From patchwork Fri Jan 20 17:55:54 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 13110343 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id D37E7C25B4E for ; Fri, 20 Jan 2023 17:58:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230409AbjATR6l (ORCPT ); Fri, 20 Jan 2023 12:58:41 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:46792 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229596AbjATR61 (ORCPT ); Fri, 20 Jan 2023 12:58:27 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EEEE64F374 for ; Fri, 20 Jan 2023 09:56:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674237381; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=QX1h8EIb8MUDuVwndBiO27rWOJbbjgtov60pgMyP8j8=; b=VbuM/+DSCT1F2ILcY6ZGvHqVfzcV81v/XyRLLx6H0aNsHmXjozJuHLP4C8MvxcsPLQ17C1 vov1QTaqeerrdTKySYiYFkTo4TWbgQr0SfKY2iCsH6nXn9lbvTbG/rFQCnfZmJSA2SVJ08 jGAls7rdAdemDqUHoSFI/VXrdUmo/t0= Received: from mimecast-mx02.redhat.com (mx3-rdu2.redhat.com [66.187.233.73]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-492-Run05T5QMhCwWBqWatVMjA-1; Fri, 20 Jan 2023 12:56:15 -0500 X-MC-Unique: Run05T5QMhCwWBqWatVMjA-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.rdu2.redhat.com [10.11.54.3]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4E00C2807D6F; Fri, 20 Jan 2023 17:56:15 +0000 (UTC) Received: from warthog.procyon.org.uk.com (unknown [10.33.36.23]) by smtp.corp.redhat.com (Postfix) with ESMTP id C55EF1121315; Fri, 20 Jan 2023 17:56:13 +0000 (UTC) From: David Howells To: Al Viro , Christoph Hellwig Cc: David Howells , Matthew Wilcox , Jens Axboe , Jan Kara , Jeff Layton , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig Subject: [PATCH v7 6/8] block: Make bio structs pin pages rather than ref'ing if appropriate Date: Fri, 20 Jan 2023 17:55:54 +0000 Message-Id: <20230120175556.3556978-7-dhowells@redhat.com> In-Reply-To: <20230120175556.3556978-1-dhowells@redhat.com> References: <20230120175556.3556978-1-dhowells@redhat.com> MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Convert the block layer's bio code to use iov_iter_extract_pages() instead of iov_iter_get_pages(). This will pin pages or leave them unaltered rather than getting a ref on them as appropriate to the source iterator. The pages need to be pinned for DIO-read 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 would otherwise end up only visible to the child process and not the parent). To implement this: (1) If the BIO_PAGE_REFFED flag is set, this causes attached pages to be passed to put_page() during cleanup. (2) A BIO_PAGE_PINNED flag is provided. If set, this causes attached pages to be passed to unpin_user_page() during cleanup. (3) BIO_PAGE_REFFED is set by default and BIO_PAGE_PINNED is cleared by default when the bio is (re-)initialised. (4) If iov_iter_extract_pages() indicates FOLL_GET, this causes BIO_PAGE_REFFED to be set and if FOLL_PIN is indicated, this causes BIO_PAGE_PINNED to be set. If it returns neither FOLL_* flag, then both BIO_PAGE_* flags will be cleared. Mixing sets of pages with different clean up modes is not supported. (5) Cloned bio structs have both flags cleared. (6) bio_release_pages() will do the release if either BIO_PAGE_* flag is set. [!] Note that this is tested a bit with ext4, but nothing else. Signed-off-by: David Howells cc: Al Viro cc: Jens Axboe cc: Jan Kara cc: Christoph Hellwig cc: Matthew Wilcox cc: Logan Gunthorpe cc: linux-block@vger.kernel.org Link: https://lore.kernel.org/r/167305166150.1521586.10220949115402059720.stgit@warthog.procyon.org.uk/ # v4 Link: https://lore.kernel.org/r/167344731521.2425628.5403113335062567245.stgit@warthog.procyon.org.uk/ # v5 Link: https://lore.kernel.org/r/167391056047.2311931.6772604381276147664.stgit@warthog.procyon.org.uk/ # v6 --- Notes: 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 | 34 +++++++++++++++++++--------------- block/blk-map.c | 22 +++++++++++----------- block/blk.h | 29 +++++++++++++++++++++++++++++ include/linux/bio.h | 3 ++- 4 files changed, 61 insertions(+), 27 deletions(-) diff --git a/block/bio.c b/block/bio.c index cfe11f4799d1..2a6568b58501 100644 --- a/block/bio.c +++ b/block/bio.c @@ -245,8 +245,9 @@ static void bio_free(struct bio *bio) * when IO has completed, or when the bio is released. * * We set the initial assumption that pages attached to the bio will be - * released with put_page() by setting BIO_PAGE_REFFED; if the pages - * should not be put, this flag should be cleared. + * released with put_page() by setting BIO_PAGE_REFFED, but this should be set + * to BIO_PAGE_PINNED if the page should be unpinned instead; if the pages + * should not be put or unpinned, these flags should be cleared. */ void bio_init(struct bio *bio, struct block_device *bdev, struct bio_vec *table, unsigned short max_vecs, blk_opf_t opf) @@ -819,6 +820,7 @@ static int __bio_clone(struct bio *bio, struct bio *bio_src, gfp_t gfp) { bio_set_flag(bio, BIO_CLONED); bio_clear_flag(bio, BIO_PAGE_REFFED); + bio_clear_flag(bio, BIO_PAGE_PINNED); bio->bi_ioprio = bio_src->bi_ioprio; bio->bi_iter = bio_src->bi_iter; @@ -1183,7 +1185,7 @@ void __bio_release_pages(struct bio *bio, bool mark_dirty) bio_for_each_segment_all(bvec, bio, iter_all) { if (mark_dirty && !PageCompound(bvec->bv_page)) set_page_dirty_lock(bvec->bv_page); - put_page(bvec->bv_page); + bio_release_page(bio, bvec->bv_page); } } EXPORT_SYMBOL_GPL(__bio_release_pages); @@ -1220,7 +1222,7 @@ 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; } @@ -1234,7 +1236,7 @@ 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; } @@ -1245,10 +1247,10 @@ 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_REFFED and + * BIO_PAGE_PINNED flags. 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) { @@ -1280,9 +1282,9 @@ 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, extract_flags); + size = iov_iter_extract_pages(iter, &pages, + UINT_MAX - bio->bi_iter.bi_size, + nr_pages, extract_flags, &offset); if (unlikely(size <= 0)) return size ? size : -EFAULT; @@ -1315,7 +1317,7 @@ 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; } @@ -1344,6 +1346,8 @@ int bio_iov_iter_get_pages(struct bio *bio, struct iov_iter *iter) { int ret = 0; + bio_set_cleanup_mode(bio, iter, 0); + if (iov_iter_is_bvec(iter)) { bio_iov_bvec_set(bio, iter); iov_iter_advance(iter, bio->bi_iter.bi_size); @@ -1496,8 +1500,8 @@ void bio_set_pages_dirty(struct bio *bio) * the BIO and re-dirty the pages in process context. * * It is expected that bio_check_pages_dirty() will wholly own the BIO from - * here on. It will run one put_page() against each page and will run one - * bio_put() against the BIO. + * here on. It will run one put_page() or unpin_user_page() against each page + * and will run one bio_put() against the BIO. */ static void bio_dirty_fn(struct work_struct *work); diff --git a/block/blk-map.c b/block/blk-map.c index bc111261fc82..7d1bc75b9cf2 100644 --- a/block/blk-map.c +++ b/block/blk-map.c @@ -282,20 +282,20 @@ static int bio_map_user_iov(struct request *rq, struct iov_iter *iter, if (blk_queue_pci_p2pdma(rq->q)) extract_flags |= ITER_ALLOW_P2PDMA; + bio_set_cleanup_mode(bio, iter, extract_flags); + 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, extract_flags); - } else { - bytes = iov_iter_get_pages_alloc(iter, &pages, - LONG_MAX, &offs, extract_flags); - } + if (nr_vecs > ARRAY_SIZE(stack_pages)) + pages = NULL; + + bytes = iov_iter_extract_pages(iter, &pages, LONG_MAX, + nr_vecs, extract_flags, &offs); if (unlikely(bytes <= 0)) { ret = bytes ? bytes : -EFAULT; goto out_unmap; @@ -317,7 +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; } @@ -329,7 +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? */ diff --git a/block/blk.h b/block/blk.h index 4c3b3325219a..16c8a7a84a16 100644 --- a/block/blk.h +++ b/block/blk.h @@ -425,6 +425,35 @@ int bio_add_hw_page(struct request_queue *q, struct bio *bio, struct page *page, unsigned int len, unsigned int offset, unsigned int max_sectors, bool *same_page); +/* + * Set the cleanup mode for a bio from an iterator and the extraction flags. + */ +static inline void bio_set_cleanup_mode(struct bio *bio, struct iov_iter *iter, + unsigned int extract_flags) +{ + unsigned int cleanup_mode; + + bio_clear_flag(bio, BIO_PAGE_REFFED); + cleanup_mode = iov_iter_extract_mode(iter, extract_flags); + if (cleanup_mode & FOLL_GET) + bio_set_flag(bio, BIO_PAGE_REFFED); + if (cleanup_mode & FOLL_PIN) + bio_set_flag(bio, BIO_PAGE_PINNED); +} + +/* + * Clean up a page appropriately, where the page may be pinned, may have a + * ref taken on it or neither. + */ +static inline void bio_release_page(struct bio *bio, struct page *page) +{ + unsigned int gup_flags = 0; + + gup_flags |= bio_flagged(bio, BIO_PAGE_REFFED) ? FOLL_GET : 0; + gup_flags |= bio_flagged(bio, BIO_PAGE_PINNED) ? FOLL_PIN : 0; + page_put_unpin(page, gup_flags); +} + struct request_queue *blk_alloc_queue(int node_id); int disk_scan_partitions(struct gendisk *disk, fmode_t mode, void *owner); diff --git a/include/linux/bio.h b/include/linux/bio.h index 63bfd91793f9..1c6f051f6ff2 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -482,7 +482,8 @@ void zero_fill_bio(struct bio *bio); static inline void bio_release_pages(struct bio *bio, bool mark_dirty) { - if (bio_flagged(bio, BIO_PAGE_REFFED)) + if (bio_flagged(bio, BIO_PAGE_REFFED) || + bio_flagged(bio, BIO_PAGE_PINNED)) __bio_release_pages(bio, mark_dirty); }