[PATCH 3/9] XFS: use wait_var_event() when waiting of i_pincount.

[NeilBrown <neilb@suse.de>]

__xfs_iunpin_wait() is nearly an open-coded version of wait_var_event().
The bit XFS_IPINNED in ->i_flags is never used (not set, cleared,
or tested).  Its only role is in choosing a wait_queue.

The code is more transparent if we discard that flag bit and use
wait_var_event() to wait for the pincount to reach zero, which is
signalled by wake_up_var() - or more specifically
atomic_dec_and_wake_up_var()

In order to use io_schedule(), we actually use ___wait_var_event().

Signed-off-by: NeilBrown <neilb@suse.de>
---
 fs/xfs/xfs_inode.c      | 24 +++++-------------------
 fs/xfs/xfs_inode.h      |  2 --
 fs/xfs/xfs_inode_item.c |  3 +--
 3 files changed, 6 insertions(+), 23 deletions(-)

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index 7dc6f326936c..a855295363b5 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -1899,29 +1899,15 @@ xfs_iunpin(
 
 }
 
-static void
-__xfs_iunpin_wait(
-	struct xfs_inode	*ip)
-{
-	wait_queue_head_t *wq = bit_waitqueue(&ip->i_flags, __XFS_IPINNED_BIT);
-	DEFINE_WAIT_BIT(wait, &ip->i_flags, __XFS_IPINNED_BIT);
-
-	xfs_iunpin(ip);
-
-	do {
-		prepare_to_wait(wq, &wait.wq_entry, TASK_UNINTERRUPTIBLE);
-		if (xfs_ipincount(ip))
-			io_schedule();
-	} while (xfs_ipincount(ip));
-	finish_wait(wq, &wait.wq_entry);
-}
-
 void
 xfs_iunpin_wait(
 	struct xfs_inode	*ip)
 {
-	if (xfs_ipincount(ip))
-		__xfs_iunpin_wait(ip);
+	if (xfs_ipincount(ip)) {
+		xfs_iunpin(ip);
+		___wait_var_event(&ip->i_pincount, xfs_ipincount(ip) == 0,
+				  TASK_UNINTERRUPTIBLE, 0, 0, io_schedule());
+	}
 }
 
 /*
diff --git a/fs/xfs/xfs_inode.h b/fs/xfs/xfs_inode.h
index 51defdebef30..5062580034ec 100644
--- a/fs/xfs/xfs_inode.h
+++ b/fs/xfs/xfs_inode.h
@@ -337,8 +337,6 @@ static inline bool xfs_inode_has_bigrtalloc(struct xfs_inode *ip)
 #define XFS_ITRUNCATED		(1 << 5) /* truncated down so flush-on-close */
 #define XFS_IDIRTY_RELEASE	(1 << 6) /* dirty release already seen */
 #define XFS_IFLUSHING		(1 << 7) /* inode is being flushed */
-#define __XFS_IPINNED_BIT	8	 /* wakeup key for zero pin count */
-#define XFS_IPINNED		(1 << __XFS_IPINNED_BIT)
 #define XFS_IEOFBLOCKS		(1 << 9) /* has the preallocblocks tag set */
 #define XFS_NEED_INACTIVE	(1 << 10) /* see XFS_INACTIVATING below */
 /*
diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index b509cbd191f4..7fee751c7dfd 100644
--- a/fs/xfs/xfs_inode_item.c
+++ b/fs/xfs/xfs_inode_item.c
@@ -712,8 +712,7 @@ xfs_inode_item_unpin(
 	trace_xfs_inode_unpin(ip, _RET_IP_);
 	ASSERT(lip->li_buf || xfs_iflags_test(ip, XFS_ISTALE));
 	ASSERT(atomic_read(&ip->i_pincount) > 0);
-	if (atomic_dec_and_test(&ip->i_pincount))
-		wake_up_bit(&ip->i_flags, __XFS_IPINNED_BIT);
+	atomic_dec_and_wake_up_var(&ip->i_pincount);
 }
 
 STATIC uint
-- 
2.44.0