diff options
Diffstat (limited to 'fs/quota/dquot.c')
| -rw-r--r-- | fs/quota/dquot.c | 66 |
1 files changed, 39 insertions, 27 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("a_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, "a_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)) { |