[PATCH v2 5/8] fsdax: dedupe: iter two files at the same time

[Shiyang Ruan]

The iomap_iter() on a range of one file may loop more than once.  In
this case, the inner dst_iter can update its iomap but the outer
src_iter can't.  This may cause the wrong remapping in filesystem.  Let
them called at the same time.

Signed-off-by: Shiyang Ruan <ruansy.f...@fujitsu.com>
---
 fs/dax.c | 16 ++++++++--------
 1 file changed, 8 insertions(+), 8 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index f1eb59bee0b5..354be56750c2 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1964,15 +1964,15 @@ int dax_dedupe_file_range_compare(struct inode *src, 
loff_t srcoff,
                .len            = len,
                .flags          = IOMAP_DAX,
        };
-       int ret;
+       int ret, compared = 0;
 
-       while ((ret = iomap_iter(&src_iter, ops)) > 0) {
-               while ((ret = iomap_iter(&dst_iter, ops)) > 0) {
-                       dst_iter.processed = dax_range_compare_iter(&src_iter,
-                                               &dst_iter, len, same);
-               }
-               if (ret <= 0)
-                       src_iter.processed = ret;
+       while ((ret = iomap_iter(&src_iter, ops)) > 0 &&
+              (ret = iomap_iter(&dst_iter, ops)) > 0) {
+               compared = dax_range_compare_iter(&src_iter, &dst_iter, len,
+                                                 same);
+               if (compared < 0)
+                       return ret;
+               src_iter.processed = dst_iter.processed = compared;
        }
        return ret;
 }
-- 
2.38.1