1 files changed, 167 insertions, 75 deletions

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 4b3f1b92cddd..532c4aab20f2 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -5404,6 +5404,120 @@ error0:
 }
 
 /*
+ * Determine whether an extent shift can be accomplished by a merge with the
+ * extent that precedes the target hole of the shift.
+ */
+STATIC bool
+xfs_bmse_can_merge(
+	struct xfs_bmbt_irec	*left,	/* preceding extent */
+	struct xfs_bmbt_irec	*got,	/* current extent to shift */
+	xfs_fileoff_t		shift)	/* shift fsb */
+{
+	xfs_fileoff_t		startoff;
+
+	startoff = got->br_startoff - shift;
+
+	/*
+	 * The extent, once shifted, must be adjacent in-file and on-disk with
+	 * the preceding extent.
+	 */
+	if ((left->br_startoff + left->br_blockcount != startoff) ||
+	    (left->br_startblock + left->br_blockcount != got->br_startblock) ||
+	    (left->br_state != got->br_state) ||
+	    (left->br_blockcount + got->br_blockcount > MAXEXTLEN))
+		return false;
+
+	return true;
+}
+
+/*
+ * A bmap extent shift adjusts the file offset of an extent to fill a preceding
+ * hole in the file. If an extent shift would result in the extent being fully
+ * adjacent to the extent that currently precedes the hole, we can merge with
+ * the preceding extent rather than do the shift.
+ *
+ * This function assumes the caller has verified a shift-by-merge is possible
+ * with the provided extents via xfs_bmse_can_merge().
+ */
+STATIC int
+xfs_bmse_merge(
+	struct xfs_inode		*ip,
+	int				whichfork,
+	xfs_fileoff_t			shift,		/* shift fsb */
+	int				current_ext,	/* idx of gotp */
+	struct xfs_bmbt_rec_host	*gotp,		/* extent to shift */
+	struct xfs_bmbt_rec_host	*leftp,		/* preceding extent */
+	struct xfs_btree_cur		*cur,
+	int				*logflags)	/* output */
+{
+	struct xfs_ifork		*ifp;
+	struct xfs_bmbt_irec		got;
+	struct xfs_bmbt_irec		left;
+	xfs_filblks_t			blockcount;
+	int				error, i;
+
+	ifp = XFS_IFORK_PTR(ip, whichfork);
+	xfs_bmbt_get_all(gotp, &got);
+	xfs_bmbt_get_all(leftp, &left);
+	blockcount = left.br_blockcount + got.br_blockcount;
+
+	ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
+	ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
+	ASSERT(xfs_bmse_can_merge(&left, &got, shift));
+
+	/*
+	 * Merge the in-core extents. Note that the host record pointers and
+	 * current_ext index are invalid once the extent has been removed via
+	 * xfs_iext_remove().
+	 */
+	xfs_bmbt_set_blockcount(leftp, blockcount);
+	xfs_iext_remove(ip, current_ext, 1, 0);
+
+	/*
+	 * Update the on-disk extent count, the btree if necessary and log the
+	 * inode.
+	 */
+	XFS_IFORK_NEXT_SET(ip, whichfork,
+			   XFS_IFORK_NEXTENTS(ip, whichfork) - 1);
+	*logflags |= XFS_ILOG_CORE;
+	if (!cur) {
+		*logflags |= XFS_ILOG_DEXT;
+		return 0;
+	}
+
+	/* lookup and remove the extent to merge */
+	error = xfs_bmbt_lookup_eq(cur, got.br_startoff, got.br_startblock,
+				   got.br_blockcount, &i);
+	if (error)
+		goto out_error;
+	XFS_WANT_CORRUPTED_GOTO(i == 1, out_error);
+
+	error = xfs_btree_delete(cur, &i);
+	if (error)
+		goto out_error;
+	XFS_WANT_CORRUPTED_GOTO(i == 1, out_error);
+
+	/* lookup and update size of the previous extent */
+	error = xfs_bmbt_lookup_eq(cur, left.br_startoff, left.br_startblock,
+				   left.br_blockcount, &i);
+	if (error)
+		goto out_error;
+	XFS_WANT_CORRUPTED_GOTO(i == 1, out_error);
+
+	left.br_blockcount = blockcount;
+
+	error = xfs_bmbt_update(cur, left.br_startoff, left.br_startblock,
+				left.br_blockcount, left.br_state);
+	if (error)
+		goto out_error;
+
+	return 0;
+
+out_error:
+	return error;
+}
+
+/*
  * Shift extent records to the left to cover a hole.
  *
  * The maximum number of extents to be shifted in a single operation is
@@ -5427,6 +5541,7 @@ xfs_bmap_shift_extents(
 {
 	struct xfs_btree_cur		*cur = NULL;
 	struct xfs_bmbt_rec_host	*gotp;
+	struct xfs_bmbt_rec_host	*leftp;
 	struct xfs_bmbt_irec            got;
 	struct xfs_bmbt_irec		left;
 	struct xfs_mount		*mp = ip->i_mount;
@@ -5438,7 +5553,6 @@ xfs_bmap_shift_extents(
 	int				i;
 	int				whichfork = XFS_DATA_FORK;
 	int				logflags = 0;
-	xfs_filblks_t			blockcount = 0;
 	int				total_extents;
 
 	if (unlikely(XFS_TEST_ERROR(
@@ -5464,6 +5578,13 @@ xfs_bmap_shift_extents(
 			return error;
 	}
 
+	if (ifp->if_flags & XFS_IFBROOT) {
+		cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
+		cur->bc_private.b.firstblock = *firstblock;
+		cur->bc_private.b.flist = flist;
+		cur->bc_private.b.flags = 0;
+	}
+
 	/*
 	 * Look up the extent index for the fsb where we start shifting. We can
 	 * henceforth iterate with current_ext as extent list changes are locked
@@ -5476,14 +5597,17 @@ xfs_bmap_shift_extents(
 	gotp = xfs_iext_bno_to_ext(ifp, start_fsb, &current_ext);
 	if (!gotp) {
 		*done = 1;
-		return 0;
+		goto del_cursor;
 	}
+	xfs_bmbt_get_all(gotp, &got);
 
-	if (ifp->if_flags & XFS_IFBROOT) {
-		cur = xfs_bmbt_init_cursor(mp, tp, ip, whichfork);
-		cur->bc_private.b.firstblock = *firstblock;
-		cur->bc_private.b.flist = flist;
-		cur->bc_private.b.flags = 0;
+	/*
+	 * If the first extent is shifted, offset_shift_fsb cannot be larger
+	 * than the starting offset of the first extent.
+	 */
+	if (current_ext == 0 && got.br_startoff < offset_shift_fsb) {
+		error = -EINVAL;
+		goto del_cursor;
 	}
 
 	/*
@@ -5493,30 +5617,41 @@ xfs_bmap_shift_extents(
 	 */
 	total_extents = ifp->if_bytes / sizeof(xfs_bmbt_rec_t);
 	while (nexts++ < num_exts && current_ext < total_extents) {
-
-		gotp = xfs_iext_get_ext(ifp, current_ext);
-		xfs_bmbt_get_all(gotp, &got);
 		startoff = got.br_startoff - offset_shift_fsb;
 
-		/*
-		 * Before shifting extent into hole, make sure that the hole is
-		 * large enough to accommodate the shift.
-		 */
+		/* grab the left extent and check for a potential merge */
 		if (current_ext > 0) {
-			xfs_bmbt_get_all(xfs_iext_get_ext(ifp, current_ext - 1),
-					 &left);
-			if (startoff < left.br_startoff + left.br_blockcount)
+			leftp = xfs_iext_get_ext(ifp, current_ext - 1);
+			xfs_bmbt_get_all(leftp, &left);
+
+			/* make sure hole is large enough for shift */
+			if (startoff < left.br_startoff + left.br_blockcount) {
 				error = -EINVAL;
-		} else if (offset_shift_fsb > got.br_startoff) {
-			/*
-			 * When first extent is shifted, offset_shift_fsb should
-			 * be less than the stating offset of the first extent.
-			 */
-			error = -EINVAL;
+				goto del_cursor;
+			}
+
+			if (xfs_bmse_can_merge(&left, &got, offset_shift_fsb)) {
+				error = xfs_bmse_merge(ip, whichfork,
+						offset_shift_fsb, current_ext, gotp,
+						leftp, cur, &logflags);
+				if (error)
+					goto del_cursor;
+
+				/*
+				 * The extent was merged so adjust the extent
+				 * index and move onto the next.
+				 */
+				current_ext--;
+				goto next;
+			}
 		}
-		if (error)
-			goto del_cursor;
 
+		/*
+		 * We didn't merge the extent so do the shift. Update the start
+		 * offset in the in-core extent and btree, if necessary.
+		 */
+		xfs_bmbt_set_startoff(gotp, startoff);
+		logflags |= XFS_ILOG_CORE;
 		if (cur) {
 			error = xfs_bmbt_lookup_eq(cur, got.br_startoff,
 						   got.br_startblock,
@@ -5525,53 +5660,8 @@ xfs_bmap_shift_extents(
 			if (error)
 				goto del_cursor;
 			XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
-		}
-
-		/* Check if we can merge 2 adjacent extents */
-		if (current_ext &&
-		    left.br_startoff + left.br_blockcount == startoff &&
-		    left.br_startblock + left.br_blockcount ==
-				got.br_startblock &&
-		    left.br_state == got.br_state &&
-		    left.br_blockcount + got.br_blockcount <= MAXEXTLEN) {
-			blockcount = left.br_blockcount +
-				got.br_blockcount;
-			xfs_iext_remove(ip, current_ext, 1, 0);
-			logflags |= XFS_ILOG_CORE;
-			if (cur) {
-				error = xfs_btree_delete(cur, &i);
-				if (error)
-					goto del_cursor;
-				XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
-			} else {
-				logflags |= XFS_ILOG_DEXT;
-			}
-			XFS_IFORK_NEXT_SET(ip, whichfork,
-				XFS_IFORK_NEXTENTS(ip, whichfork) - 1);
-			gotp = xfs_iext_get_ext(ifp, --current_ext);
-			xfs_bmbt_get_all(gotp, &got);
-
-			/* Make cursor point to the extent we will update */
-			if (cur) {
-				error = xfs_bmbt_lookup_eq(cur, got.br_startoff,
-							   got.br_startblock,
-							   got.br_blockcount,
-							   &i);
-				if (error)
-					goto del_cursor;
-				XFS_WANT_CORRUPTED_GOTO(i == 1, del_cursor);
-			}
 
-			xfs_bmbt_set_blockcount(gotp, blockcount);
-			got.br_blockcount = blockcount;
-		} else {
-			/* We have to update the startoff */
-			xfs_bmbt_set_startoff(gotp, startoff);
 			got.br_startoff = startoff;
-		}
-
-		logflags |= XFS_ILOG_CORE;
-		if (cur) {
 			error = xfs_bmbt_update(cur, got.br_startoff,
 						got.br_startblock,
 						got.br_blockcount,
@@ -5582,18 +5672,20 @@ xfs_bmap_shift_extents(
 			logflags |= XFS_ILOG_DEXT;
 		}
 
-		current_ext++;
+next:
+		/* update total extent count and grab the next record */
 		total_extents = ifp->if_bytes / sizeof(xfs_bmbt_rec_t);
+		if (++current_ext >= total_extents)
+			break;
+		gotp = xfs_iext_get_ext(ifp, current_ext);
+		xfs_bmbt_get_all(gotp, &got);
 	}
 
 	/* Check if we are done */
 	if (current_ext == total_extents)
 		*done = 1;
-	else if (next_fsb) {
-		gotp = xfs_iext_get_ext(ifp, current_ext);
-		xfs_bmbt_get_all(gotp, &got);
+	else if (next_fsb)
 		*next_fsb = got.br_startoff;
-	}
 
 del_cursor:
 	if (cur)