xfs: regression fixes for 3.5-rc7

- Really fix a cursor leak in xfs_alloc_ag_vextent_near
  - Fix a performance regression related to doing allocation in workqueues
  - Prevent recursion in xfs_buf_iorequest which is causing stack overflows
  - Don't call xfs_bdstrat_cb in xfs_buf_iodone callbacks
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Merge tag 'for-linus-v3.5-rc7' of git://oss.sgi.com/xfs/xfs

Pull xfs regression fixes from Ben Myers:
 - Really fix a cursor leak in xfs_alloc_ag_vextent_near
 - Fix a performance regression related to doing allocation in
   workqueues
 - Prevent recursion in xfs_buf_iorequest which is causing stack
   overflows
 - Don't call xfs_bdstrat_cb in xfs_buf_iodone callbacks

* tag 'for-linus-v3.5-rc7' of git://oss.sgi.com/xfs/xfs:
  xfs: do not call xfs_bdstrat_cb in xfs_buf_iodone_callbacks
  xfs: prevent recursion in xfs_buf_iorequest
  xfs: don't defer metadata allocation to the workqueue
  xfs: really fix the cursor leak in xfs_alloc_ag_vextent_near

fs/xfs/xfs_alloc.c

@@ -1074,13 +1074,13 @@ restart:
 	 * If we couldn't get anything, give up.
 	 */
 	if (bno_cur_lt == NULL && bno_cur_gt == NULL) {
+		xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
+
 		if (!forced++) {
 			trace_xfs_alloc_near_busy(args);
 			xfs_log_force(args->mp, XFS_LOG_SYNC);
 			goto restart;
 		}
-
-		xfs_btree_del_cursor(cnt_cur, XFS_BTREE_NOERROR);
 		trace_xfs_alloc_size_neither(args);
 		args->agbno = NULLAGBLOCK;
 		return 0;
@@ -2434,13 +2434,22 @@ xfs_alloc_vextent_worker(
 	current_restore_flags_nested(&pflags, PF_FSTRANS);
 }
 
-
-int				/* error */
+/*
+ * Data allocation requests often come in with little stack to work on. Push
+ * them off to a worker thread so there is lots of stack to use. Metadata
+ * requests, OTOH, are generally from low stack usage paths, so avoid the
+ * context switch overhead here.
+ */
+int
 xfs_alloc_vextent(
-	xfs_alloc_arg_t	*args)	/* allocation argument structure */
+	struct xfs_alloc_arg	*args)
 {
 	DECLARE_COMPLETION_ONSTACK(done);
 
+	if (!args->userdata)
+		return __xfs_alloc_vextent(args);
+
+
 	args->done = &done;
 	INIT_WORK_ONSTACK(&args->work, xfs_alloc_vextent_worker);
 	queue_work(xfs_alloc_wq, &args->work);

fs/xfs/xfs_buf.c

@@ -989,27 +989,6 @@ xfs_buf_ioerror_alert(
 		(__uint64_t)XFS_BUF_ADDR(bp), func, bp->b_error, bp->b_length);
 }
 
-int
-xfs_bwrite(
-	struct xfs_buf		*bp)
-{
-	int			error;
-
-	ASSERT(xfs_buf_islocked(bp));
-
-	bp->b_flags |= XBF_WRITE;
-	bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q);
-
-	xfs_bdstrat_cb(bp);
-
-	error = xfs_buf_iowait(bp);
-	if (error) {
-		xfs_force_shutdown(bp->b_target->bt_mount,
-				   SHUTDOWN_META_IO_ERROR);
-	}
-	return error;
-}
-
 /*
  * Called when we want to stop a buffer from getting written or read.
  * We attach the EIO error, muck with its flags, and call xfs_buf_ioend
@@ -1079,14 +1058,7 @@ xfs_bioerror_relse(
 	return EIO;
 }
 
-
-/*
- * All xfs metadata buffers except log state machine buffers
- * get this attached as their b_bdstrat callback function.
- * This is so that we can catch a buffer
- * after prematurely unpinning it to forcibly shutdown the filesystem.
- */
-int
+STATIC int
 xfs_bdstrat_cb(
 	struct xfs_buf	*bp)
 {
@@ -1107,6 +1079,27 @@ xfs_bdstrat_cb(
 	return 0;
 }
 
+int
+xfs_bwrite(
+	struct xfs_buf		*bp)
+{
+	int			error;
+
+	ASSERT(xfs_buf_islocked(bp));
+
+	bp->b_flags |= XBF_WRITE;
+	bp->b_flags &= ~(XBF_ASYNC | XBF_READ | _XBF_DELWRI_Q);
+
+	xfs_bdstrat_cb(bp);
+
+	error = xfs_buf_iowait(bp);
+	if (error) {
+		xfs_force_shutdown(bp->b_target->bt_mount,
+				   SHUTDOWN_META_IO_ERROR);
+	}
+	return error;
+}
+
 /*
  * Wrapper around bdstrat so that we can stop data from going to disk in case
  * we are shutting down the filesystem.  Typically user data goes thru this
@@ -1243,7 +1236,7 @@ xfs_buf_iorequest(
 	 */
 	atomic_set(&bp->b_io_remaining, 1);
 	_xfs_buf_ioapply(bp);
-	_xfs_buf_ioend(bp, 0);
+	_xfs_buf_ioend(bp, 1);
 
 	xfs_buf_rele(bp);
 }

fs/xfs/xfs_buf.h

@@ -180,7 +180,6 @@ extern void xfs_buf_unlock(xfs_buf_t *);
 extern int xfs_bwrite(struct xfs_buf *bp);
 
 extern void xfsbdstrat(struct xfs_mount *, struct xfs_buf *);
-extern int xfs_bdstrat_cb(struct xfs_buf *);
 
 extern void xfs_buf_ioend(xfs_buf_t *,	int);
 extern void xfs_buf_ioerror(xfs_buf_t *, int);

fs/xfs/xfs_buf_item.c

@@ -954,7 +954,7 @@ xfs_buf_iodone_callbacks(
 
 		if (!XFS_BUF_ISSTALE(bp)) {
 			bp->b_flags |= XBF_WRITE | XBF_ASYNC | XBF_DONE;
-			xfs_bdstrat_cb(bp);
+			xfs_buf_iorequest(bp);
 		} else {
 			xfs_buf_relse(bp);
 		}