From patchwork Wed Jan 11 14:28:12 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 13096808 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 C8AE0C46467 for ; Wed, 11 Jan 2023 14:32:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S239278AbjAKOcx (ORCPT ); Wed, 11 Jan 2023 09:32:53 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42998 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S238622AbjAKOcB (ORCPT ); Wed, 11 Jan 2023 09:32:01 -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 D63131EC63 for ; Wed, 11 Jan 2023 06:28:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673447301; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=qnUzA+R5KfP2NcqZCCm2WVAch9Sq+rIedNIRc+Rrk4Y=; b=bV0CreZ8FVPfrjtIoDfKiOpgREP1ulwVyUsX4+CdGv77byad5U1pdWAolmY8IIwuj5ylSc zzFKelkpwS5vbzyGVWQAVtw2lZyIB/Wovb1U54MS6EbaccEO6gVKAzRaqLoq3DWUXmUc2/ XvMxafv1L4J8FJ7qOutoVcLMcfPFzcE= 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-18-D8hwKHlfMBi3d7eLYkyNYA-1; Wed, 11 Jan 2023 09:28:16 -0500 X-MC-Unique: D8hwKHlfMBi3d7eLYkyNYA-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 4290218E6C41; Wed, 11 Jan 2023 14:28:15 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.33.36.87]) by smtp.corp.redhat.com (Postfix) with ESMTP id 63C391121314; Wed, 11 Jan 2023 14:28:13 +0000 (UTC) Organization: Red Hat UK Ltd. 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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH v5 5/9] netfs: Add a function to extract a UBUF or IOVEC into a BVEC iterator From: David Howells To: Al Viro Cc: Jeff Layton , Steve French , Shyam Prasad N , Rohith Surabattula , linux-cachefs@redhat.com, linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, dhowells@redhat.com, Christoph Hellwig , 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 Date: Wed, 11 Jan 2023 14:28:12 +0000 Message-ID: <167344729278.2425628.3277966637577509831.stgit@warthog.procyon.org.uk> In-Reply-To: <167344725490.2425628.13771289553670112965.stgit@warthog.procyon.org.uk> References: <167344725490.2425628.13771289553670112965.stgit@warthog.procyon.org.uk> User-Agent: StGit/1.5 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.3 Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org Add a function to extract the pages from a user-space supplied iterator (UBUF- or IOVEC-type) into a BVEC-type iterator, retaining the pages by getting a ref on them (ITER_SOURCE, ie. WRITE) or pinning them (ITER_DEST, ie. READ) as we go. This is useful in three situations: (1) A userspace thread may have a sibling that unmaps or remaps the process's VM during the operation, changing the assignment of the pages and potentially causing an error. Retaining the pages keeps some pages around, even if this occurs; futher, we find out at the point of extraction if EFAULT is going to be incurred. (2) Pages might get swapped out/discarded if not retained, so we want to retain them to avoid the reload causing a deadlock due to a DIO from/to an mmapped region on the same file. (3) The iterator may get passed to sendmsg() by the filesystem. If a fault occurs, we may get a short write to a TCP stream that's then tricky to recover from. We don't deal with other types of iterator here, leaving it to other mechanisms to retain the pages (eg. PG_locked, PG_writeback and the pipe lock). Changes: ======== ver #3) - Switch to using EXPORT_SYMBOL_GPL to prevent indirect 3rd-party access to get/pin_user_pages_fast()[1]. Signed-off-by: David Howells cc: Jeff Layton cc: Steve French cc: Shyam Prasad N cc: Rohith Surabattula cc: linux-cachefs@redhat.com cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/Y3zFzdWnWlEJ8X8/@infradead.org/ [1] Link: https://lore.kernel.org/r/166697255265.61150.6289490555867717077.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166732026503.3186319.12020462741051772825.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166869690376.3723671.8813331570219190705.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166920904810.1461876.11603559311247187100.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/166997422579.9475.12101700945635692496.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/167305164634.1521586.12199658904363317567.stgit@warthog.procyon.org.uk/ # v4 --- fs/netfs/Makefile | 1 fs/netfs/iterator.c | 99 +++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/netfs.h | 3 + 3 files changed, 103 insertions(+) create mode 100644 fs/netfs/iterator.c diff --git a/fs/netfs/Makefile b/fs/netfs/Makefile index f684c0cd1ec5..386d6fb92793 100644 --- a/fs/netfs/Makefile +++ b/fs/netfs/Makefile @@ -3,6 +3,7 @@ netfs-y := \ buffered_read.o \ io.o \ + iterator.o \ main.o \ objects.o diff --git a/fs/netfs/iterator.c b/fs/netfs/iterator.c new file mode 100644 index 000000000000..7d802d21b9c5 --- /dev/null +++ b/fs/netfs/iterator.c @@ -0,0 +1,99 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* Iterator helpers. + * + * Copyright (C) 2022 Red Hat, Inc. All Rights Reserved. + * Written by David Howells (dhowells@redhat.com) + */ + +#include +#include +#include +#include +#include "internal.h" + +/** + * netfs_extract_user_iter - Extract the pages from a user iterator into a bvec + * @orig: The original iterator + * @orig_len: The amount of iterator to copy + * @new: The iterator to be set up + * @cleanup_mode: Where to indicate the cleanup mode + * + * Extract the page fragments from the given amount of the source iterator and + * build up a second iterator that refers to all of those bits. This allows + * the original iterator to disposed of. + * + * On success, the number of elements in the bvec is returned, the original + * iterator will have been advanced by the amount extracted and @*cleanup_mode + * will have been set to FOLL_GET, FOLL_PIN or 0. + */ +ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len, + struct iov_iter *new, unsigned int *cleanup_mode) +{ + struct bio_vec *bv = NULL; + struct page **pages; + unsigned int cur_npages; + unsigned int max_pages; + unsigned int npages = 0; + unsigned int i; + ssize_t ret; + size_t count = orig_len, offset, len; + size_t bv_size, pg_size; + + if (WARN_ON_ONCE(!iter_is_ubuf(orig) && !iter_is_iovec(orig))) + return -EIO; + + max_pages = iov_iter_npages(orig, INT_MAX); + bv_size = array_size(max_pages, sizeof(*bv)); + bv = kvmalloc(bv_size, GFP_KERNEL); + if (!bv) + return -ENOMEM; + + *cleanup_mode = 0; + + /* Put the page list at the end of the bvec list storage. bvec + * elements are larger than page pointers, so as long as we work + * 0->last, we should be fine. + */ + pg_size = array_size(max_pages, sizeof(*pages)); + pages = (void *)bv + bv_size - pg_size; + + while (count && npages < max_pages) { + ret = iov_iter_extract_pages(orig, &pages, count, + max_pages - npages, 0, + &offset, cleanup_mode); + if (ret < 0) { + pr_err("Couldn't get user pages (rc=%zd)\n", ret); + break; + } + + if (ret > count) { + pr_err("get_pages rc=%zd more than %zu\n", ret, count); + break; + } + + count -= ret; + ret += offset; + cur_npages = DIV_ROUND_UP(ret, PAGE_SIZE); + + if (npages + cur_npages > max_pages) { + pr_err("Out of bvec array capacity (%u vs %u)\n", + npages + cur_npages, max_pages); + break; + } + + for (i = 0; i < cur_npages; i++) { + len = ret > PAGE_SIZE ? PAGE_SIZE : ret; + bv[npages + i].bv_page = *pages++; + bv[npages + i].bv_offset = offset; + bv[npages + i].bv_len = len - offset; + ret -= len; + offset = 0; + } + + npages += cur_npages; + } + + iov_iter_bvec(new, iov_iter_rw(orig), bv, npages, orig_len - count); + return npages; +} +EXPORT_SYMBOL_GPL(netfs_extract_user_iter); diff --git a/include/linux/netfs.h b/include/linux/netfs.h index 4c76ddfb6a67..26fe3e6bafa1 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -296,6 +296,9 @@ void netfs_get_subrequest(struct netfs_io_subrequest *subreq, void netfs_put_subrequest(struct netfs_io_subrequest *subreq, bool was_async, enum netfs_sreq_ref_trace what); void netfs_stats_show(struct seq_file *); +ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len, + struct iov_iter *new, + unsigned int *cleanup_mode); /** * netfs_inode - Get the netfs inode context from the inode From patchwork Wed Jan 11 14:28:20 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: David Howells X-Patchwork-Id: 13096809 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 8401DC46467 for ; Wed, 11 Jan 2023 14:34:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234429AbjAKOeM (ORCPT ); Wed, 11 Jan 2023 09:34:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43042 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S239115AbjAKOcL (ORCPT ); Wed, 11 Jan 2023 09:32:11 -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 6D1381E3CA for ; Wed, 11 Jan 2023 06:28:29 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1673447308; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=XSPT0NesBpkhjthipOTtnN5lzQWDCwieFj4pGP0L1Wo=; b=VkbgDbh4a/2jj8KrEfgG5/CYZqyxhm3VBEKZdiuLcSs5a6TTDnGy1AsqMVXiYEEvgImD9J szVowPbfTUYIYaYaTSif0R0BdEp8cr97rz6q7k2dTRTWiQMvJKVxTxyvcSCV5CDBSqLBDs GQGLsCPT/mM6h+mTQDwwRefrY1nTEpY= 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-118-23Hj1xZWOe2kvc8Rnlcp5Q-1; Wed, 11 Jan 2023 09:28:23 -0500 X-MC-Unique: 23Hj1xZWOe2kvc8Rnlcp5Q-1 Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.rdu2.redhat.com [10.11.54.2]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id D9DBA88904B; Wed, 11 Jan 2023 14:28:22 +0000 (UTC) Received: from warthog.procyon.org.uk (unknown [10.33.36.87]) by smtp.corp.redhat.com (Postfix) with ESMTP id 0A85640C1141; Wed, 11 Jan 2023 14:28:20 +0000 (UTC) Organization: Red Hat UK Ltd. 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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH v5 6/9] netfs: Add a function to extract an iterator into a scatterlist From: David Howells To: Al Viro Cc: Jeff Layton , Steve French , Shyam Prasad N , Rohith Surabattula , linux-cachefs@redhat.com, linux-cifs@vger.kernel.org, linux-fsdevel@vger.kernel.org, dhowells@redhat.com, Christoph Hellwig , 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 Date: Wed, 11 Jan 2023 14:28:20 +0000 Message-ID: <167344730041.2425628.14391053364759792950.stgit@warthog.procyon.org.uk> In-Reply-To: <167344725490.2425628.13771289553670112965.stgit@warthog.procyon.org.uk> References: <167344725490.2425628.13771289553670112965.stgit@warthog.procyon.org.uk> User-Agent: StGit/1.5 MIME-Version: 1.0 X-Scanned-By: MIMEDefang 3.1 on 10.11.54.2 Precedence: bulk List-ID: X-Mailing-List: linux-cifs@vger.kernel.org Provide a function for filling in a scatterlist from the list of pages contained in an iterator. If the iterator is UBUF- or IOBUF-type, the pages have a ref (ITER_SOURCE, ie. WRITE) or a pin (ITER_DEST, ie. READ) taken on them. If the iterator is BVEC-, KVEC- or XARRAY-type, no ref is taken on the pages and it is left to the caller to manage their lifetime. It cannot be assumed that a ref can be validly taken, particularly in the case of a KVEC iterator. Changes: ======== ver #3) - Switch to using EXPORT_SYMBOL_GPL to prevent indirect 3rd-party access to get/pin_user_pages_fast()[1]. Signed-off-by: David Howells cc: Jeff Layton cc: Steve French cc: Shyam Prasad N cc: Rohith Surabattula cc: linux-cachefs@redhat.com cc: linux-cifs@vger.kernel.org cc: linux-fsdevel@vger.kernel.org Link: https://lore.kernel.org/r/Y3zFzdWnWlEJ8X8/@infradead.org/ [1] Link: https://lore.kernel.org/r/166697255985.61150.16489950598033809487.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166732027275.3186319.5186488812166611598.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166869691313.3723671.10714823767342163891.stgit@warthog.procyon.org.uk/ # rfc Link: https://lore.kernel.org/r/166920905749.1461876.12079195122363691498.stgit@warthog.procyon.org.uk/ # v2 Link: https://lore.kernel.org/r/166997423514.9475.11145024341505464337.stgit@warthog.procyon.org.uk/ # v3 Link: https://lore.kernel.org/r/167305165398.1521586.12353215176136705725.stgit@warthog.procyon.org.uk/ # v4 --- fs/netfs/iterator.c | 268 +++++++++++++++++++++++++++++++++++++++++++++++++ include/linux/netfs.h | 4 + mm/vmalloc.c | 1 3 files changed, 273 insertions(+) diff --git a/fs/netfs/iterator.c b/fs/netfs/iterator.c index 7d802d21b9c5..82c46e3caf1d 100644 --- a/fs/netfs/iterator.c +++ b/fs/netfs/iterator.c @@ -7,7 +7,9 @@ #include #include +#include #include +#include #include #include "internal.h" @@ -97,3 +99,269 @@ ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len, return npages; } EXPORT_SYMBOL_GPL(netfs_extract_user_iter); + +/* + * Extract as list of up to sg_max pages from UBUF- or IOVEC-class iterators, + * pin or get refs on them appropriate and add them to the scatterlist. + */ +static ssize_t netfs_extract_user_to_sg(struct iov_iter *iter, + ssize_t maxsize, + struct sg_table *sgtable, + unsigned int sg_max, + unsigned int *cleanup_mode) +{ + struct scatterlist *sg = sgtable->sgl + sgtable->nents; + struct page **pages; + unsigned int npages; + ssize_t ret = 0, res; + size_t len, off; + + *cleanup_mode = 0; + + /* We decant the page list into the tail of the scatterlist */ + pages = (void *)sgtable->sgl + array_size(sg_max, sizeof(struct scatterlist)); + pages -= sg_max; + + do { + res = iov_iter_extract_pages(iter, &pages, maxsize, sg_max, 0, + &off, cleanup_mode); + if (res < 0) + goto failed; + + len = res; + maxsize -= len; + ret += len; + npages = DIV_ROUND_UP(off + len, PAGE_SIZE); + sg_max -= npages; + + for (; npages < 0; npages--) { + struct page *page = *pages; + size_t seg = min_t(size_t, PAGE_SIZE - off, len); + + *pages++ = NULL; + sg_set_page(sg, page, len, off); + sgtable->nents++; + sg++; + len -= seg; + off = 0; + } + } while (maxsize > 0 && sg_max > 0); + + return ret; + +failed: + while (sgtable->nents > sgtable->orig_nents) + put_page(sg_page(&sgtable->sgl[--sgtable->nents])); + return res; +} + +/* + * Extract up to sg_max pages from a BVEC-type iterator and add them to the + * scatterlist. The pages are not pinned. + */ +static ssize_t netfs_extract_bvec_to_sg(struct iov_iter *iter, + ssize_t maxsize, + struct sg_table *sgtable, + unsigned int sg_max, + unsigned int *cleanup_mode) +{ + const struct bio_vec *bv = iter->bvec; + struct scatterlist *sg = sgtable->sgl + sgtable->nents; + unsigned long start = iter->iov_offset; + unsigned int i; + ssize_t ret = 0; + + for (i = 0; i < iter->nr_segs; i++) { + size_t off, len; + + len = bv[i].bv_len; + if (start >= len) { + start -= len; + continue; + } + + len = min_t(size_t, maxsize, len - start); + off = bv[i].bv_offset + start; + + sg_set_page(sg, bv[i].bv_page, len, off); + sgtable->nents++; + sg++; + sg_max--; + + ret += len; + maxsize -= len; + if (maxsize <= 0 || sg_max == 0) + break; + start = 0; + } + + if (ret > 0) + iov_iter_advance(iter, ret); + *cleanup_mode = 0; + return ret; +} + +/* + * Extract up to sg_max pages from a KVEC-type iterator and add them to the + * scatterlist. This can deal with vmalloc'd buffers as well as kmalloc'd or + * static buffers. The pages are not pinned. + */ +static ssize_t netfs_extract_kvec_to_sg(struct iov_iter *iter, + ssize_t maxsize, + struct sg_table *sgtable, + unsigned int sg_max, + unsigned int *cleanup_mode) +{ + const struct kvec *kv = iter->kvec; + struct scatterlist *sg = sgtable->sgl + sgtable->nents; + unsigned long start = iter->iov_offset; + unsigned int i; + ssize_t ret = 0; + + for (i = 0; i < iter->nr_segs; i++) { + struct page *page; + unsigned long kaddr; + size_t off, len, seg; + + len = kv[i].iov_len; + if (start >= len) { + start -= len; + continue; + } + + kaddr = (unsigned long)kv[i].iov_base + start; + off = kaddr & ~PAGE_MASK; + len = min_t(size_t, maxsize, len - start); + kaddr &= PAGE_MASK; + + maxsize -= len; + ret += len; + do { + seg = min_t(size_t, len, PAGE_SIZE - off); + if (is_vmalloc_or_module_addr((void *)kaddr)) + page = vmalloc_to_page((void *)kaddr); + else + page = virt_to_page(kaddr); + + sg_set_page(sg, page, len, off); + sgtable->nents++; + sg++; + sg_max--; + + len -= seg; + kaddr += PAGE_SIZE; + off = 0; + } while (len > 0 && sg_max > 0); + + if (maxsize <= 0 || sg_max == 0) + break; + start = 0; + } + + if (ret > 0) + iov_iter_advance(iter, ret); + *cleanup_mode = 0; + return ret; +} + +/* + * Extract up to sg_max folios from an XARRAY-type iterator and add them to + * the scatterlist. The pages are not pinned. + */ +static ssize_t netfs_extract_xarray_to_sg(struct iov_iter *iter, + ssize_t maxsize, + struct sg_table *sgtable, + unsigned int sg_max, + unsigned int *cleanup_mode) +{ + struct scatterlist *sg = sgtable->sgl + sgtable->nents; + struct xarray *xa = iter->xarray; + struct folio *folio; + loff_t start = iter->xarray_start + iter->iov_offset; + pgoff_t index = start / PAGE_SIZE; + ssize_t ret = 0; + size_t offset, len; + XA_STATE(xas, xa, index); + + rcu_read_lock(); + + xas_for_each(&xas, folio, ULONG_MAX) { + if (xas_retry(&xas, folio)) + continue; + if (WARN_ON(xa_is_value(folio))) + break; + if (WARN_ON(folio_test_hugetlb(folio))) + break; + + offset = offset_in_folio(folio, start); + len = min_t(size_t, maxsize, folio_size(folio) - offset); + + sg_set_page(sg, folio_page(folio, 0), len, offset); + sgtable->nents++; + sg++; + sg_max--; + + maxsize -= len; + ret += len; + if (maxsize <= 0 || sg_max == 0) + break; + } + + rcu_read_unlock(); + if (ret > 0) + iov_iter_advance(iter, ret); + *cleanup_mode = 0; + return ret; +} + +/** + * netfs_extract_iter_to_sg - Extract pages from an iterator and add ot an sglist + * @iter: The iterator to extract from + * @maxsize: The amount of iterator to copy + * @sgtable: The scatterlist table to fill in + * @sg_max: Maximum number of elements in @sgtable that may be filled + * @cleanup_mode: Where to return the cleanup mode + * + * Extract the page fragments from the given amount of the source iterator and + * add them to a scatterlist that refers to all of those bits, to a maximum + * addition of @sg_max elements. + * + * The pages referred to by UBUF- and IOVEC-type iterators are extracted and + * pinned; BVEC-, KVEC- and XARRAY-type are extracted but aren't pinned; PIPE- + * and DISCARD-type are not supported. + * + * No end mark is placed on the scatterlist; that's left to the caller. + * + * If successul, @sgtable->nents is updated to include the number of elements + * added and the number of bytes added is returned. @sgtable->orig_nents is + * left unaltered. + */ +ssize_t netfs_extract_iter_to_sg(struct iov_iter *iter, size_t maxsize, + struct sg_table *sgtable, unsigned int sg_max, + unsigned int *cleanup_mode) +{ + if (maxsize == 0) + return 0; + + switch (iov_iter_type(iter)) { + case ITER_UBUF: + case ITER_IOVEC: + return netfs_extract_user_to_sg(iter, maxsize, sgtable, sg_max, + cleanup_mode); + case ITER_BVEC: + return netfs_extract_bvec_to_sg(iter, maxsize, sgtable, sg_max, + cleanup_mode); + case ITER_KVEC: + return netfs_extract_kvec_to_sg(iter, maxsize, sgtable, sg_max, + cleanup_mode); + case ITER_XARRAY: + return netfs_extract_xarray_to_sg(iter, maxsize, sgtable, sg_max, + cleanup_mode); + default: + pr_err("netfs_extract_iter_to_sg(%u) unsupported\n", + iov_iter_type(iter)); + WARN_ON_ONCE(1); + return -EIO; + } +} +EXPORT_SYMBOL_GPL(netfs_extract_iter_to_sg); diff --git a/include/linux/netfs.h b/include/linux/netfs.h index 26fe3e6bafa1..059e49233e29 100644 --- a/include/linux/netfs.h +++ b/include/linux/netfs.h @@ -299,6 +299,10 @@ void netfs_stats_show(struct seq_file *); ssize_t netfs_extract_user_iter(struct iov_iter *orig, size_t orig_len, struct iov_iter *new, unsigned int *cleanup_mode); +struct sg_table; +ssize_t netfs_extract_iter_to_sg(struct iov_iter *iter, size_t len, + struct sg_table *sgtable, unsigned int sg_max, + unsigned int *cleanup_mode); /** * netfs_inode - Get the netfs inode context from the inode diff --git a/mm/vmalloc.c b/mm/vmalloc.c index ca71de7c9d77..61f5bec0f2b6 100644 --- a/mm/vmalloc.c +++ b/mm/vmalloc.c @@ -656,6 +656,7 @@ int is_vmalloc_or_module_addr(const void *x) #endif return is_vmalloc_addr(x); } +EXPORT_SYMBOL_GPL(is_vmalloc_or_module_addr); /* * Walk a vmap address to the struct page it maps. Huge vmap mappings will