From nobody Sun Sep 14 09:15:53 2025 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 AA6D0C54E94 for ; Tue, 24 Jan 2023 17:02:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233589AbjAXRCb (ORCPT ); Tue, 24 Jan 2023 12:02:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35222 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233001AbjAXRCT (ORCPT ); Tue, 24 Jan 2023 12:02:19 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 178DA4CE45 for ; Tue, 24 Jan 2023 09:01:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674579689; 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=DVPp/aweiCuwkqIZyia5rE0/tVWaaSEAgtUaRlyjdMQ=; b=PSsUA5wkPjOq47DzGeroQj98+TN643WDB68s4Ob8X1REC+BP8EKfryHcEpfYVaPRfKb1F6 R69Sbv/sTywxs/TX+SsaXagq7dMsegphgy7LyRFKppt5Lfisoy1PTslsVzdkhbtMT5JYbM eE9whUpKvP9LoFM/EBPI/UwcsVesQUY= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-113-zU6I3cMoNbiffxJwkQ1YaQ-1; Tue, 24 Jan 2023 12:01:23 -0500 X-MC-Unique: zU6I3cMoNbiffxJwkQ1YaQ-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 8A57C882827; Tue, 24 Jan 2023 17:01:22 +0000 (UTC) Received: from warthog.procyon.org.uk.com (unknown [10.33.36.97]) by smtp.corp.redhat.com (Postfix) with ESMTP id 069DB53A0; Tue, 24 Jan 2023 17:01:20 +0000 (UTC) From: David Howells To: Al Viro , Christoph Hellwig Cc: David Howells , Matthew Wilcox , Jens Axboe , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v9 1/8] iov_iter: Define flags to qualify page extraction. Date: Tue, 24 Jan 2023 17:01:01 +0000 Message-Id: <20230124170108.1070389-2-dhowells@redhat.com> In-Reply-To: <20230124170108.1070389-1-dhowells@redhat.com> References: <20230124170108.1070389-1-dhowells@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Define flags to qualify page extraction to pass into iov_iter_*_pages*() rather than passing in FOLL_* flags. For now only a flag to allow peer-to-peer DMA is supported. Signed-off-by: David Howells cc: Al Viro cc: Christoph Hellwig cc: Jens Axboe cc: Logan Gunthorpe cc: linux-fsdevel@vger.kernel.org cc: linux-block@vger.kernel.org Reviewed-by: Christoph Hellwig Reviewed-by: John Hubbard --- Notes: ver #9) - Change extract_flags to extraction_flags. =20 ver #7) - Don't use FOLL_* as a parameter, but rather define constants specifically to use with iov_iter_*_pages*(). - Drop the I/O direction constants for now. block/bio.c | 6 +++--- block/blk-map.c | 8 ++++---- include/linux/uio.h | 7 +++++-- lib/iov_iter.c | 14 ++++++++------ 4 files changed, 20 insertions(+), 15 deletions(-) diff --git a/block/bio.c b/block/bio.c index ab59a491a883..683444e6b711 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1249,7 +1249,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, = struct iov_iter *iter) unsigned short entries_left =3D bio->bi_max_vecs - bio->bi_vcnt; struct bio_vec *bv =3D bio->bi_io_vec + bio->bi_vcnt; struct page **pages =3D (struct page **)bv; - unsigned int gup_flags =3D 0; + unsigned int extraction_flags =3D 0; ssize_t size, left; unsigned len, i =3D 0; size_t offset, trim; @@ -1264,7 +1264,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, = struct iov_iter *iter) pages +=3D entries_left * (PAGE_PTRS_PER_BVEC - 1); =20 if (bio->bi_bdev && blk_queue_pci_p2pdma(bio->bi_bdev->bd_disk->queue)) - gup_flags |=3D FOLL_PCI_P2PDMA; + extraction_flags |=3D ITER_ALLOW_P2PDMA; =20 /* * Each segment in the iov is required to be a block size multiple. @@ -1275,7 +1275,7 @@ static int __bio_iov_iter_get_pages(struct bio *bio, = struct iov_iter *iter) */ size =3D iov_iter_get_pages(iter, pages, UINT_MAX - bio->bi_iter.bi_size, - nr_pages, &offset, gup_flags); + nr_pages, &offset, extraction_flags); if (unlikely(size <=3D 0)) return size ? size : -EFAULT; =20 diff --git a/block/blk-map.c b/block/blk-map.c index 19940c978c73..7db52ad5b2d0 100644 --- a/block/blk-map.c +++ b/block/blk-map.c @@ -267,7 +267,7 @@ static int bio_map_user_iov(struct request *rq, struct = iov_iter *iter, { unsigned int max_sectors =3D queue_max_hw_sectors(rq->q); unsigned int nr_vecs =3D iov_iter_npages(iter, BIO_MAX_VECS); - unsigned int gup_flags =3D 0; + unsigned int extraction_flags =3D 0; struct bio *bio; int ret; int j; @@ -280,7 +280,7 @@ static int bio_map_user_iov(struct request *rq, struct = iov_iter *iter, return -ENOMEM; =20 if (blk_queue_pci_p2pdma(rq->q)) - gup_flags |=3D FOLL_PCI_P2PDMA; + extraction_flags |=3D ITER_ALLOW_P2PDMA; =20 while (iov_iter_count(iter)) { struct page **pages, *stack_pages[UIO_FASTIOV]; @@ -291,10 +291,10 @@ static int bio_map_user_iov(struct request *rq, struc= t iov_iter *iter, if (nr_vecs <=3D ARRAY_SIZE(stack_pages)) { pages =3D stack_pages; bytes =3D iov_iter_get_pages(iter, pages, LONG_MAX, - nr_vecs, &offs, gup_flags); + nr_vecs, &offs, extraction_flags); } else { bytes =3D iov_iter_get_pages_alloc(iter, &pages, - LONG_MAX, &offs, gup_flags); + LONG_MAX, &offs, extraction_flags); } if (unlikely(bytes <=3D 0)) { ret =3D bytes ? bytes : -EFAULT; diff --git a/include/linux/uio.h b/include/linux/uio.h index 9f158238edba..58fda77f6847 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -252,12 +252,12 @@ void iov_iter_xarray(struct iov_iter *i, unsigned int= direction, struct xarray * loff_t start, size_t count); ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages, size_t maxsize, unsigned maxpages, size_t *start, - unsigned gup_flags); + unsigned extraction_flags); ssize_t iov_iter_get_pages2(struct iov_iter *i, struct page **pages, size_t maxsize, unsigned maxpages, size_t *start); ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages, size_t maxsize, size_t *start, - unsigned gup_flags); + unsigned extraction_flags); ssize_t iov_iter_get_pages_alloc2(struct iov_iter *i, struct page ***pages, size_t maxsize, size_t *start); int iov_iter_npages(const struct iov_iter *i, int maxpages); @@ -360,4 +360,7 @@ static inline void iov_iter_ubuf(struct iov_iter *i, un= signed int direction, }; } =20 +/* Flags for iov_iter_get/extract_pages*() */ +#define ITER_ALLOW_P2PDMA 0x01 /* Allow P2PDMA on the extracted pages */ + #endif diff --git a/lib/iov_iter.c b/lib/iov_iter.c index f9a3ff37ecd1..da7db39075c6 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1432,9 +1432,9 @@ static struct page *first_bvec_segment(const struct i= ov_iter *i, static ssize_t __iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages, size_t maxsize, unsigned int maxpages, size_t *start, - unsigned int gup_flags) + unsigned int extraction_flags) { - unsigned int n; + unsigned int n, gup_flags =3D 0; =20 if (maxsize > i->count) maxsize =3D i->count; @@ -1442,6 +1442,8 @@ static ssize_t __iov_iter_get_pages_alloc(struct iov_= iter *i, return 0; if (maxsize > MAX_RW_COUNT) maxsize =3D MAX_RW_COUNT; + if (extraction_flags & ITER_ALLOW_P2PDMA) + gup_flags |=3D FOLL_PCI_P2PDMA; =20 if (likely(user_backed_iter(i))) { unsigned long addr; @@ -1495,14 +1497,14 @@ static ssize_t __iov_iter_get_pages_alloc(struct io= v_iter *i, =20 ssize_t iov_iter_get_pages(struct iov_iter *i, struct page **pages, size_t maxsize, unsigned maxpages, - size_t *start, unsigned gup_flags) + size_t *start, unsigned extraction_flags) { if (!maxpages) return 0; BUG_ON(!pages); =20 return __iov_iter_get_pages_alloc(i, &pages, maxsize, maxpages, - start, gup_flags); + start, extraction_flags); } EXPORT_SYMBOL_GPL(iov_iter_get_pages); =20 @@ -1515,14 +1517,14 @@ EXPORT_SYMBOL(iov_iter_get_pages2); =20 ssize_t iov_iter_get_pages_alloc(struct iov_iter *i, struct page ***pages, size_t maxsize, - size_t *start, unsigned gup_flags) + size_t *start, unsigned extraction_flags) { ssize_t len; =20 *pages =3D NULL; =20 len =3D __iov_iter_get_pages_alloc(i, pages, maxsize, ~0U, start, - gup_flags); + extraction_flags); if (len <=3D 0) { kvfree(*pages); *pages =3D NULL; From nobody Sun Sep 14 09:15:53 2025 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 2A734C38142 for ; Tue, 24 Jan 2023 17:02:42 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234686AbjAXRCk (ORCPT ); Tue, 24 Jan 2023 12:02:40 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34810 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234606AbjAXRC0 (ORCPT ); Tue, 24 Jan 2023 12:02:26 -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 6C2834CE79 for ; 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Tue, 24 Jan 2023 17:01:25 +0000 (UTC) Received: from warthog.procyon.org.uk.com (unknown [10.33.36.97]) by smtp.corp.redhat.com (Postfix) with ESMTP id 2AB4E53A0; Tue, 24 Jan 2023 17:01:23 +0000 (UTC) From: David Howells To: Al Viro , Christoph Hellwig Cc: David Howells , Matthew Wilcox , Jens Axboe , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig , John Hubbard , linux-mm@kvack.org Subject: [PATCH v9 2/8] iov_iter: Add a function to extract a page list from an iterator Date: Tue, 24 Jan 2023 17:01:02 +0000 Message-Id: <20230124170108.1070389-3-dhowells@redhat.com> In-Reply-To: <20230124170108.1070389-1-dhowells@redhat.com> References: <20230124170108.1070389-1-dhowells@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Add a function, iov_iter_extract_pages(), to extract a list of pages from an iterator. The pages may be returned with a pin added or nothing, depending on the type of iterator. Add a second function, iov_iter_extract_will_pin(), to determine how the cleanup should be done. There are two cases: (1) ITER_IOVEC or ITER_UBUF iterator. Extracted pages will have pins (FOLL_PIN) obtained on them so that a concurrent fork() will forcibly copy the page so that DMA is done to/from the parent's buffer and is unavailable to/unaffected by the child process. iov_iter_extract_will_pin() will return true for this case. The caller should use something like unpin_user_page() to dispose of the page. (2) Any other sort of iterator. No refs or pins are obtained on the page, the assumption is made that the caller will manage page retention. iov_iter_extract_will_pin() will return false. The pages don't need additional disposal. Signed-off-by: David Howells cc: Al Viro cc: Christoph Hellwig cc: John Hubbard cc: David Hildenbrand cc: Matthew Wilcox cc: linux-fsdevel@vger.kernel.org cc: linux-mm@kvack.org Reviewed-by: Christoph Hellwig --- Notes: ver #9) - Rename iov_iter_extract_mode() to iov_iter_extract_will_pin() and ma= ke it return true/false not FOLL_PIN/0 as FOLL_PIN is going to be made private to mm/. - Change extract_flags to extraction_flags. =20 ver #8) - It seems that all DIO is supposed to be done under FOLL_PIN now, and= not FOLL_GET, so switch to only using pin_user_pages() for user-backed iters. - Wrap an argument in brackets in the iov_iter_extract_mode() macro. - Drop the extract_flags argument to iov_iter_extract_mode() for now [hch]. =20 ver #7) - Switch to passing in iter-specific flags rather than FOLL_* flags. - Drop the direction flags for now. - Use ITER_ALLOW_P2PDMA to request FOLL_PCI_P2PDMA. - Disallow use of ITER_ALLOW_P2PDMA with non-user-backed iter. - Add support for extraction from KVEC-type iters. - Use iov_iter_advance() rather than open-coding it. - Make BVEC- and KVEC-type skip over initial empty vectors. =20 ver #6) - Add back the function to indicate the cleanup mode. - Drop the cleanup_mode return arg to iov_iter_extract_pages(). - Pass FOLL_SOURCE/DEST_BUF in gup_flags. Check this against the iter data_source. =20 ver #4) - Use ITER_SOURCE/DEST instead of WRITE/READ. - Allow additional FOLL_* flags, such as FOLL_PCI_P2PDMA to be passed = in. =20 ver #3) - Switch to using EXPORT_SYMBOL_GPL to prevent indirect 3rd-party acce= ss to get/pin_user_pages_fast()[1]. include/linux/uio.h | 25 ++++ lib/iov_iter.c | 321 ++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 346 insertions(+) diff --git a/include/linux/uio.h b/include/linux/uio.h index 58fda77f6847..47ebb59a0202 100644 --- a/include/linux/uio.h +++ b/include/linux/uio.h @@ -363,4 +363,29 @@ static inline void iov_iter_ubuf(struct iov_iter *i, u= nsigned int direction, /* Flags for iov_iter_get/extract_pages*() */ #define ITER_ALLOW_P2PDMA 0x01 /* Allow P2PDMA on the extracted pages */ =20 +ssize_t iov_iter_extract_pages(struct iov_iter *i, struct page ***pages, + size_t maxsize, unsigned int maxpages, + unsigned int extraction_flags, size_t *offset0); + +/** + * iov_iter_extract_will_pin - Indicate how pages from the iterator will b= e retained + * @iter: The iterator + * + * Examine the iterator and indicate by returning true or false as to how,= if + * at all, pages extracted from the iterator will be retained by the extra= ction + * function. + * + * %true indicates that the pages will have a pin placed in them that the + * caller must unpin. This is must be done for DMA/async DIO to force for= k() + * to forcibly copy a page for the child (the parent must retain the origi= nal + * page). + * + * %false indicates that no measures are taken and that it's up to the cal= ler + * to retain the pages. + */ +static inline bool iov_iter_extract_will_pin(const struct iov_iter *iter) +{ + return user_backed_iter(iter); +} + #endif diff --git a/lib/iov_iter.c b/lib/iov_iter.c index da7db39075c6..2b8d3632e15d 100644 --- a/lib/iov_iter.c +++ b/lib/iov_iter.c @@ -1916,3 +1916,324 @@ void iov_iter_restore(struct iov_iter *i, struct io= v_iter_state *state) i->iov -=3D state->nr_segs - i->nr_segs; i->nr_segs =3D state->nr_segs; } + +/* + * Extract a list of contiguous pages from an ITER_PIPE iterator. This do= es + * not get references of its own on the pages, nor does it get a pin on th= em. + * If there's a partial page, it adds that first and will then allocate an= d add + * pages into the pipe to make up the buffer space to the amount required. + * + * The caller must hold the pipe locked and only transferring into a pipe = is + * supported. + */ +static ssize_t iov_iter_extract_pipe_pages(struct iov_iter *i, + struct page ***pages, size_t maxsize, + unsigned int maxpages, + unsigned int extraction_flags, + size_t *offset0) +{ + unsigned int nr, offset, chunk, j; + struct page **p; + size_t left; + + if (!sanity(i)) + return -EFAULT; + + offset =3D pipe_npages(i, &nr); + if (!nr) + return -EFAULT; + *offset0 =3D offset; + + maxpages =3D min_t(size_t, nr, maxpages); + maxpages =3D want_pages_array(pages, maxsize, offset, maxpages); + if (!maxpages) + return -ENOMEM; + p =3D *pages; + + left =3D maxsize; + for (j =3D 0; j < maxpages; j++) { + struct page *page =3D append_pipe(i, left, &offset); + if (!page) + break; + chunk =3D min_t(size_t, left, PAGE_SIZE - offset); + left -=3D chunk; + *p++ =3D page; + } + if (!j) + return -EFAULT; + return maxsize - left; +} + +/* + * Extract a list of contiguous pages from an ITER_XARRAY iterator. This = does not + * get references on the pages, nor does it get a pin on them. + */ +static ssize_t iov_iter_extract_xarray_pages(struct iov_iter *i, + struct page ***pages, size_t maxsize, + unsigned int maxpages, + unsigned int extraction_flags, + size_t *offset0) +{ + struct page *page, **p; + unsigned int nr =3D 0, offset; + loff_t pos =3D i->xarray_start + i->iov_offset; + pgoff_t index =3D pos >> PAGE_SHIFT; + XA_STATE(xas, i->xarray, index); + + offset =3D pos & ~PAGE_MASK; + *offset0 =3D offset; + + maxpages =3D want_pages_array(pages, maxsize, offset, maxpages); + if (!maxpages) + return -ENOMEM; + p =3D *pages; + + rcu_read_lock(); + for (page =3D xas_load(&xas); page; page =3D xas_next(&xas)) { + if (xas_retry(&xas, page)) + continue; + + /* Has the page moved or been split? */ + if (unlikely(page !=3D xas_reload(&xas))) { + xas_reset(&xas); + continue; + } + + p[nr++] =3D find_subpage(page, xas.xa_index); + if (nr =3D=3D maxpages) + break; + } + rcu_read_unlock(); + + maxsize =3D min_t(size_t, nr * PAGE_SIZE - offset, maxsize); + iov_iter_advance(i, maxsize); + return maxsize; +} + +/* + * Extract a list of contiguous pages from an ITER_BVEC iterator. This do= es + * not get references on the pages, nor does it get a pin on them. + */ +static ssize_t iov_iter_extract_bvec_pages(struct iov_iter *i, + struct page ***pages, size_t maxsize, + unsigned int maxpages, + unsigned int extraction_flags, + size_t *offset0) +{ + struct page **p, *page; + size_t skip =3D i->iov_offset, offset; + int k; + + for (;;) { + if (i->nr_segs =3D=3D 0) + return 0; + maxsize =3D min(maxsize, i->bvec->bv_len - skip); + if (maxsize) + break; + i->iov_offset =3D 0; + i->nr_segs--; + i->kvec++; + skip =3D 0; + } + + skip +=3D i->bvec->bv_offset; + page =3D i->bvec->bv_page + skip / PAGE_SIZE; + offset =3D skip % PAGE_SIZE; + *offset0 =3D offset; + + maxpages =3D want_pages_array(pages, maxsize, offset, maxpages); + if (!maxpages) + return -ENOMEM; + p =3D *pages; + for (k =3D 0; k < maxpages; k++) + p[k] =3D page + k; + + maxsize =3D min_t(size_t, maxsize, maxpages * PAGE_SIZE - offset); + iov_iter_advance(i, maxsize); + return maxsize; +} + +/* + * Extract a list of virtually contiguous pages from an ITER_KVEC iterator. + * This does not get references on the pages, nor does it get a pin on the= m. + */ +static ssize_t iov_iter_extract_kvec_pages(struct iov_iter *i, + struct page ***pages, size_t maxsize, + unsigned int maxpages, + unsigned int extraction_flags, + size_t *offset0) +{ + struct page **p, *page; + const void *kaddr; + size_t skip =3D i->iov_offset, offset, len; + int k; + + for (;;) { + if (i->nr_segs =3D=3D 0) + return 0; + maxsize =3D min(maxsize, i->kvec->iov_len - skip); + if (maxsize) + break; + i->iov_offset =3D 0; + i->nr_segs--; + i->kvec++; + skip =3D 0; + } + + offset =3D skip % PAGE_SIZE; + *offset0 =3D offset; + kaddr =3D i->kvec->iov_base; + + maxpages =3D want_pages_array(pages, maxsize, offset, maxpages); + if (!maxpages) + return -ENOMEM; + p =3D *pages; + + kaddr -=3D offset; + len =3D offset + maxsize; + for (k =3D 0; k < maxpages; k++) { + size_t seg =3D min_t(size_t, len, PAGE_SIZE); + + if (is_vmalloc_or_module_addr(kaddr)) + page =3D vmalloc_to_page(kaddr); + else + page =3D virt_to_page(kaddr); + + p[k] =3D page; + len -=3D seg; + kaddr +=3D PAGE_SIZE; + } + + maxsize =3D min_t(size_t, maxsize, maxpages * PAGE_SIZE - offset); + iov_iter_advance(i, maxsize); + return maxsize; +} + +/* + * Extract a list of contiguous pages from a user iterator and get a pin on + * each of them. This should only be used if the iterator is user-backed + * (IOBUF/UBUF). + * + * It does not get refs on the pages, but the pages must be unpinned by the + * caller once the transfer is complete. + * + * This is safe to be used where background IO/DMA *is* going to be modify= ing + * the buffer; using a pin rather than a ref makes forces fork() to give t= he + * child a copy of the page. + */ +static ssize_t iov_iter_extract_user_pages(struct iov_iter *i, + struct page ***pages, + size_t maxsize, + unsigned int maxpages, + unsigned int extraction_flags, + size_t *offset0) +{ + unsigned long addr; + unsigned int gup_flags =3D FOLL_PIN; + size_t offset; + int res; + + if (i->data_source =3D=3D ITER_DEST) + gup_flags |=3D FOLL_WRITE; + if (extraction_flags & ITER_ALLOW_P2PDMA) + gup_flags |=3D FOLL_PCI_P2PDMA; + if (i->nofault) + gup_flags |=3D FOLL_NOFAULT; + + addr =3D first_iovec_segment(i, &maxsize); + *offset0 =3D offset =3D addr % PAGE_SIZE; + addr &=3D PAGE_MASK; + maxpages =3D want_pages_array(pages, maxsize, offset, maxpages); + if (!maxpages) + return -ENOMEM; + res =3D pin_user_pages_fast(addr, maxpages, gup_flags, *pages); + if (unlikely(res <=3D 0)) + return res; + maxsize =3D min_t(size_t, maxsize, res * PAGE_SIZE - offset); + iov_iter_advance(i, maxsize); + return maxsize; +} + +/** + * iov_iter_extract_pages - Extract a list of contiguous pages from an ite= rator + * @i: The iterator to extract from + * @pages: Where to return the list of pages + * @maxsize: The maximum amount of iterator to extract + * @maxpages: The maximum size of the list of pages + * @extraction_flags: Flags to qualify request + * @offset0: Where to return the starting offset into (*@pages)[0] + * + * Extract a list of contiguous pages from the current point of the iterat= or, + * advancing the iterator. The maximum number of pages and the maximum am= ount + * of page contents can be set. + * + * If *@pages is NULL, a page list will be allocated to the required size = and + * *@pages will be set to its base. If *@pages is not NULL, it will be as= sumed + * that the caller allocated a page list at least @maxpages in size and th= is + * will be filled in. + * + * @extraction_flags can have ITER_ALLOW_P2PDMA set to request peer-to-pee= r DMA + * be allowed on the pages extracted. + * + * The iov_iter_extract_will_pin() function can be used to query how clean= up + * should be performed. + * + * Extra refs or pins on the pages may be obtained as follows: + * + * (*) If the iterator is user-backed (ITER_IOVEC/ITER_UBUF), pins will be + * added to the pages, but refs will not be taken. + * iov_iter_extract_will_pin() will return true. + * + * (*) If the iterator is ITER_PIPE, this must describe a destination for= the + * data. Additional pages may be allocated and added to the pipe (wh= ich + * will hold the refs), but pins will not be obtained for the caller.= The + * caller must hold the pipe lock. iov_iter_extract_will_pin() will + * return false. + * + * (*) If the iterator is ITER_KVEC, ITER_BVEC or ITER_XARRAY, the pages = are + * merely listed; no extra refs or pins are obtained. + * iov_iter_extract_will_pin() will return 0. + * + * Note also: + * + * (*) Use with ITER_DISCARD is not supported as that has no content. + * + * On success, the function sets *@pages to the new pagelist, if allocated= , and + * sets *offset0 to the offset into the first page. + * + * It may also return -ENOMEM and -EFAULT. + */ +ssize_t iov_iter_extract_pages(struct iov_iter *i, + struct page ***pages, + size_t maxsize, + unsigned int maxpages, + unsigned int extraction_flags, + size_t *offset0) +{ + maxsize =3D min_t(size_t, min_t(size_t, maxsize, i->count), MAX_RW_COUNT); + if (!maxsize) + return 0; + + if (likely(user_backed_iter(i))) + return iov_iter_extract_user_pages(i, pages, maxsize, + maxpages, extraction_flags, + offset0); + if (iov_iter_is_kvec(i)) + return iov_iter_extract_kvec_pages(i, pages, maxsize, + maxpages, extraction_flags, + offset0); + if (iov_iter_is_bvec(i)) + return iov_iter_extract_bvec_pages(i, pages, maxsize, + maxpages, extraction_flags, + offset0); + if (iov_iter_is_pipe(i)) + return iov_iter_extract_pipe_pages(i, pages, maxsize, + maxpages, extraction_flags, + offset0); + if (iov_iter_is_xarray(i)) + return iov_iter_extract_xarray_pages(i, pages, maxsize, + maxpages, extraction_flags, + offset0); + return -EFAULT; +} +EXPORT_SYMBOL_GPL(iov_iter_extract_pages); From nobody Sun Sep 14 09:15:53 2025 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 4B74FC54E94 for ; Tue, 24 Jan 2023 17:03:00 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234668AbjAXRC7 (ORCPT ); Tue, 24 Jan 2023 12:02:59 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34880 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234653AbjAXRCf (ORCPT ); Tue, 24 Jan 2023 12:02:35 -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 871F948623 for ; Tue, 24 Jan 2023 09:01:43 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674579702; 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=0nUSebggWm9hllLA5YvTDCn+df0UDsKPYU6rFIiSb24=; b=RW20oKLrtrPoUKjjy5xiTD80oWKcsqLq8RKH4snzwlTJ9u8benLGUP33txPWD5ztYZfPK7 McSA7e3NzlllhdFgo4yjDv19J3O+11lMqysYSUI37xjU1T/8DadsaKx262UqLRZR61GCCP epaXSiH746ocDJFENxeG+F42Vl46qVk= 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-658-f6AYk3koMpGXfVMWN98DXQ-1; Tue, 24 Jan 2023 12:01:39 -0500 X-MC-Unique: f6AYk3koMpGXfVMWN98DXQ-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id AE9B43C18342; Tue, 24 Jan 2023 17:01:38 +0000 (UTC) Received: from warthog.procyon.org.uk.com (unknown [10.33.36.97]) by smtp.corp.redhat.com (Postfix) with ESMTP id DF7FBC15BA0; Tue, 24 Jan 2023 17:01:25 +0000 (UTC) From: David Howells To: Al Viro , Christoph Hellwig Cc: David Howells , Matthew Wilcox , Jens Axboe , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v9 3/8] iomap: Don't get an reference on ZERO_PAGE for direct I/O block zeroing Date: Tue, 24 Jan 2023 17:01:03 +0000 Message-Id: <20230124170108.1070389-4-dhowells@redhat.com> In-Reply-To: <20230124170108.1070389-1-dhowells@redhat.com> References: <20230124170108.1070389-1-dhowells@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" ZERO_PAGE can't go away, no need to hold an extra reference. Signed-off-by: David Howells Reviewed-by: David Hildenbrand Reviewed-by: John Hubbard --- fs/iomap/direct-io.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index 9804714b1751..47db4ead1e74 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -202,7 +202,7 @@ static void iomap_dio_zero(const struct iomap_iter *ite= r, struct iomap_dio *dio, bio->bi_private =3D dio; bio->bi_end_io =3D iomap_dio_bio_end_io; =20 - get_page(page); + bio_set_flag(bio, BIO_NO_PAGE_REF); __bio_add_page(bio, page, len, 0); iomap_dio_submit_bio(iter, dio, bio, pos); } From nobody Sun Sep 14 09:15:53 2025 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 388F5C54E94 for ; Tue, 24 Jan 2023 17:02:58 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231479AbjAXRC4 (ORCPT ); Tue, 24 Jan 2023 12:02:56 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34440 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234650AbjAXRCe (ORCPT ); Tue, 24 Jan 2023 12:02:34 -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 A0C8849434 for ; Tue, 24 Jan 2023 09:01:44 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674579703; 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=u/H+JLqqGtjE96rU8y7Ek7KRkRO4zR4fLWrnb7rCy6M=; b=UPCQ5UROAJD22Yc7QuiPdXo7R9kVRLMkNeXcpRoVE4TkXBXu+jrldhS8zqFENkIRUAmDkB 1Lq3YDZ/2/gXRkp2jOy/dEu9qbTUs5V8akd9QEHPTXlpD4/suOr0iXnVg5TEYSviiejgQr l3jjB6mY9HqHcpt8uKIFyjzMrEKVd14= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-176-KoPZI-LkMeana-V6Z0IHGg-1; Tue, 24 Jan 2023 12:01:42 -0500 X-MC-Unique: KoPZI-LkMeana-V6Z0IHGg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 0ED39882833; Tue, 24 Jan 2023 17:01:41 +0000 (UTC) Received: from warthog.procyon.org.uk.com (unknown [10.33.36.97]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6BFC2C159BB; Tue, 24 Jan 2023 17:01:39 +0000 (UTC) From: David Howells To: Al Viro , Christoph Hellwig Cc: David Howells , Matthew Wilcox , Jens Axboe , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig Subject: [PATCH v9 4/8] block: Fix bio_flagged() so that gcc can better optimise it Date: Tue, 24 Jan 2023 17:01:04 +0000 Message-Id: <20230124170108.1070389-5-dhowells@redhat.com> In-Reply-To: <20230124170108.1070389-1-dhowells@redhat.com> References: <20230124170108.1070389-1-dhowells@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Fix bio_flagged() so that multiple instances of it, such as: if (bio_flagged(bio, BIO_PAGE_REFFED) || bio_flagged(bio, BIO_PAGE_PINNED)) can be combined by the gcc optimiser into a single test in assembly (arguably, this is a compiler optimisation issue[1]). The missed optimisation stems from bio_flagged() comparing the result of the bitwise-AND to zero. This results in an out-of-line bio_release_page() being compiled to something like: <+0>: mov 0x14(%rdi),%eax <+3>: test $0x1,%al <+5>: jne 0xffffffff816dac53 <+7>: test $0x2,%al <+9>: je 0xffffffff816dac5c <+11>: movzbl %sil,%esi <+15>: jmp 0xffffffff816daba1 <__bio_release_pages> <+20>: jmp 0xffffffff81d0b800 <__x86_return_thunk> However, the test is superfluous as the return type is bool. Removing it results in: <+0>: testb $0x3,0x14(%rdi) <+4>: je 0xffffffff816e4af4 <+6>: movzbl %sil,%esi <+10>: jmp 0xffffffff816dab7c <__bio_release_pages> <+15>: jmp 0xffffffff81d0b7c0 <__x86_return_thunk> instead. Also, the MOVZBL instruction looks unnecessary[2] - I think it's just 're-booling' the mark_dirty parameter. Signed-off-by: David Howells Reviewed-by: Christoph Hellwig cc: Jens Axboe cc: linux-block@vger.kernel.org Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108370 [1] Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D108371 [2] Link: https://lore.kernel.org/r/167391056756.2311931.356007731815807265.stg= it@warthog.procyon.org.uk/ # v6 Reviewed-by: John Hubbard --- include/linux/bio.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/include/linux/bio.h b/include/linux/bio.h index c1da63f6c808..10366b8bdb13 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -227,7 +227,7 @@ static inline void bio_cnt_set(struct bio *bio, unsigne= d int count) =20 static inline bool bio_flagged(struct bio *bio, unsigned int bit) { - return (bio->bi_flags & (1U << bit)) !=3D 0; + return bio->bi_flags & (1U << bit); } =20 static inline void bio_set_flag(struct bio *bio, unsigned int bit) From nobody Sun Sep 14 09:15:53 2025 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 753A3C25B4E for ; Tue, 24 Jan 2023 17:03:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234602AbjAXRDC (ORCPT ); Tue, 24 Jan 2023 12:03:02 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34438 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234660AbjAXRCg (ORCPT ); Tue, 24 Jan 2023 12:02:36 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 712264B1A7 for ; Tue, 24 Jan 2023 09:01:48 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674579707; 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=J0g/m29YfoRQ3He4ADW0GiFq635ufDIaXkn3qdmeao4=; b=fSN6DhyLIFAo48WK4LtjpOXInsM3BngXlp+NeyA3qzgrvtJU9I2PuFz7pbRF3ecdhI7geO 4taSy2nEB/wEvJYeGftuTvH2v+UnW45+QcTmRWzYndM0a3luNgUi0LUptCAP727TtNyU7J s5g5uzWNdh/UhKBm0YcguV7GWacNnzM= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-439-TbIaFIU1MyWlp-Hc-YVrNw-1; Tue, 24 Jan 2023 12:01:44 -0500 X-MC-Unique: TbIaFIU1MyWlp-Hc-YVrNw-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.rdu2.redhat.com [10.11.54.5]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4A4E3802C18; Tue, 24 Jan 2023 17:01:43 +0000 (UTC) Received: from warthog.procyon.org.uk.com (unknown [10.33.36.97]) by smtp.corp.redhat.com (Postfix) with ESMTP id A08C053A0; Tue, 24 Jan 2023 17:01:41 +0000 (UTC) From: David Howells To: Al Viro , Christoph Hellwig Cc: David Howells , Matthew Wilcox , Jens Axboe , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig Subject: [PATCH v9 5/8] block: Replace BIO_NO_PAGE_REF with BIO_PAGE_REFFED with inverted logic Date: Tue, 24 Jan 2023 17:01:05 +0000 Message-Id: <20230124170108.1070389-6-dhowells@redhat.com> In-Reply-To: <20230124170108.1070389-1-dhowells@redhat.com> References: <20230124170108.1070389-1-dhowells@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" From: Christoph Hellwig Replace BIO_NO_PAGE_REF with a BIO_PAGE_REFFED flag that has the inverted meaning is only set when a page reference has been acquired that needs to be released by bio_release_pages(). Signed-off-by: David Howells cc: Al Viro cc: Jens Axboe cc: Jan Kara cc: Matthew Wilcox cc: Logan Gunthorpe cc: linux-block@vger.kernel.org Reviewed-by: Christoph Hellwig Reviewed-by: John Hubbard --- Notes: ver #8) - Don't default to BIO_PAGE_REFFED [hch]. =20 ver #5) - Split from patch that uses iov_iter_extract_pages(). block/bio.c | 2 +- block/blk-map.c | 1 + fs/direct-io.c | 2 ++ fs/iomap/direct-io.c | 1 - include/linux/bio.h | 2 +- include/linux/blk_types.h | 2 +- 6 files changed, 6 insertions(+), 4 deletions(-) diff --git a/block/bio.c b/block/bio.c index 683444e6b711..851c23641a0d 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1198,7 +1198,6 @@ void bio_iov_bvec_set(struct bio *bio, struct iov_ite= r *iter) bio->bi_io_vec =3D (struct bio_vec *)iter->bvec; bio->bi_iter.bi_bvec_done =3D iter->iov_offset; bio->bi_iter.bi_size =3D size; - bio_set_flag(bio, BIO_NO_PAGE_REF); bio_set_flag(bio, BIO_CLONED); } =20 @@ -1343,6 +1342,7 @@ int bio_iov_iter_get_pages(struct bio *bio, struct io= v_iter *iter) return 0; } =20 + bio_set_flag(bio, BIO_PAGE_REFFED); do { ret =3D __bio_iov_iter_get_pages(bio, iter); } while (!ret && iov_iter_count(iter) && !bio_full(bio, 0)); diff --git a/block/blk-map.c b/block/blk-map.c index 7db52ad5b2d0..0e2b0a861ba3 100644 --- a/block/blk-map.c +++ b/block/blk-map.c @@ -282,6 +282,7 @@ static int bio_map_user_iov(struct request *rq, struct = iov_iter *iter, if (blk_queue_pci_p2pdma(rq->q)) extraction_flags |=3D ITER_ALLOW_P2PDMA; =20 + bio_set_flag(bio, BIO_PAGE_REFFED); while (iov_iter_count(iter)) { struct page **pages, *stack_pages[UIO_FASTIOV]; ssize_t bytes; diff --git a/fs/direct-io.c b/fs/direct-io.c index 03d381377ae1..07810465fc9d 100644 --- a/fs/direct-io.c +++ b/fs/direct-io.c @@ -403,6 +403,8 @@ dio_bio_alloc(struct dio *dio, struct dio_submit *sdio, bio->bi_end_io =3D dio_bio_end_aio; else bio->bi_end_io =3D dio_bio_end_io; + /* for now require references for all pages */ + bio_set_flag(bio, BIO_PAGE_REFFED); sdio->bio =3D bio; sdio->logical_offset_in_bio =3D sdio->cur_page_fs_offset; } diff --git a/fs/iomap/direct-io.c b/fs/iomap/direct-io.c index 47db4ead1e74..c0e75900e754 100644 --- a/fs/iomap/direct-io.c +++ b/fs/iomap/direct-io.c @@ -202,7 +202,6 @@ static void iomap_dio_zero(const struct iomap_iter *ite= r, struct iomap_dio *dio, bio->bi_private =3D dio; bio->bi_end_io =3D iomap_dio_bio_end_io; =20 - bio_set_flag(bio, BIO_NO_PAGE_REF); __bio_add_page(bio, page, len, 0); iomap_dio_submit_bio(iter, dio, bio, pos); } diff --git a/include/linux/bio.h b/include/linux/bio.h index 10366b8bdb13..805957c99147 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -484,7 +484,7 @@ void zero_fill_bio(struct bio *bio); =20 static inline void bio_release_pages(struct bio *bio, bool mark_dirty) { - if (!bio_flagged(bio, BIO_NO_PAGE_REF)) + if (bio_flagged(bio, BIO_PAGE_REFFED)) __bio_release_pages(bio, mark_dirty); } =20 diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index 99be590f952f..7daa261f4f98 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -318,7 +318,7 @@ struct bio { * bio flags */ enum { - BIO_NO_PAGE_REF, /* don't put release vec pages */ + BIO_PAGE_REFFED, /* put pages in bio_release_pages() */ BIO_CLONED, /* doesn't own data */ BIO_BOUNCED, /* bio is a bounce bio */ BIO_QUIET, /* Make BIO Quiet */ From nobody Sun Sep 14 09:15:53 2025 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 4F7ECC25B4E for ; 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Tue, 24 Jan 2023 12:01:46 -0500 X-MC-Unique: UEKnBzFdMTKx7HDKATbAZg-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id B7B2D1C02D2A; Tue, 24 Jan 2023 17:01:45 +0000 (UTC) Received: from warthog.procyon.org.uk.com (unknown [10.33.36.97]) by smtp.corp.redhat.com (Postfix) with ESMTP id E24DEC15BA0; Tue, 24 Jan 2023 17:01:43 +0000 (UTC) From: David Howells To: Al Viro , Christoph Hellwig Cc: David Howells , Matthew Wilcox , Jens Axboe , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig Subject: [PATCH v9 6/8] block: Switch to pinning pages. Date: Tue, 24 Jan 2023 17:01:06 +0000 Message-Id: <20230124170108.1070389-7-dhowells@redhat.com> In-Reply-To: <20230124170108.1070389-1-dhowells@redhat.com> References: <20230124170108.1070389-1-dhowells@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" Add BIO_PAGE_PINNED to indicate that the pages in a bio are pinned (FOLL_PIN) and that the pin will need removing. 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 Reviewed-by: Christoph Hellwig Reviewed-by: John Hubbard --- Notes: ver #9) - Only consider pinning in bio_set_cleanup_mode(). Ref'ing pages in struct bio is going away. - page_put_unpin() is removed; call unpin_user_page() and put_page() directly. - Use bio_release_page() in __bio_release_pages(). - BIO_PAGE_PINNED and BIO_PAGE_REFFED can't both be set, so use if-else when testing both of them. =20 ver #8) - Move the infrastructure to clean up pinned pages to this patch [hch]. - Put BIO_PAGE_PINNED before BIO_PAGE_REFFED as the latter should probably be removed at some point. FOLL_PIN can then be renumbered first. block/bio.c | 6 +++--- block/blk.h | 21 +++++++++++++++++++++ include/linux/bio.h | 3 ++- include/linux/blk_types.h | 1 + 4 files changed, 27 insertions(+), 4 deletions(-) diff --git a/block/bio.c b/block/bio.c index 851c23641a0d..fc45aaa97696 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1176,7 +1176,7 @@ void __bio_release_pages(struct bio *bio, bool mark_d= irty) 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); @@ -1496,8 +1496,8 @@ 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 unpin each page and will run one bio_put() against the + * BIO. */ =20 static void bio_dirty_fn(struct work_struct *work); diff --git a/block/blk.h b/block/blk.h index 4c3b3325219a..32b252903f9a 100644 --- a/block/blk.h +++ b/block/blk.h @@ -425,6 +425,27 @@ int bio_add_hw_page(struct request_queue *q, struct bi= o *bio, struct page *page, unsigned int len, unsigned int offset, unsigned int max_sectors, bool *same_page); =20 +/* + * Set the cleanup mode for a bio from an iterator and the extraction flag= s. + */ +static inline void bio_set_cleanup_mode(struct bio *bio, struct iov_iter *= iter) +{ + if (iov_iter_extract_will_pin(iter)) + 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) +{ + if (bio_flagged(bio, BIO_PAGE_PINNED)) + unpin_user_page(page); + else if (bio_flagged(bio, BIO_PAGE_REFFED)) + put_page(page); +} + struct request_queue *blk_alloc_queue(int node_id); =20 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 805957c99147..b2c09997d79c 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -484,7 +484,8 @@ void zero_fill_bio(struct bio *bio); =20 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); } =20 diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h index 7daa261f4f98..a0e339ff3d09 100644 --- a/include/linux/blk_types.h +++ b/include/linux/blk_types.h @@ -318,6 +318,7 @@ struct bio { * bio flags */ enum { + BIO_PAGE_PINNED, /* Unpin pages in bio_release_pages() */ BIO_PAGE_REFFED, /* put pages in bio_release_pages() */ BIO_CLONED, /* doesn't own data */ BIO_BOUNCED, /* bio is a bounce bio */ From nobody Sun Sep 14 09:15:53 2025 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 D347CC38142 for ; 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Tue, 24 Jan 2023 12:01:49 -0500 X-MC-Unique: qZNJFshYNKOhvUR4Bsre3Q-1 Received: from smtp.corp.redhat.com (int-mx09.intmail.prod.int.rdu2.redhat.com [10.11.54.9]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 6ADE2183B3C1; Tue, 24 Jan 2023 17:01:48 +0000 (UTC) Received: from warthog.procyon.org.uk.com (unknown [10.33.36.97]) by smtp.corp.redhat.com (Postfix) with ESMTP id 779AC492C18; Tue, 24 Jan 2023 17:01:46 +0000 (UTC) From: David Howells To: Al Viro , Christoph Hellwig Cc: David Howells , Matthew Wilcox , Jens Axboe , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig Subject: [PATCH v9 7/8] block: Convert bio_iov_iter_get_pages to use iov_iter_extract_pages Date: Tue, 24 Jan 2023 17:01:07 +0000 Message-Id: <20230124170108.1070389-8-dhowells@redhat.com> In-Reply-To: <20230124170108.1070389-1-dhowells@redhat.com> References: <20230124170108.1070389-1-dhowells@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.9 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 cc: Al Viro cc: Jens Axboe cc: Jan Kara cc: Christoph Hellwig cc: Matthew Wilcox cc: Logan Gunthorpe cc: linux-block@vger.kernel.org Reviewed-by: Christoph Hellwig Reviewed-by: John Hubbard --- Notes: 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. =20 ver #7) - Don't treat BIO_PAGE_REFFED/PINNED as being the same as FOLL_GET/PIN. =20 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 | 22 +++++++++++----------- 1 file changed, 11 insertions(+), 11 deletions(-) diff --git a/block/bio.c b/block/bio.c index fc45aaa97696..936301519e6c 100644 --- a/block/bio.c +++ b/block/bio.c @@ -1212,7 +1212,7 @@ static int bio_iov_add_page(struct bio *bio, struct p= age *page, } =20 if (same_page) - put_page(page); + bio_release_page(bio, page); return 0; } =20 @@ -1226,7 +1226,7 @@ static int bio_iov_add_zone_append_page(struct bio *b= io, struct page *page, queue_max_zone_append_sectors(q), &same_page) !=3D len) return -EINVAL; if (same_page) - put_page(page); + bio_release_page(bio, page); return 0; } =20 @@ -1237,10 +1237,10 @@ 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 p= ages + * 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) { @@ -1272,9 +1272,9 @@ 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 =3D iov_iter_get_pages(iter, pages, - UINT_MAX - bio->bi_iter.bi_size, - nr_pages, &offset, extraction_flags); + size =3D iov_iter_extract_pages(iter, &pages, + UINT_MAX - bio->bi_iter.bi_size, + nr_pages, extraction_flags, &offset); if (unlikely(size <=3D 0)) return size ? size : -EFAULT; =20 @@ -1307,7 +1307,7 @@ 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++]); =20 return ret; } @@ -1342,7 +1342,7 @@ int bio_iov_iter_get_pages(struct bio *bio, struct io= v_iter *iter) return 0; } =20 - bio_set_flag(bio, BIO_PAGE_REFFED); + bio_set_cleanup_mode(bio, iter); do { ret =3D __bio_iov_iter_get_pages(bio, iter); } while (!ret && iov_iter_count(iter) && !bio_full(bio, 0)); From nobody Sun Sep 14 09:15:53 2025 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 ED0B8C38142 for ; Tue, 24 Jan 2023 17:03:22 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232753AbjAXRDV (ORCPT ); Tue, 24 Jan 2023 12:03:21 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35230 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234702AbjAXRCr (ORCPT ); Tue, 24 Jan 2023 12:02:47 -0500 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.129.124]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 62F5349010 for ; Tue, 24 Jan 2023 09:01:57 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1674579716; 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=/VYBInuQuOZkbnPAeLMLfVK65/N8eTFHDXxeC7cDBQE=; b=DskKA2/M6WRt+2I0Y9AgS2Evd2qmp3NJfiZxhQGt32WORYEWUPAypoHq4S9jSZEewwRC5H LSb7OwaDX+VHfZL4buO9Z+WKNkJVFu/6jGJj3ccwnfBC911R+Zn/az05BDZuhl3M6R+q8d na1d68eGLic8HkhtTSdPbUapnSfVg5M= Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-523-GK62Won7NQWIhcktuj4p4w-1; Tue, 24 Jan 2023 12:01:52 -0500 X-MC-Unique: GK62Won7NQWIhcktuj4p4w-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D5E56882820; Tue, 24 Jan 2023 17:01:50 +0000 (UTC) Received: from warthog.procyon.org.uk.com (unknown [10.33.36.97]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0FFC4C15BA0; Tue, 24 Jan 2023 17:01:48 +0000 (UTC) From: David Howells To: Al Viro , Christoph Hellwig Cc: David Howells , Matthew Wilcox , Jens Axboe , Jan Kara , Jeff Layton , David Hildenbrand , Jason Gunthorpe , Logan Gunthorpe , linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, Christoph Hellwig Subject: [PATCH v9 8/8] block: convert bio_map_user_iov to use iov_iter_extract_pages Date: Tue, 24 Jan 2023 17:01:08 +0000 Message-Id: <20230124170108.1070389-9-dhowells@redhat.com> In-Reply-To: <20230124170108.1070389-1-dhowells@redhat.com> References: <20230124170108.1070389-1-dhowells@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-Scanned-By: MIMEDefang 3.1 on 10.11.54.8 Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Type: text/plain; charset="utf-8" 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 cc: Al Viro cc: Jens Axboe cc: Jan Kara cc: Christoph Hellwig cc: Matthew Wilcox cc: Logan Gunthorpe cc: linux-block@vger.kernel.org Reviewed-by: Christoph Hellwig Reviewed-by: John Hubbard --- Notes: 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. =20 ver #7) - Don't treat BIO_PAGE_REFFED/PINNED as being the same as FOLL_GET/PIN. =20 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 | 22 ++++++++++------------ 1 file changed, 10 insertions(+), 12 deletions(-) diff --git a/block/blk-map.c b/block/blk-map.c index 0e2b0a861ba3..4e22dccdbe9b 100644 --- a/block/blk-map.c +++ b/block/blk-map.c @@ -282,21 +282,19 @@ static int bio_map_user_iov(struct request *rq, struc= t iov_iter *iter, if (blk_queue_pci_p2pdma(rq->q)) extraction_flags |=3D ITER_ALLOW_P2PDMA; =20 - bio_set_flag(bio, BIO_PAGE_REFFED); + bio_set_cleanup_mode(bio, iter); while (iov_iter_count(iter)) { - struct page **pages, *stack_pages[UIO_FASTIOV]; + struct page *stack_pages[UIO_FASTIOV]; + struct page **pages =3D stack_pages; ssize_t bytes; size_t offs; int npages; =20 - if (nr_vecs <=3D ARRAY_SIZE(stack_pages)) { - pages =3D stack_pages; - bytes =3D iov_iter_get_pages(iter, pages, LONG_MAX, - nr_vecs, &offs, extraction_flags); - } else { - bytes =3D iov_iter_get_pages_alloc(iter, &pages, - LONG_MAX, &offs, extraction_flags); - } + if (nr_vecs > ARRAY_SIZE(stack_pages)) + pages =3D NULL; + + bytes =3D iov_iter_extract_pages(iter, &pages, LONG_MAX, + nr_vecs, extraction_flags, &offs); if (unlikely(bytes <=3D 0)) { ret =3D bytes ? bytes : -EFAULT; goto out_unmap; @@ -318,7 +316,7 @@ 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; } =20 @@ -330,7 +328,7 @@ 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 !=3D stack_pages) kvfree(pages); /* couldn't stuff something into bio? */