I have a valid btrfs image which contains, ... item 10 key (1103101952 BLOCK_GROUP_ITEM 1288372224) itemoff 15947 itemsize 24 block group used 655360 chunk_objectid 256 flags DATA|RAID5 item 11 key (1103364096 EXTENT_ITEM 131072) itemoff 15894 itemsize 53 extent refs 1 gen 11 flags DATA extent data backref root 5 objectid 258 offset 0 count 1 item 12 key (1103888384 EXTENT_ITEM 262144) itemoff 15841 itemsize 53 extent refs 1 gen 15 flags DATA extent data backref root 1 objectid 256 offset 0 count 1 item 13 key (1104281600 EXTENT_ITEM 262144) itemoff 15788 itemsize 53 extent refs 1 gen 15 flags DATA extent data backref root 1 objectid 257 offset 0 count 1 ...
The extent [1103364096, 131072) has length 131072, but if we run "btrfs-map-logical -l 1103364096 -b $((65536 * 3)) /dev/sda" it will return mapping info 's of non-existing extents. It's because it assumes that extents's are contiguous on logical address, when it's not true, after one loop (cur_logical += cur_len) and mapping the next extent, we can get an extent that is out of our search range and we end up with a negative @real_len and printing all mapping infos till the disk end. Signed-off-by: Liu Bo <bo.li....@oracle.com> --- btrfs-map-logical.c | 5 +++++ 1 file changed, 5 insertions(+) diff --git a/btrfs-map-logical.c b/btrfs-map-logical.c index fd0286d..f421a50 100644 --- a/btrfs-map-logical.c +++ b/btrfs-map-logical.c @@ -329,6 +329,11 @@ int main(int argc, char **argv) goto out_close_fd; if (ret > 0) break; + /* check again if there is overlap. */ + if (cur_logical + cur_len < logical || + cur_logical >= logical + bytes) + break; + real_logical = max(logical, cur_logical); real_len = min(logical + bytes, cur_logical + cur_len) - real_logical; -- 2.5.0 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html