From patchwork Mon Aug 5 20:05:01 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jeffrey Layton X-Patchwork-Id: 11077725 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id EBEDA912 for ; Mon, 5 Aug 2019 20:05:06 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id DB501287B4 for ; Mon, 5 Aug 2019 20:05:06 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id CDF3A288D0; Mon, 5 Aug 2019 20:05:06 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id EA860287B4 for ; Mon, 5 Aug 2019 20:05:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730457AbfHEUFE (ORCPT ); Mon, 5 Aug 2019 16:05:04 -0400 Received: from mail.kernel.org ([198.145.29.99]:59020 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727802AbfHEUFD (ORCPT ); Mon, 5 Aug 2019 16:05:03 -0400 Received: from tleilax.poochiereds.net (cpe-71-70-156-158.nc.res.rr.com [71.70.156.158]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8503B20665; Mon, 5 Aug 2019 20:05:02 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1565035503; bh=V2AjWznxs9ahJCi+JaX7ad+f1VaKXlfKf6I2i+TThz0=; h=From:To:Cc:Subject:Date:From; b=FLvf33y1y2eTFpcp5s97J/x3ULARMWupJDtsu4IY0klIExI2C1J0VUJC+5COK+nBJ LBN76NditSyeQOa1FsSZayKdP3D+VuCzutD6f3RDnuo+Ug4KecwT8OfYqAktQFIgED HHudYt9BISRS4+PjV4YKmNhKCabyfLw5d32PRLvw= From: Jeff Layton To: ceph-devel@vger.kernel.org Cc: idryomov@gmail.com, sage@redhat.com, ukernel@gmail.com Subject: [PATCH] ceph: add buffered/direct exclusionary locking for reads and writes Date: Mon, 5 Aug 2019 16:05:01 -0400 Message-Id: <20190805200501.17905-1-jlayton@kernel.org> X-Mailer: git-send-email 2.21.0 MIME-Version: 1.0 Sender: ceph-devel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: ceph-devel@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP xfstest generic/451 intermittently fails. The test does O_DIRECT writes to a file, and then reads back the result using buffered I/O, while running a separate set of tasks that are also doing buffered reads. The client will invalidate the cache prior to a direct write, but it's easy for one of the other readers' replies to race in and reinstantiate the invalidated range with stale data. To fix this, we must to serialize direct I/O writes and buffered reads. We could just sprinkle in some shared locks on the i_rwsem for reads, and increase the exclusive footprint on the write side, but that would cause O_DIRECT writes to end up serialized vs. other direct requests. Instead, borrow the scheme used by nfs.ko. Buffered writes take the i_rwsem exclusively, but buffered reads and all O_DIRECT requests take a shared lock, allowing them to run in parallel. To fix the bug though, we need buffered reads and O_DIRECT I/O to not run in parallel. A flag on the ceph_inode_info is used to indicate whether it's in direct or buffered I/O mode. When a conflicting request is submitted, it will block until the inode can flip to the necessary mode. Signed-off-by: Jeff Layton --- fs/ceph/Makefile | 2 +- fs/ceph/file.c | 28 ++++++-- fs/ceph/io.c | 163 +++++++++++++++++++++++++++++++++++++++++++++++ fs/ceph/io.h | 12 ++++ fs/ceph/super.h | 2 +- 5 files changed, 198 insertions(+), 9 deletions(-) create mode 100644 fs/ceph/io.c create mode 100644 fs/ceph/io.h diff --git a/fs/ceph/Makefile b/fs/ceph/Makefile index a699e320393f..c1da294418d1 100644 --- a/fs/ceph/Makefile +++ b/fs/ceph/Makefile @@ -6,7 +6,7 @@ obj-$(CONFIG_CEPH_FS) += ceph.o ceph-y := super.o inode.o dir.o file.o locks.o addr.o ioctl.o \ - export.o caps.o snap.o xattr.o quota.o \ + export.o caps.o snap.o xattr.o quota.o io.o \ mds_client.o mdsmap.o strings.o ceph_frag.o \ debugfs.o diff --git a/fs/ceph/file.c b/fs/ceph/file.c index 5182e1a49d6f..d7d264e05303 100644 --- a/fs/ceph/file.c +++ b/fs/ceph/file.c @@ -15,6 +15,7 @@ #include "super.h" #include "mds_client.h" #include "cache.h" +#include "io.h" static __le32 ceph_flags_sys2wire(u32 flags) { @@ -1284,12 +1285,16 @@ static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to) if (ci->i_inline_version == CEPH_INLINE_NONE) { if (!retry_op && (iocb->ki_flags & IOCB_DIRECT)) { + ceph_start_io_direct(inode); ret = ceph_direct_read_write(iocb, to, NULL, NULL); + ceph_end_io_direct(inode); if (ret >= 0 && ret < len) retry_op = CHECK_EOF; } else { + ceph_start_io_read(inode); ret = ceph_sync_read(iocb, to, &retry_op); + ceph_end_io_read(inode); } } else { retry_op = READ_INLINE; @@ -1300,7 +1305,9 @@ static ssize_t ceph_read_iter(struct kiocb *iocb, struct iov_iter *to) inode, ceph_vinop(inode), iocb->ki_pos, (unsigned)len, ceph_cap_string(got)); ceph_add_rw_context(fi, &rw_ctx); + ceph_start_io_read(inode); ret = generic_file_read_iter(iocb, to); + ceph_end_io_read(inode); ceph_del_rw_context(fi, &rw_ctx); } dout("aio_read %p %llx.%llx dropping cap refs on %s = %d\n", @@ -1409,7 +1416,10 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from) return -ENOMEM; retry_snap: - inode_lock(inode); + if (iocb->ki_flags & IOCB_DIRECT) + ceph_start_io_direct(inode); + else + ceph_start_io_write(inode); /* We can write back this queue in page reclaim */ current->backing_dev_info = inode_to_bdi(inode); @@ -1480,7 +1490,6 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from) (ci->i_ceph_flags & CEPH_I_ERROR_WRITE)) { struct ceph_snap_context *snapc; struct iov_iter data; - inode_unlock(inode); spin_lock(&ci->i_ceph_lock); if (__ceph_have_pending_cap_snap(ci)) { @@ -1497,11 +1506,14 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from) /* we might need to revert back to that point */ data = *from; - if (iocb->ki_flags & IOCB_DIRECT) + if (iocb->ki_flags & IOCB_DIRECT) { written = ceph_direct_read_write(iocb, &data, snapc, &prealloc_cf); - else + ceph_end_io_direct(inode); + } else { written = ceph_sync_write(iocb, &data, pos, snapc); + ceph_end_io_write(inode); + } if (written > 0) iov_iter_advance(from, written); ceph_put_snap_context(snapc); @@ -1516,7 +1528,7 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from) written = generic_perform_write(file, from, pos); if (likely(written >= 0)) iocb->ki_pos = pos + written; - inode_unlock(inode); + ceph_end_io_write(inode); } if (written >= 0) { @@ -1551,9 +1563,11 @@ static ssize_t ceph_write_iter(struct kiocb *iocb, struct iov_iter *from) } goto out_unlocked; - out: - inode_unlock(inode); + if (iocb->ki_flags & IOCB_DIRECT) + ceph_end_io_direct(inode); + else + ceph_end_io_write(inode); out_unlocked: ceph_free_cap_flush(prealloc_cf); current->backing_dev_info = NULL; diff --git a/fs/ceph/io.c b/fs/ceph/io.c new file mode 100644 index 000000000000..8367cbcc81e8 --- /dev/null +++ b/fs/ceph/io.c @@ -0,0 +1,163 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * Copyright (c) 2016 Trond Myklebust + * Copyright (c) 2019 Jeff Layton + * + * I/O and data path helper functionality. + * + * Heavily borrowed from equivalent code in fs/nfs/io.c + */ + +#include + +#include +#include +#include +#include + +#include "super.h" +#include "io.h" + +/* Call with exclusively locked inode->i_rwsem */ +static void ceph_block_o_direct(struct ceph_inode_info *ci, struct inode *inode) +{ + lockdep_assert_held_write(&inode->i_rwsem); + + if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT) { + spin_lock(&ci->i_ceph_lock); + ci->i_ceph_flags &= ~CEPH_I_ODIRECT; + spin_unlock(&ci->i_ceph_lock); + inode_dio_wait(inode); + } +} + +/** + * ceph_start_io_read - declare the file is being used for buffered reads + * @inode: file inode + * + * Declare that a buffered read operation is about to start, and ensure + * that we block all direct I/O. + * On exit, the function ensures that the CEPH_I_ODIRECT flag is unset, + * and holds a shared lock on inode->i_rwsem to ensure that the flag + * cannot be changed. + * In practice, this means that buffered read operations are allowed to + * execute in parallel, thanks to the shared lock, whereas direct I/O + * operations need to wait to grab an exclusive lock in order to set + * CEPH_I_ODIRECT. + * Note that buffered writes and truncates both take a write lock on + * inode->i_rwsem, meaning that those are serialised w.r.t. the reads. + */ +void +ceph_start_io_read(struct inode *inode) +{ + struct ceph_inode_info *ci = ceph_inode(inode); + + /* Be an optimist! */ + down_read(&inode->i_rwsem); + if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)) + return; + up_read(&inode->i_rwsem); + /* Slow path.... */ + down_write(&inode->i_rwsem); + ceph_block_o_direct(ci, inode); + downgrade_write(&inode->i_rwsem); +} + +/** + * ceph_end_io_read - declare that the buffered read operation is done + * @inode: file inode + * + * Declare that a buffered read operation is done, and release the shared + * lock on inode->i_rwsem. + */ +void +ceph_end_io_read(struct inode *inode) +{ + up_read(&inode->i_rwsem); +} + +/** + * ceph_start_io_write - declare the file is being used for buffered writes + * @inode: file inode + * + * Declare that a buffered read operation is about to start, and ensure + * that we block all direct I/O. + */ +void +ceph_start_io_write(struct inode *inode) +{ + down_write(&inode->i_rwsem); + ceph_block_o_direct(ceph_inode(inode), inode); +} + +/** + * ceph_end_io_write - declare that the buffered write operation is done + * @inode: file inode + * + * Declare that a buffered write operation is done, and release the + * lock on inode->i_rwsem. + */ +void +ceph_end_io_write(struct inode *inode) +{ + up_write(&inode->i_rwsem); +} + +/* Call with exclusively locked inode->i_rwsem */ +static void ceph_block_buffered(struct ceph_inode_info *ci, struct inode *inode) +{ + lockdep_assert_held_write(&inode->i_rwsem); + + if (!(READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT)) { + spin_lock(&ci->i_ceph_lock); + ci->i_ceph_flags |= CEPH_I_ODIRECT; + spin_unlock(&ci->i_ceph_lock); + /* FIXME: unmap_mapping_range? */ + filemap_write_and_wait(inode->i_mapping); + } +} + +/** + * ceph_end_io_direct - declare the file is being used for direct i/o + * @inode: file inode + * + * Declare that a direct I/O operation is about to start, and ensure + * that we block all buffered I/O. + * On exit, the function ensures that the CEPH_I_ODIRECT flag is set, + * and holds a shared lock on inode->i_rwsem to ensure that the flag + * cannot be changed. + * In practice, this means that direct I/O operations are allowed to + * execute in parallel, thanks to the shared lock, whereas buffered I/O + * operations need to wait to grab an exclusive lock in order to clear + * CEPH_I_ODIRECT. + * Note that buffered writes and truncates both take a write lock on + * inode->i_rwsem, meaning that those are serialised w.r.t. O_DIRECT. + */ +void +ceph_start_io_direct(struct inode *inode) +{ + struct ceph_inode_info *ci = ceph_inode(inode); + + /* Be an optimist! */ + down_read(&inode->i_rwsem); + if (READ_ONCE(ci->i_ceph_flags) & CEPH_I_ODIRECT) + return; + up_read(&inode->i_rwsem); + /* Slow path.... */ + down_write(&inode->i_rwsem); + ceph_block_buffered(ci, inode); + downgrade_write(&inode->i_rwsem); +} + +/** + * ceph_end_io_direct - declare that the direct i/o operation is done + * @inode: file inode + * + * Declare that a direct I/O operation is done, and release the shared + * lock on inode->i_rwsem. + */ +void +ceph_end_io_direct(struct inode *inode) +{ + up_read(&inode->i_rwsem); +} diff --git a/fs/ceph/io.h b/fs/ceph/io.h new file mode 100644 index 000000000000..fa594cd77348 --- /dev/null +++ b/fs/ceph/io.h @@ -0,0 +1,12 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef _FS_CEPH_IO_H +#define _FS_CEPH_IO_H + +void ceph_start_io_read(struct inode *inode); +void ceph_end_io_read(struct inode *inode); +void ceph_start_io_write(struct inode *inode); +void ceph_end_io_write(struct inode *inode); +void ceph_start_io_direct(struct inode *inode); +void ceph_end_io_direct(struct inode *inode); + +#endif /* FS_CEPH_IO_H */ diff --git a/fs/ceph/super.h b/fs/ceph/super.h index 03e4828c7635..46a64293a3f7 100644 --- a/fs/ceph/super.h +++ b/fs/ceph/super.h @@ -516,7 +516,7 @@ static inline struct inode *ceph_find_inode(struct super_block *sb, #define CEPH_I_FLUSH_SNAPS (1 << 9) /* need flush snapss */ #define CEPH_I_ERROR_WRITE (1 << 10) /* have seen write errors */ #define CEPH_I_ERROR_FILELOCK (1 << 11) /* have seen file lock errors */ - +#define CEPH_I_ODIRECT (1 << 12) /* active direct I/O in progress */ /* * Masks of ceph inode work.