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afs: Make vnode->cb_interest RCU safe

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Use RCU-based freeing for afs_cb_interest struct objects and use RCU on
vnode->cb_interest.  Use that change to allow afs_check_validity() to use
read_seqbegin_or_lock() instead of read_seqlock_excl().

This also requires the caller of afs_check_validity() to hold the RCU read
lock across the call.

Signed-off-by: David Howells <dhowells@redhat.com>
This commit is contained in:
David Howells 2019-05-13 16:14:32 +01:00
parent c925bd0ac4
commit f642404a04
7 changed files with 99 additions and 58 deletions
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21
fs/afs/callback.c
View File

@ -94,15 +94,15 @@ int afs_register_server_cb_interest(struct afs_vnode *vnode,
struct afs_server *server = entry->server;
again:
if (vnode->cb_interest &&
likely(vnode->cb_interest == entry->cb_interest))
vcbi = rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->io_lock));
if (vcbi && likely(vcbi == entry->cb_interest))
return 0;
read_lock(&slist->lock);
cbi = afs_get_cb_interest(entry->cb_interest);
read_unlock(&slist->lock);
vcbi = vnode->cb_interest;
if (vcbi) {
if (vcbi == cbi) {
afs_put_cb_interest(afs_v2net(vnode), cbi);
@ -114,8 +114,9 @@ again:
*/
if (cbi && vcbi->server == cbi->server) {
write_seqlock(&vnode->cb_lock);
old = vnode->cb_interest;
vnode->cb_interest = cbi;
old = rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->cb_lock.lock));
rcu_assign_pointer(vnode->cb_interest, cbi);
write_sequnlock(&vnode->cb_lock);
afs_put_cb_interest(afs_v2net(vnode), old);
return 0;
@ -160,8 +161,9 @@ again:
*/
write_seqlock(&vnode->cb_lock);
old = vnode->cb_interest;
vnode->cb_interest = cbi;
old = rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->cb_lock.lock));
rcu_assign_pointer(vnode->cb_interest, cbi);
vnode->cb_s_break = cbi->server->cb_s_break;
vnode->cb_v_break = vnode->volume->cb_v_break;
clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
@ -191,10 +193,11 @@ void afs_put_cb_interest(struct afs_net *net, struct afs_cb_interest *cbi)
vi = NULL;
write_unlock(&cbi->server->cb_break_lock);
kfree(vi);
if (vi)
kfree_rcu(vi, rcu);
afs_put_server(net, cbi->server);
}
kfree(cbi);
kfree_rcu(cbi, rcu);
}
}

15
fs/afs/dir.c
View File

@ -638,11 +638,12 @@ static struct inode *afs_do_lookup(struct inode *dir, struct dentry *dentry,
struct key *key)
{
struct afs_lookup_cookie *cookie;
struct afs_cb_interest *cbi = NULL;
struct afs_cb_interest *dcbi, *cbi = NULL;
struct afs_super_info *as = dir->i_sb->s_fs_info;
struct afs_status_cb *scb;
struct afs_iget_data data;
struct afs_fs_cursor fc;
struct afs_server *server;
struct afs_vnode *dvnode = AFS_FS_I(dir);
struct inode *inode = NULL;
int ret, i;
@ -658,10 +659,14 @@ static struct inode *afs_do_lookup(struct inode *dir, struct dentry *dentry,
cookie->nr_fids = 1; /* slot 0 is saved for the fid we actually want */
read_seqlock_excl(&dvnode->cb_lock);
if (dvnode->cb_interest &&
dvnode->cb_interest->server &&
test_bit(AFS_SERVER_FL_NO_IBULK, &dvnode->cb_interest->server->flags))
cookie->one_only = true;
dcbi = rcu_dereference_protected(dvnode->cb_interest,
lockdep_is_held(&dvnode->cb_lock.lock));
if (dcbi) {
server = dcbi->server;
if (server &&
test_bit(AFS_SERVER_FL_NO_IBULK, &server->flags))
cookie->one_only = true;
}
read_sequnlock_excl(&dvnode->cb_lock);
for (i = 0; i < 50; i++)

79
fs/afs/inode.c
View File

@ -139,9 +139,10 @@ static int afs_inode_init_from_status(struct afs_vnode *vnode, struct key *key,
vnode->cb_expires_at = ktime_get_real_seconds();
} else {
vnode->cb_expires_at = scb->callback.expires_at;
old_cbi = vnode->cb_interest;
old_cbi = rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->cb_lock.lock));
if (cbi != old_cbi)
vnode->cb_interest = afs_get_cb_interest(cbi);
rcu_assign_pointer(vnode->cb_interest, afs_get_cb_interest(cbi));
else
old_cbi = NULL;
set_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
@ -245,9 +246,10 @@ static void afs_apply_callback(struct afs_fs_cursor *fc,
if (!afs_cb_is_broken(cb_break, vnode, fc->cbi)) {
vnode->cb_expires_at = cb->expires_at;
old = vnode->cb_interest;
old = rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->cb_lock.lock));
if (old != fc->cbi) {
vnode->cb_interest = afs_get_cb_interest(fc->cbi);
rcu_assign_pointer(vnode->cb_interest, afs_get_cb_interest(fc->cbi));
afs_put_cb_interest(afs_v2net(vnode), old);
}
set_bit(AFS_VNODE_CB_PROMISED, &vnode->flags);
@ -565,36 +567,46 @@ void afs_zap_data(struct afs_vnode *vnode)
*/
bool afs_check_validity(struct afs_vnode *vnode)
{
struct afs_cb_interest *cbi;
struct afs_server *server;
struct afs_volume *volume = vnode->volume;
time64_t now = ktime_get_real_seconds();
bool valid;
unsigned int cb_break, cb_s_break, cb_v_break;
int seq = 0;
/* Quickly check the callback state. Ideally, we'd use read_seqbegin
* here, but we have no way to pass the net namespace to the RCU
* cleanup for the server record.
*/
read_seqlock_excl(&vnode->cb_lock);
do {
read_seqbegin_or_lock(&vnode->cb_lock, &seq);
cb_v_break = READ_ONCE(volume->cb_v_break);
cb_break = vnode->cb_break;
if (test_bit(AFS_VNODE_CB_PROMISED, &vnode->flags)) {
if (vnode->cb_s_break != vnode->cb_interest->server->cb_s_break ||
vnode->cb_v_break != vnode->volume->cb_v_break) {
vnode->cb_s_break = vnode->cb_interest->server->cb_s_break;
vnode->cb_v_break = vnode->volume->cb_v_break;
valid = false;
} else if (test_bit(AFS_VNODE_ZAP_DATA, &vnode->flags)) {
valid = false;
} else if (vnode->cb_expires_at - 10 <= now) {
valid = false;
} else {
if (test_bit(AFS_VNODE_CB_PROMISED, &vnode->flags)) {
cbi = rcu_dereference(vnode->cb_interest);
server = rcu_dereference(cbi->server);
cb_s_break = READ_ONCE(server->cb_s_break);
if (vnode->cb_s_break != cb_s_break ||
vnode->cb_v_break != cb_v_break) {
vnode->cb_s_break = cb_s_break;
vnode->cb_v_break = cb_v_break;
valid = false;
} else if (test_bit(AFS_VNODE_ZAP_DATA, &vnode->flags)) {
valid = false;
} else if (vnode->cb_expires_at - 10 <= now) {
valid = false;
} else {
valid = true;
}
} else if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
valid = true;
} else {
vnode->cb_v_break = cb_v_break;
valid = false;
}
} else if (test_bit(AFS_VNODE_DELETED, &vnode->flags)) {
valid = true;
} else {
vnode->cb_v_break = vnode->volume->cb_v_break;
valid = false;
}
read_sequnlock_excl(&vnode->cb_lock);
} while (need_seqretry(&vnode->cb_lock, seq));
done_seqretry(&vnode->cb_lock, seq);
return valid;
}
@ -616,7 +628,9 @@ int afs_validate(struct afs_vnode *vnode, struct key *key)
vnode->fid.vid, vnode->fid.vnode, vnode->flags,
key_serial(key));
rcu_read_lock();
valid = afs_check_validity(vnode);
rcu_read_unlock();
if (test_bit(AFS_VNODE_DELETED, &vnode->flags))
clear_nlink(&vnode->vfs_inode);
@ -703,6 +717,7 @@ int afs_drop_inode(struct inode *inode)
*/
void afs_evict_inode(struct inode *inode)
{
struct afs_cb_interest *cbi;
struct afs_vnode *vnode;
vnode = AFS_FS_I(inode);
@ -719,10 +734,14 @@ void afs_evict_inode(struct inode *inode)
truncate_inode_pages_final(&inode->i_data);
clear_inode(inode);
if (vnode->cb_interest) {
afs_put_cb_interest(afs_i2net(inode), vnode->cb_interest);
vnode->cb_interest = NULL;
write_seqlock(&vnode->cb_lock);
cbi = rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->cb_lock.lock));
if (cbi) {
afs_put_cb_interest(afs_i2net(inode), cbi);
rcu_assign_pointer(vnode->cb_interest, NULL);
}
write_sequnlock(&vnode->cb_lock);
while (!list_empty(&vnode->wb_keys)) {
struct afs_wb_key *wbk = list_entry(vnode->wb_keys.next,

12
fs/afs/internal.h
View File

@ -554,7 +554,10 @@ struct afs_server {
struct afs_vol_interest {
struct hlist_node srv_link; /* Link in server->cb_volumes */
struct hlist_head cb_interests; /* List of callback interests on the server */
afs_volid_t vid; /* Volume ID to match */
union {
struct rcu_head rcu;
afs_volid_t vid; /* Volume ID to match */
};
unsigned int usage;
};
@ -566,7 +569,10 @@ struct afs_cb_interest {
struct afs_vol_interest *vol_interest;
struct afs_server *server; /* Server on which this interest resides */
struct super_block *sb; /* Superblock on which inodes reside */
afs_volid_t vid; /* Volume ID to match */
union {
struct rcu_head rcu;
afs_volid_t vid; /* Volume ID to match */
};
refcount_t usage;
};
@ -676,7 +682,7 @@ struct afs_vnode {
afs_lock_type_t lock_type : 8;
/* outstanding callback notification on this file */
struct afs_cb_interest *cb_interest; /* Server on which this resides */
struct afs_cb_interest __rcu *cb_interest; /* Server on which this resides */
unsigned int cb_s_break; /* Mass break counter on ->server */
unsigned int cb_v_break; /* Mass break counter on ->volume */
unsigned int cb_break; /* Break counter on vnode */

18
fs/afs/rotate.c
View File

@ -66,7 +66,8 @@ static bool afs_start_fs_iteration(struct afs_fs_cursor *fc,
fc->untried = (1UL << fc->server_list->nr_servers) - 1;
fc->index = READ_ONCE(fc->server_list->preferred);
cbi = vnode->cb_interest;
cbi = rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->io_lock));
if (cbi) {
/* See if the vnode's preferred record is still available */
for (i = 0; i < fc->server_list->nr_servers; i++) {
@ -87,8 +88,8 @@ static bool afs_start_fs_iteration(struct afs_fs_cursor *fc,
/* Note that the callback promise is effectively broken */
write_seqlock(&vnode->cb_lock);
ASSERTCMP(cbi, ==, vnode->cb_interest);
vnode->cb_interest = NULL;
ASSERTCMP(cbi, ==, rcu_access_pointer(vnode->cb_interest));
rcu_assign_pointer(vnode->cb_interest, NULL);
if (test_and_clear_bit(AFS_VNODE_CB_PROMISED, &vnode->flags))
vnode->cb_break++;
write_sequnlock(&vnode->cb_lock);
@ -417,7 +418,9 @@ selected_server:
if (error < 0)
goto failed_set_error;
fc->cbi = afs_get_cb_interest(vnode->cb_interest);
fc->cbi = afs_get_cb_interest(
rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->io_lock)));
read_lock(&server->fs_lock);
alist = rcu_dereference_protected(server->addresses,
@ -487,12 +490,15 @@ failed:
bool afs_select_current_fileserver(struct afs_fs_cursor *fc)
{
struct afs_vnode *vnode = fc->vnode;
struct afs_cb_interest *cbi = vnode->cb_interest;
struct afs_cb_interest *cbi;
struct afs_addr_list *alist;
int error = fc->ac.error;
_enter("");
cbi = rcu_dereference_protected(vnode->cb_interest,
lockdep_is_held(&vnode->io_lock));
switch (error) {
case SHRT_MAX:
if (!cbi) {
@ -501,7 +507,7 @@ bool afs_select_current_fileserver(struct afs_fs_cursor *fc)
return false;
}
fc->cbi = afs_get_cb_interest(vnode->cb_interest);
fc->cbi = afs_get_cb_interest(cbi);
read_lock(&cbi->server->fs_lock);
alist = rcu_dereference_protected(cbi->server->addresses,

8
fs/afs/security.c
View File

@ -146,7 +146,7 @@ void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
}
if (afs_cb_is_broken(cb_break, vnode,
vnode->cb_interest)) {
rcu_dereference(vnode->cb_interest))) {
changed = true;
break;
}
@ -176,7 +176,7 @@ void afs_cache_permit(struct afs_vnode *vnode, struct key *key,
}
}
if (afs_cb_is_broken(cb_break, vnode, vnode->cb_interest))
if (afs_cb_is_broken(cb_break, vnode, rcu_dereference(vnode->cb_interest)))
goto someone_else_changed_it;
/* We need a ref on any permits list we want to copy as we'll have to
@ -253,14 +253,16 @@ found:
kfree(new);
rcu_read_lock();
spin_lock(&vnode->lock);
zap = rcu_access_pointer(vnode->permit_cache);
if (!afs_cb_is_broken(cb_break, vnode, vnode->cb_interest) &&
if (!afs_cb_is_broken(cb_break, vnode, rcu_dereference(vnode->cb_interest)) &&
zap == permits)
rcu_assign_pointer(vnode->permit_cache, replacement);
else
zap = replacement;
spin_unlock(&vnode->lock);
rcu_read_unlock();
afs_put_permits(zap);
out_put:
afs_put_permits(permits);

4
fs/afs/super.c
View File

@ -677,7 +677,7 @@ static struct inode *afs_alloc_inode(struct super_block *sb)
vnode->volume = NULL;
vnode->lock_key = NULL;
vnode->permit_cache = NULL;
vnode->cb_interest = NULL;
RCU_INIT_POINTER(vnode->cb_interest, NULL);
#ifdef CONFIG_AFS_FSCACHE
vnode->cache = NULL;
#endif
@ -707,7 +707,7 @@ static void afs_destroy_inode(struct inode *inode)
_debug("DESTROY INODE %p", inode);
ASSERTCMP(vnode->cb_interest, ==, NULL);
ASSERTCMP(rcu_access_pointer(vnode->cb_interest), ==, NULL);
atomic_dec(&afs_count_active_inodes);
}