From: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Date: Wed, 22 Mar 2023 11:11:09 +0000
Subject: [PATCH] fsdax: unshare: zero destination if srcmap is HOLE or
 UNWRITTEN
References: bsc#1012628
Patch-mainline: 6.2.11
Git-commit: 13dd4e04625f600e5affb1b3f0b6c35268ab839b

commit 13dd4e04625f600e5affb1b3f0b6c35268ab839b upstream.

unshare copies data from source to destination.  But if the source is
HOLE or UNWRITTEN extents, we should zero the destination, otherwise
the HOLE or UNWRITTEN part will be user-visible old data of the new
allocated extent.

Found by running generic/649 while mounting with -o dax=always on pmem.

Link: https://lkml.kernel.org/r/1679483469-2-1-git-send-email-ruansy.fnst@fujitsu.com
Fixes: d984648e428b ("fsdax,xfs: port unshare to fsdax")
Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Darrick J. Wong <djwong@kernel.org>
Cc: Jan Kara <jack@suse.cz>
Cc: Matthew Wilcox (Oracle) <willy@infradead.org>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Jason Gunthorpe <jgg@nvidia.com>
Cc: John Hubbard <jhubbard@nvidia.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
 fs/dax.c | 11 ++++++++---
 1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 9800b93e..5d2e9b10 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1258,15 +1258,20 @@ static s64 dax_unshare_iter(struct iomap_iter *iter)
 	/* don't bother with blocks that are not shared to start with */
 	if (!(iomap->flags & IOMAP_F_SHARED))
 		return length;
-	/* don't bother with holes or unwritten extents */
-	if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
-		return length;
 
 	id = dax_read_lock();
 	ret = dax_iomap_direct_access(iomap, pos, length, &daddr, NULL);
 	if (ret < 0)
 		goto out_unlock;
 
+	/* zero the distance if srcmap is HOLE or UNWRITTEN */
+	if (srcmap->flags & IOMAP_F_SHARED || srcmap->type == IOMAP_UNWRITTEN) {
+		memset(daddr, 0, length);
+		dax_flush(iomap->dax_dev, daddr, length);
+		ret = length;
+		goto out_unlock;
+	}
+
 	ret = dax_iomap_direct_access(srcmap, pos, length, &saddr, NULL);
 	if (ret < 0)
 		goto out_unlock;
-- 
2.35.3