Re: [PATCH 11/13] iomap: factor out a iomap_writepage_map_block helper

Darrick J. Wong
2023-11-29T05:06:43Z

On Sun, Nov 26, 2023 at 01:47:18PM +0100, Christoph Hellwig wrote:
> Split the loop body that calls into the file system to map a block and
> add it to the ioend into a separate helper to prefer for refactoring of
> the surrounding code.
>
> Note that this was the only place in iomap_writepage_map that could
> return an error, so include the call to ->discard_folio into the new
> helper as that will help to avoid code duplication in the future.
>
> Signed-off-by: Christoph Hellwig <hch@lst.de>

Simple enough hoist,
Reviewed-by: Darrick J. Wong <djwong@kernel.org>

--D

> ---
> fs/iomap/buffered-io.c | 72 +++++++++++++++++++++++++-----------------
> 1 file changed, 43 insertions(+), 29 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index e1d5076251702d..9f223820f60d22 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -1723,6 +1723,45 @@ static void iomap_add_to_ioend(struct iomap_writepage_ctx *wpc,
> wbc_account_cgroup_owner(wbc, &folio->page, len);
> }
>
> +static int iomap_writepage_map_blocks(struct iomap_writepage_ctx *wpc,
> + struct writeback_control *wbc, struct folio *folio,
> + struct inode *inode, u64 pos, unsigned *count,
> + struct list_head *submit_list)
> +{
> + int error;
> +
> + error = wpc->ops->map_blocks(wpc, inode, pos);
> + if (error)
> + goto fail;
> + trace_iomap_writepage_map(inode, &wpc->iomap);
> +
> + switch (wpc->iomap.type) {
> + case IOMAP_INLINE:
> + WARN_ON_ONCE(1);
> + error = -EIO;
> + break;
> + case IOMAP_HOLE:
> + break;
> + default:
> + iomap_add_to_ioend(wpc, wbc, folio, inode, pos, submit_list);
> + (*count)++;
> + }
> +
> +fail:
> + /*
> + * We cannot cancel the ioend directly here on error. We may have
> + * already set other pages under writeback and hence we have to run I/O
> + * completion to mark the error state of the pages under writeback
> + * appropriately.
> + *
> + * Just let the file system know what portion of the folio failed to
> + * map.
> + */
> + if (error && wpc->ops->discard_folio)
> + wpc->ops->discard_folio(folio, pos);
> + return error;
> +}
> +
> /*
> * Check interaction of the folio with the file end.
> *
> @@ -1807,7 +1846,8 @@ static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
> unsigned nblocks = i_blocks_per_folio(inode, folio);
> u64 pos = folio_pos(folio);
> u64 end_pos = pos + folio_size(folio);
> - int error = 0, count = 0, i;
> + unsigned count = 0;
> + int error = 0, i;
> LIST_HEAD(submit_list);
>
> trace_iomap_writepage(inode, pos, folio_size(folio));
> @@ -1833,19 +1873,10 @@ static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
> for (i = 0; i < nblocks && pos < end_pos; i++, pos += len) {
> if (ifs && !ifs_block_is_dirty(folio, ifs, i))
> continue;
> -
> - error = wpc->ops->map_blocks(wpc, inode, pos);
> + error = iomap_writepage_map_blocks(wpc, wbc, folio, inode, pos,
> + &count, &submit_list);
> if (error)
> break;
> - trace_iomap_writepage_map(inode, &wpc->iomap);
> - if (WARN_ON_ONCE(wpc->iomap.type == IOMAP_INLINE)) {
> - error = -EIO;
> - break;
> - }
> - if (wpc->iomap.type == IOMAP_HOLE)
> - continue;
> - iomap_add_to_ioend(wpc, wbc, folio, inode, pos, &submit_list);
> - count++;
> }
> if (count)
> wpc->nr_folios++;
> @@ -1855,23 +1886,6 @@ static int iomap_writepage_map(struct iomap_writepage_ctx *wpc,
> WARN_ON_ONCE(folio_test_writeback(folio));
> WARN_ON_ONCE(folio_test_dirty(folio));
>
> - /*
> - * We cannot cancel the ioend directly here on error. We may have
> - * already set other pages under writeback and hence we have to run I/O
> - * completion to mark the error state of the pages under writeback
> - * appropriately.
> - */
> - if (unlikely(error)) {
> - /*
> - * Let the filesystem know what portion of the current page
> - * failed to map. If the page hasn't been added to ioend, it
> - * won't be affected by I/O completion and we must unlock it
> - * now.
> - */
> - if (wpc->ops->discard_folio)
> - wpc->ops->discard_folio(folio, pos);
> - }
> -
> /*
> * We can have dirty bits set past end of file in page_mkwrite path
> * while mapping the last partial folio. Hence it's better to clear
> --
> 2.39.2
>
>