6.1-stable review patch. If anyone has any objections, please let me know.
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From: Darrick J. Wong djwong@kernel.org
[ 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@fr... 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;