xfs: also truncate holes covered by COW blocks

This only matters if we want to write data through the COW fork that is
not actually an overwrite of existing data.  Reasons for that are
speculative COW fork allocations using the cowextsize, or a mode where
we always write through the COW fork.  Currently both can't actually
happen, but I plan to enable them.

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>

diff --git a/fs/xfs/xfs_aops.c b/fs/xfs/xfs_aops.c
index 2ed8733eca49ef492e0172b5887e8e19b2dac193..983d11c27d3299908bbca6e66b79566ea53ad869 100644 (file)
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -447,28 +447,29 @@ retry:
 
        wpc->fork = XFS_DATA_FORK;
 
+       /* landed in a hole or beyond EOF? */
        if (imap.br_startoff > offset_fsb) {
-               /* landed in a hole or beyond EOF */
                imap.br_blockcount = imap.br_startoff - offset_fsb;
                imap.br_startoff = offset_fsb;
                imap.br_startblock = HOLESTARTBLOCK;
                imap.br_state = XFS_EXT_NORM;
-       } else {
-               /*
-                * Truncate to the next COW extent if there is one.  This is the
-                * only opportunity to do this because we can skip COW fork
-                * lookups for the subsequent blocks in the mapping; however,
-                * the requirement to treat the COW range separately remains.
-                */
-               if (cow_fsb != NULLFILEOFF &&
-                   cow_fsb < imap.br_startoff + imap.br_blockcount)
-                       imap.br_blockcount = cow_fsb - imap.br_startoff;
-
-               /* got a delalloc extent? */
-               if (isnullstartblock(imap.br_startblock))
-                       goto allocate_blocks;
        }
 
+       /*
+        * Truncate to the next COW extent if there is one.  This is the only
+        * opportunity to do this because we can skip COW fork lookups for the
+        * subsequent blocks in the mapping; however, the requirement to treat
+        * the COW range separately remains.
+        */
+       if (cow_fsb != NULLFILEOFF &&
+           cow_fsb < imap.br_startoff + imap.br_blockcount)
+               imap.br_blockcount = cow_fsb - imap.br_startoff;
+
+       /* got a delalloc extent? */
+       if (imap.br_startblock != HOLESTARTBLOCK &&
+           isnullstartblock(imap.br_startblock))
+               goto allocate_blocks;
+
        wpc->imap = imap;
        trace_xfs_map_blocks_found(ip, offset, count, wpc->fork, &imap);
        return 0;