quota: Remove dq_wait_unused from dquot

Currently every dquot carries a wait_queue_head_t used only when we are
turning quotas off to wait for last users to drop dquot references.
Since such rare case is not performance sensitive in any means, just use
a global waitqueue for this and save space in struct dquot. Also convert
the logic to use wait_event() instead of open-coding it.

Signed-off-by: Jan Kara <jack@suse.cz>

1 files changed, 7 insertions, 10 deletions

diff --git a/fs/quota/dquot.c b/fs/quota/dquot.c
index 93adcdd6a260..361a2a6f13e1 100644
--- a/fs/quota/dquot.c
+++ b/fs/quota/dquot.c
@@ -126,6 +126,8 @@ __cacheline_aligned_in_smp DEFINE_SPINLOCK(dq_data_lock);
 EXPORT_SYMBOL(dq_data_lock);
 DEFINE_STATIC_SRCU(dquot_srcu);
 
+static DECLARE_WAIT_QUEUE_HEAD(dquot_ref_wq);
+
 void __quota_error(struct super_block *sb, const char *func,
 		   const char *fmt, ...)
 {
@@ -527,22 +529,18 @@ restart:
 			continue;
 		/* Wait for dquot users */
 		if (atomic_read(&dquot->dq_count)) {
-			DEFINE_WAIT(wait);
-
 			dqgrab(dquot);
-			prepare_to_wait(&dquot->dq_wait_unused, &wait,
-					TASK_UNINTERRUPTIBLE);
 			spin_unlock(&dq_list_lock);
-			/* Once dqput() wakes us up, we know it's time to free
+			/*
+			 * Once dqput() wakes us up, we know it's time to free
 			 * the dquot.
 			 * IMPORTANT: we rely on the fact that there is always
 			 * at most one process waiting for dquot to free.
 			 * Otherwise dq_count would be > 1 and we would never
 			 * wake up.
 			 */
-			if (atomic_read(&dquot->dq_count) > 1)
-				schedule();
-			finish_wait(&dquot->dq_wait_unused, &wait);
+			wait_event(dquot_ref_wq,
+				   atomic_read(&dquot->dq_count) == 1);
 			dqput(dquot);
 			/* At this moment dquot() need not exist (it could be
 			 * reclaimed by prune_dqcache(). Hence we must
@@ -754,7 +752,7 @@ we_slept:
 		/* Releasing dquot during quotaoff phase? */
 		if (!sb_has_quota_active(dquot->dq_sb, dquot->dq_id.type) &&
 		    atomic_read(&dquot->dq_count) == 1)
-			wake_up(&dquot->dq_wait_unused);
+			wake_up(&dquot_ref_wq);
 		spin_unlock(&dq_list_lock);
 		return;
 	}
@@ -809,7 +807,6 @@ static struct dquot *get_empty_dquot(struct super_block *sb, int type)
 	INIT_LIST_HEAD(&dquot->dq_inuse);
 	INIT_HLIST_NODE(&dquot->dq_hash);
 	INIT_LIST_HEAD(&dquot->dq_dirty);
-	init_waitqueue_head(&dquot->dq_wait_unused);
 	dquot->dq_sb = sb;
 	dquot->dq_id = make_kqid_invalid(type);
 	atomic_set(&dquot->dq_count, 1);