From 97eacab2d54d6a7ebd62d7a7b8e7ec46a75e5d15 Mon Sep 17 00:00:00 2001
From: "Darrick J. Wong" <djwong@kernel.org>
Date: Thu, 3 Oct 2024 08:09:32 -0700
Subject: [PATCH] fsdax: remove zeroing code from dax_unshare_iter
[ Upstream commit 95472274b6fed8f2d30fbdda304e12174b3d4099 ]
Remove the code in dax_unshare_iter that zeroes the destination memory
because it's not necessary.
If srcmap is unwritten, we don't have to do anything because that
unwritten extent came from the regular file mapping, and unwritten
extents cannot be shared. The same applies to holes.
Furthermore, zeroing to unshare a mapping is just plain wrong because
unsharing means copy on write, and we should be copying data.
This is effectively a revert of commit 13dd4e04625f ("fsdax: unshare:
zero destination if srcmap is HOLE or UNWRITTEN")
Cc: ruansy.fnst@fujitsu.com
Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Link: https://lore.kernel.org/r/172796813311.1131942.16033376284752798632.stgit@frogsfrogsfrogs
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Christian Brauner <brauner@kernel.org>
Stable-dep-of: 50793801fc7f ("fsdax: dax_unshare_iter needs to copy entire blocks")
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/dax.c | 8 --------
1 file changed, 8 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index 74f9a14565f59..fa5a82b27c2f6 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -1239,14 +1239,6 @@ static s64 dax_unshare_iter(struct iomap_iter *iter)
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;
--
GitLab