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Tue, 23 May 2023 08:14:46 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id J77vJfZ1bGSgNAAAMHmgww (envelope-from ); Tue, 23 May 2023 08:14:46 +0000 Received: by quack3.suse.cz (Postfix, from userid 1000) id 2515FA075D; Tue, 23 May 2023 10:14:46 +0200 (CEST) Date: Tue, 23 May 2023 10:14:46 +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 6/6] block: convert bio_map_user_iov to use iov_iter_extract_pages Message-ID: <20230523081446.qny4fmk5vlg3sxmg@quack3> References: <20230522205744.2825689-1-dhowells@redhat.com> <20230522205744.2825689-7-dhowells@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230522205744.2825689-7-dhowells@redhat.com> X-Rspamd-Queue-Id: 0C633140017 X-Rspam-User: X-Rspamd-Server: rspam11 X-Stat-Signature: m1cch3ya6h5g4k6dxitx8du9eewcr13r X-HE-Tag: 1684829687-67134 X-HE-Meta: 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 WdOqmm2s 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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 21:57:44, 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 > 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/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 SUSE Labs, CR