xfs: accumulate iextent records when checking bmap

Source kernel commit: 634d4a79e76691020ba73f50416da37a30779e9e

Currently, the bmap scrubber checks file fork mappings individually.  In
the case that the file uses multiple mappings to a single contiguous
piece of space, the scrubber repeatedly locks the AG to check the
existence of a reverse mapping that overlaps this file mapping.  If the
reverse mapping starts before or ends after the mapping we're checking,
it will also crawl around in the bmbt checking correspondence for
adjacent extents.

This is not very time efficient because it does the crawling while
holding the AGF buffer, and checks the middle mappings multiple times.
Instead, create a custom iextent record iterator function that combines
multiple adjacent allocated mappings into one large incore bmbt record.
This is feasible because the incore bmbt record length is 64-bits wide.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Dave Chinner <dchinner@redhat.com>
Signed-off-by: Carlos Maiolino <cem@kernel.org>

diff --git a/libxfs/xfs_bmap.h b/libxfs/xfs_bmap.h
index 9ff030d1298157c19322021fddc7dcc0cfd0db35..e33470e39728d58fec33907f34860db700634d12 100644 (file)
--- a/libxfs/xfs_bmap.h
+++ b/libxfs/xfs_bmap.h
@@ -145,7 +145,7 @@ static inline int xfs_bmapi_whichfork(uint32_t bmapi_flags)
        { BMAP_COWFORK,         "COW" }
 
 /* Return true if the extent is an allocated extent, written or not. */
-static inline bool xfs_bmap_is_real_extent(struct xfs_bmbt_irec *irec)
+static inline bool xfs_bmap_is_real_extent(const struct xfs_bmbt_irec *irec)
 {
        return irec->br_startblock != HOLESTARTBLOCK &&
                irec->br_startblock != DELAYSTARTBLOCK &&