xfs: simplify xfs_map_blocks by using xfs_iext_lookup_extent directly

xfs_bmapi_read adds zero value in xfs_map_blocks.  Replace it with a
direct call to the low-level extent lookup function.

Note that we now always pass a 0 length to the trace points as we ask
for an unspecified len.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Brian Foster <bfoster@redhat.com>
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 5c5d8c8..0bfcc2d 100644 (file)
--- a/fs/xfs/xfs_aops.c
+++ b/fs/xfs/xfs_aops.c
@@ -375,7 +375,6 @@ xfs_map_blocks(
        int                     whichfork = XFS_DATA_FORK;
        struct xfs_iext_cursor  icur;
        int                     error = 0;
-       int                     nimaps = 1;
 
        if (XFS_FORCED_SHUTDOWN(mp))
                return -EIO;
@@ -431,24 +430,16 @@ xfs_map_blocks(
         * offset.  This will convert delayed allocations (including COW ones)
         * into real extents.
         */
-       error = xfs_bmapi_read(ip, offset_fsb, end_fsb - offset_fsb,
-                               &imap, &nimaps, XFS_BMAPI_ENTIRE);
+       if (!xfs_iext_lookup_extent(ip, &ip->i_df, offset_fsb, &icur, &imap))
+               imap.br_startoff = end_fsb;     /* fake a hole past EOF */
        xfs_iunlock(ip, XFS_ILOCK_SHARED);
-       if (error)
-               return error;
 
-       if (!nimaps) {
-               /*
-                * Lookup returns no match? Beyond eof? regardless,
-                * return it as a hole so we don't write it
-                */
+       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_blockcount = end_fsb - offset_fsb;
                imap.br_startblock = HOLESTARTBLOCK;
                wpc->io_type = XFS_IO_HOLE;
-       } else if (imap.br_startblock == HOLESTARTBLOCK) {
-               /* landed in a hole */
-               wpc->io_type = XFS_IO_HOLE;
        } else {
                if (isnullstartblock(imap.br_startblock)) {
                        /* got a delalloc extent */