid losing too many bits of hash
* information, yet avoid using a prime hash-size or similar.
*/
static unsigned int d_hash_shift __ro_after_init;
static struct hlist_bl_head *dentry_hashtable __ro_after_init;
static inline struct hlist_bl_head *d_hash(unsigned long hashlen)
{
return runtime_const_ptr(dentry_hashtable) +
runtime_const_shift_right_32(hashlen, d_hash_shift);
}
#define IN_LOOKUP_SHIFT 10
static struct hlist_bl_head in_lookup_hashtable[1 << IN_LOOKUP_SHIFT];
static inline struct hlist_bl_head *in_lookup_hash(const struct dentry *parent,
unsigned int hash)
{
hash += (unsigned long) parent / L1_CACHE_BYTES;
return in_lookup_hashtable + hash_32(hash, IN_LOOKUP_SHIFT);
}
struct dentry_stat_t {
long nr_dentry;
long nr_unused;
long age_limit; /* age in seconds */
long want_pages; /* pages requested by system */
long nr_negative; /* # of unused negative dentries */
long dummy; /* Reserved for future use */
};
static DEFINE_PER_CPU(long, nr_dentry);
static DEFINE_PER_CPU(long, nr_dentry_unused);
static DEFINE_PER_CPU(long, nr_dentry_negative);
#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
/* Statistics gathering. */
static struct dentry_stat_t dentry_stat = {
.age_limit = 45,
};
/*
* Here we resort to our own counters instead of using generic per-cpu counters
* for consistency with what the vfs inode code does. We are expected to harvest
* better code and performance by having our own specialized counters.
*
* Please note that the loop is done over all possible CPUs, not over all online
* CPUs. The reason for this is that we don't want to play games with CPUs going
* on and off. If one of them goes off, we will just keep their counters.
*
* glommer: See cffbc8a for details, and if you ever intend to change this,
* please update all vfs counters to match.
*/
static long get_nr_dentry(void)
{
int i;
long sum = 0;
for_each_possible_cpu(i)
sum += per_cpu(nr_dentry, i);
return sum < 0 ? 0 : sum;
}
static long get_nr_dentry_unused(void)
{
int i;
long sum = 0;
for_each_possible_cpu(i)
sum += per_cpu(nr_dentry_unused, i);
return sum < 0 ? 0 : sum;
}
static long get_nr_dentry_negative(void)
{
int i;
long sum = 0;
for_each_possible_cpu(i)
sum += per_cpu(nr_dentry_negative, i);
return sum < 0 ? 0 : sum;
}
static int proc_nr_dentry(const struct ctl_table *table, int write, void *buffer,
size_t *lenp, loff_t *ppos)
{
dentry_stat.nr_dentry = get_nr_dentry();
dentry_stat.nr_unused = get_nr_dentry_unused();
dentry_stat.nr_negative = get_nr_dentry_negative();
return proc_doulongvec_minmax(table, write, buffer, lenp, ppos);
}
static struct ctl_table fs_dcache_sysctls[] = {
{
.procname = "dentry-state",
.data = &dentry_stat,
.maxlen = 6*sizeof(long),
.mode = 0444,
.proc_handler = proc_nr_dentry,
},
};
static int __init init_fs_dcache_sysctls(void)
{
register_sysctl_init("fs", fs_dcache_sysctls);
return 0;
}
fs_initcall(init_fs_dcache_sysctls);
#endif
/*
* Compare 2 name strings, return 0 if they match, otherwise non-zero.
* The strings are both count bytes long, and count is non-zero.
*/
#ifdef CONFIG_DCACHE_WORD_ACCESS
#include <asm/word-at-a-time.h>
/*
* NOTE! 'cs' and 'scount' come from a dentry, so it has a
* aligned allocation for this particular component. We don't
* strictly need the load_unaligned_zeropad() safety, but it
* doesn't hurt either.
*
* In contrast, 'ct' and 'tcount' can be from a pathname, and do
* need the careful unaligned handling.
*/
static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
{
unsigned long a,b,mask;
for (;;) {
a = read_word_at_a_time(cs);
b = load_unaligned_zeropad(ct);
if (tcount < sizeof(unsigned long))
break;
if (unlikely(a != b))
return 1;
cs += sizeof(unsigned long);
ct += sizeof(unsigned long);
tcount -= sizeof(unsigned long);
if (!tcount)
return 0;
}
mask = bytemask_from_count(tcount);
return unlikely(!!((a ^ b) & mask));
}
#else
static inline int dentry_string_cmp(const unsigned char *cs, const unsigned char *ct, unsigned tcount)
{
do {
if (*cs != *ct)
return 1;
cs++;
ct++;
tcount--;
} while (tcount);
return 0;
}
#endif
static inline int dentry_cmp(const struct dentry *dentry, const unsigned char *ct, unsigned tcount)
{
/*
* Be careful about RCU walk racing with rename:
* use 'READ_ONCE' to fetch the name pointer.
*
* NOTE! Even if a rename will mean that the length
* was not loaded atomically, we don't care. The
* RCU walk will check the sequence count eventually,
* and catch it. And we won't overrun the buffer,
* because we're reading the name pointer atomically,
* and a dentry name is guaranteed to be properly
* terminated with a NUL byte.
*
* End result: even if 'len' is wrong, we'll exit
* early because the data cannot match (there can
* be no NUL in the ct/tcount data)
*/
const unsigned char *cs = READ_ONCE(dentry->d_name.name);
return dentry_string_cmp(cs, ct, tcount);
}
struct external_name {
union {
atomic_t count;
struct rcu_head head;
} u;
unsigned char name[];
};
static inline struct external_name *external_name(struct dentry *dentry)
{
return container_of(dentry->d_name.name, struct external_name, name[0]);
}
static void __d_free(struct rcu_head *head)
{
struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
kmem_cache_free(dentry_cache, dentry);
}
static void __d_free_external(struct rcu_head *head)
{
struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
kfree(external_name(dentry));
kmem_cache_free(dentry_cache, dentry);
}
static inline int dname_external(const struct dentry *dentry)
{
return dentry->d_name.name != dentry->d_iname;
}
void take_dentry_name_snapshot(struct name_snapshot *name, struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
name->name = dentry->d_name;
if (unlikely(dname_external(dentry))) {
atomic_inc(&external_name(dentry)->u.count);
} else {
memcpy(name->inline_name, dentry->d_iname,
dentry->d_name.len + 1);
name->name.name = name->inline_name;
}
spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(take_dentry_name_snapshot);
void release_dentry_name_snapshot(struct name_snapshot *name)
{
if (unlikely(name->name.name != name->inline_name)) {
struct external_name *p;
p = container_of(name->name.name, struct external_name, name[0]);
if (unlikely(atomic_dec_and_test(&p->u.count)))
kfree_rcu(p, u.head);
}
}
EXPORT_SYMBOL(release_dentry_name_snapshot);
static inline void __d_set_inode_and_type(struct dentry *dentry,
struct inode *inode,
unsigned type_flags)
{
unsigned flags;
dentry->d_inode = inode;
flags = READ_ONCE(dentry->d_flags);
flags &= ~DCACHE_ENTRY_TYPE;
flags |= type_flags;
smp_store_release(&dentry->d_flags, flags);
}
static inline void __d_clear_type_and_inode(struct dentry *dentry)
{
unsigned flags = READ_ONCE(dentry->d_flags);
flags &= ~DCACHE_ENTRY_TYPE;
WRITE_ONCE(dentry->d_flags, flags);
dentry->d_inode = NULL;
/*
* The negative counter only tracks dentries on the LRU. Don't inc if
* d_lru is on another list.
*/
if ((flags & (DCACHE_LRU_LIST|DCACHE_SHRINK_LIST)) == DCACHE_LRU_LIST)
this_cpu_inc(nr_dentry_negative);
}
static void dentry_free(struct dentry *dentry)
{
WARN_ON(!hlist_unhashed(&dentry->d_u.d_alias));
if (unlikely(dname_external(dentry))) {
struct external_name *p = external_name(dentry);
if (likely(atomic_dec_and_test(&p->u.count))) {
call_rcu(&dentry->d_u.d_rcu, __d_free_external);
return;
}
}
/* if dentry was never visible to RCU, immediate free is OK */
if (dentry->d_flags & DCACHE_NORCU)
__d_free(&dentry->d_u.d_rcu);
else
call_rcu(&dentry->d_u.d_rcu, __d_free);
}
/*
* Release the dentry's inode, using the filesystem
* d_iput() operation if defined.
*/
static void dentry_unlink_inode(struct dentry * dentry)
__releases(dentry->d_lock)
__releases(dentry->d_inode->i_lock)
{
struct inode *inode = dentry->d_inode;
raw_write_seqcount_begin(&dentry->d_seq);
__d_clear_type_and_inode(dentry);
hlist_del_init(&dentry->d_u.d_alias);
raw_write_seqcount_end(&dentry->d_seq);
spin_unlock(&dentry->d_lock);
spin_unlock(&inode->i_lock);
if (!inode->i_nlink)
fsnotify_inoderemove(inode);
if (dentry->d_op && dentry->d_op->d_iput)
dentry->d_op->d_iput(dentry, inode);
else
iput(inode);
}
/*
* The DCACHE_LRU_LIST bit is set whenever the 'd_lru' entry
* is in use - which includes both the "real" per-superblock
* LRU list _and_ the DCACHE_SHRINK_LIST use.
*
* The DCACHE_SHRINK_LIST bit is set whenever the dentry is
* on the shrink list (ie not on the superblock LRU list).
*
* The per-cpu "nr_dentry_unused" counters are updated with
* the DCACHE_LRU_LIST bit.
*
* The per-cpu "nr_dentry_negative" counters are only updated
* when deleted from or added to the per-superblock LRU list, not
* from/to the shrink list. That is to avoid an unneeded dec/inc
* pair when moving from LRU to shrink list in select_collect().
*
* These helper functions make sure we always follow the
* rules. d_lock must be held by the caller.
*/
#define D_FLAG_VERIFY(dentry,x) WARN_ON_ONCE(((dentry)->d_flags & (DCACHE_LRU_LIST | DCACHE_SHRINK_LIST)) != (x))
static void d_lru_add(struct dentry *dentry)
{
D_FLAG_VERIFY(dentry, 0);
dentry->d_flags |= DCACHE_LRU_LIST;
this_cpu_inc(nr_dentry_unused);
if (d_is_negative(dentry))
this_cpu_inc(nr_dentry_negative);
WARN_ON_ONCE(!list_lru_add_obj(
&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
}
static void d_lru_del(struct dentry *dentry)
{
D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
dentry->d_flags &= ~DCACHE_LRU_LIST;
this_cpu_dec(nr_dentry_unused);
if (d_is_negative(dentry))
this_cpu_dec(nr_dentry_negative);
WARN_ON_ONCE(!list_lru_del_obj(
&dentry->d_sb->s_dentry_lru, &dentry->d_lru));
}
static void d_shrink_del(struct dentry *dentry)
{
D_FLAG_VERIFY(dentry, DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
list_del_init(&dentry->d_lru);
dentry->d_flags &= ~(DCACHE_SHRINK_LIST | DCACHE_LRU_LIST);
this_cpu_dec(nr_dentry_unused);
}
static void d_shrink_add(struct dentry *dentry, struct list_head *list)
{
D_FLAG_VERIFY(dentry, 0);
list_add(&dentry->d_lru, list);
dentry->d_flags |= DCACHE_SHRINK_LIST | DCACHE_LRU_LIST;
this_cpu_inc(nr_dentry_unused);
}
/*
* These can only be called under the global LRU lock, ie during the
* callback for freeing the LRU list. "isolate" removes it from the
* LRU lists entirely, while shrink_move moves it to the indicated
* private list.
*/
static void d_lru_isolate(struct list_lru_one *lru, struct dentry *dentry)
{
D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
dentry->d_flags &= ~DCACHE_LRU_LIST;
this_cpu_dec(nr_dentry_unused);
if (d_is_negative(dentry))
this_cpu_dec(nr_dentry_negative);
list_lru_isolate(lru, &dentry->d_lru);
}
static void d_lru_shrink_move(struct list_lru_one *lru, struct dentry *dentry,
struct list_head *list)
{
D_FLAG_VERIFY(dentry, DCACHE_LRU_LIST);
dentry->d_flags |= DCACHE_SHRINK_LIST;
if (d_is_negative(dentry))
this_cpu_dec(nr_dentry_negative);
list_lru_isolate_move(lru, &dentry->d_lru, list);
}
static void ___d_drop(struct dentry *dentry)
{
struct hlist_bl_head *b;
/*
* Hashed dentries are normally on the dentry hashtable,
* with the exception of those newly allocated by
* d_obtain_root, which are always IS_ROOT:
*/
if (unlikely(IS_ROOT(dentry)))
b = &dentry->d_sb->s_roots;
else
b = d_hash(dentry->d_name.hash);
hlist_bl_lock(b);
__hlist_bl_del(&dentry->d_hash);
hlist_bl_unlock(b);
}
void __d_drop(struct dentry *dentry)
{
if (!d_unhashed(dentry)) {
___d_drop(dentry);
dentry->d_hash.pprev = NULL;
write_seqcount_invalidate(&dentry->d_seq);
}
}
EXPORT_SYMBOL(__d_drop);
/**
* d_drop - drop a dentry
* @dentry: dentry to drop
*
* d_drop() unhashes the entry from the parent dentry hashes, so that it won't
* be found through a VFS lookup any more. Note that this is different from
* deleting the dentry - d_delete will try to mark the dentry negative if
* possible, giving a successful _negative_ lookup, while d_drop will
* just make the cache lookup fail.
*
* d_drop() is used mainly for stuff that wants to invalidate a dentry for some
* reason (NFS timeouts or autofs deletes).
*
* __d_drop requires dentry->d_lock
*
* ___d_drop doesn't mark dentry as "unhashed"
* (dentry->d_hash.pprev will be LIST_POISON2, not NULL).
*/
void d_drop(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(d_drop);
static inline void dentry_unlist(struct dentry *dentry)
{
struct dentry *next;
/*
* Inform d_walk() and shrink_dentry_list() that we are no longer
* attached to the dentry tree
*/
dentry->d_flags |= DCACHE_DENTRY_KILLED;
if (unlikely(hlist_unhashed(&dentry->d_sib)))
return;
__hlist_del(&dentry->d_sib);
/*
* Cursors can move around the list of children. While we'd been
* a normal list member, it didn't matter - ->d_sib.next would've
* been updated. However, from now on it won't be and for the
* things like d_walk() it might end up with a nasty surprise.
* Normally d_walk() doesn't care about cursors moving around -
* ->d_lock on parent prevents that and since a cursor has no children
* of its own, we get through it without ever unlocking the parent.
* There is one exception, though - if we ascend from a child that
* gets killed as soon as we unlock it, the next sibling is found
* using the value left in its ->d_sib.next. And if _that_
* pointed to a cursor, and cursor got moved (e.g. by lseek())
* before d_walk() regains parent->d_lock, we'll end up skipping
* everything the cursor had been moved past.
*
* Solution: make sure that the pointer left behind in ->d_sib.next
* points to something that won't be moving around. I.e. skip the
* cursors.
*/
while (dentry->d_sib.next) {
next = hlist_entry(dentry->d_sib.next, struct dentry, d_sib);
if (likely(!(next->d_flags & DCACHE_DENTRY_CURSOR)))
break;
dentry->d_sib.next = next->d_sib.next;
}
}
static struct dentry *__dentry_kill(struct dentry *dentry)
{
struct dentry *parent = NULL;
bool can_free = true;
/*
* The dentry is now unrecoverably dead to the world.
*/
lockref_mark_dead(&dentry->d_lockref);
/*
* inform the fs via d_prune that this dentry is about to be
* unhashed and destroyed.
*/
if (dentry->d_flags & DCACHE_OP_PRUNE)
dentry->d_op->d_prune(dentry);
if (dentry->d_flags & DCACHE_LRU_LIST) {
if (!(dentry->d_flags & DCACHE_SHRINK_LIST))
d_lru_del(dentry);
}
/* if it was on the hash then remove it */
__d_drop(dentry);
if (dentry->d_inode)
dentry_unlink_inode(dentry);
else
spin_unlock(&dentry->d_lock);
this_cpu_dec(nr_dentry);
if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
cond_resched();
/* now that it's negative, ->d_parent is stable */
if (!IS_ROOT(dentry)) {
parent = dentry->d_parent;
spin_lock(&parent->d_lock);
}
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
dentry_unlist(dentry);
if (dentry->d_flags & DCACHE_SHRINK_LIST)
can_free = false;
spin_unlock(&dentry->d_lock);
if (likely(can_free))
dentry_free(dentry);
if (parent && --parent->d_lockref.count) {
spin_unlock(&parent->d_lock);
return NULL;
}
return parent;
}
/*
* Lock a dentry for feeding it to __dentry_kill().
* Called under rcu_read_lock() and dentry->d_lock; the former
* guarantees that nothing we access will be freed under us.
* Note that dentry is *not* protected from concurrent dentry_kill(),
* d_delete(), etc.
*
* Return false if dentry is busy. Otherwise, return true and have
* that dentry's inode locked.
*/
static bool lock_for_kill(struct dentry *dentry)
{
struct inode *inode = dentry->d_inode;
if (unlikely(dentry->d_lockref.count))
return false;
if (!inode || likely(spin_trylock(&inode->i_lock)))
return true;
do {
spin_unlock(&dentry->d_lock);
spin_lock(&inode->i_lock);
spin_lock(&dentry->d_lock);
if (likely(inode == dentry->d_inode))
break;
spin_unlock(&inode->i_lock);
inode = dentry->d_inode;
} while (inode);
if (likely(!dentry->d_lockref.count))
return true;
if (inode)
spin_unlock(&inode->i_lock);
return false;
}
/*
* Decide if dentry is worth retaining. Usually this is called with dentry
* locked; if not locked, we are more limited and might not be able to tell
* without a lock. False in this case means "punt to locked path and recheck".
*
* In case we aren't locked, these predicates are not "stable". However, it is
* sufficient that at some point after we dropped the reference the dentry was
* hashed and the flags had the proper value. Other dentry users may have
* re-gotten a reference to the dentry and change that, but our work is done -
* we can leave the dentry around with a zero refcount.
*/
static inline bool retain_dentry(struct dentry *dentry, bool locked)
{
unsigned int d_flags;
smp_rmb();
d_flags = READ_ONCE(dentry->d_flags);
// Unreachable? Nobody would be able to look it up, no point retaining
if (unlikely(d_unhashed(dentry)))
return false;
// Same if it's disconnected
if (unlikely(d_flags & DCACHE_DISCONNECTED))
return false;
// ->d_delete() might tell us not to bother, but that requires
// ->d_lock; can't decide without it
if (unlikely(d_flags & DCACHE_OP_DELETE)) {
if (!locked || dentry->d_op->d_delete(dentry))
return false;
}
// Explicitly told not to bother
if (unlikely(d_flags & DCACHE_DONTCACHE))
return false;
// At this point it looks like we ought to keep it. We also might
// need to do something - put it on LRU if it wasn't there already
// and mark it referenced if it was on LRU, but not marked yet.
// Unfortunately, both actions require ->d_lock, so in lockless
// case we'd have to punt rather than doing those.
if (unlikely(!(d_flags & DCACHE_LRU_LIST))) {
if (!locked)
return false;
d_lru_add(dentry);
} else if (unlikely(!(d_flags & DCACHE_REFERENCED))) {
if (!locked)
return false;
dentry->d_flags |= DCACHE_REFERENCED;
}
return true;
}
void d_mark_dontcache(struct inode *inode)
{
struct dentry *de;
spin_lock(&inode->i_lock);
hlist_for_each_entry(de, &inode->i_dentry, d_u.d_alias) {
spin_lock(&de->d_lock);
de->d_flags |= DCACHE_DONTCACHE;
spin_unlock(&de->d_lock);
}
inode->i_state |= I_DONTCACHE;
spin_unlock(&inode->i_lock);
}
EXPORT_SYMBOL(d_mark_dontcache);
/*
* Try to do a lockless dput(), and return whether that was successful.
*
* If unsuccessful, we return false, having already taken the dentry lock.
* In that case refcount is guaranteed to be zero and we have already
* decided that it's not worth keeping around.
*
* The caller needs to hold the RCU read lock, so that the dentry is
* guaranteed to stay around even if the refcount goes down to zero!
*/
static inline bool fast_dput(struct dentry *dentry)
{
int ret;
/*
* try to decrement the lockref optimistically.
*/
ret = lockref_put_return(&dentry->d_lockref);
/*
* If the lockref_put_return() failed due to the lock being held
* by somebody else, the fast path has failed. We will need to
* get the lock, and then check the count again.
*/
if (unlikely(ret < 0)) {
spin_lock(&dentry->d_lock);
if (WARN_ON_ONCE(dentry->d_lockref.count <= 0)) {
spin_unlock(&dentry->d_lock);
return true;
}
dentry->d_lockref.count--;
goto locked;
}
/*
* If we weren't the last ref, we're done.
*/
if (ret)
return true;
/*
* Can we decide that decrement of refcount is all we needed without
* taking the lock? There's a very common case when it's all we need -
* dentry looks like it ought to be retained and there's nothing else
* to do.
*/
if (retain_dentry(dentry, false))
return true;
/*
* Either not worth retaining or we can't tell without the lock.
* Get the lock, then. We've already decremented the refcount to 0,
* but we'll need to re-check the situation after getting the lock.
*/
spin_lock(&dentry->d_lock);
/*
* Did somebody else grab a reference to it in the meantime, and
* we're no longer the last user after all? Alternatively, somebody
* else could have killed it and marked it dead. Either way, we
* don't need to do anything else.
*/
locked:
if (dentry->d_lockref.count || retain_dentry(dentry, true)) {
spin_unlock(&dentry->d_lock);
return true;
}
return false;
}
/*
* This is dput
*
* This is complicated by the fact that we do not want to put
* dentries that are no longer on any hash chain on the unused
* list: we'd much rather just get rid of them immediately.
*
* However, that implies that we have to traverse the dentry
* tree upwards to the parents which might _also_ now be
* scheduled for deletion (it may have been only waiting for
* its last child to go away).
*
* This tail recursion is done by hand as we don't want to depend
* on the compiler to always get this right (gcc generally doesn't).
* Real recursion would eat up our stack space.
*/
/*
* dput - release a dentry
* @dentry: dentry to release
*
* Release a dentry. This will drop the usage count and if appropriate
* call the dentry unlink method as well as removing it from the queues and
* releasing its resources. If the parent dentries were scheduled for release
* they too may now get deleted.
*/
void dput(struct dentry *dentry)
{
if (!dentry)
return;
might_sleep();
rcu_read_lock();
if (likely(fast_dput(dentry))) {
rcu_read_unlock();
return;
}
while (lock_for_kill(dentry)) {
rcu_read_unlock();
dentry = __dentry_kill(dentry);
if (!dentry)
return;
if (retain_dentry(dentry, true)) {
spin_unlock(&dentry->d_lock);
return;
}
rcu_read_lock();
}
rcu_read_unlock();
spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(dput);
static void to_shrink_list(struct dentry *dentry, struct list_head *list)
__must_hold(&dentry->d_lock)
{
if (!(dentry->d_flags & DCACHE_SHRINK_LIST)) {
if (dentry->d_flags & DCACHE_LRU_LIST)
d_lru_del(dentry);
d_shrink_add(dentry, list);
}
}
void dput_to_list(struct dentry *dentry, struct list_head *list)
{
rcu_read_lock();
if (likely(fast_dput(dentry))) {
rcu_read_unlock();
return;
}
rcu_read_unlock();
to_shrink_list(dentry, list);
spin_unlock(&dentry->d_lock);
}
struct dentry *dget_parent(struct dentry *dentry)
{
int gotref;
struct dentry *ret;
unsigned seq;
/*
* Do optimistic parent lookup without any
* locking.
*/
rcu_read_lock();
seq = raw_seqcount_begin(&dentry->d_seq);
ret = READ_ONCE(dentry->d_parent);
gotref = lockref_get_not_zero(&ret->d_lockref);
rcu_read_unlock();
if (likely(gotref)) {
if (!read_seqcount_retry(&dentry->d_seq, seq))
return ret;
dput(ret);
}
repeat:
/*
* Don't need rcu_dereference because we re-check it was correct under
* the lock.
*/
rcu_read_lock();
ret = dentry->d_parent;
spin_lock(&ret->d_lock);
if (unlikely(ret != dentry->d_parent)) {
spin_unlock(&ret->d_lock);
rcu_read_unlock();
goto repeat;
}
rcu_read_unlock();
BUG_ON(!ret->d_lockref.count);
ret->d_lockref.count++;
spin_unlock(&ret->d_lock);
return ret;
}
EXPORT_SYMBOL(dget_parent);
static struct dentry * __d_find_any_alias(struct inode *inode)
{
struct dentry *alias;
if (hlist_empty(&inode->i_dentry))
return NULL;
alias = hlist_entry(inode->i_dentry.first, struct dentry, d_u.d_alias);
lockref_get(&alias->d_lockref);
return alias;
}
/**
* d_find_any_alias - find any alias for a given inode
* @inode: inode to find an alias for
*
* If any aliases exist for the given inode, take and return a
* reference for one of them. If no aliases exist, return %NULL.
*/
struct dentry *d_find_any_alias(struct inode *inode)
{
struct dentry *de;
spin_lock(&inode->i_lock);
de = __d_find_any_alias(inode);
spin_unlock(&inode->i_lock);
return de;
}
EXPORT_SYMBOL(d_find_any_alias);
static struct dentry *__d_find_alias(struct inode *inode)
{
struct dentry *alias;
if (S_ISDIR(inode->i_mode))
return __d_find_any_alias(inode);
hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
spin_lock(&alias->d_lock);
if (!d_unhashed(alias)) {
dget_dlock(alias);
spin_unlock(&alias->d_lock);
return alias;
}
spin_unlock(&alias->d_lock);
}
return NULL;
}
/**
* d_find_alias - grab a hashed alias of inode
* @inode: inode in question
*
* If inode has a hashed alias, or is a directory and has any alias,
* acquire the reference to alias and return it. Otherwise return NULL.
* Notice that if inode is a directory there can be only one alias and
* it can be unhashed only if it has no children, or if it is the root
* of a filesystem, or if the directory was renamed and d_revalidate
* was the first vfs operation to notice.
*
* If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
* any other hashed alias over that one.
*/
struct dentry *d_find_alias(struct inode *inode)
{
struct dentry *de = NULL;
if (!hlist_empty(&inode->i_dentry)) {
spin_lock(&inode->i_lock);
de = __d_find_alias(inode);
spin_unlock(&inode->i_lock);
}
return de;
}
EXPORT_SYMBOL(d_find_alias);
/*
* Caller MUST be holding rcu_read_lock() and be guaranteed
* that inode won't get freed until rcu_read_unlock().
*/
struct dentry *d_find_alias_rcu(struct inode *inode)
{
struct hlist_head *l = &inode->i_dentry;
struct dentry *de = NULL;
spin_lock(&inode->i_lock);
// ->i_dentry and ->i_rcu are colocated, but the latter won't be
// used without having I_FREEING set, which means no aliases left
if (likely(!(inode->i_state & I_FREEING) && !hlist_empty(l))) {
if (S_ISDIR(inode->i_mode)) {
de = hlist_entry(l->first, struct dentry, d_u.d_alias);
} else {
hlist_for_each_entry(de, l, d_u.d_alias)
if (!d_unhashed(de))
break;
}
}
spin_unlock(&inode->i_lock);
return de;
}
/*
* Try to kill dentries associated with this inode.
* WARNING: you must own a reference to inode.
*/
void d_prune_aliases(struct inode *inode)
{
LIST_HEAD(dispose);
struct dentry *dentry;
spin_lock(&inode->i_lock);
hlist_for_each_entry(dentry, &inode->i_dentry, d_u.d_alias) {
spin_lock(&dentry->d_lock);
if (!dentry->d_lockref.count)
to_shrink_list(dentry, &dispose);
spin_unlock(&dentry->d_lock);
}
spin_unlock(&inode->i_lock);
shrink_dentry_list(&dispose);
}
EXPORT_SYMBOL(d_prune_aliases);
static inline void shrink_kill(struct dentry *victim)
{
do {
rcu_read_unlock();
victim = __dentry_kill(victim);
rcu_read_lock();
} while (victim && lock_for_kill(victim));
rcu_read_unlock();
if (victim)
spin_unlock(&victim->d_lock);
}
void shrink_dentry_list(struct list_head *list)
{
while (!list_empty(list)) {
struct dentry *dentry;
dentry = list_entry(list->prev, struct dentry, d_lru);
spin_lock(&dentry->d_lock);
rcu_read_lock();
if (!lock_for_kill(dentry)) {
bool can_free;
rcu_read_unlock();
d_shrink_del(dentry);
can_free = dentry->d_flags & DCACHE_DENTRY_KILLED;
spin_unlock(&dentry->d_lock);
if (can_free)
dentry_free(dentry);
continue;
}
d_shrink_del(dentry);
shrink_kill(dentry);
}
}
static enum lru_status dentry_lru_isolate(struct list_head *item,
struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
{
struct list_head *freeable = arg;
struct dentry *dentry = container_of(item, struct dentry, d_lru);
/*
* we are inverting the lru lock/dentry->d_lock here,
* so use a trylock. If we fail to get the lock, just skip
* it
*/
if (!spin_trylock(&dentry->d_lock))
return LRU_SKIP;
/*
* Referenced dentries are still in use. If they have active
* counts, just remove them from the LRU. Otherwise give them
* another pass through the LRU.
*/
if (dentry->d_lockref.count) {
d_lru_isolate(lru, dentry);
spin_unlock(&dentry->d_lock);
return LRU_REMOVED;
}
if (dentry->d_flags & DCACHE_REFERENCED) {
dentry->d_flags &= ~DCACHE_REFERENCED;
spin_unlock(&dentry->d_lock);
/*
* The list move itself will be made by the common LRU code. At
* this point, we've dropped the dentry->d_lock but keep the
* lru lock. This is safe to do, since every list movement is
* protected by the lru lock even if both locks are held.
*
* This is guaranteed by the fact that all LRU management
* functions are intermediated by the LRU API calls like
* list_lru_add_obj and list_lru_del_obj. List movement in this file
* only ever occur through this functions or through callbacks
* like this one, that are called from the LRU API.
*
* The only exceptions to this are functions like
* shrink_dentry_list, and code that first checks for the
* DCACHE_SHRINK_LIST flag. Those are guaranteed to be
* operating only with stack provided lists after they are
* properly isolated from the main list. It is thus, always a
* local access.
*/
return LRU_ROTATE;
}
d_lru_shrink_move(lru, dentry, freeable);
spin_unlock(&dentry->d_lock);
return LRU_REMOVED;
}
/**
* prune_dcache_sb - shrink the dcache
* @sb: superblock
* @sc: shrink control, passed to list_lru_shrink_walk()
*
* Attempt to shrink the superblock dcache LRU by @sc->nr_to_scan entries. This
* is done when we need more memory and called from the superblock shrinker
* function.
*
* This function may fail to free any resources if all the dentries are in
* use.
*/
long prune_dcache_sb(struct super_block *sb, struct shrink_control *sc)
{
LIST_HEAD(dispose);
long freed;
freed = list_lru_shrink_walk(&sb->s_dentry_lru, sc,
dentry_lru_isolate, &dispose);
shrink_dentry_list(&dispose);
return freed;
}
static enum lru_status dentry_lru_isolate_shrink(struct list_head *item,
struct list_lru_one *lru, spinlock_t *lru_lock, void *arg)
{
struct list_head *freeable = arg;
struct dentry *dentry = container_of(item, struct dentry, d_lru);
/*
* we are inverting the lru lock/dentry->d_lock here,
* so use a trylock. If we fail to get the lock, just skip
* it
*/
if (!spin_trylock(&dentry->d_lock))
return LRU_SKIP;
d_lru_shrink_move(lru, dentry, freeable);
spin_unlock(&dentry->d_lock);
return LRU_REMOVED;
}
/**
* shrink_dcache_sb - shrink dcache for a superblock
* @sb: superblock
*
* Shrink the dcache for the specified super block. This is used to free
* the dcache before unmounting a file system.
*/
void shrink_dcache_sb(struct super_block *sb)
{
do {
LIST_HEAD(dispose);
list_lru_walk(&sb->s_dentry_lru,
dentry_lru_isolate_shrink, &dispose, 1024);
shrink_dentry_list(&dispose);
} while (list_lru_count(&sb->s_dentry_lru) > 0);
}
EXPORT_SYMBOL(shrink_dcache_sb);
/**
* enum d_walk_ret - action to talke during tree walk
* @D_WALK_CONTINUE: contrinue walk
* @D_WALK_QUIT: quit walk
* @D_WALK_NORETRY: quit when retry is needed
* @D_WALK_SKIP: skip this dentry and its children
*/
enum d_walk_ret {
D_WALK_CONTINUE,
D_WALK_QUIT,
D_WALK_NORETRY,
D_WALK_SKIP,
};
/**
* d_walk - walk the dentry tree
* @parent: start of walk
* @data: data passed to @enter() and @finish()
* @enter: callback when first entering the dentry
*
* The @enter() callbacks are called with d_lock held.
*/
static void d_walk(struct dentry *parent, void *data,
enum d_walk_ret (*enter)(void *, struct dentry *))
{
struct dentry *this_parent, *dentry;
unsigned seq = 0;
enum d_walk_ret ret;
bool retry = true;
again:
read_seqbegin_or_lock(&rename_lock, &seq);
this_parent = parent;
spin_lock(&this_parent->d_lock);
ret = enter(data, this_parent);
switch (ret) {
case D_WALK_CONTINUE:
break;
case D_WALK_QUIT:
case D_WALK_SKIP:
goto out_unlock;
case D_WALK_NORETRY:
retry = false;
break;
}
repeat:
dentry = d_first_child(this_parent);
resume:
hlist_for_each_entry_from(dentry, d_sib) {
if (unlikely(dentry->d_flags & DCACHE_DENTRY_CURSOR))
continue;
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
ret = enter(data, dentry);
switch (ret) {
case D_WALK_CONTINUE:
break;
case D_WALK_QUIT:
spin_unlock(&dentry->d_lock);
goto out_unlock;
case D_WALK_NORETRY:
retry = false;
break;
case D_WALK_SKIP:
spin_unlock(&dentry->d_lock);
continue;
}
if (!hlist_empty(&dentry->d_children)) {
spin_unlock(&this_parent->d_lock);
spin_release(&dentry->d_lock.dep_map, _RET_IP_);
this_parent = dentry;
spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
goto repeat;
}
spin_unlock(&dentry->d_lock);
}
/*
* All done at this level ... ascend and resume the search.
*/
rcu_read_lock();
ascend:
if (this_parent != parent) {
dentry = this_parent;
this_parent = dentry->d_parent;
spin_unlock(&dentry->d_lock);
spin_lock(&this_parent->d_lock);
/* might go back up the wrong parent if we have had a rename. */
if (need_seqretry(&rename_lock, seq))
goto rename_retry;
/* go into the first sibling still alive */
hlist_for_each_entry_continue(dentry, d_sib) {
if (likely(!(dentry->d_flags & DCACHE_DENTRY_KILLED))) {
rcu_read_unlock();
goto resume;
}
}
goto ascend;
}
if (need_seqretry(&rename_lock, seq))
goto rename_retry;
rcu_read_unlock();
out_unlock:
spin_unlock(&this_parent->d_lock);
done_seqretry(&rename_lock, seq);
return;
rename_retry:
spin_unlock(&this_parent->d_lock);
rcu_read_unlock();
BUG_ON(seq & 1);
if (!retry)
return;
seq = 1;
goto again;
}
struct check_mount {
struct vfsmount *mnt;
unsigned int mounted;
};
static enum d_walk_ret path_check_mount(void *data, struct dentry *dentry)
{
struct check_mount *info = data;
struct path path = { .mnt = info->mnt, .dentry = dentry };
if (likely(!d_mountpoint(dentry)))
return D_WALK_CONTINUE;
if (__path_is_mountpoint(&path)) {
info->mounted = 1;
return D_WALK_QUIT;
}
return D_WALK_CONTINUE;
}
/**
* path_has_submounts - check for mounts over a dentry in the
* current namespace.
* @parent: path to check.
*
* Return true if the parent or its subdirectories contain
* a mount point in the current namespace.
*/
int path_has_submounts(const struct path *parent)
{
struct check_mount data = { .mnt = parent->mnt, .mounted = 0 };
read_seqlock_excl(&mount_lock);
d_walk(parent->dentry, &data, path_check_mount);
read_sequnlock_excl(&mount_lock);
return data.mounted;
}
EXPORT_SYMBOL(path_has_submounts);
/*
* Called by mount code to set a mountpoint and check if the mountpoint is
* reachable (e.g. NFS can unhash a directory dentry and then the complete
* subtree can become unreachable).
*
* Only one of d_invalidate() and d_set_mounted() must succeed. For
* this reason take rename_lock and d_lock on dentry and ancestors.
*/
int d_set_mounted(struct dentry *dentry)
{
struct dentry *p;
int ret = -ENOENT;
write_seqlock(&rename_lock);
for (p = dentry->d_parent; !IS_ROOT(p); p = p->d_parent) {
/* Need exclusion wrt. d_invalidate() */
spin_lock(&p->d_lock);
if (unlikely(d_unhashed(p))) {
spin_unlock(&p->d_lock);
goto out;
}
spin_unlock(&p->d_lock);
}
spin_lock(&dentry->d_lock);
if (!d_unlinked(dentry)) {
ret = -EBUSY;
if (!d_mountpoint(dentry)) {
dentry->d_flags |= DCACHE_MOUNTED;
ret = 0;
}
}
spin_unlock(&dentry->d_lock);
out:
write_sequnlock(&rename_lock);
return ret;
}
/*
* Search the dentry child list of the specified parent,
* and move any unused dentries to the end of the unused
* list for prune_dcache(). We descend to the next level
* whenever the d_children list is non-empty and continue
* searching.
*
* It returns zero iff there are no unused children,
* otherwise it returns the number of children moved to
* the end of the unused list. This may not be the total
* number of unused children, because select_parent can
* drop the lock and return early due to latency
* constraints.
*/
struct select_data {
struct dentry *start;
union {
long found;
struct dentry *victim;
};
struct list_head dispose;
};
static enum d_walk_ret select_collect(void *_data, struct dentry *dentry)
{
struct select_data *data = _data;
enum d_walk_ret ret = D_WALK_CONTINUE;
if (data->start == dentry)
goto out;
if (dentry->d_flags & DCACHE_SHRINK_LIST) {
data->found++;
} else if (!dentry->d_lockref.count) {
to_shrink_list(dentry, &data->dispose);
data->found++;
} else if (dentry->d_lockref.count < 0) {
data->found++;
}
/*
* We can return to the caller if we have found some (this
* ensures forward progress). We'll be coming back to find
* the rest.
*/
if (!list_empty(&data->dispose))
ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
out:
return ret;
}
static enum d_walk_ret select_collect2(void *_data, struct dentry *dentry)
{
struct select_data *data = _data;
enum d_walk_ret ret = D_WALK_CONTINUE;
if (data->start == dentry)
goto out;
if (!dentry->d_lockref.count) {
if (dentry->d_flags & DCACHE_SHRINK_LIST) {
rcu_read_lock();
data->victim = dentry;
return D_WALK_QUIT;
}
to_shrink_list(dentry, &data->dispose);
}
/*
* We can return to the caller if we have found some (this
* ensures forward progress). We'll be coming back to find
* the rest.
*/
if (!list_empty(&data->dispose))
ret = need_resched() ? D_WALK_QUIT : D_WALK_NORETRY;
out:
return ret;
}
/**
* shrink_dcache_parent - prune dcache
* @parent: parent of entries to prune
*
* Prune the dcache to remove unused children of the parent dentry.
*/
void shrink_dcache_parent(struct dentry *parent)
{
for (;;) {
struct select_data data = {.start = parent};
INIT_LIST_HEAD(&data.dispose);
d_walk(parent, &data, select_collect);
if (!list_empty(&data.dispose)) {
shrink_dentry_list(&data.dispose);
continue;
}
cond_resched();
if (!data.found)
break;
data.victim = NULL;
d_walk(parent, &data, select_collect2);
if (data.victim) {
spin_lock(&data.victim->d_lock);
if (!lock_for_kill(data.victim)) {
spin_unlock(&data.victim->d_lock);
rcu_read_unlock();
} else {
shrink_kill(data.victim);
}
}
if (!list_empty(&data.dispose))
shrink_dentry_list(&data.dispose);
}
}
EXPORT_SYMBOL(shrink_dcache_parent);
static enum d_walk_ret umount_check(void *_data, struct dentry *dentry)
{
/* it has busy descendents; complain about those instead */
if (!hlist_empty(&dentry->d_children))
return D_WALK_CONTINUE;
/* root with refcount 1 is fine */
if (dentry == _data && dentry->d_lockref.count == 1)
return D_WALK_CONTINUE;
WARN(1, "BUG: Dentry %p{i=%lx,n=%pd} "
" still in use (%d) [unmount of %s %s]\n",
dentry,
dentry->d_inode ?
dentry->d_inode->i_ino : 0UL,
dentry,
dentry->d_lockref.count,
dentry->d_sb->s_type->name,
dentry->d_sb->s_id);
return D_WALK_CONTINUE;
}
static void do_one_tree(struct dentry *dentry)
{
shrink_dcache_parent(dentry);
d_walk(dentry, dentry, umount_check);
d_drop(dentry);
dput(dentry);
}
/*
* destroy the dentries attached to a superblock on unmounting
*/
void shrink_dcache_for_umount(struct super_block *sb)
{
struct dentry *dentry;
rwsem_assert_held_write(&sb->s_umount);
dentry = sb->s_root;
sb->s_root = NULL;
do_one_tree(dentry);
while (!hlist_bl_empty(&sb->s_roots)) {
dentry = dget(hlist_bl_entry(hlist_bl_first(&sb->s_roots), struct dentry, d_hash));
do_one_tree(dentry);
}
}
static enum d_walk_ret find_submount(void *_data, struct dentry *dentry)
{
struct dentry **victim = _data;
if (d_mountpoint(dentry)) {
*victim = dget_dlock(dentry);
return D_WALK_QUIT;
}
return D_WALK_CONTINUE;
}
/**
* d_invalidate - detach submounts, prune dcache, and drop
* @dentry: dentry to invalidate (aka detach, prune and drop)
*/
void d_invalidate(struct dentry *dentry)
{
bool had_submounts = false;
spin_lock(&dentry->d_lock);
if (d_unhashed(dentry)) {
spin_unlock(&dentry->d_lock);
return;
}
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
/* Negative dentries can be dropped without further checks */
if (!dentry->d_inode)
return;
shrink_dcache_parent(dentry);
for (;;) {
struct dentry *victim = NULL;
d_walk(dentry, &victim, find_submount);
if (!victim) {
if (had_submounts)
shrink_dcache_parent(dentry);
return;
}
had_submounts = true;
detach_mounts(victim);
dput(victim);
}
}
EXPORT_SYMBOL(d_invalidate);
/**
* __d_alloc - allocate a dcache entry
* @sb: filesystem it will belong to
* @name: qstr of the name
*
* Allocates a dentry. It returns %NULL if there is insufficient memory
* available. On a success the dentry is returned. The name passed in is
* copied and the copy passed in may be reused after this call.
*/
static struct dentry *__d_alloc(struct super_block *sb, const struct qstr *name)
{
struct dentry *dentry;
char *dname;
int err;
dentry = kmem_cache_alloc_lru(dentry_cache, &sb->s_dentry_lru,
GFP_KERNEL);
if (!dentry)
return NULL;
/*
* We guarantee that the inline name is always NUL-terminated.
* This way the memcpy() done by the name switching in rename
* will still always have a NUL at the end, even if we might
* be overwriting an internal NUL character
*/
dentry->d_iname[DNAME_INLINE_LEN-1] = 0;
if (unlikely(!name)) {
name = &slash_name;
dname = dentry->d_iname;
} else if (name->len > DNAME_INLINE_LEN-1) {
size_t size = offsetof(struct external_name, name[1]);
struct external_name *p = kmalloc(size + name->len,
GFP_KERNEL_ACCOUNT |
__GFP_RECLAIMABLE);
if (!p) {
kmem_cache_free(dentry_cache, dentry);
return NULL;
}
atomic_set(&p->u.count, 1);
dname = p->name;
} else {
dname = dentry->d_iname;
}
dentry->d_name.len = name->len;
dentry->d_name.hash = name->hash;
memcpy(dname, name->name, name->len);
dname[name->len] = 0;
/* Make sure we always see the terminating NUL character */
smp_store_release(&dentry->d_name.name, dname); /* ^^^ */
dentry->d_lockref.count = 1;
dentry->d_flags = 0;
spin_lock_init(&dentry->d_lock);
seqcount_spinlock_init(&dentry->d_seq, &dentry->d_lock);
dentry->d_inode = NULL;
dentry->d_parent = dentry;
dentry->d_sb = sb;
dentry->d_op = NULL;
dentry->d_fsdata = NULL;
INIT_HLIST_BL_NODE(&dentry->d_hash);
INIT_LIST_HEAD(&dentry->d_lru);
INIT_HLIST_HEAD(&dentry->d_children);
INIT_HLIST_NODE(&dentry->d_u.d_alias);
INIT_HLIST_NODE(&dentry->d_sib);
d_set_d_op(dentry, dentry->d_sb->s_d_op);
if (dentry->d_op && dentry->d_op->d_init) {
err = dentry->d_op->d_init(dentry);
if (err) {
if (dname_external(dentry))
kfree(external_name(dentry));
kmem_cache_free(dentry_cache, dentry);
return NULL;
}
}
this_cpu_inc(nr_dentry);
return dentry;
}
/**
* d_alloc - allocate a dcache entry
* @parent: parent of entry to allocate
* @name: qstr of the name
*
* Allocates a dentry. It returns %NULL if there is insufficient memory
* available. On a success the dentry is returned. The name passed in is
* copied and the copy passed in may be reused after this call.
*/
struct dentry *d_alloc(struct dentry * parent, const struct qstr *name)
{
struct dentry *dentry = __d_alloc(parent->d_sb, name);
if (!dentry)
return NULL;
spin_lock(&parent->d_lock);
/*
* don't need child lock because it is not subject
* to concurrency here
*/
dentry->d_parent = dget_dlock(parent);
hlist_add_head(&dentry->d_sib, &parent->d_children);
spin_unlock(&parent->d_lock);
return dentry;
}
EXPORT_SYMBOL(d_alloc);
struct dentry *d_alloc_anon(struct super_block *sb)
{
return __d_alloc(sb, NULL);
}
EXPORT_SYMBOL(d_alloc_anon);
struct dentry *d_alloc_cursor(struct dentry * parent)
{
struct dentry *dentry = d_alloc_anon(parent->d_sb);
if (dentry) {
dentry->d_flags |= DCACHE_DENTRY_CURSOR;
dentry->d_parent = dget(parent);
}
return dentry;
}
/**
* d_alloc_pseudo - allocate a dentry (for lookup-less filesystems)
* @sb: the superblock
* @name: qstr of the name
*
* For a filesystem that just pins its dentries in memory and never
* performs lookups at all, return an unhashed IS_ROOT dentry.
* This is used for pipes, sockets et.al. - the stuff that should
* never be anyone's children or parents. Unlike all other
* dentries, these will not have RCU delay between dropping the
* last reference and freeing them.
*
* The only user is alloc_file_pseudo() and that's what should
* be considered a public interface. Don't use directly.
*/
struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
{
static const struct dentry_operations anon_ops = {
.d_dname = simple_dname
};
struct dentry *dentry = __d_alloc(sb, name);
if (likely(dentry)) {
dentry->d_flags |= DCACHE_NORCU;
if (!sb->s_d_op)
d_set_d_op(dentry, &anon_ops);
}
return dentry;
}
struct dentry *d_alloc_name(struct dentry *parent, const char *name)
{
struct qstr q;
q.name = name;
q.hash_len = hashlen_string(parent, name);
return d_alloc(parent, &q);
}
EXPORT_SYMBOL(d_alloc_name);
void d_set_d_op(struct dentry *dentry, const struct dentry_operations *op)
{
WARN_ON_ONCE(dentry->d_op);
WARN_ON_ONCE(dentry->d_flags & (DCACHE_OP_HASH |
DCACHE_OP_COMPARE |
DCACHE_OP_REVALIDATE |
DCACHE_OP_WEAK_REVALIDATE |
DCACHE_OP_DELETE |
DCACHE_OP_REAL));
dentry->d_op = op;
if (!op)
return;
if (op->d_hash)
dentry->d_flags |= DCACHE_OP_HASH;
if (op->d_compare)
dentry->d_flags |= DCACHE_OP_COMPARE;
if (op->d_revalidate)
dentry->d_flags |= DCACHE_OP_REVALIDATE;
if (op->d_weak_revalidate)
dentry->d_flags |= DCACHE_OP_WEAK_REVALIDATE;
if (op->d_delete)
dentry->d_flags |= DCACHE_OP_DELETE;
if (op->d_prune)
dentry->d_flags |= DCACHE_OP_PRUNE;
if (op->d_real)
dentry->d_flags |= DCACHE_OP_REAL;
}
EXPORT_SYMBOL(d_set_d_op);
static unsigned d_flags_for_inode(struct inode *inode)
{
unsigned add_flags = DCACHE_REGULAR_TYPE;
if (!inode)
return DCACHE_MISS_TYPE;
if (S_ISDIR(inode->i_mode)) {
add_flags = DCACHE_DIRECTORY_TYPE;
if (unlikely(!(inode->i_opflags & IOP_LOOKUP))) {
if (unlikely(!inode->i_op->lookup))
add_flags = DCACHE_AUTODIR_TYPE;
else
inode->i_opflags |= IOP_LOOKUP;
}
goto type_determined;
}
if (unlikely(!(inode->i_opflags & IOP_NOFOLLOW))) {
if (unlikely(inode->i_op->get_link)) {
add_flags = DCACHE_SYMLINK_TYPE;
goto type_determined;
}
inode->i_opflags |= IOP_NOFOLLOW;
}
if (unlikely(!S_ISREG(inode->i_mode)))
add_flags = DCACHE_SPECIAL_TYPE;
type_determined:
if (unlikely(IS_AUTOMOUNT(inode)))
add_flags |= DCACHE_NEED_AUTOMOUNT;
return add_flags;
}
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
{
unsigned add_flags = d_flags_for_inode(inode);
WARN_ON(d_in_lookup(dentry));
spin_lock(&dentry->d_lock);
/*
* The negative counter only tracks dentries on the LRU. Don't dec if
* d_lru is on another list.
*/
if ((dentry->d_flags &
(DCACHE_LRU_LIST|DCACHE_SHRINK_LIST)) == DCACHE_LRU_LIST)
this_cpu_dec(nr_dentry_negative);
hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
raw_write_seqcount_begin(&dentry->d_seq);
__d_set_inode_and_type(dentry, inode, add_flags);
raw_write_seqcount_end(&dentry->d_seq);
fsnotify_update_flags(dentry);
spin_unlock(&dentry->d_lock);
}
/**
* d_instantiate - fill in inode information for a dentry
* @entry: dentry to complete
* @inode: inode to attach to this dentry
*
* Fill in inode information in the entry.
*
* This turns negative dentries into productive full members
* of society.
*
* NOTE! This assumes that the inode count has been incremented
* (or otherwise set) by the caller to indicate that it is now
* in use by the dcache.
*/
void d_instantiate(struct dentry *entry, struct inode * inode)
{
BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
if (inode) {
security_d_instantiate(entry, inode);
spin_lock(&inode->i_lock);
__d_instantiate(entry, inode);
spin_unlock(&inode->i_lock);
}
}
EXPORT_SYMBOL(d_instantiate);
/*
* This should be equivalent to d_instantiate() + unlock_new_inode(),
* with lockdep-related part of unlock_new_inode() done before
* anything else. Use that instead of open-coding d_instantiate()/
* unlock_new_inode() combinations.
*/
void d_instantiate_new(struct dentry *entry, struct inode *inode)
{
BUG_ON(!hlist_unhashed(&entry->d_u.d_alias));
BUG_ON(!inode);
lockdep_annotate_inode_mutex_key(inode);
security_d_instantiate(entry, inode);
spin_lock(&inode->i_lock);
__d_instantiate(entry, inode);
WARN_ON(!(inode->i_state & I_NEW));
inode->i_state &= ~I_NEW & ~I_CREATING;
smp_mb();
wake_up_bit(&inode->i_state, __I_NEW);
spin_unlock(&inode->i_lock);
}
EXPORT_SYMBOL(d_instantiate_new);
struct dentry *d_make_root(struct inode *root_inode)
{
struct dentry *res = NULL;
if (root_inode) {
res = d_alloc_anon(root_inode->i_sb);
if (res)
d_instantiate(res, root_inode);
else
iput(root_inode);
}
return res;
}
EXPORT_SYMBOL(d_make_root);
static struct dentry *__d_obtain_alias(struct inode *inode, bool disconnected)
{
struct super_block *sb;
struct dentry *new, *res;
if (!inode)
return ERR_PTR(-ESTALE);
if (IS_ERR(inode))
return ERR_CAST(inode);
sb = inode->i_sb;
res = d_find_any_alias(inode); /* existing alias? */
if (res)
goto out;
new = d_alloc_anon(sb);
if (!new) {
res = ERR_PTR(-ENOMEM);
goto out;
}
security_d_instantiate(new, inode);
spin_lock(&inode->i_lock);
res = __d_find_any_alias(inode); /* recheck under lock */
if (likely(!res)) { /* still no alias, attach a disconnected dentry */
unsigned add_flags = d_flags_for_inode(inode);
if (disconnected)
add_flags |= DCACHE_DISCONNECTED;
spin_lock(&new->d_lock);
__d_set_inode_and_type(new, inode, add_flags);
hlist_add_head(&new->d_u.d_alias, &inode->i_dentry);
if (!disconnected) {
hlist_bl_lock(&sb->s_roots);
hlist_bl_add_head(&new->d_hash, &sb->s_roots);
hlist_bl_unlock(&sb->s_roots);
}
spin_unlock(&new->d_lock);
spin_unlock(&inode->i_lock);
inode = NULL; /* consumed by new->d_inode */
res = new;
} else {
spin_unlock(&inode->i_lock);
dput(new);
}
out:
iput(inode);
return res;
}
/**
* d_obtain_alias - find or allocate a DISCONNECTED dentry for a given inode
* @inode: inode to allocate the dentry for
*
* Obtain a dentry for an inode resulting from NFS filehandle conversion or
* similar open by handle operations. The returned dentry may be anonymous,
* or may have a full name (if the inode was already in the cache).
*
* When called on a directory inode, we must ensure that the inode only ever
* has one dentry. If a dentry is found, that is returned instead of
* allocating a new one.
*
* On successful return, the reference to the inode has been transferred
* to the dentry. In case of an error the reference on the inode is released.
* To make it easier to use in export operations a %NULL or IS_ERR inode may
* be passed in and the error will be propagated to the return value,
* with a %NULL @inode replaced by ERR_PTR(-ESTALE).
*/
struct dentry *d_obtain_alias(struct inode *inode)
{
return __d_obtain_alias(inode, true);
}
EXPORT_SYMBOL(d_obtain_alias);
/**
* d_obtain_root - find or allocate a dentry for a given inode
* @inode: inode to allocate the dentry for
*
* Obtain an IS_ROOT dentry for the root of a filesystem.
*
* We must ensure that directory inodes only ever have one dentry. If a
* dentry is found, that is returned instead of allocating a new one.
*
* On successful return, the reference to the inode has been transferred
* to the dentry. In case of an error the reference on the inode is
* released. A %NULL or IS_ERR inode may be passed in and will be the
* error will be propagate to the return value, with a %NULL @inode
* replaced by ERR_PTR(-ESTALE).
*/
struct dentry *d_obtain_root(struct inode *inode)
{
return __d_obtain_alias(inode, false);
}
EXPORT_SYMBOL(d_obtain_root);
/**
* d_add_ci - lookup or allocate new dentry with case-exact name
* @inode: the inode case-insensitive lookup has found
* @dentry: the negative dentry that was passed to the parent's lookup func
* @name: the case-exact name to be associated with the returned dentry
*
* This is to avoid filling the dcache with case-insensitive names to the
* same inode, only the actual correct case is stored in the dcache for
* case-insensitive filesystems.
*
* For a case-insensitive lookup match and if the case-exact dentry
* already exists in the dcache, use it and return it.
*
* If no entry exists with the exact case name, allocate new dentry with
* the exact case, and return the spliced entry.
*/
struct dentry *d_add_ci(struct dentry *dentry, struct inode *inode,
struct qstr *name)
{
struct dentry *found, *res;
/*
* First check if a dentry matching the name already exists,
* if not go ahead and create it now.
*/
found = d_hash_and_lookup(dentry->d_parent, name);
if (found) {
iput(inode);
return found;
}
if (d_in_lookup(dentry)) {
found = d_alloc_parallel(dentry->d_parent, name,
dentry->d_wait);
if (IS_ERR(found) || !d_in_lookup(found)) {
iput(inode);
return found;
}
} else {
found = d_alloc(dentry->d_parent, name);
if (!found) {
iput(inode);
return ERR_PTR(-ENOMEM);
}
}
res = d_splice_alias(inode, found);
if (res) {
d_lookup_done(found);
dput(found);
return res;
}
return found;
}
EXPORT_SYMBOL(d_add_ci);
/**
* d_same_name - compare dentry name with case-exact name
* @parent: parent dentry
* @dentry: the negative dentry that was passed to the parent's lookup func
* @name: the case-exact name to be associated with the returned dentry
*
* Return: true if names are same, or false
*/
bool d_same_name(const struct dentry *dentry, const struct dentry *parent,
const struct qstr *name)
{
if (likely(!(parent->d_flags & DCACHE_OP_COMPARE))) {
if (dentry->d_name.len != name->len)
return false;
return dentry_cmp(dentry, name->name, name->len) == 0;
}
return parent->d_op->d_compare(dentry,
dentry->d_name.len, dentry->d_name.name,
name) == 0;
}
EXPORT_SYMBOL_GPL(d_same_name);
/*
* This is __d_lookup_rcu() when the parent dentry has
* DCACHE_OP_COMPARE, which makes things much nastier.
*/
static noinline struct dentry *__d_lookup_rcu_op_compare(
const struct dentry *parent,
const struct qstr *name,
unsigned *seqp)
{
u64 hashlen = name->hash_len;
struct hlist_bl_head *b = d_hash(hashlen);
struct hlist_bl_node *node;
struct dentry *dentry;
hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
int tlen;
const char *tname;
unsigned seq;
seqretry:
seq = raw_seqcount_begin(&dentry->d_seq);
if (dentry->d_parent != parent)
continue;
if (d_unhashed(dentry))
continue;
if (dentry->d_name.hash != hashlen_hash(hashlen))
continue;
tlen = dentry->d_name.len;
tname = dentry->d_name.name;
/* we want a consistent (name,len) pair */
if (read_seqcount_retry(&dentry->d_seq, seq)) {
cpu_relax();
goto seqretry;
}
if (parent->d_op->d_compare(dentry, tlen, tname, name) != 0)
continue;
*seqp = seq;
return dentry;
}
return NULL;
}
/**
* __d_lookup_rcu - search for a dentry (racy, store-free)
* @parent: parent dentry
* @name: qstr of name we wish to find
* @seqp: returns d_seq value at the point where the dentry was found
* Returns: dentry, or NULL
*
* __d_lookup_rcu is the dcache lookup function for rcu-walk name
* resolution (store-free path walking) design described in
* Documentation/filesystems/path-lookup.txt.
*
* This is not to be used outside core vfs.
*
* __d_lookup_rcu must only be used in rcu-walk mode, ie. with vfsmount lock
* held, and rcu_read_lock held. The returned dentry must not be stored into
* without taking d_lock and checking d_seq sequence count against @seq
* returned here.
*
* A refcount may be taken on the found dentry with the d_rcu_to_refcount
* function.
*
* Alternatively, __d_lookup_rcu may be called again to look up the child of
* the returned dentry, so long as its parent's seqlock is checked after the
* child is looked up. Thus, an interlocking stepping of sequence lock checks
* is formed, giving integrity down the path walk.
*
* NOTE! The caller *has* to check the resulting dentry against the sequence
* number we've returned before using any of the resulting dentry state!
*/
struct dentry *__d_lookup_rcu(const struct dentry *parent,
const struct qstr *name,
unsigned *seqp)
{
u64 hashlen = name->hash_len;
const unsigned char *str = name->name;
struct hlist_bl_head *b = d_hash(hashlen);
struct hlist_bl_node *node;
struct dentry *dentry;
/*
* Note: There is significant duplication with __d_lookup_rcu which is
* required to prevent single threaded performance regressions
* especially on architectures where smp_rmb (in seqcounts) are costly.
* Keep the two functions in sync.
*/
if (unlikely(parent->d_flags & DCACHE_OP_COMPARE))
return __d_lookup_rcu_op_compare(parent, name, seqp);
/*
* The hash list is protected using RCU.
*
* Carefully use d_seq when comparing a candidate dentry, to avoid
* races with d_move().
*
* It is possible that concurrent renames can mess up our list
* walk here and result in missing our dentry, resulting in the
* false-negative result. d_lookup() protects against concurrent
* renames using rename_lock seqlock.
*
* See Documentation/filesystems/path-lookup.txt for more details.
*/
hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
unsigned seq;
/*
* The dentry sequence count protects us from concurrent
* renames, and thus protects parent and name fields.
*
* The caller must perform a seqcount check in order
* to do anything useful with the returned dentry.
*
* NOTE! We do a "raw" seqcount_begin here. That means that
* we don't wait for the sequence count to stabilize if it
* is in the middle of a sequence change. If we do the slow
* dentry compare, we will do seqretries until it is stable,
* and if we end up with a successful lookup, we actually
* want to exit RCU lookup anyway.
*
* Note that raw_seqcount_begin still *does* smp_rmb(), so
* we are still guaranteed NUL-termination of ->d_name.name.
*/
seq = raw_seqcount_begin(&dentry->d_seq);
if (dentry->d_parent != parent)
continue;
if (d_unhashed(dentry))
continue;
if (dentry->d_name.hash_len != hashlen)
continue;
if (dentry_cmp(dentry, str, hashlen_len(hashlen)) != 0)
continue;
*seqp = seq;
return dentry;
}
return NULL;
}
/**
* d_lookup - search for a dentry
* @parent: parent dentry
* @name: qstr of name we wish to find
* Returns: dentry, or NULL
*
* d_lookup searches the children of the parent dentry for the name in
* question. If the dentry is found its reference count is incremented and the
* dentry is returned. The caller must use dput to free the entry when it has
* finished using it. %NULL is returned if the dentry does not exist.
*/
struct dentry *d_lookup(const struct dentry *parent, const struct qstr *name)
{
struct dentry *dentry;
unsigned seq;
do {
seq = read_seqbegin(&rename_lock);
dentry = __d_lookup(parent, name);
if (dentry)
break;
} while (read_seqretry(&rename_lock, seq));
return dentry;
}
EXPORT_SYMBOL(d_lookup);
/**
* __d_lookup - search for a dentry (racy)
* @parent: parent dentry
* @name: qstr of name we wish to find
* Returns: dentry, or NULL
*
* __d_lookup is like d_lookup, however it may (rarely) return a
* false-negative result due to unrelated rename activity.
*
* __d_lookup is slightly faster by avoiding rename_lock read seqlock,
* however it must be used carefully, eg. with a following d_lookup in
* the case of failure.
*
* __d_lookup callers must be commented.
*/
struct dentry *__d_lookup(const struct dentry *parent, const struct qstr *name)
{
unsigned int hash = name->hash;
struct hlist_bl_head *b = d_hash(hash);
struct hlist_bl_node *node;
struct dentry *found = NULL;
struct dentry *dentry;
/*
* Note: There is significant duplication with __d_lookup_rcu which is
* required to prevent single threaded performance regressions
* especially on architectures where smp_rmb (in seqcounts) are costly.
* Keep the two functions in sync.
*/
/*
* The hash list is protected using RCU.
*
* Take d_lock when comparing a candidate dentry, to avoid races
* with d_move().
*
* It is possible that concurrent renames can mess up our list
* walk here and result in missing our dentry, resulting in the
* false-negative result. d_lookup() protects against concurrent
* renames using rename_lock seqlock.
*
* See Documentation/filesystems/path-lookup.txt for more details.
*/
rcu_read_lock();
hlist_bl_for_each_entry_rcu(dentry, node, b, d_hash) {
if (dentry->d_name.hash != hash)
continue;
spin_lock(&dentry->d_lock);
if (dentry->d_parent != parent)
goto next;
if (d_unhashed(dentry))
goto next;
if (!d_same_name(dentry, parent, name))
goto next;
dentry->d_lockref.count++;
found = dentry;
spin_unlock(&dentry->d_lock);
break;
next:
spin_unlock(&dentry->d_lock);
}
rcu_read_unlock();
return found;
}
/**
* d_hash_and_lookup - hash the qstr then search for a dentry
* @dir: Directory to search in
* @name: qstr of name we wish to find
*
* On lookup failure NULL is returned; on bad name - ERR_PTR(-error)
*/
struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
{
/*
* Check for a fs-specific hash function. Note that we must
* calculate the standard hash first, as the d_op->d_hash()
* routine may choose to leave the hash value unchanged.
*/
name->hash = full_name_hash(dir, name->name, name->len);
if (dir->d_flags & DCACHE_OP_HASH) {
int err = dir->d_op->d_hash(dir, name);
if (unlikely(err < 0))
return ERR_PTR(err);
}
return d_lookup(dir, name);
}
EXPORT_SYMBOL(d_hash_and_lookup);
/*
* When a file is deleted, we have two options:
* - turn this dentry into a negative dentry
* - unhash this dentry and free it.
*
* Usually, we want to just turn this into
* a negative dentry, but if anybody else is
* currently using the dentry or the inode
* we can't do that and we fall back on removing
* it from the hash queues and waiting for
* it to be deleted later when it has no users
*/
/**
* d_delete - delete a dentry
* @dentry: The dentry to delete
*
* Turn the dentry into a negative dentry if possible, otherwise
* remove it from the hash queues so it can be deleted later
*/
void d_delete(struct dentry * dentry)
{
struct inode *inode = dentry->d_inode;
spin_lock(&inode->i_lock);
spin_lock(&dentry->d_lock);
/*
* Are we the only user?
*/
if (dentry->d_lockref.count == 1) {
dentry->d_flags &= ~DCACHE_CANT_MOUNT;
dentry_unlink_inode(dentry);
} else {
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&inode->i_lock);
}
}
EXPORT_SYMBOL(d_delete);
static void __d_rehash(struct dentry *entry)
{
struct hlist_bl_head *b = d_hash(entry->d_name.hash);
hlist_bl_lock(b);
hlist_bl_add_head_rcu(&entry->d_hash, b);
hlist_bl_unlock(b);
}
/**
* d_rehash - add an entry back to the hash
* @entry: dentry to add to the hash
*
* Adds a dentry to the hash according to its name.
*/
void d_rehash(struct dentry * entry)
{
spin_lock(&entry->d_lock);
__d_rehash(entry);
spin_unlock(&entry->d_lock);
}
EXPORT_SYMBOL(d_rehash);
static inline unsigned start_dir_add(struct inode *dir)
{
preempt_disable_nested();
for (;;) {
unsigned n = dir->i_dir_seq;
if (!(n & 1) && cmpxchg(&dir->i_dir_seq, n, n + 1) == n)
return n;
cpu_relax();
}
}
static inline void end_dir_add(struct inode *dir, unsigned int n,
wait_queue_head_t *d_wait)
{
smp_store_release(&dir->i_dir_seq, n + 2);
preempt_enable_nested();
wake_up_all(d_wait);
}
static void d_wait_lookup(struct dentry *dentry)
{
if (d_in_lookup(dentry)) {
DECLARE_WAITQUEUE(wait, current);
add_wait_queue(dentry->d_wait, &wait);
do {
set_current_state(TASK_UNINTERRUPTIBLE);
spin_unlock(&dentry->d_lock);
schedule();
spin_lock(&dentry->d_lock);
} while (d_in_lookup(dentry));
}
}
struct dentry *d_alloc_parallel(struct dentry *parent,
const struct qstr *name,
wait_queue_head_t *wq)
{
unsigned int hash = name->hash;
struct hlist_bl_head *b = in_lookup_hash(parent, hash);
struct hlist_bl_node *node;
struct dentry *new = d_alloc(parent, name);
struct dentry *dentry;
unsigned seq, r_seq, d_seq;
if (unlikely(!new))
return ERR_PTR(-ENOMEM);
retry:
rcu_read_lock();
seq = smp_load_acquire(&parent->d_inode->i_dir_seq);
r_seq = read_seqbegin(&rename_lock);
dentry = __d_lookup_rcu(parent, name, &d_seq);
if (unlikely(dentry)) {
if (!lockref_get_not_dead(&dentry->d_lockref)) {
rcu_read_unlock();
goto retry;
}
if (read_seqcount_retry(&dentry->d_seq, d_seq)) {
rcu_read_unlock();
dput(dentry);
goto retry;
}
rcu_read_unlock();
dput(new);
return dentry;
}
if (unlikely(read_seqretry(&rename_lock, r_seq))) {
rcu_read_unlock();
goto retry;
}
if (unlikely(seq & 1)) {
rcu_read_unlock();
goto retry;
}
hlist_bl_lock(b);
if (unlikely(READ_ONCE(parent->d_inode->i_dir_seq) != seq)) {
hlist_bl_unlock(b);
rcu_read_unlock();
goto retry;
}
/*
* No changes for the parent since the beginning of d_lookup().
* Since all removals from the chain happen with hlist_bl_lock(),
* any potential in-lookup matches are going to stay here until
* we unlock the chain. All fields are stable in everything
* we encounter.
*/
hlist_bl_for_each_entry(dentry, node, b, d_u.d_in_lookup_hash) {
if (dentry->d_name.hash != hash)
continue;
if (dentry->d_parent != parent)
continue;
if (!d_same_name(dentry, parent, name))
continue;
hlist_bl_unlock(b);
/* now we can try to grab a reference */
if (!lockref_get_not_dead(&dentry->d_lockref)) {
rcu_read_unlock();
goto retry;
}
rcu_read_unlock();
/*
* somebody is likely to be still doing lookup for it;
* wait for them to finish
*/
spin_lock(&dentry->d_lock);
d_wait_lookup(dentry);
/*
* it's not in-lookup anymore; in principle we should repeat
* everything from dcache lookup, but it's likely to be what
* d_lookup() would've found anyway. If it is, just return it;
* otherwise we really have to repeat the whole thing.
*/
if (unlikely(dentry->d_name.hash != hash))
goto mismatch;
if (unlikely(dentry->d_parent != parent))
goto mismatch;
if (unlikely(d_unhashed(dentry)))
goto mismatch;
if (unlikely(!d_same_name(dentry, parent, name)))
goto mismatch;
/* OK, it *is* a hashed match; return it */
spin_unlock(&dentry->d_lock);
dput(new);
return dentry;
}
rcu_read_unlock();
/* we can't take ->d_lock here; it's OK, though. */
new->d_flags |= DCACHE_PAR_LOOKUP;
new->d_wait = wq;
hlist_bl_add_head(&new->d_u.d_in_lookup_hash, b);
hlist_bl_unlock(b);
return new;
mismatch:
spin_unlock(&dentry->d_lock);
dput(dentry);
goto retry;
}
EXPORT_SYMBOL(d_alloc_parallel);
/*
* - Unhash the dentry
* - Retrieve and clear the waitqueue head in dentry
* - Return the waitqueue head
*/
static wait_queue_head_t *__d_lookup_unhash(struct dentry *dentry)
{
wait_queue_head_t *d_wait;
struct hlist_bl_head *b;
lockdep_assert_held(&dentry->d_lock);
b = in_lookup_hash(dentry->d_parent, dentry->d_name.hash);
hlist_bl_lock(b);
dentry->d_flags &= ~DCACHE_PAR_LOOKUP;
__hlist_bl_del(&dentry->d_u.d_in_lookup_hash);
d_wait = dentry->d_wait;
dentry->d_wait = NULL;
hlist_bl_unlock(b);
INIT_HLIST_NODE(&dentry->d_u.d_alias);
INIT_LIST_HEAD(&dentry->d_lru);
return d_wait;
}
void __d_lookup_unhash_wake(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
wake_up_all(__d_lookup_unhash(dentry));
spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(__d_lookup_unhash_wake);
/* inode->i_lock held if inode is non-NULL */
static inline void __d_add(struct dentry *dentry, struct inode *inode)
{
wait_queue_head_t *d_wait;
struct inode *dir = NULL;
unsigned n;
spin_lock(&dentry->d_lock);
if (unlikely(d_in_lookup(dentry))) {
dir = dentry->d_parent->d_inode;
n = start_dir_add(dir);
d_wait = __d_lookup_unhash(dentry);
}
if (inode) {
unsigned add_flags = d_flags_for_inode(inode);
hlist_add_head(&dentry->d_u.d_alias, &inode->i_dentry);
raw_write_seqcount_begin(&dentry->d_seq);
__d_set_inode_and_type(dentry, inode, add_flags);
raw_write_seqcount_end(&dentry->d_seq);
fsnotify_update_flags(dentry);
}
__d_rehash(dentry);
if (dir)
end_dir_add(dir, n, d_wait);
spin_unlock(&dentry->d_lock);
if (inode)
spin_unlock(&inode->i_lock);
}
/**
* d_add - add dentry to hash queues
* @entry: dentry to add
* @inode: The inode to attach to this dentry
*
* This adds the entry to the hash queues and initializes @inode.
* The entry was actually filled in earlier during d_alloc().
*/
void d_add(struct dentry *entry, struct inode *inode)
{
if (inode) {
security_d_instantiate(entry, inode);
spin_lock(&inode->i_lock);
}
__d_add(entry, inode);
}
EXPORT_SYMBOL(d_add);
/**
* d_exact_alias - find and hash an exact unhashed alias
* @entry: dentry to add
* @inode: The inode to go with this dentry
*
* If an unhashed dentry with the same name/parent and desired
* inode already exists, hash and return it. Otherwise, return
* NULL.
*
* Parent directory should be locked.
*/
struct dentry *d_exact_alias(struct dentry *entry, struct inode *inode)
{
struct dentry *alias;
unsigned int hash = entry->d_name.hash;
spin_lock(&inode->i_lock);
hlist_for_each_entry(alias, &inode->i_dentry, d_u.d_alias) {
/*
* Don't need alias->d_lock here, because aliases with
* d_parent == entry->d_parent are not subject to name or
* parent changes, because the parent inode i_mutex is held.
*/
if (alias->d_name.hash != hash)
continue;
if (alias->d_parent != entry->d_parent)
continue;
if (!d_same_name(alias, entry->d_parent, &entry->d_name))
continue;
spin_lock(&alias->d_lock);
if (!d_unhashed(alias)) {
spin_unlock(&alias->d_lock);
alias = NULL;
} else {
dget_dlock(alias);
__d_rehash(alias);
spin_unlock(&alias->d_lock);
}
spin_unlock(&inode->i_lock);
return alias;
}
spin_unlock(&inode->i_lock);
return NULL;
}
EXPORT_SYMBOL(d_exact_alias);
static void swap_names(struct dentry *dentry, struct dentry *target)
{
if (unlikely(dname_external(target))) {
if (unlikely(dname_external(dentry))) {
/*
* Both external: swap the pointers
*/
swap(target->d_name.name, dentry->d_name.name);
} else {
/*
* dentry:internal, target:external. Steal target's
* storage and make target internal.
*/
memcpy(target->d_iname, dentry->d_name.name,
dentry->d_name.len + 1);
dentry->d_name.name = target->d_name.name;
target->d_name.name = target->d_iname;
}
} else {
if (unlikely(dname_external(dentry))) {
/*
* dentry:external, target:internal. Give dentry's
* storage to target and make dentry internal
*/
memcpy(dentry->d_iname, target->d_name.name,
target->d_name.len + 1);
target->d_name.name = dentry->d_name.name;
dentry->d_name.name = dentry->d_iname;
} else {
/*
* Both are internal.
*/
unsigned int i;
BUILD_BUG_ON(!IS_ALIGNED(DNAME_INLINE_LEN, sizeof(long)));
for (i = 0; i < DNAME_INLINE_LEN / sizeof(long); i++) {
swap(((long *) &dentry->d_iname)[i],
((long *) &target->d_iname)[i]);
}
}
}
swap(dentry->d_name.hash_len, target->d_name.hash_len);
}
static void copy_name(struct dentry *dentry, struct dentry *target)
{
struct external_name *old_name = NULL;
if (unlikely(dname_external(dentry)))
old_name = external_name(dentry);
if (unlikely(dname_external(target))) {
atomic_inc(&external_name(target)->u.count);
dentry->d_name = target->d_name;
} else {
memcpy(dentry->d_iname, target->d_name.name,
target->d_name.len + 1);
dentry->d_name.name = dentry->d_iname;
dentry->d_name.hash_len = target->d_name.hash_len;
}
if (old_name && likely(atomic_dec_and_test(&old_name->u.count)))
kfree_rcu(old_name, u.head);
}
/*
* __d_move - move a dentry
* @dentry: entry to move
* @target: new dentry
* @exchange: exchange the two dentries
*
* Update the dcache to reflect the move of a file name. Negative
* dcache entries should not be moved in this way. Caller must hold
* rename_lock, the i_mutex of the source and target directories,
* and the sb->s_vfs_rename_mutex if they differ. See lock_rename().
*/
static void __d_move(struct dentry *dentry, struct dentry *target,
bool exchange)
{
struct dentry *old_parent, *p;
wait_queue_head_t *d_wait;
struct inode *dir = NULL;
unsigned n;
WARN_ON(!dentry->d_inode);
if (WARN_ON(dentry == target))
return;
BUG_ON(d_ancestor(target, dentry));
old_parent = dentry->d_parent;
p = d_ancestor(old_parent, target);
if (IS_ROOT(dentry)) {
BUG_ON(p);
spin_lock(&target->d_parent->d_lock);
} else if (!p) {
/* target is not a descendent of dentry->d_parent */
spin_lock(&target->d_parent->d_lock);
spin_lock_nested(&old_parent->d_lock, DENTRY_D_LOCK_NESTED);
} else {
BUG_ON(p == dentry);
spin_lock(&old_parent->d_lock);
if (p != target)
spin_lock_nested(&target->d_parent->d_lock,
DENTRY_D_LOCK_NESTED);
}
spin_lock_nested(&dentry->d_lock, 2);
spin_lock_nested(&target->d_lock, 3);
if (unlikely(d_in_lookup(target))) {
dir = target->d_parent->d_inode;
n = start_dir_add(dir);
d_wait = __d_lookup_unhash(target);
}
write_seqcount_begin(&dentry->d_seq);
write_seqcount_begin_nested(&target->d_seq, DENTRY_D_LOCK_NESTED);
/* unhash both */
if (!d_unhashed(dentry))
___d_drop(dentry);
if (!d_unhashed(target))
___d_drop(target);
/* ... and switch them in the tree */
dentry->d_parent = target->d_parent;
if (!exchange) {
copy_name(dentry, target);
target->d_hash.pprev = NULL;
dentry->d_parent->d_lockref.count++;
if (dentry != old_parent) /* wasn't IS_ROOT */
WARN_ON(!--old_parent->d_lockref.count);
} else {
target->d_parent = old_parent;
swap_names(dentry, target);
if (!hlist_unhashed(&target->d_sib))
__hlist_del(&target->d_sib);
hlist_add_head(&target->d_sib, &target->d_parent->d_children);
__d_rehash(target);
fsnotify_update_flags(target);
}
if (!hlist_unhashed(&dentry->d_sib))
__hlist_del(&dentry->d_sib);
hlist_add_head(&dentry->d_sib, &dentry->d_parent->d_children);
__d_rehash(dentry);
fsnotify_update_flags(dentry);
fscrypt_handle_d_move(dentry);
write_seqcount_end(&target->d_seq);
write_seqcount_end(&dentry->d_seq);
if (dir)
end_dir_add(dir, n, d_wait);
if (dentry->d_parent != old_parent)
spin_unlock(&dentry->d_parent->d_lock);
if (dentry != old_parent)
spin_unlock(&old_parent->d_lock);
spin_unlock(&target->d_lock);
spin_unlock(&dentry->d_lock);
}
/*
* d_move - move a dentry
* @dentry: entry to move
* @target: new dentry
*
* Update the dcache to reflect the move of a file name. Negative
* dcache entries should not be moved in this way. See the locking
* requirements for __d_move.
*/
void d_move(struct dentry *dentry, struct dentry *target)
{
write_seqlock(&rename_lock);
__d_move(dentry, target, false);
write_sequnlock(&rename_lock);
}
EXPORT_SYMBOL(d_move);
/*
* d_exchange - exchange two dentries
* @dentry1: first dentry
* @dentry2: second dentry
*/
void d_exchange(struct dentry *dentry1, struct dentry *dentry2)
{
write_seqlock(&rename_lock);
WARN_ON(!dentry1->d_inode);
WARN_ON(!dentry2->d_inode);
WARN_ON(IS_ROOT(dentry1));
WARN_ON(IS_ROOT(dentry2));
__d_move(dentry1, dentry2, true);
write_sequnlock(&rename_lock);
}
/**
* d_ancestor - search for an ancestor
* @p1: ancestor dentry
* @p2: child dentry
*
* Returns the ancestor dentry of p2 which is a child of p1, if p1 is
* an ancestor of p2, else NULL.
*/
struct dentry *d_ancestor(struct dentry *p1, struct dentry *p2)
{
struct dentry *p;
for (p = p2; !IS_ROOT(p); p = p->d_parent) {
if (p->d_parent == p1)
return p;
}
return NULL;
}
/*
* This helper attempts to cope with remotely renamed directories
*
* It assumes that the caller is already holding
* dentry->d_parent->d_inode->i_mutex, and rename_lock
*
* Note: If ever the locking in lock_rename() changes, then please
* remember to update this too...
*/
static int __d_unalias(struct dentry *dentry, struct dentry *alias)
{
struct mutex *m1 = NULL;
struct rw_semaphore *m2 = NULL;
int ret = -ESTALE;
/* If alias and dentry share a parent, then no extra locks required */
if (alias->d_parent == dentry->d_parent)
goto out_unalias;
/* See lock_rename() */
if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
goto out_err;
m1 = &dentry->d_sb->s_vfs_rename_mutex;
if (!inode_trylock_shared(alias->d_parent->d_inode))
goto out_err;
m2 = &alias->d_parent->d_inode->i_rwsem;
out_unalias:
__d_move(alias, dentry, false);
ret = 0;
out_err:
if (m2)
up_read(m2);
if (m1)
mutex_unlock(m1);
return ret;
}
/**
* d_splice_alias - splice a disconnected dentry into the tree if one exists
* @inode: the inode which may have a disconnected dentry
* @dentry: a negative dentry which we want to point to the inode.
*
* If inode is a directory and has an IS_ROOT alias, then d_move that in
* place of the given dentry and return it, else simply d_add the inode
* to the dentry and return NULL.
*
* If a non-IS_ROOT directory is found, the filesystem is corrupt, and
* we should error out: directories can't have multiple aliases.
*
* This is needed in the lookup routine of any filesystem that is exportable
* (via knfsd) so that we can build dcache paths to directories effectively.
*
* If a dentry was found and moved, then it is returned. Otherwise NULL
* is returned. This matches the expected return value of ->lookup.
*
* Cluster filesystems may call this function with a negative, hashed dentry.
* In that case, we know that the inode will be a regular file, and also this
* will only occur during atomic_open. So we need to check for the dentry
* being already hashed only in the final case.
*/
struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
{
if (IS_ERR(inode))
return ERR_CAST(inode);
BUG_ON(!d_unhashed(dentry));
if (!inode)
goto out;
security_d_instantiate(dentry, inode);
spin_lock(&inode->i_lock);
if (S_ISDIR(inode->i_mode)) {
struct dentry *new = __d_find_any_alias(inode);
if (unlikely(new)) {
/* The reference to new ensures it remains an alias */
spin_unlock(&inode->i_lock);
write_seqlock(&rename_lock);
if (unlikely(d_ancestor(new, dentry))) {
write_sequnlock(&rename_lock);
dput(new);
new = ERR_PTR(-ELOOP);
pr_warn_ratelimited(
"VFS: Lookup of '%s' in %s %s"
" would have caused loop\n",
dentry->d_name.name,
inode->i_sb->s_type->name,
inode->i_sb->s_id);
} else if (!IS_ROOT(new)) {
struct dentry *old_parent = dget(new->d_parent);
int err = __d_unalias(dentry, new);
write_sequnlock(&rename_lock);
if (err) {
dput(new);
new = ERR_PTR(err);
}
dput(old_parent);
} else {
__d_move(new, dentry, false);
write_sequnlock(&rename_lock);
}
iput(inode);
return new;
}
}
out:
__d_add(dentry, inode);
return NULL;
}
EXPORT_SYMBOL(d_splice_alias);
/*
* Test whether new_dentry is a subdirectory of old_dentry.
*
* Trivially implemented using the dcache structure
*/
/**
* is_subdir - is new dentry a subdirectory of old_dentry
* @new_dentry: new dentry
* @old_dentry: old dentry
*
* Returns true if new_dentry is a subdirectory of the parent (at any depth).
* Returns false otherwise.
* Caller must ensure that "new_dentry" is pinned before calling is_subdir()
*/
bool is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
{
bool subdir;
unsigned seq;
if (new_dentry == old_dentry)
return true;
/* Access d_parent under rcu as d_move() may change it. */
rcu_read_lock();
seq = read_seqbegin(&rename_lock);
subdir = d_ancestor(old_dentry, new_dentry);
/* Try lockless once... */
if (read_seqretry(&rename_lock, seq)) {
/* ...else acquire lock for progress even on deep chains. */
read_seqlock_excl(&rename_lock);
subdir = d_ancestor(old_dentry, new_dentry);
read_sequnlock_excl(&rename_lock);
}
rcu_read_unlock();
return subdir;
}
EXPORT_SYMBOL(is_subdir);
static enum d_walk_ret d_genocide_kill(void *data, struct dentry *dentry)
{
struct dentry *root = data;
if (dentry != root) {
if (d_unhashed(dentry) || !dentry->d_inode)
return D_WALK_SKIP;
if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
dentry->d_flags |= DCACHE_GENOCIDE;
dentry->d_lockref.count--;
}
}
return D_WALK_CONTINUE;
}
void d_genocide(struct dentry *parent)
{
d_walk(parent, parent, d_genocide_kill);
}
void d_mark_tmpfile(struct file *file, struct inode *inode)
{
struct dentry *dentry = file->f_path.dentry;
BUG_ON(dentry->d_name.name != dentry->d_iname ||
!hlist_unhashed(&dentry->d_u.d_alias) ||
!d_unlinked(dentry));
spin_lock(&dentry->d_parent->d_lock);
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
dentry->d_name.len = sprintf(dentry->d_iname, "#%llu",
(unsigned long long)inode->i_ino);
spin_unlock(&dentry->d_lock);
spin_unlock(&dentry->d_parent->d_lock);
}
EXPORT_SYMBOL(d_mark_tmpfile);
void d_tmpfile(struct file *file, struct inode *inode)
{
struct dentry *dentry = file->f_path.dentry;
inode_dec_link_count(inode);
d_mark_tmpfile(file, inode);
d_instantiate(dentry, inode);
}
EXPORT_SYMBOL(d_tmpfile);
/*
* Obtain inode number of the parent dentry.
*/
ino_t d_parent_ino(struct dentry *dentry)
{
struct dentry *parent;
struct inode *iparent;
unsigned seq;
ino_t ret;
scoped_guard(rcu) {
seq = raw_seqcount_begin(&dentry->d_seq);
parent = READ_ONCE(dentry->d_parent);
iparent = d_inode_rcu(parent);
if (likely(iparent)) {
ret = iparent->i_ino;
if (!read_seqcount_retry(&dentry->d_seq, seq))
return ret;
}
}
spin_lock(&dentry->d_lock);
ret = dentry->d_parent->d_inode->i_ino;
spin_unlock(&dentry->d_lock);
return ret;
}
EXPORT_SYMBOL(d_parent_ino);
static __initdata unsigned long dhash_entries;
static int __init set_dhash_entries(char *str)
{
if (!str)
return 0;
dhash_entries = simple_strtoul(str, &str, 0);
return 1;
}
__setup("dhash_entries=", set_dhash_entries);
static void __init dcache_init_early(void)
{
/* If hashes are distributed across NUMA nodes, defer
* hash allocation until vmalloc space is available.
*/
if (hashdist)
return;
dentry_hashtable =
alloc_large_system_hash("Dentry cache",
sizeof(struct hlist_bl_head),
dhash_entries,
13,
HASH_EARLY | HASH_ZERO,
&d_hash_shift,
NULL,
0,
0);
d_hash_shift = 32 - d_hash_shift;
runtime_const_init(shift, d_hash_shift);
runtime_const_init(ptr, dentry_hashtable);
}
static void __init dcache_init(void)
{
/*
* A constructor could be added for stable state like the lists,
* but it is probably not worth it because of the cache nature
* of the dcache.
*/
dentry_cache = KMEM_CACHE_USERCOPY(dentry,
SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_ACCOUNT,
d_iname);
/* Hash may have been set up in dcache_init_early */
if (!hashdist)
return;
dentry_hashtable =
alloc_large_system_hash("Dentry cache",
sizeof(struct hlist_bl_head),
dhash_entries,
13,
HASH_ZERO,
&d_hash_shift,
NULL,
0,
0);
d_hash_shift = 32 - d_hash_shift;
runtime_const_init(shift, d_hash_shift);
runtime_const_init(ptr, dentry_hashtable);
}
/* SLAB cache for __getname() consumers */
struct kmem_cache *names_cachep __ro_after_init;
EXPORT_SYMBOL(names_cachep);
void __init vfs_caches_init_early(void)
{
int i;
for (i = 0; i < ARRAY_SIZE(in_lookup_hashtable); i++)
INIT_HLIST_BL_HEAD(&in_lookup_hashtable[i]);
dcache_init_early();
inode_init_early();
}
void __init vfs_caches_init(void)
{
names_cachep = kmem_cache_create_usercopy("names_cache", PATH_MAX, 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC, 0, PATH_MAX, NULL);
dcache_init();
inode_init();
files_init();
files_maxfiles_init();
mnt_init();
bdev_cache_init();
chrdev_init();
}
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