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

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Date:   Thu, 1 Dec 2022 15:31:41 +0000
From:   Shiyang Ruan <ruansy.fnst@...itsu.com>
To:     <linux-kernel@...r.kernel.org>, <linux-xfs@...r.kernel.org>,
        <nvdimm@...ts.linux.dev>, <linux-fsdevel@...r.kernel.org>
CC:     <djwong@...nel.org>, <david@...morbit.com>,
        <dan.j.williams@...el.com>, <akpm@...ux-foundation.org>
Subject: [PATCH v2 5/8] fsdax: dedupe: iter two files at the same time

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.fnst@...itsu.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