On Thu, Dec 01, 2022 at 03:28:52PM +0000, Shiyang Ruan wrote:
> CoW changes the share state of a dax page, but the share count of the
> page isn't updated. The next time access this page, it should have been
> a newly accessed, but old association exists. So, we need to clear the
> share state when CoW happens, in both dax_iomap_rw() and
> dax_zero_iter().
>
> Signed-off-by: Shiyang Ruan <ruansy.f...@fujitsu.com>
Looks ok,
Reviewed-by: Darrick J. Wong <djw...@kernel.org>
--D
> ---
> fs/dax.c | 17 +++++++++++++----
> 1 file changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 85b81963ea31..482dda85ccaf 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -1264,6 +1264,15 @@ static s64 dax_zero_iter(struct iomap_iter *iter, bool
> *did_zero)
> if (srcmap->type == IOMAP_HOLE || srcmap->type == IOMAP_UNWRITTEN)
> return length;
>
> + /*
> + * invalidate the pages whose sharing state is to be changed
> + * because of CoW.
> + */
> + if (iomap->flags & IOMAP_F_SHARED)
> + invalidate_inode_pages2_range(iter->inode->i_mapping,
> + pos >> PAGE_SHIFT,
> + (pos + length - 1) >> PAGE_SHIFT);
> +
> do {
> unsigned offset = offset_in_page(pos);
> unsigned size = min_t(u64, PAGE_SIZE - offset, length);
> @@ -1324,12 +1333,13 @@ static loff_t dax_iomap_iter(const struct iomap_iter
> *iomi,
> struct iov_iter *iter)
> {
> const struct iomap *iomap = &iomi->iomap;
> - const struct iomap *srcmap = &iomi->srcmap;
> + const struct iomap *srcmap = iomap_iter_srcmap(iomi);
> loff_t length = iomap_length(iomi);
> loff_t pos = iomi->pos;
> struct dax_device *dax_dev = iomap->dax_dev;
> loff_t end = pos + length, done = 0;
> bool write = iov_iter_rw(iter) == WRITE;
> + bool cow = write && iomap->flags & IOMAP_F_SHARED;
> ssize_t ret = 0;
> size_t xfer;
> int id;
> @@ -1356,7 +1366,7 @@ static loff_t dax_iomap_iter(const struct iomap_iter
> *iomi,
> * into page tables. We have to tear down these mappings so that data
> * written by write(2) is visible in mmap.
> */
> - if (iomap->flags & IOMAP_F_NEW) {
> + if (iomap->flags & IOMAP_F_NEW || cow) {
> invalidate_inode_pages2_range(iomi->inode->i_mapping,
> pos >> PAGE_SHIFT,
> (end - 1) >> PAGE_SHIFT);
> @@ -1390,8 +1400,7 @@ static loff_t dax_iomap_iter(const struct iomap_iter
> *iomi,
> break;
> }
>
> - if (write &&
> - srcmap->type != IOMAP_HOLE && srcmap->addr != iomap->addr) {
> + if (cow) {
> ret = dax_iomap_cow_copy(pos, length, PAGE_SIZE, srcmap,
> kaddr);
> if (ret)
> --
> 2.38.1
>
