[XFS] replace the XFS buf iodone semaphore with a completion

The xfs_buf_t b_iodonesema is really just a semaphore that wants to be a
completion. Change it to a completion and remove the last user of the
sema_t from XFS.

SGI-PV: 981498

SGI-Modid: xfs-linux-melb:xfs-kern:31815a

Signed-off-by: David Chinner <david@fromorbit.com>
Signed-off-by: Lachlan McIlroy <lachlan@sgi.com>

fs/xfs/linux-2.6/xfs_buf.c

@@ -253,7 +253,7 @@ _xfs_buf_initialize(
 
 	memset(bp, 0, sizeof(xfs_buf_t));
 	atomic_set(&bp->b_hold, 1);
-	init_MUTEX_LOCKED(&bp->b_iodonesema);
+	init_completion(&bp->b_iowait);
 	INIT_LIST_HEAD(&bp->b_list);
 	INIT_LIST_HEAD(&bp->b_hash_list);
 	init_MUTEX_LOCKED(&bp->b_sema); /* held, no waiters */
@@ -1033,7 +1033,7 @@ xfs_buf_ioend(
 			xfs_buf_iodone_work(&bp->b_iodone_work);
 		}
 	} else {
-		up(&bp->b_iodonesema);
+		complete(&bp->b_iowait);
 	}
 }
 
@@ -1271,7 +1271,7 @@ xfs_buf_iowait(
 	XB_TRACE(bp, "iowait", 0);
 	if (atomic_read(&bp->b_io_remaining))
 		blk_run_address_space(bp->b_target->bt_mapping);
-	down(&bp->b_iodonesema);
+	wait_for_completion(&bp->b_iowait);
 	XB_TRACE(bp, "iowaited", (long)bp->b_error);
 	return bp->b_error;
 }

fs/xfs/linux-2.6/xfs_buf.h

@@ -157,7 +157,7 @@ typedef struct xfs_buf {
 	xfs_buf_iodone_t	b_iodone;	/* I/O completion function */
 	xfs_buf_relse_t		b_relse;	/* releasing function */
 	xfs_buf_bdstrat_t	b_strat;	/* pre-write function */
-	struct semaphore	b_iodonesema;	/* Semaphore for I/O waiters */
+	struct completion	b_iowait;	/* queue for I/O waiters */
 	void			*b_fspriv;
 	void			*b_fspriv2;
 	void			*b_fspriv3;
@@ -352,7 +352,7 @@ extern void xfs_buf_trace(xfs_buf_t *, char *, void *, void *);
 #define XFS_BUF_CPSEMA(bp)	(xfs_buf_cond_lock(bp) == 0)
 #define XFS_BUF_VSEMA(bp)	xfs_buf_unlock(bp)
 #define XFS_BUF_PSEMA(bp,x)	xfs_buf_lock(bp)
-#define XFS_BUF_V_IODONESEMA(bp) up(&bp->b_iodonesema);
+#define XFS_BUF_FINISH_IOWAIT(bp)	complete(&bp->b_iowait);
 
 #define XFS_BUF_SET_TARGET(bp, target)	((bp)->b_target = (target))
 #define XFS_BUF_TARGET(bp)		((bp)->b_target)

fs/xfs/xfs_buf_item.c

@@ -1056,7 +1056,7 @@ xfs_buf_iodone_callbacks(
 			   anyway. */
 			XFS_BUF_SET_BRELSE_FUNC(bp,xfs_buf_error_relse);
 			XFS_BUF_DONE(bp);
-			XFS_BUF_V_IODONESEMA(bp);
+			XFS_BUF_FINISH_IOWAIT(bp);
 		}
 		return;
 	}

fs/xfs/xfs_rw.c

@@ -314,7 +314,7 @@ xfs_bioerror_relse(
 		 * ASYNC buffers.
 		 */
 		XFS_BUF_ERROR(bp, EIO);
-		XFS_BUF_V_IODONESEMA(bp);
+		XFS_BUF_FINISH_IOWAIT(bp);
 	} else {
 		xfs_buf_relse(bp);
 	}