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Registered in England and Wales under Company Registration No. 3798903 Subject: [PATCH v6 22/34] nfs: Pin pages rather than ref'ing if appropriate From: David Howells To: Al Viro Cc: Trond Myklebust , Anna Schumaker , Jeff Layton , linux-nfs@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: Mon, 16 Jan 2023 23:10:39 +0000 Message-ID: <167391063989.2311931.13252453380684759087.stgit@warthog.procyon.org.uk> In-Reply-To: <167391047703.2311931.8115712773222260073.stgit@warthog.procyon.org.uk> References: <167391047703.2311931.8115712773222260073.stgit@warthog.procyon.org.uk> User-Agent: StGit/1.5 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 3.1 on 10.11.54.5 Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org Convert the NFS direct I/O 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 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). Signed-off-by: David Howells cc: Trond Myklebust cc: Anna Schumaker cc: Jeff Layton cc: linux-nfs@vger.kernel.org --- fs/nfs/direct.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-) diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c index 42af84685f20..4a3108db2cb6 100644 --- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -142,11 +142,15 @@ int nfs_swap_rw(struct kiocb *iocb, struct iov_iter *iter) return 0; } -static void nfs_direct_release_pages(struct page **pages, unsigned int npages) +static void nfs_direct_release_pages(struct page **pages, unsigned int npages, + unsigned int cleanup_mode) { unsigned int i; - for (i = 0; i < npages; i++) - put_page(pages[i]); + + if (cleanup_mode) { + for (i = 0; i < npages; i++) + page_put_unpin(pages[i], cleanup_mode); + } } void nfs_init_cinfo_from_dreq(struct nfs_commit_info *cinfo, @@ -327,17 +331,16 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq, inode_dio_begin(inode); while (iov_iter_count(iter)) { - struct page **pagevec; + struct page **pagevec = NULL; size_t bytes; size_t pgbase; unsigned npages, i; - result = iov_iter_get_pages_alloc(iter, &pagevec, - rsize, &pgbase, - FOLL_DEST_BUF); + result = iov_iter_extract_pages(iter, &pagevec, rsize, INT_MAX, + FOLL_DEST_BUF, &pgbase); if (result < 0) break; - + bytes = result; npages = (result + pgbase + PAGE_SIZE - 1) / PAGE_SIZE; for (i = 0; i < npages; i++) { @@ -363,7 +366,8 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq, pos += req_len; dreq->bytes_left -= req_len; } - nfs_direct_release_pages(pagevec, npages); + nfs_direct_release_pages(pagevec, npages, + iov_iter_extract_mode(iter, FOLL_DEST_BUF)); kvfree(pagevec); if (result < 0) break; @@ -787,14 +791,13 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq, NFS_I(inode)->write_io += iov_iter_count(iter); while (iov_iter_count(iter)) { - struct page **pagevec; + struct page **pagevec = NULL; size_t bytes; size_t pgbase; unsigned npages, i; - result = iov_iter_get_pages_alloc(iter, &pagevec, - wsize, &pgbase, - FOLL_SOURCE_BUF); + result = iov_iter_extract_pages(iter, &pagevec, wsize, INT_MAX, + FOLL_SOURCE_BUF, &pgbase); if (result < 0) break; @@ -831,7 +834,8 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq, pos += req_len; dreq->bytes_left -= req_len; } - nfs_direct_release_pages(pagevec, npages); + nfs_direct_release_pages(pagevec, npages, + iov_iter_extract_mode(iter, FOLL_SOURCE_BUF)); kvfree(pagevec); if (result < 0) break;