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-rw-r--r--fs/quota/dquot.c66
-rw-r--r--include/linux/quota.h4
-rw-r--r--include/linux/quotaops.h2
3 files changed, 43 insertions, 29 deletions
diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 9e72bfe8bbad..31e897ad5e6a 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -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 @@ restart:
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);
/*
@@ -606,6 +602,15 @@ 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 @@ restart:
}
/* 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 @@ we_slept:
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)) {
diff --git a/include/linux/quota.h b/include/linux/quota.h
index fd692b4a41d5..07071e64abf3 100644
--- a/include/linux/quota.h
+++ b/include/linux/quota.h
@@ -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\
diff --git a/include/linux/quotaops.h b/include/linux/quotaops.h
index 11a4becff3a9..4fa4ef0a173a 100644
--- a/include/linux/quotaops.h
+++ b/include/linux/quotaops.h
@@ -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;
}