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Merge tag 'fs_for_v6.6-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs

Pull quota regression fix from Jan Kara.

* tag 'fs_for_v6.6-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/jack/linux-fs:
  quota: Fix slow quotaoff
This commit is contained in:
Linus Torvalds 2023-10-11 14:21:15 -07:00
commit 401644852d
3 changed files with 43 additions and 29 deletions
Show stats Download patch file Download diff file Expand all files Collapse all files

66
fs/quota/dquot.c
View file

@ -233,19 +233,18 @@ static void put_quota_format(struct quota_format_type *fmt)
* All dquots are placed to the end of inuse_list when first created, and this
* list is used for invalidate operation, which must look at every dquot.
*
* When the last reference of a dquot will be dropped, the dquot will be
* added to releasing_dquots. We'd then queue work item which would call
* When the last reference of a dquot is dropped, the dquot is added to
* releasing_dquots. We'll then queue work item which will call
* synchronize_srcu() and after that perform the final cleanup of all the
* dquots on the list. Both releasing_dquots and free_dquots use the
* dq_free list_head in the dquot struct. When a dquot is removed from
* releasing_dquots, a reference count is always subtracted, and if
* dq_count == 0 at that point, the dquot will be added to the free_dquots.
* dquots on the list. Each cleaned up dquot is moved to free_dquots list.
* Both releasing_dquots and free_dquots use the dq_free list_head in the dquot
* struct.
*
* Unused dquots (dq_count == 0) are added to the free_dquots list when freed,
* and this list is searched whenever we need an available dquot. Dquots are
* removed from the list as soon as they are used again, and
* dqstats.free_dquots gives the number of dquots on the list. When
* dquot is invalidated it's completely released from memory.
* Unused and cleaned up dquots are in the free_dquots list and this list is
* searched whenever we need an available dquot. Dquots are removed from the
* list as soon as they are used again and dqstats.free_dquots gives the number
* of dquots on the list. When dquot is invalidated it's completely released
* from memory.
*
* Dirty dquots are added to the dqi_dirty_list of quota_info when mark
* dirtied, and this list is searched when writing dirty dquots back to
@ -321,6 +320,7 @@ static inline void put_dquot_last(struct dquot *dquot)
static inline void put_releasing_dquots(struct dquot *dquot)
{
list_add_tail(&dquot->dq_free, &releasing_dquots);
set_bit(DQ_RELEASING_B, &dquot->dq_flags);
}
static inline void remove_free_dquot(struct dquot *dquot)
@ -328,8 +328,10 @@ static inline void remove_free_dquot(struct dquot *dquot)
if (list_empty(&dquot->dq_free))
return;
list_del_init(&dquot->dq_free);
if (!atomic_read(&dquot->dq_count))
if (!test_bit(DQ_RELEASING_B, &dquot->dq_flags))
dqstats_dec(DQST_FREE_DQUOTS);
else
clear_bit(DQ_RELEASING_B, &dquot->dq_flags);
}
static inline void put_inuse(struct dquot *dquot)
@ -581,12 +583,6 @@ static void invalidate_dquots(struct super_block *sb, int type)
continue;
/* Wait for dquot users */
if (atomic_read(&dquot->dq_count)) {
/* dquot in releasing_dquots, flush and retry */
if (!list_empty(&dquot->dq_free)) {
spin_unlock(&dq_list_lock);
goto restart;
}
atomic_inc(&dquot->dq_count);
spin_unlock(&dq_list_lock);
/*
@ -605,6 +601,15 @@ static void invalidate_dquots(struct super_block *sb, int type)
* restart. */
goto restart;
}
/*
* The last user already dropped its reference but dquot didn't
* get fully cleaned up yet. Restart the scan which flushes the
* work cleaning up released dquots.
*/
if (test_bit(DQ_RELEASING_B, &dquot->dq_flags)) {
spin_unlock(&dq_list_lock);
goto restart;
}
/*
* Quota now has no users and it has been written on last
* dqput()
@ -696,6 +701,13 @@ int dquot_writeback_dquots(struct super_block *sb, int type)
dq_dirty);
WARN_ON(!dquot_active(dquot));
/* If the dquot is releasing we should not touch it */
if (test_bit(DQ_RELEASING_B, &dquot->dq_flags)) {
spin_unlock(&dq_list_lock);
flush_delayed_work(&quota_release_work);
spin_lock(&dq_list_lock);
continue;
}
/* Now we have active dquot from which someone is
* holding reference so we can safely just increase
@ -809,18 +821,18 @@ static void quota_release_workfn(struct work_struct *work)
/* Exchange the list head to avoid livelock. */
list_replace_init(&releasing_dquots, &rls_head);
spin_unlock(&dq_list_lock);
synchronize_srcu(&dquot_srcu);
restart:
synchronize_srcu(&dquot_srcu);
spin_lock(&dq_list_lock);
while (!list_empty(&rls_head)) {
dquot = list_first_entry(&rls_head, struct dquot, dq_free);
/* Dquot got used again? */
if (atomic_read(&dquot->dq_count) > 1) {
remove_free_dquot(dquot);
atomic_dec(&dquot->dq_count);
continue;
}
WARN_ON_ONCE(atomic_read(&dquot->dq_count));
/*
* Note that DQ_RELEASING_B protects us from racing with
* invalidate_dquots() calls so we are safe to work with the
* dquot even after we drop dq_list_lock.
*/
if (dquot_dirty(dquot)) {
spin_unlock(&dq_list_lock);
/* Commit dquot before releasing */
@ -834,7 +846,6 @@ static void quota_release_workfn(struct work_struct *work)
}
/* Dquot is inactive and clean, now move it to free list */
remove_free_dquot(dquot);
atomic_dec(&dquot->dq_count);
put_dquot_last(dquot);
}
spin_unlock(&dq_list_lock);
@ -875,6 +886,7 @@ void dqput(struct dquot *dquot)
BUG_ON(!list_empty(&dquot->dq_free));
#endif
put_releasing_dquots(dquot);
atomic_dec(&dquot->dq_count);
spin_unlock(&dq_list_lock);
queue_delayed_work(system_unbound_wq, &quota_release_work, 1);
}
@ -963,7 +975,7 @@ struct dquot *dqget(struct super_block *sb, struct kqid qid)
dqstats_inc(DQST_LOOKUPS);
}
/* Wait for dq_lock - after this we know that either dquot_release() is
* already finished or it will be canceled due to dq_count > 1 test */
* already finished or it will be canceled due to dq_count > 0 test */
wait_on_dquot(dquot);
/* Read the dquot / allocate space in quota file */
if (!dquot_active(dquot)) {

4
include/linux/quota.h
View file

@ -285,7 +285,9 @@ static inline void dqstats_dec(unsigned int type)
#define DQ_FAKE_B 3 /* no limits only usage */
#define DQ_READ_B 4 /* dquot was read into memory */
#define DQ_ACTIVE_B 5 /* dquot is active (dquot_release not called) */
#define DQ_LASTSET_B 6 /* Following 6 bits (see QIF_) are reserved\
#define DQ_RELEASING_B 6 /* dquot is in releasing_dquots list waiting
* to be cleaned up */
#define DQ_LASTSET_B 7 /* Following 6 bits (see QIF_) are reserved\
* for the mask of entries set via SETQUOTA\
* quotactl. They are set under dq_data_lock\
* and the quota format handling dquot can\

2
include/linux/quotaops.h
View file

@ -57,7 +57,7 @@ static inline bool dquot_is_busy(struct dquot *dquot)
{
if (test_bit(DQ_MOD_B, &dquot->dq_flags))
return true;
if (atomic_read(&dquot->dq_count) > 1)
if (atomic_read(&dquot->dq_count) > 0)
return true;
return false;
}