xfs: bugfixes for 3.7-rc7

- fix attr tree double split corruption
 - fix broken error handling in xfs_vm_writepage
 - drop buffer io reference when a bad bio is built
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Merge tag 'for-linus-v3.7-rc7' of git://oss.sgi.com/xfs/xfs

Pull xfs bugfixes from Ben Myers:

 - fix attr tree double split corruption

 - fix broken error handling in xfs_vm_writepage

 - drop buffer io reference when a bad bio is built

* tag 'for-linus-v3.7-rc7' of git://oss.sgi.com/xfs/xfs:
  xfs: drop buffer io reference when a bad bio is built
  xfs: fix broken error handling in xfs_vm_writepage
  xfs: fix attr tree double split corruption

fs/xfs/xfs_aops.c

@@ -481,11 +481,17 @@ static inline int bio_add_buffer(struct bio *bio, struct buffer_head *bh)
  *
  * The fix is two passes across the ioend list - one to start writeback on the
  * buffer_heads, and then submit them for I/O on the second pass.
+ *
+ * If @fail is non-zero, it means that we have a situation where some part of
+ * the submission process has failed after we have marked paged for writeback
+ * and unlocked them. In this situation, we need to fail the ioend chain rather
+ * than submit it to IO. This typically only happens on a filesystem shutdown.
  */
 STATIC void
 xfs_submit_ioend(
 	struct writeback_control *wbc,
-	xfs_ioend_t		*ioend)
+	xfs_ioend_t		*ioend,
+	int			fail)
 {
 	xfs_ioend_t		*head = ioend;
 	xfs_ioend_t		*next;
@@ -506,6 +512,18 @@ xfs_submit_ioend(
 		next = ioend->io_list;
 		bio = NULL;
 
+		/*
+		 * If we are failing the IO now, just mark the ioend with an
+		 * error and finish it. This will run IO completion immediately
+		 * as there is only one reference to the ioend at this point in
+		 * time.
+		 */
+		if (fail) {
+			ioend->io_error = -fail;
+			xfs_finish_ioend(ioend);
+			continue;
+		}
+
 		for (bh = ioend->io_buffer_head; bh; bh = bh->b_private) {
 
 			if (!bio) {
@@ -1060,7 +1078,18 @@ xfs_vm_writepage(
 
 	xfs_start_page_writeback(page, 1, count);
 
-	if (ioend && imap_valid) {
+	/* if there is no IO to be submitted for this page, we are done */
+	if (!ioend)
+		return 0;
+
+	ASSERT(iohead);
+
+	/*
+	 * Any errors from this point onwards need tobe reported through the IO
+	 * completion path as we have marked the initial page as under writeback
+	 * and unlocked it.
+	 */
+	if (imap_valid) {
 		xfs_off_t		end_index;
 
 		end_index = imap.br_startoff + imap.br_blockcount;
@@ -1079,20 +1108,15 @@ xfs_vm_writepage(
 				  wbc, end_index);
 	}
 
-	if (iohead) {
-		/*
-		 * Reserve log space if we might write beyond the on-disk
-		 * inode size.
-		 */
-		if (ioend->io_type != XFS_IO_UNWRITTEN &&
-		    xfs_ioend_is_append(ioend)) {
-			err = xfs_setfilesize_trans_alloc(ioend);
-			if (err)
-				goto error;
-		}
 
-		xfs_submit_ioend(wbc, iohead);
+	/*
-	}
+	 * Reserve log space if we might write beyond the on-disk inode size.
+	 */
+	err = 0;
+	if (ioend->io_type != XFS_IO_UNWRITTEN && xfs_ioend_is_append(ioend))
+		err = xfs_setfilesize_trans_alloc(ioend);
+
+	xfs_submit_ioend(wbc, iohead, err);
 
 	return 0;
 

fs/xfs/xfs_attr_leaf.c

@@ -1291,6 +1291,7 @@ xfs_attr_leaf_rebalance(xfs_da_state_t *state, xfs_da_state_blk_t *blk1,
 	leaf2 = blk2->bp->b_addr;
 	ASSERT(leaf1->hdr.info.magic == cpu_to_be16(XFS_ATTR_LEAF_MAGIC));
 	ASSERT(leaf2->hdr.info.magic == cpu_to_be16(XFS_ATTR_LEAF_MAGIC));
+	ASSERT(leaf2->hdr.count == 0);
 	args = state->args;
 
 	trace_xfs_attr_leaf_rebalance(args);
@@ -1361,6 +1362,7 @@ xfs_attr_leaf_rebalance(xfs_da_state_t *state, xfs_da_state_blk_t *blk1,
 		 * I assert that since all callers pass in an empty
 		 * second buffer, this code should never execute.
 		 */
+		ASSERT(0);
 
 		/*
 		 * Figure the total bytes to be added to the destination leaf.
@@ -1422,10 +1424,24 @@ xfs_attr_leaf_rebalance(xfs_da_state_t *state, xfs_da_state_blk_t *blk1,
 			args->index2 = 0;
 			args->blkno2 = blk2->blkno;
 		} else {
+			/*
+			 * On a double leaf split, the original attr location
+			 * is already stored in blkno2/index2, so don't
+			 * overwrite it overwise we corrupt the tree.
+			 */
 			blk2->index = blk1->index
 				    - be16_to_cpu(leaf1->hdr.count);
-			args->index = args->index2 = blk2->index;
+			args->index = blk2->index;
-			args->blkno = args->blkno2 = blk2->blkno;
+			args->blkno = blk2->blkno;
+			if (!state->extravalid) {
+				/*
+				 * set the new attr location to match the old
+				 * one and let the higher level split code
+				 * decide where in the leaf to place it.
+				 */
+				args->index2 = blk2->index;
+				args->blkno2 = blk2->blkno;
+			}
 		}
 	} else {
 		ASSERT(state->inleaf == 1);

fs/xfs/xfs_buf.c

@@ -1197,9 +1197,14 @@ xfs_buf_bio_end_io(
 {
 	xfs_buf_t		*bp = (xfs_buf_t *)bio->bi_private;
 
-	xfs_buf_ioerror(bp, -error);
+	/*
+	 * don't overwrite existing errors - otherwise we can lose errors on
+	 * buffers that require multiple bios to complete.
+	 */
+	if (!bp->b_error)
+		xfs_buf_ioerror(bp, -error);
 
-	if (!error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
+	if (!bp->b_error && xfs_buf_is_vmapped(bp) && (bp->b_flags & XBF_READ))
 		invalidate_kernel_vmap_range(bp->b_addr, xfs_buf_vmap_len(bp));
 
 	_xfs_buf_ioend(bp, 1);
@@ -1279,6 +1284,11 @@ next_chunk:
 		if (size)
 			goto next_chunk;
 	} else {
+		/*
+		 * This is guaranteed not to be the last io reference count
+		 * because the caller (xfs_buf_iorequest) holds a count itself.
+		 */
+		atomic_dec(&bp->b_io_remaining);
 		xfs_buf_ioerror(bp, EIO);
 		bio_put(bio);
 	}