1 files changed, 6 insertions, 3 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 583d98bd065e..fe443fece851 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4048,7 +4048,7 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
         }
 
         while (!end) {
-                u64 offset_in_extent;
+                u64 offset_in_extent = 0;
 
                 /* break if the extent we found is outside the range */
                 if (em->start >= max || extent_map_end(em) < off)
@@ -4064,9 +4064,12 @@ int extent_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,
 
                 /*
                  * record the offset from the start of the extent
-                 * for adjusting the disk offset below
+                 * for adjusting the disk offset below.  Only do this if the
+                 * extent isn't compressed since our in ram offset may be past
+                 * what we have actually allocated on disk.
                  */
-                offset_in_extent = em_start - em->start;
+                if (!test_bit(EXTENT_FLAG_COMPRESSED, &em->flags))
+                        offset_in_extent = em_start - em->start;
                 em_end = extent_map_end(em);
                 em_len = em_end - em_start;
                 emflags = em->flags;