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Commit 9af25465 authored by Tao Ma's avatar Tao Ma Committed by Alex Elder
Browse files

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: default avatarTao Ma <tao.ma@oracle.com>
Signed-off-by: default avatarAlex Elder <aelder@sgi.com>
parent 23963e54

fs/xfs/linux-2.6/xfs_iops.c

+1 −1
Original line number Diff line number Diff line
@@ -664,7 +664,7 @@ xfs_vn_fiemap( 
					fieinfo->fi_extents_max + 1;

	bm.bmv_count = min_t(__s32, bm.bmv_count,

			     (PAGE_SIZE * 16 / sizeof(struct getbmapx)));

	bm.bmv_iflags = BMV_IF_PREALLOC;

	bm.bmv_iflags = BMV_IF_PREALLOC | BMV_IF_NO_HOLES;

	if (fieinfo->fi_flags & FIEMAP_FLAG_XATTR)

		bm.bmv_iflags |= BMV_IF_ATTRFORK;

	if (!(fieinfo->fi_flags & FIEMAP_FLAG_SYNC))

fs/xfs/xfs_bmap.c

+13 −1
Original line number Diff line number Diff line
@@ -5533,12 +5533,24 @@ xfs_getbmap( 
					map[i].br_startblock))

				goto out_free_map;



			nexleft--;

			bmv->bmv_offset =

				out[cur_ext].bmv_offset +

				out[cur_ext].bmv_length;

			bmv->bmv_length =

				max_t(__int64_t, 0, bmvend - bmv->bmv_offset);



			/*

			 * In case we don't want to return the hole,

			 * don't increase cur_ext so that we can reuse

			 * it in the next loop.

			 */

			if ((iflags & BMV_IF_NO_HOLES) &&

			    map[i].br_startblock == HOLESTARTBLOCK) {

				memset(&out[cur_ext], 0, sizeof(out[cur_ext]));

				continue;

			}



			nexleft--;

			bmv->bmv_entries++;

			cur_ext++;

		}

fs/xfs/xfs_fs.h

+3 −1
Original line number Diff line number Diff line
@@ -114,8 +114,10 @@ struct getbmapx { 
#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 */