xfs: replace i_flock with a sleeping bitlock

We almost never block on i_flock, the exception is synchronous inode
flushing.  Instead of bloating the inode with a 16/24-byte completion
that we abuse as a semaphore just implement it as a bitlock that uses
a bit waitqueue for the rare sleeping path.  This primarily is a
tradeoff between a much smaller inode and a faster non-blocking
path vs faster wakeups, and we are much better off with the former.

A small downside is that we will lose lockdep checking for i_flock, but
given that it's always taken inside the ilock that should be acceptable.

Note that for example the inode writeback locking is implemented in a
very similar way.

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

1 files changed, 2 insertions, 2 deletions

diff --git a/fs/xfs/xfs_inode_item.c b/fs/xfs/xfs_inode_item.c
index 2b6b4fcef49e..c8d4ce0efd5a 100644
--- a/fs/xfs/xfs_inode_item.c
+++ b/fs/xfs/xfs_inode_item.c
@@ -717,7 +717,7 @@ xfs_inode_item_pushbuf(
          * If a flush is not in progress anymore, chances are that the
          * inode was taken off the AIL. So, just get out.
          */
-        if (completion_done(&ip->i_flush) ||
+        if (!xfs_isiflocked(ip) ||
             !(lip->li_flags & XFS_LI_IN_AIL)) {
                 xfs_iunlock(ip, XFS_ILOCK_SHARED);
                 return true;
@@ -750,7 +750,7 @@ xfs_inode_item_push(
         struct xfs_inode        *ip = iip->ili_inode;
 
         ASSERT(xfs_isilocked(ip, XFS_ILOCK_SHARED));
-        ASSERT(!completion_done(&ip->i_flush));
+        ASSERT(xfs_isiflocked(ip));
 
         /*
          * Since we were able to lock the inode's flush lock and