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Date: Thu, 26 May 2022 11:25:36 -0700
From: "Darrick J. Wong" <djwong@kernel.org>
To: Stefan Roesch <shr@fb.com>
Cc: io-uring@vger.kernel.org, kernel-team@fb.com, linux-mm@kvack.org,
linux-xfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
david@fromorbit.com, jack@suse.cz, hch@infradead.org
Subject: Re: [PATCH v6 04/16] iomap: Add flags parameter to
iomap_page_create()
Message-ID: <Yo/GIF1EoK7Acvmy@magnolia>
References: <20220526173840.578265-1-shr@fb.com>
<20220526173840.578265-5-shr@fb.com>
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On Thu, May 26, 2022 at 10:38:28AM -0700, Stefan Roesch wrote:
> Add the kiocb flags parameter to the function iomap_page_create().
> Depending on the value of the flags parameter it enables different gfp
> flags.
>
> No intended functional changes in this patch.
>
> Signed-off-by: Stefan Roesch <shr@fb.com>
> Reviewed-by: Jan Kara <jack@suse.cz>
> ---
> fs/iomap/buffered-io.c | 19 +++++++++++++------
> 1 file changed, 13 insertions(+), 6 deletions(-)
>
> diff --git a/fs/iomap/buffered-io.c b/fs/iomap/buffered-io.c
> index 8ce8720093b9..d6ddc54e190e 100644
> --- a/fs/iomap/buffered-io.c
> +++ b/fs/iomap/buffered-io.c
> @@ -44,16 +44,21 @@ static inline struct iomap_page *to_iomap_page(struct folio *folio)
> static struct bio_set iomap_ioend_bioset;
>
> static struct iomap_page *
> -iomap_page_create(struct inode *inode, struct folio *folio)
> +iomap_page_create(struct inode *inode, struct folio *folio, unsigned int flags)
> {
> struct iomap_page *iop = to_iomap_page(folio);
> unsigned int nr_blocks = i_blocks_per_folio(inode, folio);
> + gfp_t gfp = GFP_NOFS | __GFP_NOFAIL;
>
> if (iop || nr_blocks <= 1)
> return iop;
>
> + if (flags & IOMAP_NOWAIT)
> + gfp = GFP_NOWAIT;
Hmm. GFP_NOWAIT means we don't wait for reclaim or IO or filesystem
callbacks, and NOFAIL means we retry indefinitely. What happens in the
NOWAIT|NOFAIL case? Does that imply that the kzalloc loops without
triggering direct reclaim until someone else frees enough memory?
--D
> +
> iop = kzalloc(struct_size(iop, uptodate, BITS_TO_LONGS(nr_blocks)),
> - GFP_NOFS | __GFP_NOFAIL);
> + gfp);
> +
> spin_lock_init(&iop->uptodate_lock);
> if (folio_test_uptodate(folio))
> bitmap_fill(iop->uptodate, nr_blocks);
> @@ -226,7 +231,7 @@ static int iomap_read_inline_data(const struct iomap_iter *iter,
> if (WARN_ON_ONCE(size > iomap->length))
> return -EIO;
> if (offset > 0)
> - iop = iomap_page_create(iter->inode, folio);
> + iop = iomap_page_create(iter->inode, folio, iter->flags);
> else
> iop = to_iomap_page(folio);
>
> @@ -264,7 +269,7 @@ static loff_t iomap_readpage_iter(const struct iomap_iter *iter,
> return iomap_read_inline_data(iter, folio);
>
> /* zero post-eof blocks as the page may be mapped */
> - iop = iomap_page_create(iter->inode, folio);
> + iop = iomap_page_create(iter->inode, folio, iter->flags);
> iomap_adjust_read_range(iter->inode, folio, &pos, length, &poff, &plen);
> if (plen == 0)
> goto done;
> @@ -550,7 +555,7 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
> size_t len, struct folio *folio)
> {
> const struct iomap *srcmap = iomap_iter_srcmap(iter);
> - struct iomap_page *iop = iomap_page_create(iter->inode, folio);
> + struct iomap_page *iop;
> loff_t block_size = i_blocksize(iter->inode);
> loff_t block_start = round_down(pos, block_size);
> loff_t block_end = round_up(pos + len, block_size);
> @@ -561,6 +566,8 @@ static int __iomap_write_begin(const struct iomap_iter *iter, loff_t pos,
> return 0;
> folio_clear_error(folio);
>
> + iop = iomap_page_create(iter->inode, folio, iter->flags);
> +
> do {
> iomap_adjust_read_range(iter->inode, folio, &block_start,
> block_end - block_start, &poff, &plen);
> @@ -1332,7 +1339,7 @@ iomap_writepage_map(struct iomap_writepage_ctx *wpc,
> struct writeback_control *wbc, struct inode *inode,
> struct folio *folio, u64 end_pos)
> {
> - struct iomap_page *iop = iomap_page_create(inode, folio);
> + struct iomap_page *iop = iomap_page_create(inode, folio, 0);
> struct iomap_ioend *ioend, *next;
> unsigned len = i_blocksize(inode);
> unsigned nblocks = i_blocks_per_folio(inode, folio);
> --
> 2.30.2
>