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Tue, 23 May 2023 08:15:07 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id lj7RLgt2bGTdNAAAMHmgww (envelope-from ); Tue, 23 May 2023 08:15:07 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 49B4AA075D; Tue, 23 May 2023 10:15:07 +0200 (CEST) Date: Tue, 23 May 2023 10:15:07 +0200 From: Jan Kara To: David Howells Cc: Jens Axboe , Al Viro , Christoph Hellwig , Matthew Wilcox , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , Hillf Danton , Christian Brauner , Linus Torvalds , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, Christoph Hellwig , John Hubbard Subject: Re: [PATCH v21 5/6] block: Convert bio_iov_iter_get_pages to use iov_iter_extract_pages Message-ID: <20230523081507.sjzaau75hhw3oyul@quack3> References: <20230522205744.2825689-1-dhowells@redhat.com> <20230522205744.2825689-6-dhowells@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230522205744.2825689-6-dhowells@redhat.com> X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 33F304000F X-Stat-Signature: z98yziafdxn1sef8ox71che18njbb3sw X-HE-Tag: 1684829708-721785 X-HE-Meta: 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 q88tqE7g 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Mon 22-05-23 21:57:43, 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 affected by/visible to the > child process). > > Signed-off-by: David Howells > Reviewed-by: Christoph Hellwig > Reviewed-by: John Hubbard > cc: Al Viro > cc: Jens Axboe > cc: Jan Kara > cc: Matthew Wilcox > cc: Logan Gunthorpe > cc: linux-block@vger.kernel.org > --- Looks good. Feel free to add: Reviewed-by: Jan Kara 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/bio.c | 23 ++++++++++++----------- > 1 file changed, 12 insertions(+), 11 deletions(-) > > diff --git a/block/bio.c b/block/bio.c > index 17bd01ecde36..798cc4cf3bd2 100644 > --- a/block/bio.c > +++ b/block/bio.c > @@ -1205,7 +1205,7 @@ static int bio_iov_add_page(struct bio *bio, struct page *page, > } > > if (same_page) > - put_page(page); > + bio_release_page(bio, page); > return 0; > } > > @@ -1219,7 +1219,7 @@ static int bio_iov_add_zone_append_page(struct bio *bio, struct page *page, > queue_max_zone_append_sectors(q), &same_page) != len) > return -EINVAL; > if (same_page) > - put_page(page); > + bio_release_page(bio, page); > return 0; > } > > @@ -1230,10 +1230,10 @@ static int bio_iov_add_zone_append_page(struct bio *bio, struct page *page, > * @bio: bio to add pages to > * @iter: iov iterator describing the region to be mapped > * > - * Pins pages from *iter and appends them to @bio's bvec array. The > - * pages will have to be released using put_page() when done. > - * For multi-segment *iter, this function only adds pages from the > - * next non-empty segment of the iov iterator. > + * Extracts pages from *iter and appends them to @bio's bvec array. The pages > + * will have to be cleaned up in the way indicated by the BIO_PAGE_PINNED flag. > + * For a multi-segment *iter, this function only adds pages from the next > + * non-empty segment of the iov iterator. > */ > static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) > { > @@ -1265,9 +1265,9 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) > * result to ensure the bio's total size is correct. The remainder of > * the iov data will be picked up in the next bio iteration. > */ > - size = iov_iter_get_pages(iter, pages, > - UINT_MAX - bio->bi_iter.bi_size, > - nr_pages, &offset, extraction_flags); > + size = iov_iter_extract_pages(iter, &pages, > + UINT_MAX - bio->bi_iter.bi_size, > + nr_pages, extraction_flags, &offset); > if (unlikely(size <= 0)) > return size ? size : -EFAULT; > > @@ -1300,7 +1300,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) > iov_iter_revert(iter, left); > out: > while (i < nr_pages) > - put_page(pages[i++]); > + bio_release_page(bio, pages[i++]); > > return ret; > } > @@ -1335,7 +1335,8 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) > return 0; > } > > - bio_set_flag(bio, BIO_PAGE_REFFED); > + if (iov_iter_extract_will_pin(iter)) > + bio_set_flag(bio, BIO_PAGE_PINNED); > do { > ret = __bio_iov_iter_get_pages(bio, iter); > } while (!ret && iov_iter_count(iter) && !bio_full(bio, 0)); > -- Jan Kara SUSE Labs, CR