From: Jan Kara <jack@suse.cz>
To: David Howells <dhowells@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>, Al Viro <viro@zeniv.linux.org.uk>,
Christoph Hellwig <hch@infradead.org>,
Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
Jeff Layton <jlayton@kernel.org>,
David Hildenbrand <david@redhat.com>,
Jason Gunthorpe <jgg@nvidia.com>,
Logan Gunthorpe <logang@deltatee.com>,
Hillf Danton <hdanton@sina.com>,
Christian Brauner <brauner@kernel.org>,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
Christoph Hellwig <hch@lst.de>,
John Hubbard <jhubbard@nvidia.com>
Subject: Re: [PATCH v21 6/6] block: convert bio_map_user_iov to use iov_iter_extract_pages
Date: Tue, 23 May 2023 10:14:46 +0200 [thread overview]
Message-ID: <20230523081446.qny4fmk5vlg3sxmg@quack3> (raw)
In-Reply-To: <20230522205744.2825689-7-dhowells@redhat.com>
On Mon 22-05-23 21:57:44, David Howells wrote:
> This will pin pages or leave them unaltered rather than getting a ref on
> them as appropriate to the iterator.
>
> The pages need to be pinned for DIO rather than having refs taken on them
> to prevent VM copy-on-write from malfunctioning during a concurrent fork()
> (the result of the I/O could otherwise end up being visible to/affected by
> the child process).
>
> Signed-off-by: David Howells <dhowells@redhat.com>
> Reviewed-by: Christoph Hellwig <hch@lst.de>
> Reviewed-by: John Hubbard <jhubbard@nvidia.com>
> cc: Al Viro <viro@zeniv.linux.org.uk>
> cc: Jens Axboe <axboe@kernel.dk>
> cc: Jan Kara <jack@suse.cz>
> cc: Matthew Wilcox <willy@infradead.org>
> cc: Logan Gunthorpe <logang@deltatee.com>
> cc: linux-block@vger.kernel.org
> ---
Looks good. Feel free to add:
Reviewed-by: Jan Kara <jack@suse.cz>
Honza
>
> Notes:
> ver #10)
> - Drop bio_set_cleanup_mode(), open coding it instead.
>
> ver #8)
> - Split the patch up a bit [hch].
> - We should only be using pinned/non-pinned pages and not ref'd pages,
> so adjust the comments appropriately.
>
> ver #7)
> - Don't treat BIO_PAGE_REFFED/PINNED as being the same as FOLL_GET/PIN.
>
> ver #5)
> - Transcribe the FOLL_* flags returned by iov_iter_extract_pages() to
> BIO_* flags and got rid of bi_cleanup_mode.
> - Replaced BIO_NO_PAGE_REF to BIO_PAGE_REFFED in the preceding patch.
>
> block/blk-map.c | 23 +++++++++++------------
> 1 file changed, 11 insertions(+), 12 deletions(-)
>
> diff --git a/block/blk-map.c b/block/blk-map.c
> index 33d9f6e89ba6..3551c3ff17cf 100644
> --- a/block/blk-map.c
> +++ b/block/blk-map.c
> @@ -281,22 +281,21 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
>
> if (blk_queue_pci_p2pdma(rq->q))
> extraction_flags |= ITER_ALLOW_P2PDMA;
> + if (iov_iter_extract_will_pin(iter))
> + bio_set_flag(bio, BIO_PAGE_PINNED);
>
> - bio_set_flag(bio, BIO_PAGE_REFFED);
> while (iov_iter_count(iter)) {
> - struct page **pages, *stack_pages[UIO_FASTIOV];
> + struct page *stack_pages[UIO_FASTIOV];
> + struct page **pages = stack_pages;
> ssize_t bytes;
> size_t offs;
> int npages;
>
> - if (nr_vecs <= ARRAY_SIZE(stack_pages)) {
> - pages = stack_pages;
> - bytes = iov_iter_get_pages(iter, pages, LONG_MAX,
> - nr_vecs, &offs, extraction_flags);
> - } else {
> - bytes = iov_iter_get_pages_alloc(iter, &pages,
> - LONG_MAX, &offs, extraction_flags);
> - }
> + if (nr_vecs > ARRAY_SIZE(stack_pages))
> + pages = NULL;
> +
> + bytes = iov_iter_extract_pages(iter, &pages, LONG_MAX,
> + nr_vecs, extraction_flags, &offs);
> if (unlikely(bytes <= 0)) {
> ret = bytes ? bytes : -EFAULT;
> goto out_unmap;
> @@ -318,7 +317,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
> if (!bio_add_hw_page(rq->q, bio, page, n, offs,
> max_sectors, &same_page)) {
> if (same_page)
> - put_page(page);
> + bio_release_page(bio, page);
> break;
> }
>
> @@ -330,7 +329,7 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter,
> * release the pages we didn't map into the bio, if any
> */
> while (j < npages)
> - put_page(pages[j++]);
> + bio_release_page(bio, pages[j++]);
> if (pages != stack_pages)
> kvfree(pages);
> /* couldn't stuff something into bio? */
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR
next prev parent reply other threads:[~2023-05-23 8:17 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-05-22 20:57 [PATCH v21 0/6] block: Use page pinning David Howells
2023-05-22 20:57 ` [PATCH v21 1/6] iomap: Don't get an reference on ZERO_PAGE for direct I/O block zeroing David Howells
2023-05-23 8:07 ` Jan Kara
2023-05-23 12:35 ` Christian Brauner
2023-05-22 20:57 ` [PATCH v21 2/6] block: Fix bio_flagged() so that gcc can better optimise it David Howells
2023-05-23 8:07 ` Jan Kara
2023-05-23 12:37 ` Christian Brauner
2023-05-22 20:57 ` [PATCH v21 3/6] block: Replace BIO_NO_PAGE_REF with BIO_PAGE_REFFED with inverted logic David Howells
2023-05-23 8:07 ` Jan Kara
2023-05-22 20:57 ` [PATCH v21 4/6] block: Add BIO_PAGE_PINNED and associated infrastructure David Howells
2023-05-23 8:08 ` Jan Kara
2023-05-22 20:57 ` [PATCH v21 5/6] block: Convert bio_iov_iter_get_pages to use iov_iter_extract_pages David Howells
2023-05-23 8:15 ` Jan Kara
2023-05-22 20:57 ` [PATCH v21 6/6] block: convert bio_map_user_iov " David Howells
2023-05-23 8:14 ` Jan Kara [this message]
2023-05-23 6:39 ` [PATCH v21 0/6] block: Use page pinning Christoph Hellwig
2023-05-23 20:16 ` Extending page pinning into fs/direct-io.c David Howells
2023-05-24 5:55 ` Christoph Hellwig
2023-05-24 7:06 ` David Hildenbrand
2023-05-24 8:47 ` David Howells
2023-05-25 9:51 ` Christoph Hellwig
2023-05-25 16:31 ` Linus Torvalds
2023-05-25 16:45 ` David Hildenbrand
2023-05-25 17:04 ` Linus Torvalds
2023-05-25 17:15 ` David Howells
2023-05-25 17:25 ` Linus Torvalds
2023-05-25 17:07 ` David Howells
2023-05-25 17:17 ` Linus Torvalds
2023-05-25 17:00 ` David Howells
2023-05-25 17:13 ` Linus Torvalds
2023-05-23 21:38 ` [PATCH v21 0/6] block: Use page pinning Jens Axboe
2023-05-24 5:52 ` Christoph Hellwig
2023-05-24 14:43 ` Jens Axboe
2023-05-24 7:35 ` David Howells
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