fs: btrfs: support sparse extents
When logical address of a regular extent is 0, the extent is sparse and
consists of all zeros.
Without this when sparse extents are used in a file reading fails with
Cannot map logical address 0 to physical
Signed-off-by: Marek Behún <marek.behun@nic.cz>
diff --git a/fs/btrfs/extent-io.c b/fs/btrfs/extent-io.c
index 66d0e1c..2e4599c 100644
--- a/fs/btrfs/extent-io.c
+++ b/fs/btrfs/extent-io.c
@@ -78,6 +78,12 @@
if (size > dlen - offset)
size = dlen - offset;
+ /* sparse extent */
+ if (extent->disk_bytenr == 0) {
+ memset(out, 0, size);
+ return size;
+ }
+
physical = btrfs_map_logical_to_physical(extent->disk_bytenr);
if (physical == -1ULL)
return -1ULL;