From ea8efc74bd0402b4d5f663d007b4e25fa29ea778 Mon Sep 17 00:00:00 2001 From: Chris Mason Date: Tue, 8 Mar 2011 11:54:40 -0500 Subject: Btrfs: make sure not to return overlapping extents to fiemap The btrfs fiemap code was incorrectly returning duplicate or overlapping extents in some cases. cp was blindly trusting this result and we would end up with a destination file that was bigger than the original because some bytes were copied twice. The fix here adjusts our offsets to make sure we're always moving forward in the fiemap results. Signed-off-by: Chris Mason --- fs/btrfs/extent_io.c | 33 +++++++++++++++++++++++++++------ 1 file changed, 27 insertions(+), 6 deletions(-) diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c index ff45b80d90f0..9fcb5ede6b72 100644 --- a/fs/btrfs/extent_io.c +++ b/fs/btrfs/extent_io.c @@ -3046,17 +3046,38 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, } while (!end) { - off = extent_map_end(em); - if (off >= max) - end = 1; + u64 offset_in_extent; + + /* break if the extent we found is outside the range */ + if (em->start >= max || extent_map_end(em) < off) + break; + + /* + * get_extent may return an extent that starts before our + * requested range. We have to make sure the ranges + * we return to fiemap always move forward and don't + * overlap, so adjust the offsets here + */ + em_start = max(em->start, off); - em_start = em->start; - em_len = em->len; + /* + * record the offset from the start of the extent + * for adjusting the disk offset below + */ + offset_in_extent = em_start - em->start; em_end = extent_map_end(em); + em_len = em_end - em_start; emflags = em->flags; disko = 0; flags = 0; + /* + * bump off for our next call to get_extent + */ + off = extent_map_end(em); + if (off >= max) + end = 1; + if (em->block_start == EXTENT_MAP_LAST_BYTE) { end = 1; flags |= FIEMAP_EXTENT_LAST; @@ -3067,7 +3088,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo, flags |= (FIEMAP_EXTENT_DELALLOC | FIEMAP_EXTENT_UNKNOWN); } else { - disko = em->block_start; + disko = em->block_start + offset_in_extent; } if (test_bit(EXTENT_FLAG_COMPRESSED, &em->flags)) flags |= FIEMAP_EXTENT_ENCODED; -- cgit v1.2.3