@@ -2487,13 +2487,43 @@ static int emit_fiemap_extent(struct fiemap_extent_info *fieinfo,
goto assign;
/*
- * Sanity check, extent_fiemap() should have ensured that new
- * fiemap extent won't overlap with cached one.
- * Not recoverable.
+ * When iterating the extents of the inode, at extent_fiemap(), we may
+ * find an extent that starts at an offset behind the end offset of the
+ * previous extent we processed. This happens if fiemap is called
+ * without FIEMAP_FLAG_SYNC and there are ordered extents completing
+ * while we call btrfs_next_leaf() (through fiemap_next_leaf_item()).
*
- * NOTE: Physical address can overlap, due to compression
+ * For example we are in leaf X processing its last item, which is the
+ * file extent item for file range [512K, 1M[, and after
+ * btrfs_next_leaf() releases the path, there's an ordered extent that
+ * completes for the file range [768K, 2M[, and that results in trimming
+ * the file extent item so that it now corresponds to the file range
+ * [512K, 768K[ and a new file extent item is inserted for the file
+ * range [768K, 2M[, which may end up as the last item of leaf X or as
+ * the first item of the next leaf - in either case btrfs_next_leaf()
+ * will leave us with a path pointing to the new extent item, for the
+ * file range [768K, 2M[, since that's the first key that follows the
+ * last one we processed. So in order not to report overlapping extents
+ * to user space, we trim the length of the previously cached extent and
+ * emit it.
+ *
+ * Upon calling btrfs_next_leaf() we may also find an extent with an
+ * offset smaller than cache->offset, and this happens when we had a
+ * hole or prealloc extent with several delalloc subranges, but after
+ * btrfs_next_leaf() released the path, delalloc completed as well as
+ * the ordered extents and we're now with a smaller offset. In this
+ * case just discard what we have in the cache and start from this
+ * current extent.
*/
if (cache->offset + cache->len > offset) {
+ if (offset < cache->offset) {
+ goto assign;
+ } else if (offset > cache->offset) {
+ cache->len = offset - cache->offset;
+ goto emit;
+ }
+
+ /* cache->offset == offset, should never happen. */
WARN_ON(1);
return -EINVAL;
}
@@ -2515,6 +2545,7 @@ static int emit_fiemap_extent(struct fiemap_extent_info *fieinfo,
return 0;
}
+emit:
/* Not mergeable, need to submit cached one */
ret = fiemap_fill_next_extent(fieinfo, cache->offset, cache->phys,
cache->len, cache->flags);