xfs: move some code around inside xfs_bmap_shift_extents

For the first right move we need to look up next_fsb.  That means
our last fsb that contains next_fsb must also be the current extent,
so take advantage of that by moving the code around a bit.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Darrick J. Wong <darrick.wong@oracle.com>
Signed-off-by: Darrick J. Wong <darrick.wong@oracle.com>

1 files changed, 29 insertions, 25 deletions

diff --git a/fs/xfs/libxfs/xfs_bmap.c b/fs/xfs/libxfs/xfs_bmap.c
index 99b5fa5c4b8d..e529bed6be41 100644
--- a/fs/xfs/libxfs/xfs_bmap.c
+++ b/fs/xfs/libxfs/xfs_bmap.c
@@ -6127,7 +6127,6 @@ xfs_bmap_shift_extents(
         ASSERT(xfs_isilocked(ip, XFS_IOLOCK_EXCL));
         ASSERT(xfs_isilocked(ip, XFS_ILOCK_EXCL));
         ASSERT(direction == SHIFT_LEFT || direction == SHIFT_RIGHT);
-        ASSERT(*next_fsb != NULLFSBLOCK || direction == SHIFT_RIGHT);
 
         ifp = XFS_IFORK_PTR(ip, whichfork);
         if (!(ifp->if_flags & XFS_IFEXTENTS)) {
@@ -6159,43 +6158,48 @@ xfs_bmap_shift_extents(
          * In case of first right shift, we need to initialize next_fsb
          */
         if (*next_fsb == NULLFSBLOCK) {
-                gotp = xfs_iext_get_ext(ifp, total_extents - 1);
+                ASSERT(direction == SHIFT_RIGHT);
+
+                current_ext = total_extents - 1;
+                gotp = xfs_iext_get_ext(ifp, current_ext);
                 xfs_bmbt_get_all(gotp, &got);
                 *next_fsb = got.br_startoff;
                 if (stop_fsb > *next_fsb) {
                         *done = 1;
                         goto del_cursor;
                 }
+        } else {
+                /*
+                 * 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
+                 * out via ilock.
+                 *
+                 * gotp can be null in 2 cases: 1) if there are no extents or 2)
+                 * *next_fsb lies in a hole beyond which there are no extents. Either
+                 * way, we are done.
+                 */
+                gotp = xfs_iext_bno_to_ext(ifp, *next_fsb, &current_ext);
+                if (!gotp) {
+                        *done = 1;
+                        goto del_cursor;
+                }
         }
 
         /* Lookup the extent index at which we have to stop */
         if (direction == SHIFT_RIGHT) {
-                gotp = xfs_iext_bno_to_ext(ifp, stop_fsb, &stop_extent);
+                xfs_iext_bno_to_ext(ifp, stop_fsb, &stop_extent);
                 /* Make stop_extent exclusive of shift range */
                 stop_extent--;
-        } else
+                if (current_ext <= stop_extent) {
+                        error = -EIO;
+                        goto del_cursor;
+                }
+        } else {
                 stop_extent = total_extents;
-
-        /*
-         * 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
-         * out via ilock.
-         *
-         * gotp can be null in 2 cases: 1) if there are no extents or 2)
-         * *next_fsb lies in a hole beyond which there are no extents. Either
-         * way, we are done.
-         */
-        gotp = xfs_iext_bno_to_ext(ifp, *next_fsb, &current_ext);
-        if (!gotp) {
-                *done = 1;
-                goto del_cursor;
-        }
-
-        /* some sanity checking before we finally start shifting extents */
-        if ((direction == SHIFT_LEFT && current_ext >= stop_extent) ||
-             (direction == SHIFT_RIGHT && current_ext <= stop_extent)) {
-                error = -EIO;
-                goto del_cursor;
+                if (current_ext >= stop_extent) {
+                        error = -EIO;
+                        goto del_cursor;
+                }
         }
 
         while (nexts++ < num_exts) {