xfs: replace i_pin_wait with a bit waitqueue

Replace i_pin_wait, which is only used during synchronous inode flushing
with a bit waitqueue.  This trades off a much smaller inode against
slightly slower wakeup performance, and saves 12 (32-bit) or 20 (64-bit)
bytes in the XFS inode.

Reviewed-by: Alex Elder <aelder@sgi.com>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Ben Myers <bpm@sgi.com>

1 files changed, 21 insertions, 6 deletions

diff --git a/fs/xfs/xfs_inode.c b/fs/xfs/xfs_inode.c
index eeb60d31b08..62603369b52 100644
--- a/fs/xfs/xfs_inode.c
+++ b/fs/xfs/xfs_inode.c
@@ -2037,7 +2037,7 @@ xfs_idestroy_fork(
  * once someone is waiting for it to be unpinned.
  */
 static void
-xfs_iunpin_nowait(
+xfs_iunpin(
         struct xfs_inode        *ip)
 {
         ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL|XFS_ILOCK_SHARED));
@@ -2049,14 +2049,29 @@ xfs_iunpin_nowait(
 
 }
 
+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.wait, TASK_UNINTERRUPTIBLE);
+                if (xfs_ipincount(ip))
+                        io_schedule();
+        } while (xfs_ipincount(ip));
+        finish_wait(wq, &wait.wait);
+}
+
 void
 xfs_iunpin_wait(
         struct xfs_inode        *ip)
 {
-        if (xfs_ipincount(ip)) {
-                xfs_iunpin_nowait(ip);
-                wait_event(ip->i_ipin_wait, (xfs_ipincount(ip) == 0));
-        }
+        if (xfs_ipincount(ip))
+                __xfs_iunpin_wait(ip);
 }
 
 /*
@@ -2415,7 +2430,7 @@ xfs_iflush(
          * out for us if they occur after the log force completes.
          */
         if (!(flags & SYNC_WAIT) && xfs_ipincount(ip)) {
-                xfs_iunpin_nowait(ip);
+                xfs_iunpin(ip);
                 xfs_ifunlock(ip);
                 return EAGAIN;
         }