gfs2: Clarify gfs2_block_map

Add a comment about the logical block size for directories.  Rename
"bsize" in gfs2_block_map to "factor".  Fix a typo in the description of
metaptr1.

Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
Signed-off-by: Bob Peterson <rpeterso@redhat.com>

diff --git a/fs/gfs2/bmap.c b/fs/gfs2/bmap.c
index 3dd0cceefa435bb623de0b1ee8dd33d83a6bdba8..8830e2903a349df89ee2a904ca17bed5d61a10e6 100644 (file)
--- a/fs/gfs2/bmap.c
+++ b/fs/gfs2/bmap.c
@@ -248,7 +248,7 @@ static inline unsigned int metapath_branch_start(const struct metapath *mp)
 }
 
 /**
- * metaptr1 - Return the first possible metadata pointer in a metaath buffer
+ * metaptr1 - Return the first possible metadata pointer in a metapath buffer
  * @height: The metadata height (0 = dinode)
  * @mp: The metapath
  */
@@ -659,7 +659,7 @@ int gfs2_block_map(struct inode *inode, sector_t lblock,
 {
        struct gfs2_inode *ip = GFS2_I(inode);
        struct gfs2_sbd *sdp = GFS2_SB(inode);
-       unsigned int bsize = sdp->sd_sb.sb_bsize;
+       unsigned int factor = sdp->sd_sb.sb_bsize;
        const size_t maxlen = bh_map->b_size >> inode->i_blkbits;
        const u64 *arr = sdp->sd_heightsize;
        __be64 *ptr;
@@ -679,8 +679,14 @@ int gfs2_block_map(struct inode *inode, sector_t lblock,
        clear_buffer_new(bh_map);
        clear_buffer_boundary(bh_map);
        trace_gfs2_bmap(ip, bh_map, lblock, create, 1);
+
+       /*
+        * Directory data blocks have a struct gfs2_meta_header header, so the
+        * remaining size is smaller than the filesystem block size.  Logical
+        * block numbers for directories are in units of this remaining size!
+        */
        if (gfs2_is_dir(ip)) {
-               bsize = sdp->sd_jbsize;
+               factor = sdp->sd_jbsize;
                arr = sdp->sd_jheightsize;
        }
 
@@ -689,7 +695,7 @@ int gfs2_block_map(struct inode *inode, sector_t lblock,
                goto out;
 
        height = ip->i_height;
-       size = (lblock + 1) * bsize;
+       size = (lblock + 1) * factor;
        while (size > arr[height])
                height++;
        find_metapath(sdp, lblock, &mp, height);