xfs: clean up mapping size calculation in __xfs_get_blocks

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Alex Elder <aelder@sgi.com>

1 files changed, 16 insertions, 9 deletions

diff --git a/fs/xfs/linux-2.6/xfs_aops.c b/fs/xfs/linux-2.6/xfs_aops.c
index 6feecd279470..1d51bdde5748 100644
--- a/fs/xfs/linux-2.6/xfs_aops.c
+++ b/fs/xfs/linux-2.6/xfs_aops.c
@@ -1536,16 +1536,23 @@ __xfs_get_blocks(
                 }
         }
 
+        /*
+         * If this is O_DIRECT or the mpage code calling tell them how large
+         * the mapping is, so that we can avoid repeated get_blocks calls.
+         */
         if (direct || size > (1 << inode->i_blkbits)) {
-                struct xfs_mount        *mp = XFS_I(inode)->i_mount;
-                xfs_off_t               iomap_offset = XFS_FSB_TO_B(mp, imap.br_startoff);
-                xfs_off_t               iomap_delta = offset - iomap_offset;
-                xfs_off_t               iomap_bsize = XFS_FSB_TO_B(mp, imap.br_blockcount);
-
-                ASSERT(iomap_bsize - iomap_delta > 0);
-                offset = min_t(xfs_off_t,
-                                iomap_bsize - iomap_delta, size);
-                bh_result->b_size = (ssize_t)min_t(xfs_off_t, LONG_MAX, offset);
+                xfs_off_t               mapping_size;
+
+                mapping_size = imap.br_startoff + imap.br_blockcount - iblock;
+                mapping_size <<= inode->i_blkbits;
+
+                ASSERT(mapping_size > 0);
+                if (mapping_size > size)
+                        mapping_size = size;
+                if (mapping_size > LONG_MAX)
+                        mapping_size = LONG_MAX;
+
+                bh_result->b_size = mapping_size;
         }
 
         return 0;