The patch titled
Subject: fsdax: unshare: zero destination if srcmap is HOLE or UNWRITTEN
has been added to the -mm mm-hotfixes-unstable branch. Its filename is
fsdax-unshare-zero-destination-if-srcmap-is-hole-or-unwritten.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fsdax-unshare-zero-destination-if-srcmap-is-hole-or-unwritten.patch
This patch will later appear in the mm-hotfixes-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
Subject: fsdax: unshare: zero destination if srcmap is HOLE or UNWRITTEN
Date: Wed, 22 Mar 2023 11:11:09 +0000
unshare copies data from source to destination. But if the source is HOLE
or UNWRITTEN extents, we should zero the destination, otherwise the result
will be unexpectable.
Link: https://lkml.kernel.org/r/1679483469-2-1-git-send-email-ruansy.fnst@xxxxxxxxxxx
Fixes: d984648e428b ("fsdax,xfs: port unshare to fsdax")
Signed-off-by: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Darrick J. Wong <djwong@xxxxxxxxxx>
Cc: Jan Kara <jack@xxxxxxx>
Cc: Matthew Wilcox (Oracle) <willy@xxxxxxxxxxxxx>
Cc: Alistair Popple <apopple@xxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxx>
Cc: John Hubbard <jhubbard@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
--- a/fs/dax.c~fsdax-unshare-zero-destination-if-srcmap-is-hole-or-unwritten
+++ a/fs/dax.c
@@ -1258,15 +1258,20 @@ static s64 dax_unshare_iter(struct iomap
/* 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;
_
Patches currently in -mm which might be from ruansy.fnst@xxxxxxxxxxx are
fsdax-unshare-zero-destination-if-srcmap-is-hole-or-unwritten.patch
