From: Shiyang Ruan <ruansy.fnst@xxxxxxxxxxx> 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@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> Cc: <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx> --- fs/dax.c | 11 ++++++++--- 1 file changed, 8 insertions(+), 3 deletions(-) --- a/fs/dax.c +++ b/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;
