From mboxrd@z Thu Jan 1 00:00:00 1970 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 A5D34C352B6 for ; Thu, 14 Apr 2022 14:11:11 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1344074AbiDNOJk (ORCPT ); Thu, 14 Apr 2022 10:09:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57316 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1344091AbiDNNaV (ORCPT ); Thu, 14 Apr 2022 09:30:21 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A71466265; Thu, 14 Apr 2022 06:27:56 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 4377960C14; Thu, 14 Apr 2022 13:27:56 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 4B3EAC385A1; Thu, 14 Apr 2022 13:27:55 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1649942875; bh=a1iPLyt3/Czrbu1gWemAJpCnIFWibewpU8fc5Nmz7O4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=RJlFDdRmh20T6i46KywZuwpON/43tnjmX8O9UITh5tYTE1+d4sfCYtnjKU1tgwjOA TtQx5WwaL9sjS4g9K1MwIQfDRPC22cioLR5bFmhcV9XPQVaaccM6uQ8JeXhw3ZuY+i jgH353cnGuuKVXjop6TD3z37a5ZsM9lOudWk/WC4= From: Greg Kroah-Hartman To: linux-kernel@vger.kernel.org Cc: Greg Kroah-Hartman , stable@vger.kernel.org, NeilBrown , Trond Myklebust , Sasha Levin Subject: [PATCH 4.19 294/338] NFS: swap IO handling is slightly different for O_DIRECT IO Date: Thu, 14 Apr 2022 15:13:17 +0200 Message-Id: <20220414110847.255786443@linuxfoundation.org> X-Mailer: git-send-email 2.35.2 In-Reply-To: <20220414110838.883074566@linuxfoundation.org> References: <20220414110838.883074566@linuxfoundation.org> User-Agent: quilt/0.66 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: NeilBrown [ Upstream commit 64158668ac8b31626a8ce48db4cad08496eb8340 ] 1/ Taking the i_rwsem for swap IO triggers lockdep warnings regarding possible deadlocks with "fs_reclaim". These deadlocks could, I believe, eventuate if a buffered read on the swapfile was attempted. We don't need coherence with the page cache for a swap file, and buffered writes are forbidden anyway. There is no other need for i_rwsem during direct IO. So never take it for swap_rw() 2/ generic_write_checks() explicitly forbids writes to swap, and performs checks that are not needed for swap. So bypass it for swap_rw(). Signed-off-by: NeilBrown Signed-off-by: Trond Myklebust Signed-off-by: Sasha Levin --- fs/nfs/direct.c | 42 ++++++++++++++++++++++++++++-------------- fs/nfs/file.c | 4 ++-- include/linux/nfs_fs.h | 8 ++++---- 3 files changed, 34 insertions(+), 20 deletions(-) diff --git a/fs/nfs/direct.c b/fs/nfs/direct.c index e5da9d7fb69e..41ff316cd6ad 100644 --- a/fs/nfs/direct.c +++ b/fs/nfs/direct.c @@ -288,8 +288,8 @@ ssize_t nfs_direct_IO(struct kiocb *iocb, struct iov_iter *iter) VM_BUG_ON(iov_iter_count(iter) != PAGE_SIZE); if (iov_iter_rw(iter) == READ) - return nfs_file_direct_read(iocb, iter); - return nfs_file_direct_write(iocb, iter); + return nfs_file_direct_read(iocb, iter, true); + return nfs_file_direct_write(iocb, iter, true); } static void nfs_direct_release_pages(struct page **pages, unsigned int npages) @@ -553,6 +553,7 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq, * nfs_file_direct_read - file direct read operation for NFS files * @iocb: target I/O control block * @iter: vector of user buffers into which to read data + * @swap: flag indicating this is swap IO, not O_DIRECT IO * * We use this function for direct reads instead of calling * generic_file_aio_read() in order to avoid gfar's check to see if @@ -568,7 +569,8 @@ static ssize_t nfs_direct_read_schedule_iovec(struct nfs_direct_req *dreq, * client must read the updated atime from the server back into its * cache. */ -ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter) +ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter, + bool swap) { struct file *file = iocb->ki_filp; struct address_space *mapping = file->f_mapping; @@ -610,12 +612,14 @@ ssize_t nfs_file_direct_read(struct kiocb *iocb, struct iov_iter *iter) if (iter_is_iovec(iter)) dreq->flags = NFS_ODIRECT_SHOULD_DIRTY; - nfs_start_io_direct(inode); + if (!swap) + nfs_start_io_direct(inode); NFS_I(inode)->read_io += count; requested = nfs_direct_read_schedule_iovec(dreq, iter, iocb->ki_pos); - nfs_end_io_direct(inode); + if (!swap) + nfs_end_io_direct(inode); if (requested > 0) { result = nfs_direct_wait(dreq); @@ -971,6 +975,7 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq, * nfs_file_direct_write - file direct write operation for NFS files * @iocb: target I/O control block * @iter: vector of user buffers from which to write data + * @swap: flag indicating this is swap IO, not O_DIRECT IO * * We use this function for direct writes instead of calling * generic_file_aio_write() in order to avoid taking the inode @@ -987,7 +992,8 @@ static ssize_t nfs_direct_write_schedule_iovec(struct nfs_direct_req *dreq, * Note that O_APPEND is not supported for NFS direct writes, as there * is no atomic O_APPEND write facility in the NFS protocol. */ -ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter) +ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter, + bool swap) { ssize_t result = -EINVAL, requested; size_t count; @@ -1001,7 +1007,11 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter) dfprintk(FILE, "NFS: direct write(%pD2, %zd@%Ld)\n", file, iov_iter_count(iter), (long long) iocb->ki_pos); - result = generic_write_checks(iocb, iter); + if (swap) + /* bypass generic checks */ + result = iov_iter_count(iter); + else + result = generic_write_checks(iocb, iter); if (result <= 0) return result; count = result; @@ -1031,16 +1041,20 @@ ssize_t nfs_file_direct_write(struct kiocb *iocb, struct iov_iter *iter) if (!is_sync_kiocb(iocb)) dreq->iocb = iocb; - nfs_start_io_direct(inode); + if (swap) { + requested = nfs_direct_write_schedule_iovec(dreq, iter, pos); + } else { + nfs_start_io_direct(inode); - requested = nfs_direct_write_schedule_iovec(dreq, iter, pos); + requested = nfs_direct_write_schedule_iovec(dreq, iter, pos); - if (mapping->nrpages) { - invalidate_inode_pages2_range(mapping, - pos >> PAGE_SHIFT, end); - } + if (mapping->nrpages) { + invalidate_inode_pages2_range(mapping, + pos >> PAGE_SHIFT, end); + } - nfs_end_io_direct(inode); + nfs_end_io_direct(inode); + } if (requested > 0) { result = nfs_direct_wait(dreq); diff --git a/fs/nfs/file.c b/fs/nfs/file.c index 29553fdba8af..62a86c414391 100644 --- a/fs/nfs/file.c +++ b/fs/nfs/file.c @@ -157,7 +157,7 @@ nfs_file_read(struct kiocb *iocb, struct iov_iter *to) ssize_t result; if (iocb->ki_flags & IOCB_DIRECT) - return nfs_file_direct_read(iocb, to); + return nfs_file_direct_read(iocb, to, false); dprintk("NFS: read(%pD2, %zu@%lu)\n", iocb->ki_filp, @@ -606,7 +606,7 @@ ssize_t nfs_file_write(struct kiocb *iocb, struct iov_iter *from) return result; if (iocb->ki_flags & IOCB_DIRECT) - return nfs_file_direct_write(iocb, from); + return nfs_file_direct_write(iocb, from, false); dprintk("NFS: write(%pD2, %zu@%Ld)\n", file, iov_iter_count(from), (long long) iocb->ki_pos); diff --git a/include/linux/nfs_fs.h b/include/linux/nfs_fs.h index 0ff7dd2bf8a4..8ea7ceed8285 100644 --- a/include/linux/nfs_fs.h +++ b/include/linux/nfs_fs.h @@ -475,10 +475,10 @@ static inline struct rpc_cred *nfs_file_cred(struct file *file) * linux/fs/nfs/direct.c */ extern ssize_t nfs_direct_IO(struct kiocb *, struct iov_iter *); -extern ssize_t nfs_file_direct_read(struct kiocb *iocb, - struct iov_iter *iter); -extern ssize_t nfs_file_direct_write(struct kiocb *iocb, - struct iov_iter *iter); +ssize_t nfs_file_direct_read(struct kiocb *iocb, + struct iov_iter *iter, bool swap); +ssize_t nfs_file_direct_write(struct kiocb *iocb, + struct iov_iter *iter, bool swap); /* * linux/fs/nfs/dir.c -- 2.35.1