RE: [PATCH 1/2] fsdax,xfs: fix warning messages at dax_[dis]associate_entry()

Dan Williams
2022-11-30T04:12:33Z

Shiyang Ruan wrote:
> This patch fixes the warning message reported in dax_associate_entry()
> and dax_disassociate_entry().

Can you include the xfstest test number and a snippet of the warning
message.

> 1. reset page->mapping and ->index when refcount counting down to 0.
> 2. set IOMAP_F_SHARED flag when iomap read to allow one dax page to be
> associated more than once for not only write but also read.
> 3. should zero the edge (when not aligned) if srcmap is HOLE or
> UNWRITTEN.
> 4. iterator of two files in dedupe should be executed side by side, not
> nested.
> 5. use xfs_dax_write_iomap_ops for xfs zero and truncate.

Do these all need to be done at once, or is this 5 patches?

>
> Signed-off-by: Shiyang Ruan <ruansy.fnst@fujitsu.com>
> ---
> fs/dax.c | 114 ++++++++++++++++++++++++++-------------------
> fs/xfs/xfs_iomap.c | 6 +--
> 2 files changed, 69 insertions(+), 51 deletions(-)
>
> diff --git a/fs/dax.c b/fs/dax.c
> index 1c6867810cbd..5ea7c0926b7f 100644
> --- a/fs/dax.c
> +++ b/fs/dax.c
> @@ -398,7 +398,7 @@ static void dax_disassociate_entry(void *entry, struct address_space *mapping,
> WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
> if (dax_mapping_is_cow(page->mapping)) {
> /* keep the CoW flag if this page is still shared */
> - if (page->index-- > 0)
> + if (page->index-- > 1)

I think this wants either a helper function to make it clear that
->index is being used as a share count, or go ahead and rename that
field in this context with something like:

diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 910d880e67eb..1a409288f39d 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -103,7 +103,10 @@ struct page {
};
/* See page-flags.h for PAGE_MAPPING_FLAGS */
struct address_space *mapping;
- pgoff_t index; /* Our offset within mapping. */
+ union {
+ pgoff_t index; /* Our offset within mapping. */
+ unsigned long share;
+ };
/**
* @private: Mapping-private opaque data.
* Usually used for buffer_heads if PagePrivate.