xfs: Make fiemap work with sparse files
In xfs_vn_fiemap, we set bvm_count to fi_extent_max + 1 and want
to return fi_extent_max extents, but actually it won't work for
a sparse file. The reason is that in xfs_getbmap we will
calculate holes and set it in 'out', while out is malloced by
bmv_count(fi_extent_max+1) which didn't consider holes. So in the
worst case, if 'out' vector looks like
[hole, extent, hole, extent, hole, ... hole, extent, hole],
we will only return half of fi_extent_max extents.
This patch add a new parameter BMV_IF_NO_HOLES for bvm_iflags.
So with this flags, we don't use our 'out' in xfs_getbmap for
a hole. The solution is a bit ugly by just don't increasing
index of 'out' vector. I felt that it is not easy to skip it
at the very beginning since we have the complicated check and
some function like xfs_getbmapx_fix_eof_hole to adjust 'out'.
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Tao Ma <tao.ma@oracle.com>
Signed-off-by: Alex Elder <aelder@sgi.com>
diff --git a/fs/xfs/xfs_fs.h b/fs/xfs/xfs_fs.h
index 7cf7220..87c2e9d 100644
--- a/fs/xfs/xfs_fs.h
+++ b/fs/xfs/xfs_fs.h
@@ -114,8 +114,10 @@
#define BMV_IF_NO_DMAPI_READ 0x2 /* Do not generate DMAPI read event */
#define BMV_IF_PREALLOC 0x4 /* rtn status BMV_OF_PREALLOC if req */
#define BMV_IF_DELALLOC 0x8 /* rtn status BMV_OF_DELALLOC if req */
+#define BMV_IF_NO_HOLES 0x10 /* Do not return holes */
#define BMV_IF_VALID \
- (BMV_IF_ATTRFORK|BMV_IF_NO_DMAPI_READ|BMV_IF_PREALLOC|BMV_IF_DELALLOC)
+ (BMV_IF_ATTRFORK|BMV_IF_NO_DMAPI_READ|BMV_IF_PREALLOC| \
+ BMV_IF_DELALLOC|BMV_IF_NO_HOLES)
/* bmv_oflags values - returned for each non-header segment */
#define BMV_OF_PREALLOC 0x1 /* segment = unwritten pre-allocation */