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fs: make insert_inode_locked() wait for inode destruction

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This is the only routine which instead skipped instead of waiting.

The current behavior is arguably a bug as it results in a corner case
where the inode hash can have *two* matching inodes, one of which is on
its way out.

Ironing out this difference is an incremental step towards sanitizing
the API.

Signed-off-by: Mateusz Guzik <mjguzik@gmail.com>
Link: https://patch.msgid.link/20260114094717.236202-1-mjguzik@gmail.com
Signed-off-by: Christian Brauner <brauner@kernel.org>
This commit is contained in:
Mateusz Guzik 2026-01-14 10:47:16 +01:00 committed by Christian Brauner
parent aaf7683961
commit 88ec797c46
No known key found for this signature in database
GPG Key ID: 91C61BC06578DCA2
1 changed files with 24 additions and 17 deletions
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41
fs/inode.c
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@ -1028,19 +1028,20 @@ long prune_icache_sb(struct super_block *sb, struct shrink_control *sc)
return freed; return freed;
} }
static void __wait_on_freeing_inode(struct inode *inode, bool is_inode_hash_locked); static void __wait_on_freeing_inode(struct inode *inode, bool hash_locked, bool rcu_locked);
/* /*
* Called with the inode lock held. * Called with the inode lock held.
*/ */
static struct inode *find_inode(struct super_block *sb, static struct inode *find_inode(struct super_block *sb,
struct hlist_head *head, struct hlist_head *head,
int (*test)(struct inode *, void *), int (*test)(struct inode *, void *),
void *data, bool is_inode_hash_locked, void *data, bool hash_locked,
bool *isnew) bool *isnew)
{ {
struct inode *inode = NULL; struct inode *inode = NULL;
if (is_inode_hash_locked) if (hash_locked)
lockdep_assert_held(&inode_hash_lock); lockdep_assert_held(&inode_hash_lock);
else else
lockdep_assert_not_held(&inode_hash_lock); lockdep_assert_not_held(&inode_hash_lock);
@ -1054,7 +1055,7 @@ static struct inode *find_inode(struct super_block *sb,
continue; continue;
spin_lock(&inode->i_lock); spin_lock(&inode->i_lock);
if (inode_state_read(inode) & (I_FREEING | I_WILL_FREE)) { if (inode_state_read(inode) & (I_FREEING | I_WILL_FREE)) {
__wait_on_freeing_inode(inode, is_inode_hash_locked); __wait_on_freeing_inode(inode, hash_locked, true);
goto repeat; goto repeat;
} }
if (unlikely(inode_state_read(inode) & I_CREATING)) { if (unlikely(inode_state_read(inode) & I_CREATING)) {
@ -1078,11 +1079,11 @@ static struct inode *find_inode(struct super_block *sb,
*/ */
static struct inode *find_inode_fast(struct super_block *sb, static struct inode *find_inode_fast(struct super_block *sb,
struct hlist_head *head, unsigned long ino, struct hlist_head *head, unsigned long ino,
bool is_inode_hash_locked, bool *isnew) bool hash_locked, bool *isnew)
{ {
struct inode *inode = NULL; struct inode *inode = NULL;
if (is_inode_hash_locked) if (hash_locked)
lockdep_assert_held(&inode_hash_lock); lockdep_assert_held(&inode_hash_lock);
else else
lockdep_assert_not_held(&inode_hash_lock); lockdep_assert_not_held(&inode_hash_lock);
@ -1096,7 +1097,7 @@ static struct inode *find_inode_fast(struct super_block *sb,
continue; continue;
spin_lock(&inode->i_lock); spin_lock(&inode->i_lock);
if (inode_state_read(inode) & (I_FREEING | I_WILL_FREE)) { if (inode_state_read(inode) & (I_FREEING | I_WILL_FREE)) {
__wait_on_freeing_inode(inode, is_inode_hash_locked); __wait_on_freeing_inode(inode, hash_locked, true);
goto repeat; goto repeat;
} }
if (unlikely(inode_state_read(inode) & I_CREATING)) { if (unlikely(inode_state_read(inode) & I_CREATING)) {
@ -1832,16 +1833,13 @@ int insert_inode_locked(struct inode *inode)
while (1) { while (1) {
struct inode *old = NULL; struct inode *old = NULL;
spin_lock(&inode_hash_lock); spin_lock(&inode_hash_lock);
repeat:
hlist_for_each_entry(old, head, i_hash) { hlist_for_each_entry(old, head, i_hash) {
if (old->i_ino != ino) if (old->i_ino != ino)
continue; continue;
if (old->i_sb != sb) if (old->i_sb != sb)
continue; continue;
spin_lock(&old->i_lock); spin_lock(&old->i_lock);
if (inode_state_read(old) & (I_FREEING | I_WILL_FREE)) {
spin_unlock(&old->i_lock);
continue;
}
break; break;
} }
if (likely(!old)) { if (likely(!old)) {
@ -1852,6 +1850,11 @@ int insert_inode_locked(struct inode *inode)
spin_unlock(&inode_hash_lock); spin_unlock(&inode_hash_lock);
return 0; return 0;
} }
if (inode_state_read(old) & (I_FREEING | I_WILL_FREE)) {
__wait_on_freeing_inode(old, true, false);
old = NULL;
goto repeat;
}
if (unlikely(inode_state_read(old) & I_CREATING)) { if (unlikely(inode_state_read(old) & I_CREATING)) {
spin_unlock(&old->i_lock); spin_unlock(&old->i_lock);
spin_unlock(&inode_hash_lock); spin_unlock(&inode_hash_lock);
@ -2504,16 +2507,18 @@ EXPORT_SYMBOL(inode_needs_sync);
* wake_up_bit(&inode->i_state, __I_NEW) after removing from the hash list * wake_up_bit(&inode->i_state, __I_NEW) after removing from the hash list
* will DTRT. * will DTRT.
*/ */
static void __wait_on_freeing_inode(struct inode *inode, bool is_inode_hash_locked) static void __wait_on_freeing_inode(struct inode *inode, bool hash_locked, bool rcu_locked)
{ {
struct wait_bit_queue_entry wqe; struct wait_bit_queue_entry wqe;
struct wait_queue_head *wq_head; struct wait_queue_head *wq_head;
VFS_BUG_ON(!hash_locked && !rcu_locked);
/* /*
* Handle racing against evict(), see that routine for more details. * Handle racing against evict(), see that routine for more details.
*/ */
if (unlikely(inode_unhashed(inode))) { if (unlikely(inode_unhashed(inode))) {
WARN_ON(is_inode_hash_locked); WARN_ON(hash_locked);
spin_unlock(&inode->i_lock); spin_unlock(&inode->i_lock);
return; return;
} }
@ -2521,14 +2526,16 @@ static void __wait_on_freeing_inode(struct inode *inode, bool is_inode_hash_lock
wq_head = inode_bit_waitqueue(&wqe, inode, __I_NEW); wq_head = inode_bit_waitqueue(&wqe, inode, __I_NEW);
prepare_to_wait_event(wq_head, &wqe.wq_entry, TASK_UNINTERRUPTIBLE); prepare_to_wait_event(wq_head, &wqe.wq_entry, TASK_UNINTERRUPTIBLE);
spin_unlock(&inode->i_lock); spin_unlock(&inode->i_lock);
rcu_read_unlock(); if (rcu_locked)
if (is_inode_hash_locked) rcu_read_unlock();
if (hash_locked)
spin_unlock(&inode_hash_lock); spin_unlock(&inode_hash_lock);
schedule(); schedule();
finish_wait(wq_head, &wqe.wq_entry); finish_wait(wq_head, &wqe.wq_entry);
if (is_inode_hash_locked) if (hash_locked)
spin_lock(&inode_hash_lock); spin_lock(&inode_hash_lock);
rcu_read_lock(); if (rcu_locked)
rcu_read_lock();
} }
static __initdata unsigned long ihash_entries; static __initdata unsigned long ihash_entries;