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linux/fs/dcache.c
Christoph Hellwig 1879fd6a26 add hlist_bl_lock/unlock helpers 
Now that the whole dcache_hash_bucket crap is gone, go all the way and
also remove the weird locking layering violations for locking the hash
buckets.  Add hlist_bl_lock/unlock helpers to move the locking into the
list abstraction instead of requiring each caller to open code it.
After all allowing for the bit locks is the whole point of these helpers
over the plain hlist variant.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2011-04-25 18:14:10 -07:00

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/*
* 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/syscalls.h>
#include <linux/string.h>
#include <linux/mm.h>
#include <linux/fs.h>
#include <linux/fsnotify.h>
#include <linux/slab.h>
#include <linux/init.h>
#include <linux/hash.h>
#include <linux/cache.h>
#include <linux/module.h>
#include <linux/mount.h>
#include <linux/file.h>
#include <asm/uaccess.h>
#include <linux/security.h>
#include <linux/seqlock.h>
#include <linux/swap.h>
#include <linux/bootmem.h>
#include <linux/fs_struct.h>
#include <linux/hardirq.h>
#include <linux/bit_spinlock.h>
#include <linux/rculist_bl.h>
#include "internal.h"
/*
* Usage:
* dcache->d_inode->i_lock protects:
* - i_dentry, d_alias, d_inode of aliases
* dcache_hash_bucket lock protects:
* - the dcache hash table
* s_anon bl list spinlock protects:
* - the s_anon list (see __d_drop)
* dcache_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_subdirs
* - childrens' d_child and d_parent
* - d_alias, d_inode
*
* Ordering:
* dentry->d_inode->i_lock
* dentry->d_lock
* dcache_lru_lock
* dcache_hash_bucket lock
* s_anon 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:
* if (dentry1 < dentry2)
* dentry1->d_lock
* dentry2->d_lock
*/
int sysctl_vfs_cache_pressure __read_mostly = 100;
EXPORT_SYMBOL_GPL(sysctl_vfs_cache_pressure);
static __cacheline_aligned_in_smp DEFINE_SPINLOCK(dcache_lru_lock);
__cacheline_aligned_in_smp DEFINE_SEQLOCK(rename_lock);
EXPORT_SYMBOL(rename_lock);
static struct kmem_cache *dentry_cache __read_mostly;
/*
* 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.
*/
#define D_HASHBITS d_hash_shift
#define D_HASHMASK d_hash_mask
static unsigned int d_hash_mask __read_mostly;
static unsigned int d_hash_shift __read_mostly;
static struct hlist_bl_head *dentry_hashtable __read_mostly;
static inline struct hlist_bl_head *d_hash(struct dentry *parent,
unsigned long hash)
{
hash += ((unsigned long) parent ^ GOLDEN_RATIO_PRIME) / L1_CACHE_BYTES;
hash = hash ^ ((hash ^ GOLDEN_RATIO_PRIME) >> D_HASHBITS);
return dentry_hashtable + (hash & D_HASHMASK);
}
/* Statistics gathering. */
struct dentry_stat_t dentry_stat = {
.age_limit = 45,
};
static DEFINE_PER_CPU(unsigned int, nr_dentry);
#if defined(CONFIG_SYSCTL) && defined(CONFIG_PROC_FS)
static int get_nr_dentry(void)
{
int i;
int sum = 0;
for_each_possible_cpu(i)
sum += per_cpu(nr_dentry, i);
return sum < 0 ? 0 : sum;
}
int proc_nr_dentry(ctl_table *table, int write, void __user *buffer,
size_t *lenp, loff_t *ppos)
{
dentry_stat.nr_dentry = get_nr_dentry();
return proc_dointvec(table, write, buffer, lenp, ppos);
}
#endif
static void __d_free(struct rcu_head *head)
{
struct dentry *dentry = container_of(head, struct dentry, d_u.d_rcu);
WARN_ON(!list_empty(&dentry->d_alias));
if (dname_external(dentry))
kfree(dentry->d_name.name);
kmem_cache_free(dentry_cache, dentry);
}
/*
* no locks, please.
*/
static void d_free(struct dentry *dentry)
{
BUG_ON(dentry->d_count);
this_cpu_dec(nr_dentry);
if (dentry->d_op && dentry->d_op->d_release)
dentry->d_op->d_release(dentry);
/* if dentry was never visible to RCU, immediate free is OK */
if (!(dentry->d_flags & DCACHE_RCUACCESS))
__d_free(&dentry->d_u.d_rcu);
else
call_rcu(&dentry->d_u.d_rcu, __d_free);
}
/**
* dentry_rcuwalk_barrier - invalidate in-progress rcu-walk lookups
* @dentry: the target dentry
* After this call, in-progress rcu-walk path lookup will fail. This
* should be called after unhashing, and after changing d_inode (if
* the dentry has not already been unhashed).
*/
static inline void dentry_rcuwalk_barrier(struct dentry *dentry)
{
assert_spin_locked(&dentry->d_lock);
/* Go through a barrier */
write_seqcount_barrier(&dentry->d_seq);
}
/*
* Release the dentry's inode, using the filesystem
* d_iput() operation if defined. Dentry has no refcount
* and is unhashed.
*/
static void dentry_iput(struct dentry * dentry)
__releases(dentry->d_lock)
__releases(dentry->d_inode->i_lock)
{
struct inode *inode = dentry->d_inode;
if (inode) {
dentry->d_inode = NULL;
list_del_init(&dentry->d_alias);
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);
} else {
spin_unlock(&dentry->d_lock);
}
}
/*
* Release the dentry's inode, using the filesystem
* d_iput() operation if defined. dentry remains in-use.
*/
static void dentry_unlink_inode(struct dentry * dentry)
__releases(dentry->d_lock)
__releases(dentry->d_inode->i_lock)
{
struct inode *inode = dentry->d_inode;
dentry->d_inode = NULL;
list_del_init(&dentry->d_alias);
dentry_rcuwalk_barrier(dentry);
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);
}
/*
* dentry_lru_(add|del|move_tail) must be called with d_lock held.
*/
static void dentry_lru_add(struct dentry *dentry)
{
if (list_empty(&dentry->d_lru)) {
spin_lock(&dcache_lru_lock);
list_add(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
dentry->d_sb->s_nr_dentry_unused++;
dentry_stat.nr_unused++;
spin_unlock(&dcache_lru_lock);
}
}
static void __dentry_lru_del(struct dentry *dentry)
{
list_del_init(&dentry->d_lru);
dentry->d_sb->s_nr_dentry_unused--;
dentry_stat.nr_unused--;
}
static void dentry_lru_del(struct dentry *dentry)
{
if (!list_empty(&dentry->d_lru)) {
spin_lock(&dcache_lru_lock);
__dentry_lru_del(dentry);
spin_unlock(&dcache_lru_lock);
}
}
static void dentry_lru_move_tail(struct dentry *dentry)
{
spin_lock(&dcache_lru_lock);
if (list_empty(&dentry->d_lru)) {
list_add_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
dentry->d_sb->s_nr_dentry_unused++;
dentry_stat.nr_unused++;
} else {
list_move_tail(&dentry->d_lru, &dentry->d_sb->s_dentry_lru);
}
spin_unlock(&dcache_lru_lock);
}
/**
* d_kill - kill dentry and return parent
* @dentry: dentry to kill
* @parent: parent dentry
*
* The dentry must already be unhashed and removed from the LRU.
*
* If this is the root of the dentry tree, return NULL.
*
* dentry->d_lock and parent->d_lock must be held by caller, and are dropped by
* d_kill.
*/
static struct dentry *d_kill(struct dentry *dentry, struct dentry *parent)
__releases(dentry->d_lock)
__releases(parent->d_lock)
__releases(dentry->d_inode->i_lock)
{
list_del(&dentry->d_u.d_child);
/*
* Inform try_to_ascend() that we are no longer attached to the
* dentry tree
*/
dentry->d_flags |= DCACHE_DISCONNECTED;
if (parent)
spin_unlock(&parent->d_lock);
dentry_iput(dentry);
/*
* dentry_iput drops the locks, at which point nobody (except
* transient RCU lookups) can reach this dentry.
*/
d_free(dentry);
return parent;
}
/**
* 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.
*/
void __d_drop(struct dentry *dentry)
{
if (!d_unhashed(dentry)) {
struct hlist_bl_head *b;
if (unlikely(dentry->d_flags & DCACHE_DISCONNECTED))
b = &dentry->d_sb->s_anon;
else
b = d_hash(dentry->d_parent, dentry->d_name.hash);
hlist_bl_lock(b);
__hlist_bl_del(&dentry->d_hash);
dentry->d_hash.pprev = NULL;
hlist_bl_unlock(b);
dentry_rcuwalk_barrier(dentry);
}
}
EXPORT_SYMBOL(__d_drop);
void d_drop(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(d_drop);
/*
* Finish off a dentry we've decided to kill.
* dentry->d_lock must be held, returns with it unlocked.
* If ref is non-zero, then decrement the refcount too.
* Returns dentry requiring refcount drop, or NULL if we're done.
*/
static inline struct dentry *dentry_kill(struct dentry *dentry, int ref)
__releases(dentry->d_lock)
{
struct inode *inode;
struct dentry *parent;
inode = dentry->d_inode;
if (inode && !spin_trylock(&inode->i_lock)) {
relock:
spin_unlock(&dentry->d_lock);
cpu_relax();
return dentry; /* try again with same dentry */
}
if (IS_ROOT(dentry))
parent = NULL;
else
parent = dentry->d_parent;
if (parent && !spin_trylock(&parent->d_lock)) {
if (inode)
spin_unlock(&inode->i_lock);
goto relock;
}
if (ref)
dentry->d_count--;
/* if dentry was on the d_lru list delete it from there */
dentry_lru_del(dentry);
/* if it was on the hash then remove it */
__d_drop(dentry);
return d_kill(dentry, parent);
}
/*
* 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;
repeat:
if (dentry->d_count == 1)
might_sleep();
spin_lock(&dentry->d_lock);
BUG_ON(!dentry->d_count);
if (dentry->d_count > 1) {
dentry->d_count--;
spin_unlock(&dentry->d_lock);
return;
}
if (dentry->d_flags & DCACHE_OP_DELETE) {
if (dentry->d_op->d_delete(dentry))
goto kill_it;
}
/* Unreachable? Get rid of it */
if (d_unhashed(dentry))
goto kill_it;
/* Otherwise leave it cached and ensure it's on the LRU */
dentry->d_flags |= DCACHE_REFERENCED;
dentry_lru_add(dentry);
dentry->d_count--;
spin_unlock(&dentry->d_lock);
return;
kill_it:
dentry = dentry_kill(dentry, 1);
if (dentry)
goto repeat;
}
EXPORT_SYMBOL(dput);
/**
* d_invalidate - invalidate a dentry
* @dentry: dentry to invalidate
*
* Try to invalidate the dentry if it turns out to be
* possible. If there are other dentries that can be
* reached through this one we can't delete it and we
* return -EBUSY. On success we return 0.
*
* no dcache lock.
*/
int d_invalidate(struct dentry * dentry)
{
/*
* If it's already been dropped, return OK.
*/
spin_lock(&dentry->d_lock);
if (d_unhashed(dentry)) {
spin_unlock(&dentry->d_lock);
return 0;
}
/*
* Check whether to do a partial shrink_dcache
* to get rid of unused child entries.
*/
if (!list_empty(&dentry->d_subdirs)) {
spin_unlock(&dentry->d_lock);
shrink_dcache_parent(dentry);
spin_lock(&dentry->d_lock);
}
/*
* Somebody else still using it?
*
* If it's a directory, we can't drop it
* for fear of somebody re-populating it
* with children (even though dropping it
* would make it unreachable from the root,
* we might still populate it if it was a
* working directory or similar).
*/
if (dentry->d_count > 1) {
if (dentry->d_inode && S_ISDIR(dentry->d_inode->i_mode)) {
spin_unlock(&dentry->d_lock);
return -EBUSY;
}
}
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
return 0;
}
EXPORT_SYMBOL(d_invalidate);
/* This must be called with d_lock held */
static inline void __dget_dlock(struct dentry *dentry)
{
dentry->d_count++;
}
static inline void __dget(struct dentry *dentry)
{
spin_lock(&dentry->d_lock);
__dget_dlock(dentry);
spin_unlock(&dentry->d_lock);
}
struct dentry *dget_parent(struct dentry *dentry)
{
struct dentry *ret;
repeat:
/*
* Don't need rcu_dereference because we re-check it was correct under
* the lock.
*/
rcu_read_lock();
ret = dentry->d_parent;
if (!ret) {
rcu_read_unlock();
goto out;
}
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_count);
ret->d_count++;
spin_unlock(&ret->d_lock);
out:
return ret;
}
EXPORT_SYMBOL(dget_parent);
/**
* d_find_alias - grab a hashed alias of inode
* @inode: inode in question
* @want_discon: flag, used by d_splice_alias, to request
* that only a DISCONNECTED alias be returned.
*
* 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.
*
* If the inode has an IS_ROOT, DCACHE_DISCONNECTED alias, then prefer
* any other hashed alias over that one unless @want_discon is set,
* in which case only return an IS_ROOT, DCACHE_DISCONNECTED alias.
*/
static struct dentry *__d_find_alias(struct inode *inode, int want_discon)
{
struct dentry *alias, *discon_alias;
again:
discon_alias = NULL;
list_for_each_entry(alias, &inode->i_dentry, d_alias) {
spin_lock(&alias->d_lock);
if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
if (IS_ROOT(alias) &&
(alias->d_flags & DCACHE_DISCONNECTED)) {
discon_alias = alias;
} else if (!want_discon) {
__dget_dlock(alias);
spin_unlock(&alias->d_lock);
return alias;
}
}
spin_unlock(&alias->d_lock);
}
if (discon_alias) {
alias = discon_alias;
spin_lock(&alias->d_lock);
if (S_ISDIR(inode->i_mode) || !d_unhashed(alias)) {
if (IS_ROOT(alias) &&
(alias->d_flags & DCACHE_DISCONNECTED)) {
__dget_dlock(alias);
spin_unlock(&alias->d_lock);
return alias;
}
}
spin_unlock(&alias->d_lock);
goto again;
}
return NULL;
}
struct dentry *d_find_alias(struct inode *inode)
{
struct dentry *de = NULL;
if (!list_empty(&inode->i_dentry)) {
spin_lock(&inode->i_lock);
de = __d_find_alias(inode, 0);
spin_unlock(&inode->i_lock);
}
return de;
}
EXPORT_SYMBOL(d_find_alias);
/*
* Try to kill dentries associated with this inode.
* WARNING: you must own a reference to inode.
*/
void d_prune_aliases(struct inode *inode)
{
struct dentry *dentry;
restart:
spin_lock(&inode->i_lock);
list_for_each_entry(dentry, &inode->i_dentry, d_alias) {
spin_lock(&dentry->d_lock);
if (!dentry->d_count) {
__dget_dlock(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&inode->i_lock);
dput(dentry);
goto restart;
}
spin_unlock(&dentry->d_lock);
}
spin_unlock(&inode->i_lock);
}
EXPORT_SYMBOL(d_prune_aliases);
/*
* Try to throw away a dentry - free the inode, dput the parent.
* Requires dentry->d_lock is held, and dentry->d_count == 0.
* Releases dentry->d_lock.
*
* This may fail if locks cannot be acquired no problem, just try again.
*/
static void try_prune_one_dentry(struct dentry *dentry)
__releases(dentry->d_lock)
{
struct dentry *parent;
parent = dentry_kill(dentry, 0);
/*
* If dentry_kill returns NULL, we have nothing more to do.
* if it returns the same dentry, trylocks failed. In either
* case, just loop again.
*
* Otherwise, we need to prune ancestors too. This is necessary
* to prevent quadratic behavior of shrink_dcache_parent(), but
* is also expected to be beneficial in reducing dentry cache
* fragmentation.
*/
if (!parent)
return;
if (parent == dentry)
return;
/* Prune ancestors. */
dentry = parent;
while (dentry) {
spin_lock(&dentry->d_lock);
if (dentry->d_count > 1) {
dentry->d_count--;
spin_unlock(&dentry->d_lock);
return;
}
dentry = dentry_kill(dentry, 1);
}
}
static void shrink_dentry_list(struct list_head *list)
{
struct dentry *dentry;
rcu_read_lock();
for (;;) {
dentry = list_entry_rcu(list->prev, struct dentry, d_lru);
if (&dentry->d_lru == list)
break; /* empty */
spin_lock(&dentry->d_lock);
if (dentry != list_entry(list->prev, struct dentry, d_lru)) {
spin_unlock(&dentry->d_lock);
continue;
}
/*
* We found an inuse dentry which was not removed from
* the LRU because of laziness during lookup. Do not free
* it - just keep it off the LRU list.
*/
if (dentry->d_count) {
dentry_lru_del(dentry);
spin_unlock(&dentry->d_lock);
continue;
}
rcu_read_unlock();
try_prune_one_dentry(dentry);
rcu_read_lock();
}
rcu_read_unlock();
}
/**
* __shrink_dcache_sb - shrink the dentry LRU on a given superblock
* @sb: superblock to shrink dentry LRU.
* @count: number of entries to prune
* @flags: flags to control the dentry processing
*
* If flags contains DCACHE_REFERENCED reference dentries will not be pruned.
*/
static void __shrink_dcache_sb(struct super_block *sb, int *count, int flags)
{
/* called from prune_dcache() and shrink_dcache_parent() */
struct dentry *dentry;
LIST_HEAD(referenced);
LIST_HEAD(tmp);
int cnt = *count;
relock:
spin_lock(&dcache_lru_lock);
while (!list_empty(&sb->s_dentry_lru)) {
dentry = list_entry(sb->s_dentry_lru.prev,
struct dentry, d_lru);
BUG_ON(dentry->d_sb != sb);
if (!spin_trylock(&dentry->d_lock)) {
spin_unlock(&dcache_lru_lock);
cpu_relax();
goto relock;
}
/*
* If we are honouring the DCACHE_REFERENCED flag and the
* dentry has this flag set, don't free it. Clear the flag
* and put it back on the LRU.
*/
if (flags & DCACHE_REFERENCED &&
dentry->d_flags & DCACHE_REFERENCED) {
dentry->d_flags &= ~DCACHE_REFERENCED;
list_move(&dentry->d_lru, &referenced);
spin_unlock(&dentry->d_lock);
} else {
list_move_tail(&dentry->d_lru, &tmp);
spin_unlock(&dentry->d_lock);
if (!--cnt)
break;
}
cond_resched_lock(&dcache_lru_lock);
}
if (!list_empty(&referenced))
list_splice(&referenced, &sb->s_dentry_lru);
spin_unlock(&dcache_lru_lock);
shrink_dentry_list(&tmp);
*count = cnt;
}
/**
* prune_dcache - shrink the dcache
* @count: number of entries to try to free
*
* Shrink the dcache. This is done when we need more memory, or simply when we
* need to unmount something (at which point we need to unuse all dentries).
*
* This function may fail to free any resources if all the dentries are in use.
*/
static void prune_dcache(int count)
{
struct super_block *sb, *p = NULL;
int w_count;
int unused = dentry_stat.nr_unused;
int prune_ratio;
int pruned;
if (unused == 0 || count == 0)
return;
if (count >= unused)
prune_ratio = 1;
else
prune_ratio = unused / count;
spin_lock(&sb_lock);
list_for_each_entry(sb, &super_blocks, s_list) {
if (list_empty(&sb->s_instances))
continue;
if (sb->s_nr_dentry_unused == 0)
continue;
sb->s_count++;
/* Now, we reclaim unused dentrins with fairness.
* We reclaim them same percentage from each superblock.
* We calculate number of dentries to scan on this sb
* as follows, but the implementation is arranged to avoid
* overflows:
* number of dentries to scan on this sb =
* count * (number of dentries on this sb /
* number of dentries in the machine)
*/
spin_unlock(&sb_lock);
if (prune_ratio != 1)
w_count = (sb->s_nr_dentry_unused / prune_ratio) + 1;
else
w_count = sb->s_nr_dentry_unused;
pruned = w_count;
/*
* We need to be sure this filesystem isn't being unmounted,
* otherwise we could race with generic_shutdown_super(), and
* end up holding a reference to an inode while the filesystem
* is unmounted. So we try to get s_umount, and make sure
* s_root isn't NULL.
*/
if (down_read_trylock(&sb->s_umount)) {
if ((sb->s_root != NULL) &&
(!list_empty(&sb->s_dentry_lru))) {
__shrink_dcache_sb(sb, &w_count,
DCACHE_REFERENCED);
pruned -= w_count;
}
up_read(&sb->s_umount);
}
spin_lock(&sb_lock);
if (p)
__put_super(p);
count -= pruned;
p = sb;
/* more work left to do? */
if (count <= 0)
break;
}
if (p)
__put_super(p);
spin_unlock(&sb_lock);
}
/**
* 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)
{
LIST_HEAD(tmp);
spin_lock(&dcache_lru_lock);
while (!list_empty(&sb->s_dentry_lru)) {
list_splice_init(&sb->s_dentry_lru, &tmp);
spin_unlock(&dcache_lru_lock);
shrink_dentry_list(&tmp);
spin_lock(&dcache_lru_lock);
}
spin_unlock(&dcache_lru_lock);
}
EXPORT_SYMBOL(shrink_dcache_sb);
/*
* destroy a single subtree of dentries for unmount
* - see the comments on shrink_dcache_for_umount() for a description of the
* locking
*/
static void shrink_dcache_for_umount_subtree(struct dentry *dentry)
{
struct dentry *parent;
unsigned detached = 0;
BUG_ON(!IS_ROOT(dentry));
/* detach this root from the system */
spin_lock(&dentry->d_lock);
dentry_lru_del(dentry);
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
for (;;) {
/* descend to the first leaf in the current subtree */
while (!list_empty(&dentry->d_subdirs)) {
struct dentry *loop;
/* this is a branch with children - detach all of them
* from the system in one go */
spin_lock(&dentry->d_lock);
list_for_each_entry(loop, &dentry->d_subdirs,
d_u.d_child) {
spin_lock_nested(&loop->d_lock,
DENTRY_D_LOCK_NESTED);
dentry_lru_del(loop);
__d_drop(loop);
spin_unlock(&loop->d_lock);
}
spin_unlock(&dentry->d_lock);
/* move to the first child */
dentry = list_entry(dentry->d_subdirs.next,
struct dentry, d_u.d_child);
}
/* consume the dentries from this leaf up through its parents
* until we find one with children or run out altogether */
do {
struct inode *inode;
if (dentry->d_count != 0) {
printk(KERN_ERR
"BUG: Dentry %p{i=%lx,n=%s}"
" still in use (%d)"
" [unmount of %s %s]\n",
dentry,
dentry->d_inode ?
dentry->d_inode->i_ino : 0UL,
dentry->d_name.name,
dentry->d_count,
dentry->d_sb->s_type->name,
dentry->d_sb->s_id);
BUG();
}
if (IS_ROOT(dentry)) {
parent = NULL;
list_del(&dentry->d_u.d_child);
} else {
parent = dentry->d_parent;
spin_lock(&parent->d_lock);
parent->d_count--;
list_del(&dentry->d_u.d_child);
spin_unlock(&parent->d_lock);
}
detached++;
inode = dentry->d_inode;
if (inode) {
dentry->d_inode = NULL;
list_del_init(&dentry->d_alias);
if (dentry->d_op && dentry->d_op->d_iput)
dentry->d_op->d_iput(dentry, inode);
else
iput(inode);
}
d_free(dentry);
/* finished when we fall off the top of the tree,
* otherwise we ascend to the parent and move to the
* next sibling if there is one */
if (!parent)
return;
dentry = parent;
} while (list_empty(&dentry->d_subdirs));
dentry = list_entry(dentry->d_subdirs.next,
struct dentry, d_u.d_child);
}
}
/*
* destroy the dentries attached to a superblock on unmounting
* - we don't need to use dentry->d_lock because:
* - the superblock is detached from all mountings and open files, so the
* dentry trees will not be rearranged by the VFS
* - s_umount is write-locked, so the memory pressure shrinker will ignore
* any dentries belonging to this superblock that it comes across
* - the filesystem itself is no longer permitted to rearrange the dentries
* in this superblock
*/
void shrink_dcache_for_umount(struct super_block *sb)
{
struct dentry *dentry;
if (down_read_trylock(&sb->s_umount))
BUG();
dentry = sb->s_root;
sb->s_root = NULL;
spin_lock(&dentry->d_lock);
dentry->d_count--;
spin_unlock(&dentry->d_lock);
shrink_dcache_for_umount_subtree(dentry);
while (!hlist_bl_empty(&sb->s_anon)) {
dentry = hlist_bl_entry(hlist_bl_first(&sb->s_anon), struct dentry, d_hash);
shrink_dcache_for_umount_subtree(dentry);
}
}
/*
* This tries to ascend one level of parenthood, but
* we can race with renaming, so we need to re-check
* the parenthood after dropping the lock and check
* that the sequence number still matches.
*/
static struct dentry *try_to_ascend(struct dentry *old, int locked, unsigned seq)
{
struct dentry *new = old->d_parent;
rcu_read_lock();
spin_unlock(&old->d_lock);
spin_lock(&new->d_lock);
/*
* might go back up the wrong parent if we have had a rename
* or deletion
*/
if (new != old->d_parent ||
(old->d_flags & DCACHE_DISCONNECTED) ||
(!locked && read_seqretry(&rename_lock, seq))) {
spin_unlock(&new->d_lock);
new = NULL;
}
rcu_read_unlock();
return new;
}
/*
* Search for at least 1 mount point in the dentry's subdirs.
* We descend to the next level whenever the d_subdirs
* list is non-empty and continue searching.
*/
/**
* have_submounts - check for mounts over a dentry
* @parent: dentry to check.
*
* Return true if the parent or its subdirectories contain
* a mount point
*/
int have_submounts(struct dentry *parent)
{
struct dentry *this_parent;
struct list_head *next;
unsigned seq;
int locked = 0;
seq = read_seqbegin(&rename_lock);
again:
this_parent = parent;
if (d_mountpoint(parent))
goto positive;
spin_lock(&this_parent->d_lock);
repeat:
next = this_parent->d_subdirs.next;
resume:
while (next != &this_parent->d_subdirs) {
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
next = tmp->next;
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
/* Have we found a mount point ? */
if (d_mountpoint(dentry)) {
spin_unlock(&dentry->d_lock);
spin_unlock(&this_parent->d_lock);
goto positive;
}
if (!list_empty(&dentry->d_subdirs)) {
spin_unlock(&this_parent->d_lock);
spin_release(&dentry->d_lock.dep_map, 1, _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.
*/
if (this_parent != parent) {
struct dentry *child = this_parent;
this_parent = try_to_ascend(this_parent, locked, seq);
if (!this_parent)
goto rename_retry;
next = child->d_u.d_child.next;
goto resume;
}
spin_unlock(&this_parent->d_lock);
if (!locked && read_seqretry(&rename_lock, seq))
goto rename_retry;
if (locked)
write_sequnlock(&rename_lock);
return 0; /* No mount points found in tree */
positive:
if (!locked && read_seqretry(&rename_lock, seq))
goto rename_retry;
if (locked)
write_sequnlock(&rename_lock);
return 1;
rename_retry:
locked = 1;
write_seqlock(&rename_lock);
goto again;
}
EXPORT_SYMBOL(have_submounts);
/*
* Search the dentry child list for 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_subdirs 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.
*/
static int select_parent(struct dentry * parent)
{
struct dentry *this_parent;
struct list_head *next;
unsigned seq;
int found = 0;
int locked = 0;
seq = read_seqbegin(&rename_lock);
again:
this_parent = parent;
spin_lock(&this_parent->d_lock);
repeat:
next = this_parent->d_subdirs.next;
resume:
while (next != &this_parent->d_subdirs) {
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
next = tmp->next;
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
/*
* move only zero ref count dentries to the end
* of the unused list for prune_dcache
*/
if (!dentry->d_count) {
dentry_lru_move_tail(dentry);
found++;
} else {
dentry_lru_del(dentry);
}
/*
* 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 (found && need_resched()) {
spin_unlock(&dentry->d_lock);
goto out;
}
/*
* Descend a level if the d_subdirs list is non-empty.
*/
if (!list_empty(&dentry->d_subdirs)) {
spin_unlock(&this_parent->d_lock);
spin_release(&dentry->d_lock.dep_map, 1, _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.
*/
if (this_parent != parent) {
struct dentry *child = this_parent;
this_parent = try_to_ascend(this_parent, locked, seq);
if (!this_parent)
goto rename_retry;
next = child->d_u.d_child.next;
goto resume;
}
out:
spin_unlock(&this_parent->d_lock);
if (!locked && read_seqretry(&rename_lock, seq))
goto rename_retry;
if (locked)
write_sequnlock(&rename_lock);
return found;
rename_retry:
if (found)
return found;
locked = 1;
write_seqlock(&rename_lock);
goto again;
}
/**
* 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)
{
struct super_block *sb = parent->d_sb;
int found;
while ((found = select_parent(parent)) != 0)
__shrink_dcache_sb(sb, &found, 0);
}
EXPORT_SYMBOL(shrink_dcache_parent);
/*
* Scan `nr' dentries and return the number which remain.
*
* We need to avoid reentering the filesystem if the caller is performing a
* GFP_NOFS allocation attempt. One example deadlock is:
*
* ext2_new_block->getblk->GFP->shrink_dcache_memory->prune_dcache->
* prune_one_dentry->dput->dentry_iput->iput->inode->i_sb->s_op->put_inode->
* ext2_discard_prealloc->ext2_free_blocks->lock_super->DEADLOCK.
*
* In this case we return -1 to tell the caller that we baled.
*/
static int shrink_dcache_memory(struct shrinker *shrink, int nr, gfp_t gfp_mask)
{
if (nr) {
if (!(gfp_mask & __GFP_FS))
return -1;
prune_dcache(nr);
}
return (dentry_stat.nr_unused / 100) * sysctl_vfs_cache_pressure;
}
static struct shrinker dcache_shrinker = {
.shrink = shrink_dcache_memory,
.seeks = DEFAULT_SEEKS,
};
/**
* 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;
char *dname;
dentry = kmem_cache_alloc(dentry_cache, GFP_KERNEL);
if (!dentry)
return NULL;
if (name->len > DNAME_INLINE_LEN-1) {
dname = kmalloc(name->len + 1, GFP_KERNEL);
if (!dname) {
kmem_cache_free(dentry_cache, dentry);
return NULL;
}
} else {
dname = dentry->d_iname;
}
dentry->d_name.name = dname;
dentry->d_name.len = name->len;
dentry->d_name.hash = name->hash;
memcpy(dname, name->name, name->len);
dname[name->len] = 0;
dentry->d_count = 1;
dentry->d_flags = 0;
spin_lock_init(&dentry->d_lock);
seqcount_init(&dentry->d_seq);
dentry->d_inode = NULL;
dentry->d_parent = NULL;
dentry->d_sb = NULL;
dentry->d_op = NULL;
dentry->d_fsdata = NULL;
INIT_HLIST_BL_NODE(&dentry->d_hash);
INIT_LIST_HEAD(&dentry->d_lru);
INIT_LIST_HEAD(&dentry->d_subdirs);
INIT_LIST_HEAD(&dentry->d_alias);
INIT_LIST_HEAD(&dentry->d_u.d_child);
if (parent) {
spin_lock(&parent->d_lock);
/*
* don't need child lock because it is not subject
* to concurrency here
*/
__dget_dlock(parent);
dentry->d_parent = parent;
dentry->d_sb = parent->d_sb;
d_set_d_op(dentry, dentry->d_sb->s_d_op);
list_add(&dentry->d_u.d_child, &parent->d_subdirs);
spin_unlock(&parent->d_lock);
}
this_cpu_inc(nr_dentry);
return dentry;
}
EXPORT_SYMBOL(d_alloc);
struct dentry *d_alloc_pseudo(struct super_block *sb, const struct qstr *name)
{
struct dentry *dentry = d_alloc(NULL, name);
if (dentry) {
dentry->d_sb = sb;
d_set_d_op(dentry, dentry->d_sb->s_d_op);
dentry->d_parent = dentry;
dentry->d_flags |= DCACHE_DISCONNECTED;
}
return dentry;
}
EXPORT_SYMBOL(d_alloc_pseudo);
struct dentry *d_alloc_name(struct dentry *parent, const char *name)
{
struct qstr q;
q.name = name;
q.len = strlen(name);
q.hash = full_name_hash(q.name, q.len);
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_DELETE ));
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_delete)
dentry->d_flags |= DCACHE_OP_DELETE;
}
EXPORT_SYMBOL(d_set_d_op);
static void __d_instantiate(struct dentry *dentry, struct inode *inode)
{
spin_lock(&dentry->d_lock);
if (inode) {
if (unlikely(IS_AUTOMOUNT(inode)))
dentry->d_flags |= DCACHE_NEED_AUTOMOUNT;
list_add(&dentry->d_alias, &inode->i_dentry);
}
dentry->d_inode = inode;
dentry_rcuwalk_barrier(dentry);
spin_unlock(&dentry->d_lock);
fsnotify_d_instantiate(dentry, inode);
}
/**
* 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(!list_empty(&entry->d_alias));
if (inode)
spin_lock(&inode->i_lock);
__d_instantiate(entry, inode);
if (inode)
spin_unlock(&inode->i_lock);
security_d_instantiate(entry, inode);
}
EXPORT_SYMBOL(d_instantiate);
/**
* d_instantiate_unique - instantiate a non-aliased dentry
* @entry: dentry to instantiate
* @inode: inode to attach to this dentry
*
* Fill in inode information in the entry. On success, it returns NULL.
* If an unhashed alias of "entry" already exists, then we return the
* aliased dentry instead and drop one reference to inode.
*
* Note that in order to avoid conflicts with rename() etc, the caller
* had better be holding the parent directory semaphore.
*
* This also 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.
*/
static struct dentry *__d_instantiate_unique(struct dentry *entry,
struct inode *inode)
{
struct dentry *alias;
int len = entry->d_name.len;
const char *name = entry->d_name.name;
unsigned int hash = entry->d_name.hash;
if (!inode) {
__d_instantiate(entry, NULL);
return NULL;
}
list_for_each_entry(alias, &inode->i_dentry, d_alias) {
struct qstr *qstr = &alias->d_name;
/*
* 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 (qstr->hash != hash)
continue;
if (alias->d_parent != entry->d_parent)
continue;
if (dentry_cmp(qstr->name, qstr->len, name, len))
continue;
__dget(alias);
return alias;
}
__d_instantiate(entry, inode);
return NULL;
}
struct dentry *d_instantiate_unique(struct dentry *entry, struct inode *inode)
{
struct dentry *result;
BUG_ON(!list_empty(&entry->d_alias));
if (inode)
spin_lock(&inode->i_lock);
result = __d_instantiate_unique(entry, inode);
if (inode)
spin_unlock(&inode->i_lock);
if (!result) {
security_d_instantiate(entry, inode);
return NULL;
}
BUG_ON(!d_unhashed(result));
iput(inode);
return result;
}
EXPORT_SYMBOL(d_instantiate_unique);
/**
* d_alloc_root - allocate root dentry
* @root_inode: inode to allocate the root for
*
* Allocate a root ("/") dentry for the inode given. The inode is
* instantiated and returned. %NULL is returned if there is insufficient
* memory or the inode passed is %NULL.
*/
struct dentry * d_alloc_root(struct inode * root_inode)
{
struct dentry *res = NULL;
if (root_inode) {
static const struct qstr name = { .name = "/", .len = 1 };
res = d_alloc(NULL, &name);
if (res) {
res->d_sb = root_inode->i_sb;
d_set_d_op(res, res->d_sb->s_d_op);
res->d_parent = res;
d_instantiate(res, root_inode);
}
}
return res;
}
EXPORT_SYMBOL(d_alloc_root);
static struct dentry * __d_find_any_alias(struct inode *inode)
{
struct dentry *alias;
if (list_empty(&inode->i_dentry))
return NULL;
alias = list_first_entry(&inode->i_dentry, struct dentry, d_alias);
__dget(alias);
return alias;
}
static 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;
}
/**
* d_obtain_alias - find or allocate a 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 will be the error will be propagate to the return value,
* with a %NULL @inode replaced by ERR_PTR(-ESTALE).
*/
struct dentry *d_obtain_alias(struct inode *inode)
{
static const struct qstr anonstring = { .name = "" };
struct dentry *tmp;
struct dentry *res;
if (!inode)
return ERR_PTR(-ESTALE);
if (IS_ERR(inode))
return ERR_CAST(inode);
res = d_find_any_alias(inode);
if (res)
goto out_iput;
tmp = d_alloc(NULL, &anonstring);
if (!tmp) {
res = ERR_PTR(-ENOMEM);
goto out_iput;
}
tmp->d_parent = tmp; /* make sure dput doesn't croak */
spin_lock(&inode->i_lock);
res = __d_find_any_alias(inode);
if (res) {
spin_unlock(&inode->i_lock);
dput(tmp);
goto out_iput;
}
/* attach a disconnected dentry */
spin_lock(&tmp->d_lock);
tmp->d_sb = inode->i_sb;
d_set_d_op(tmp, tmp->d_sb->s_d_op);
tmp->d_inode = inode;
tmp->d_flags |= DCACHE_DISCONNECTED;
list_add(&tmp->d_alias, &inode->i_dentry);
hlist_bl_lock(&tmp->d_sb->s_anon);
hlist_bl_add_head(&tmp->d_hash, &tmp->d_sb->s_anon);
hlist_bl_unlock(&tmp->d_sb->s_anon);
spin_unlock(&tmp->d_lock);
spin_unlock(&inode->i_lock);
security_d_instantiate(tmp, inode);
return tmp;
out_iput:
if (res && !IS_ERR(res))
security_d_instantiate(res, inode);
iput(inode);
return res;
}
EXPORT_SYMBOL(d_obtain_alias);
/**
* 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 a 'disconnected' dentry (i.e. IS_ROOT and
* DCACHE_DISCONNECTED), 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.
*
* 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.
*
*/
struct dentry *d_splice_alias(struct inode *inode, struct dentry *dentry)
{
struct dentry *new = NULL;
if (inode && S_ISDIR(inode->i_mode)) {
spin_lock(&inode->i_lock);
new = __d_find_alias(inode, 1);
if (new) {
BUG_ON(!(new->d_flags & DCACHE_DISCONNECTED));
spin_unlock(&inode->i_lock);
security_d_instantiate(new, inode);
d_move(new, dentry);
iput(inode);
} else {
/* already taking inode->i_lock, so d_add() by hand */
__d_instantiate(dentry, inode);
spin_unlock(&inode->i_lock);
security_d_instantiate(dentry, inode);
d_rehash(dentry);
}
} else
d_add(dentry, inode);
return new;
}
EXPORT_SYMBOL(d_splice_alias);
/**
* 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 the case-exact dentry
* already exists in 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)
{
int error;
struct dentry *found;
struct dentry *new;
/*
* 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) {
new = d_alloc(dentry->d_parent, name);
if (!new) {
error = -ENOMEM;
goto err_out;
}
found = d_splice_alias(inode, new);
if (found) {
dput(new);
return found;
}
return new;
}
/*
* If a matching dentry exists, and it's not negative use it.
*
* Decrement the reference count to balance the iget() done
* earlier on.
*/
if (found->d_inode) {
if (unlikely(found->d_inode != inode)) {
/* This can't happen because bad inodes are unhashed. */
BUG_ON(!is_bad_inode(inode));
BUG_ON(!is_bad_inode(found->d_inode));
}
iput(inode);
return found;
}
/*
* Negative dentry: instantiate it unless the inode is a directory and
* already has a dentry.
*/
spin_lock(&inode->i_lock);
if (!S_ISDIR(inode->i_mode) || list_empty(&inode->i_dentry)) {
__d_instantiate(found, inode);
spin_unlock(&inode->i_lock);
security_d_instantiate(found, inode);
return found;
}
/*
* In case a directory already has a (disconnected) entry grab a
* reference to it, move it in place and use it.
*/
new = list_entry(inode->i_dentry.next, struct dentry, d_alias);
__dget(new);
spin_unlock(&inode->i_lock);
security_d_instantiate(found, inode);
d_move(new, found);
iput(inode);
dput(found);
return new;
err_out:
iput(inode);
return ERR_PTR(error);
}
EXPORT_SYMBOL(d_add_ci);
/**
* __d_lookup_rcu - search for a dentry (racy, store-free)
* @parent: parent dentry
* @name: qstr of name we wish to find
* @seq: returns d_seq value at the point where the dentry was found
* @inode: returns dentry->d_inode when the inode was found valid.
* 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.
*/
struct dentry *__d_lookup_rcu(struct dentry *parent, struct qstr *name,
unsigned *seq, struct inode **inode)
{
unsigned int len = name->len;
unsigned int hash = name->hash;
const unsigned char *str = name->name;
struct hlist_bl_head *b = d_hash(parent, hash);
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.
*/
/*
* 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) {
struct inode *i;
const char *tname;
int tlen;
if (dentry->d_name.hash != hash)
continue;
seqretry:
*seq = read_seqcount_begin(&dentry->d_seq);
if (dentry->d_parent != parent)
continue;
if (d_unhashed(dentry))
continue;
tlen = dentry->d_name.len;
tname = dentry->d_name.name;
i = dentry->d_inode;
prefetch(tname);
if (i)
prefetch(i);
/*
* This seqcount check is required to ensure name and
* len are loaded atomically, so as not to walk off the
* edge of memory when walking. If we could load this
* atomically some other way, we could drop this check.
*/
if (read_seqcount_retry(&dentry->d_seq, *seq))
goto seqretry;
if (parent->d_flags & DCACHE_OP_COMPARE) {
if (parent->d_op->d_compare(parent, *inode,
dentry, i,
tlen, tname, name))
continue;
} else {
if (dentry_cmp(tname, tlen, str, len))
continue;
}
/*
* No extra seqcount check is required after the name
* compare. The caller must perform a seqcount check in
* order to do anything useful with the returned dentry
* anyway.
*/
*inode = i;
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(struct dentry *parent, 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(struct dentry *parent, struct qstr *name)
{
unsigned int len = name->len;
unsigned int hash = name->hash;
const unsigned char *str = name->name;
struct hlist_bl_head *b = d_hash(parent, 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) {
const char *tname;
int tlen;
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;
/*
* It is safe to compare names since d_move() cannot
* change the qstr (protected by d_lock).
*/
tlen = dentry->d_name.len;
tname = dentry->d_name.name;
if (parent->d_flags & DCACHE_OP_COMPARE) {
if (parent->d_op->d_compare(parent, parent->d_inode,
dentry, dentry->d_inode,
tlen, tname, name))
goto next;
} else {
if (dentry_cmp(tname, tlen, str, len))
goto next;
}
dentry->d_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 hash failure or on lookup failure NULL is returned.
*/
struct dentry *d_hash_and_lookup(struct dentry *dir, struct qstr *name)
{
struct dentry *dentry = NULL;
/*
* 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(name->name, name->len);
if (dir->d_flags & DCACHE_OP_HASH) {
if (dir->d_op->d_hash(dir, dir->d_inode, name) < 0)
goto out;
}
dentry = d_lookup(dir, name);
out:
return dentry;
}
/**
* d_validate - verify dentry provided from insecure source (deprecated)
* @dentry: The dentry alleged to be valid child of @dparent
* @dparent: The parent dentry (known to be valid)
*
* An insecure source has sent us a dentry, here we verify it and dget() it.
* This is used by ncpfs in its readdir implementation.
* Zero is returned in the dentry is invalid.
*
* This function is slow for big directories, and deprecated, do not use it.
*/
int d_validate(struct dentry *dentry, struct dentry *dparent)
{
struct dentry *child;
spin_lock(&dparent->d_lock);
list_for_each_entry(child, &dparent->d_subdirs, d_u.d_child) {
if (dentry == child) {
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
__dget_dlock(dentry);
spin_unlock(&dentry->d_lock);
spin_unlock(&dparent->d_lock);
return 1;
}
}
spin_unlock(&dparent->d_lock);
return 0;
}
EXPORT_SYMBOL(d_validate);
/*
* 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;
int isdir = 0;
/*
* Are we the only user?
*/
again:
spin_lock(&dentry->d_lock);
inode = dentry->d_inode;
isdir = S_ISDIR(inode->i_mode);
if (dentry->d_count == 1) {
if (inode && !spin_trylock(&inode->i_lock)) {
spin_unlock(&dentry->d_lock);
cpu_relax();
goto again;
}
dentry->d_flags &= ~DCACHE_CANT_MOUNT;
dentry_unlink_inode(dentry);
fsnotify_nameremove(dentry, isdir);
return;
}
if (!d_unhashed(dentry))
__d_drop(dentry);
spin_unlock(&dentry->d_lock);
fsnotify_nameremove(dentry, isdir);
}
EXPORT_SYMBOL(d_delete);
static void __d_rehash(struct dentry * entry, struct hlist_bl_head *b)
{
BUG_ON(!d_unhashed(entry));
hlist_bl_lock(b);
entry->d_flags |= DCACHE_RCUACCESS;
hlist_bl_add_head_rcu(&entry->d_hash, b);
hlist_bl_unlock(b);
}
static void _d_rehash(struct dentry * entry)
{
__d_rehash(entry, d_hash(entry->d_parent, entry->d_name.hash));
}
/**
* 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);
/**
* dentry_update_name_case - update case insensitive dentry with a new name
* @dentry: dentry to be updated
* @name: new name
*
* Update a case insensitive dentry with new case of name.
*
* dentry must have been returned by d_lookup with name @name. Old and new
* name lengths must match (ie. no d_compare which allows mismatched name
* lengths).
*
* Parent inode i_mutex must be held over d_lookup and into this call (to
* keep renames and concurrent inserts, and readdir(2) away).
*/
void dentry_update_name_case(struct dentry *dentry, struct qstr *name)
{
BUG_ON(!mutex_is_locked(&dentry->d_parent->d_inode->i_mutex));
BUG_ON(dentry->d_name.len != name->len); /* d_lookup gives this */
spin_lock(&dentry->d_lock);
write_seqcount_begin(&dentry->d_seq);
memcpy((unsigned char *)dentry->d_name.name, name->name, name->len);
write_seqcount_end(&dentry->d_seq);
spin_unlock(&dentry->d_lock);
}
EXPORT_SYMBOL(dentry_update_name_case);
static void switch_names(struct dentry *dentry, struct dentry *target)
{
if (dname_external(target)) {
if (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 (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. Just copy target to dentry
*/
memcpy(dentry->d_iname, target->d_name.name,
target->d_name.len + 1);
dentry->d_name.len = target->d_name.len;
return;
}
}
swap(dentry->d_name.len, target->d_name.len);
}
static void dentry_lock_for_move(struct dentry *dentry, struct dentry *target)
{
/*
* XXXX: do we really need to take target->d_lock?
*/
if (IS_ROOT(dentry) || dentry->d_parent == target->d_parent)
spin_lock(&target->d_parent->d_lock);
else {
if (d_ancestor(dentry->d_parent, target->d_parent)) {
spin_lock(&dentry->d_parent->d_lock);
spin_lock_nested(&target->d_parent->d_lock,
DENTRY_D_LOCK_NESTED);
} else {
spin_lock(&target->d_parent->d_lock);
spin_lock_nested(&dentry->d_parent->d_lock,
DENTRY_D_LOCK_NESTED);
}
}
if (target < dentry) {
spin_lock_nested(&target->d_lock, 2);
spin_lock_nested(&dentry->d_lock, 3);
} else {
spin_lock_nested(&dentry->d_lock, 2);
spin_lock_nested(&target->d_lock, 3);
}
}
static void dentry_unlock_parents_for_move(struct dentry *dentry,
struct dentry *target)
{
if (target->d_parent != dentry->d_parent)
spin_unlock(&dentry->d_parent->d_lock);
if (target->d_parent != target)
spin_unlock(&target->d_parent->d_lock);
}
/*
* When switching names, the actual string doesn't strictly have to
* be preserved in the target - because we're dropping the target
* anyway. As such, we can just do a simple memcpy() to copy over
* the new name before we switch.
*
* Note that we have to be a lot more careful about getting the hash
* switched - we have to switch the hash value properly even if it
* then no longer matches the actual (corrupted) string of the target.
* The hash value has to match the hash queue that the dentry is on..
*/
/*
* 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.
*/
void d_move(struct dentry * dentry, struct dentry * target)
{
if (!dentry->d_inode)
printk(KERN_WARNING "VFS: moving negative dcache entry\n");
BUG_ON(d_ancestor(dentry, target));
BUG_ON(d_ancestor(target, dentry));
write_seqlock(&rename_lock);
dentry_lock_for_move(dentry, target);
write_seqcount_begin(&dentry->d_seq);
write_seqcount_begin(&target->d_seq);
/* __d_drop does write_seqcount_barrier, but they're OK to nest. */
/*
* Move the dentry to the target hash queue. Don't bother checking
* for the same hash queue because of how unlikely it is.
*/
__d_drop(dentry);
__d_rehash(dentry, d_hash(target->d_parent, target->d_name.hash));
/* Unhash the target: dput() will then get rid of it */
__d_drop(target);
list_del(&dentry->d_u.d_child);
list_del(&target->d_u.d_child);
/* Switch the names.. */
switch_names(dentry, target);
swap(dentry->d_name.hash, target->d_name.hash);
/* ... and switch the parents */
if (IS_ROOT(dentry)) {
dentry->d_parent = target->d_parent;
target->d_parent = target;
INIT_LIST_HEAD(&target->d_u.d_child);
} else {
swap(dentry->d_parent, target->d_parent);
/* And add them back to the (new) parent lists */
list_add(&target->d_u.d_child, &target->d_parent->d_subdirs);
}
list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
write_seqcount_end(&target->d_seq);
write_seqcount_end(&dentry->d_seq);
dentry_unlock_parents_for_move(dentry, target);
spin_unlock(&target->d_lock);
fsnotify_d_move(dentry);
spin_unlock(&dentry->d_lock);
write_sequnlock(&rename_lock);
}
EXPORT_SYMBOL(d_move);
/**
* 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 the inode->i_lock
*
* Note: If ever the locking in lock_rename() changes, then please
* remember to update this too...
*/
static struct dentry *__d_unalias(struct inode *inode,
struct dentry *dentry, struct dentry *alias)
{
struct mutex *m1 = NULL, *m2 = NULL;
struct dentry *ret;
/* If alias and dentry share a parent, then no extra locks required */
if (alias->d_parent == dentry->d_parent)
goto out_unalias;
/* Check for loops */
ret = ERR_PTR(-ELOOP);
if (d_ancestor(alias, dentry))
goto out_err;
/* See lock_rename() */
ret = ERR_PTR(-EBUSY);
if (!mutex_trylock(&dentry->d_sb->s_vfs_rename_mutex))
goto out_err;
m1 = &dentry->d_sb->s_vfs_rename_mutex;
if (!mutex_trylock(&alias->d_parent->d_inode->i_mutex))
goto out_err;
m2 = &alias->d_parent->d_inode->i_mutex;
out_unalias:
d_move(alias, dentry);
ret = alias;
out_err:
spin_unlock(&inode->i_lock);
if (m2)
mutex_unlock(m2);
if (m1)
mutex_unlock(m1);
return ret;
}
/*
* Prepare an anonymous dentry for life in the superblock's dentry tree as a
* named dentry in place of the dentry to be replaced.
* returns with anon->d_lock held!
*/
static void __d_materialise_dentry(struct dentry *dentry, struct dentry *anon)
{
struct dentry *dparent, *aparent;
dentry_lock_for_move(anon, dentry);
write_seqcount_begin(&dentry->d_seq);
write_seqcount_begin(&anon->d_seq);
dparent = dentry->d_parent;
aparent = anon->d_parent;
switch_names(dentry, anon);
swap(dentry->d_name.hash, anon->d_name.hash);
dentry->d_parent = (aparent == anon) ? dentry : aparent;
list_del(&dentry->d_u.d_child);
if (!IS_ROOT(dentry))
list_add(&dentry->d_u.d_child, &dentry->d_parent->d_subdirs);
else
INIT_LIST_HEAD(&dentry->d_u.d_child);
anon->d_parent = (dparent == dentry) ? anon : dparent;
list_del(&anon->d_u.d_child);
if (!IS_ROOT(anon))
list_add(&anon->d_u.d_child, &anon->d_parent->d_subdirs);
else
INIT_LIST_HEAD(&anon->d_u.d_child);
write_seqcount_end(&dentry->d_seq);
write_seqcount_end(&anon->d_seq);
dentry_unlock_parents_for_move(anon, dentry);
spin_unlock(&dentry->d_lock);
/* anon->d_lock still locked, returns locked */
anon->d_flags &= ~DCACHE_DISCONNECTED;
}
/**
* d_materialise_unique - introduce an inode into the tree
* @dentry: candidate dentry
* @inode: inode to bind to the dentry, to which aliases may be attached
*
* Introduces an dentry into the tree, substituting an extant disconnected
* root directory alias in its place if there is one
*/
struct dentry *d_materialise_unique(struct dentry *dentry, struct inode *inode)
{
struct dentry *actual;
BUG_ON(!d_unhashed(dentry));
if (!inode) {
actual = dentry;
__d_instantiate(dentry, NULL);
d_rehash(actual);
goto out_nolock;
}
spin_lock(&inode->i_lock);
if (S_ISDIR(inode->i_mode)) {
struct dentry *alias;
/* Does an aliased dentry already exist? */
alias = __d_find_alias(inode, 0);
if (alias) {
actual = alias;
/* Is this an anonymous mountpoint that we could splice
* into our tree? */
if (IS_ROOT(alias)) {
__d_materialise_dentry(dentry, alias);
__d_drop(alias);
goto found;
}
/* Nope, but we must(!) avoid directory aliasing */
actual = __d_unalias(inode, dentry, alias);
if (IS_ERR(actual))
dput(alias);
goto out_nolock;
}
}
/* Add a unique reference */
actual = __d_instantiate_unique(dentry, inode);
if (!actual)
actual = dentry;
else
BUG_ON(!d_unhashed(actual));
spin_lock(&actual->d_lock);
found:
_d_rehash(actual);
spin_unlock(&actual->d_lock);
spin_unlock(&inode->i_lock);
out_nolock:
if (actual == dentry) {
security_d_instantiate(dentry, inode);
return NULL;
}
iput(inode);
return actual;
}
EXPORT_SYMBOL_GPL(d_materialise_unique);
static int prepend(char **buffer, int *buflen, const char *str, int namelen)
{
*buflen -= namelen;
if (*buflen < 0)
return -ENAMETOOLONG;
*buffer -= namelen;
memcpy(*buffer, str, namelen);
return 0;
}
static int prepend_name(char **buffer, int *buflen, struct qstr *name)
{
return prepend(buffer, buflen, name->name, name->len);
}
/**
* prepend_path - Prepend path string to a buffer
* @path: the dentry/vfsmount to report
* @root: root vfsmnt/dentry (may be modified by this function)
* @buffer: pointer to the end of the buffer
* @buflen: pointer to buffer length
*
* Caller holds the rename_lock.
*
* If path is not reachable from the supplied root, then the value of
* root is changed (without modifying refcounts).
*/
static int prepend_path(const struct path *path, struct path *root,
char **buffer, int *buflen)
{
struct dentry *dentry = path->dentry;
struct vfsmount *vfsmnt = path->mnt;
bool slash = false;
int error = 0;
br_read_lock(vfsmount_lock);
while (dentry != root->dentry || vfsmnt != root->mnt) {
struct dentry * parent;
if (dentry == vfsmnt->mnt_root || IS_ROOT(dentry)) {
/* Global root? */
if (vfsmnt->mnt_parent == vfsmnt) {
goto global_root;
}
dentry = vfsmnt->mnt_mountpoint;
vfsmnt = vfsmnt->mnt_parent;
continue;
}
parent = dentry->d_parent;
prefetch(parent);
spin_lock(&dentry->d_lock);
error = prepend_name(buffer, buflen, &dentry->d_name);
spin_unlock(&dentry->d_lock);
if (!error)
error = prepend(buffer, buflen, "/", 1);
if (error)
break;
slash = true;
dentry = parent;
}
out:
if (!error && !slash)
error = prepend(buffer, buflen, "/", 1);
br_read_unlock(vfsmount_lock);
return error;
global_root:
/*
* Filesystems needing to implement special "root names"
* should do so with ->d_dname()
*/
if (IS_ROOT(dentry) &&
(dentry->d_name.len != 1 || dentry->d_name.name[0] != '/')) {
WARN(1, "Root dentry has weird name <%.*s>\n",
(int) dentry->d_name.len, dentry->d_name.name);
}
root->mnt = vfsmnt;
root->dentry = dentry;
goto out;
}
/**
* __d_path - return the path of a dentry
* @path: the dentry/vfsmount to report
* @root: root vfsmnt/dentry (may be modified by this function)
* @buf: buffer to return value in
* @buflen: buffer length
*
* Convert a dentry into an ASCII path name.
*
* Returns a pointer into the buffer or an error code if the
* path was too long.
*
* "buflen" should be positive.
*
* If path is not reachable from the supplied root, then the value of
* root is changed (without modifying refcounts).
*/
char *__d_path(const struct path *path, struct path *root,
char *buf, int buflen)
{
char *res = buf + buflen;
int error;
prepend(&res, &buflen, "\0", 1);
write_seqlock(&rename_lock);
error = prepend_path(path, root, &res, &buflen);
write_sequnlock(&rename_lock);
if (error)
return ERR_PTR(error);
return res;
}
/*
* same as __d_path but appends "(deleted)" for unlinked files.
*/
static int path_with_deleted(const struct path *path, struct path *root,
char **buf, int *buflen)
{
prepend(buf, buflen, "\0", 1);
if (d_unlinked(path->dentry)) {
int error = prepend(buf, buflen, " (deleted)", 10);
if (error)
return error;
}
return prepend_path(path, root, buf, buflen);
}
static int prepend_unreachable(char **buffer, int *buflen)
{
return prepend(buffer, buflen, "(unreachable)", 13);
}
/**
* d_path - return the path of a dentry
* @path: path to report
* @buf: buffer to return value in
* @buflen: buffer length
*
* Convert a dentry into an ASCII path name. If the entry has been deleted
* the string " (deleted)" is appended. Note that this is ambiguous.
*
* Returns a pointer into the buffer or an error code if the path was
* too long. Note: Callers should use the returned pointer, not the passed
* in buffer, to use the name! The implementation often starts at an offset
* into the buffer, and may leave 0 bytes at the start.
*
* "buflen" should be positive.
*/
char *d_path(const struct path *path, char *buf, int buflen)
{
char *res = buf + buflen;
struct path root;
struct path tmp;
int error;
/*
* We have various synthetic filesystems that never get mounted. On
* these filesystems dentries are never used for lookup purposes, and
* thus don't need to be hashed. They also don't need a name until a
* user wants to identify the object in /proc/pid/fd/. The little hack
* below allows us to generate a name for these objects on demand:
*/
if (path->dentry->d_op && path->dentry->d_op->d_dname)
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
get_fs_root(current->fs, &root);
write_seqlock(&rename_lock);
tmp = root;
error = path_with_deleted(path, &tmp, &res, &buflen);
if (error)
res = ERR_PTR(error);
write_sequnlock(&rename_lock);
path_put(&root);
return res;
}
EXPORT_SYMBOL(d_path);
/**
* d_path_with_unreachable - return the path of a dentry
* @path: path to report
* @buf: buffer to return value in
* @buflen: buffer length
*
* The difference from d_path() is that this prepends "(unreachable)"
* to paths which are unreachable from the current process' root.
*/
char *d_path_with_unreachable(const struct path *path, char *buf, int buflen)
{
char *res = buf + buflen;
struct path root;
struct path tmp;
int error;
if (path->dentry->d_op && path->dentry->d_op->d_dname)
return path->dentry->d_op->d_dname(path->dentry, buf, buflen);
get_fs_root(current->fs, &root);
write_seqlock(&rename_lock);
tmp = root;
error = path_with_deleted(path, &tmp, &res, &buflen);
if (!error && !path_equal(&tmp, &root))
error = prepend_unreachable(&res, &buflen);
write_sequnlock(&rename_lock);
path_put(&root);
if (error)
res = ERR_PTR(error);
return res;
}
/*
* Helper function for dentry_operations.d_dname() members
*/
char *dynamic_dname(struct dentry *dentry, char *buffer, int buflen,
const char *fmt, ...)
{
va_list args;
char temp[64];
int sz;
va_start(args, fmt);
sz = vsnprintf(temp, sizeof(temp), fmt, args) + 1;
va_end(args);
if (sz > sizeof(temp) || sz > buflen)
return ERR_PTR(-ENAMETOOLONG);
buffer += buflen - sz;
return memcpy(buffer, temp, sz);
}
/*
* Write full pathname from the root of the filesystem into the buffer.
*/
static char *__dentry_path(struct dentry *dentry, char *buf, int buflen)
{
char *end = buf + buflen;
char *retval;
prepend(&end, &buflen, "\0", 1);
if (buflen < 1)
goto Elong;
/* Get '/' right */
retval = end-1;
*retval = '/';
while (!IS_ROOT(dentry)) {
struct dentry *parent = dentry->d_parent;
int error;
prefetch(parent);
spin_lock(&dentry->d_lock);
error = prepend_name(&end, &buflen, &dentry->d_name);
spin_unlock(&dentry->d_lock);
if (error != 0 || prepend(&end, &buflen, "/", 1) != 0)
goto Elong;
retval = end;
dentry = parent;
}
return retval;
Elong:
return ERR_PTR(-ENAMETOOLONG);
}
char *dentry_path_raw(struct dentry *dentry, char *buf, int buflen)
{
char *retval;
write_seqlock(&rename_lock);
retval = __dentry_path(dentry, buf, buflen);
write_sequnlock(&rename_lock);
return retval;
}
EXPORT_SYMBOL(dentry_path_raw);
char *dentry_path(struct dentry *dentry, char *buf, int buflen)
{
char *p = NULL;
char *retval;
write_seqlock(&rename_lock);
if (d_unlinked(dentry)) {
p = buf + buflen;
if (prepend(&p, &buflen, "//deleted", 10) != 0)
goto Elong;
buflen++;
}
retval = __dentry_path(dentry, buf, buflen);
write_sequnlock(&rename_lock);
if (!IS_ERR(retval) && p)
*p = '/'; /* restore '/' overriden with '\0' */
return retval;
Elong:
return ERR_PTR(-ENAMETOOLONG);
}
/*
* NOTE! The user-level library version returns a
* character pointer. The kernel system call just
* returns the length of the buffer filled (which
* includes the ending '\0' character), or a negative
* error value. So libc would do something like
*
* char *getcwd(char * buf, size_t size)
* {
* int retval;
*
* retval = sys_getcwd(buf, size);
* if (retval >= 0)
* return buf;
* errno = -retval;
* return NULL;
* }
*/
SYSCALL_DEFINE2(getcwd, char __user *, buf, unsigned long, size)
{
int error;
struct path pwd, root;
char *page = (char *) __get_free_page(GFP_USER);
if (!page)
return -ENOMEM;
get_fs_root_and_pwd(current->fs, &root, &pwd);
error = -ENOENT;
write_seqlock(&rename_lock);
if (!d_unlinked(pwd.dentry)) {
unsigned long len;
struct path tmp = root;
char *cwd = page + PAGE_SIZE;
int buflen = PAGE_SIZE;
prepend(&cwd, &buflen, "\0", 1);
error = prepend_path(&pwd, &tmp, &cwd, &buflen);
write_sequnlock(&rename_lock);
if (error)
goto out;
/* Unreachable from current root */
if (!path_equal(&tmp, &root)) {
error = prepend_unreachable(&cwd, &buflen);
if (error)
goto out;
}
error = -ERANGE;
len = PAGE_SIZE + page - cwd;
if (len <= size) {
error = len;
if (copy_to_user(buf, cwd, len))
error = -EFAULT;
}
} else {
write_sequnlock(&rename_lock);
}
out:
path_put(&pwd);
path_put(&root);
free_page((unsigned long) page);
return error;
}
/*
* 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 1 if new_dentry is a subdirectory of the parent (at any depth).
* Returns 0 otherwise.
* Caller must ensure that "new_dentry" is pinned before calling is_subdir()
*/
int is_subdir(struct dentry *new_dentry, struct dentry *old_dentry)
{
int result;
unsigned seq;
if (new_dentry == old_dentry)
return 1;
do {
/* for restarting inner loop in case of seq retry */
seq = read_seqbegin(&rename_lock);
/*
* Need rcu_readlock to protect against the d_parent trashing
* due to d_move
*/
rcu_read_lock();
if (d_ancestor(old_dentry, new_dentry))
result = 1;
else
result = 0;
rcu_read_unlock();
} while (read_seqretry(&rename_lock, seq));
return result;
}
int path_is_under(struct path *path1, struct path *path2)
{
struct vfsmount *mnt = path1->mnt;
struct dentry *dentry = path1->dentry;
int res;
br_read_lock(vfsmount_lock);
if (mnt != path2->mnt) {
for (;;) {
if (mnt->mnt_parent == mnt) {
br_read_unlock(vfsmount_lock);
return 0;
}
if (mnt->mnt_parent == path2->mnt)
break;
mnt = mnt->mnt_parent;
}
dentry = mnt->mnt_mountpoint;
}
res = is_subdir(dentry, path2->dentry);
br_read_unlock(vfsmount_lock);
return res;
}
EXPORT_SYMBOL(path_is_under);
void d_genocide(struct dentry *root)
{
struct dentry *this_parent;
struct list_head *next;
unsigned seq;
int locked = 0;
seq = read_seqbegin(&rename_lock);
again:
this_parent = root;
spin_lock(&this_parent->d_lock);
repeat:
next = this_parent->d_subdirs.next;
resume:
while (next != &this_parent->d_subdirs) {
struct list_head *tmp = next;
struct dentry *dentry = list_entry(tmp, struct dentry, d_u.d_child);
next = tmp->next;
spin_lock_nested(&dentry->d_lock, DENTRY_D_LOCK_NESTED);
if (d_unhashed(dentry) || !dentry->d_inode) {
spin_unlock(&dentry->d_lock);
continue;
}
if (!list_empty(&dentry->d_subdirs)) {
spin_unlock(&this_parent->d_lock);
spin_release(&dentry->d_lock.dep_map, 1, _RET_IP_);
this_parent = dentry;
spin_acquire(&this_parent->d_lock.dep_map, 0, 1, _RET_IP_);
goto repeat;
}
if (!(dentry->d_flags & DCACHE_GENOCIDE)) {
dentry->d_flags |= DCACHE_GENOCIDE;
dentry->d_count--;
}
spin_unlock(&dentry->d_lock);
}
if (this_parent != root) {
struct dentry *child = this_parent;
if (!(this_parent->d_flags & DCACHE_GENOCIDE)) {
this_parent->d_flags |= DCACHE_GENOCIDE;
this_parent->d_count--;
}
this_parent = try_to_ascend(this_parent, locked, seq);
if (!this_parent)
goto rename_retry;
next = child->d_u.d_child.next;
goto resume;
}
spin_unlock(&this_parent->d_lock);
if (!locked && read_seqretry(&rename_lock, seq))
goto rename_retry;
if (locked)
write_sequnlock(&rename_lock);
return;
rename_retry:
locked = 1;
write_seqlock(&rename_lock);
goto again;
}
/**
* find_inode_number - check for dentry with name
* @dir: directory to check
* @name: Name to find.
*
* Check whether a dentry already exists for the given name,
* and return the inode number if it has an inode. Otherwise
* 0 is returned.
*
* This routine is used to post-process directory listings for
* filesystems using synthetic inode numbers, and is necessary
* to keep getcwd() working.
*/
ino_t find_inode_number(struct dentry *dir, struct qstr *name)
{
struct dentry * dentry;
ino_t ino = 0;
dentry = d_hash_and_lookup(dir, name);
if (dentry) {
if (dentry->d_inode)
ino = dentry->d_inode->i_ino;
dput(dentry);
}
return ino;
}
EXPORT_SYMBOL(find_inode_number);
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)
{
int loop;
/* 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,
&d_hash_shift,
&d_hash_mask,
0);
for (loop = 0; loop < (1 << d_hash_shift); loop++)
INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
}
static void __init dcache_init(void)
{
int loop;
/*
* 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(dentry,
SLAB_RECLAIM_ACCOUNT|SLAB_PANIC|SLAB_MEM_SPREAD);
register_shrinker(&dcache_shrinker);
/* 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,
0,
&d_hash_shift,
&d_hash_mask,
0);
for (loop = 0; loop < (1 << d_hash_shift); loop++)
INIT_HLIST_BL_HEAD(dentry_hashtable + loop);
}
/* SLAB cache for __getname() consumers */
struct kmem_cache *names_cachep __read_mostly;
EXPORT_SYMBOL(names_cachep);
EXPORT_SYMBOL(d_genocide);
void __init vfs_caches_init_early(void)
{
dcache_init_early();
inode_init_early();
}
void __init vfs_caches_init(unsigned long mempages)
{
unsigned long reserve;
/* Base hash sizes on available memory, with a reserve equal to
150% of current kernel size */
reserve = min((mempages - nr_free_pages()) * 3/2, mempages - 1);
mempages -= reserve;
names_cachep = kmem_cache_create("names_cache", PATH_MAX, 0,
SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
dcache_init();
inode_init();
files_init(mempages);
mnt_init();
bdev_cache_init();
chrdev_init();
}
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