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 00A47C4332F for ; Tue, 8 Nov 2022 14:14:29 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235332AbiKHOO2 (ORCPT ); Tue, 8 Nov 2022 09:14:28 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235333AbiKHOOW (ORCPT ); Tue, 8 Nov 2022 09:14:22 -0500 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 5AD7559FC2 for ; Tue, 8 Nov 2022 06:14:21 -0800 (PST) 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 EB5C1615B2 for ; Tue, 8 Nov 2022 14:14:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 02B87C433C1; Tue, 8 Nov 2022 14:14:19 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1667916860; bh=jG1EYzMswtq908jgt1WDPenUVQrqH9BzQUVAZzCS2G4=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=hCmB/UGtK52iLaVuF0cs4oeeQL4pxmeafk+W0GQQ4UYooH4kRNggBvZQyxDBMnDpg WeEEZTQaB/2RsT1lYhPMqA69XKkiT5JOUAHdISxfOFTaR6llSpr2A2CTzdrxRZN+7+ z7dEG1EuxUP0CdpiJ+N1PdFD7BUriBzd2etzSoFg= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, =?UTF-8?q?=D0=9C=D0=B0=D1=80=D0=BA=20=D0=9A=D0=BE=D1=80=D0=B5=D0=BD=D0=B1=D0=B5=D1=80=D0=B3?= , Filipe Manana , David Sterba Subject: [PATCH 6.0 127/197] btrfs: fix lost file sync on direct IO write with nowait and dsync iocb Date: Tue, 8 Nov 2022 14:39:25 +0100 Message-Id: <20221108133400.745299867@linuxfoundation.org> X-Mailer: git-send-email 2.38.1 In-Reply-To: <20221108133354.787209461@linuxfoundation.org> References: <20221108133354.787209461@linuxfoundation.org> User-Agent: quilt/0.67 MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: stable@vger.kernel.org From: Filipe Manana commit 8184620ae21213d51eaf2e0bd4186baacb928172 upstream. When doing a direct IO write using a iocb with nowait and dsync set, we end up not syncing the file once the write completes. This is because we tell iomap to not call generic_write_sync(), which would result in calling btrfs_sync_file(), in order to avoid a deadlock since iomap can call it while we are holding the inode's lock and btrfs_sync_file() needs to acquire the inode's lock. The deadlock happens only if the write happens synchronously, when iomap_dio_rw() calls iomap_dio_complete() before it returns. Instead we do the sync ourselves at btrfs_do_write_iter(). For a nowait write however we can end up not doing the sync ourselves at at btrfs_do_write_iter() because the write could have been queued, and therefore we get -EIOCBQUEUED returned from iomap in such case. That makes us skip the sync call at btrfs_do_write_iter(), as we don't do it for any error returned from btrfs_direct_write(). We can't simply do the call even if -EIOCBQUEUED is returned, since that would block the task waiting for IO, both for the data since there are bios still in progress as well as potentially blocking when joining a log transaction and when syncing the log (writing log trees, super blocks, etc). So let iomap do the sync call itself and in order to avoid deadlocks for the case of synchronous writes (without nowait), use __iomap_dio_rw() and have ourselves call iomap_dio_complete() after unlocking the inode. A test case will later be sent for fstests, after this is fixed in Linus' tree. Fixes: 51bd9563b678 ("btrfs: fix deadlock due to page faults during direct IO reads and writes") Reported-by: Марк Коренберг Link: https://lore.kernel.org/linux-btrfs/CAEmTpZGRKbzc16fWPvxbr6AfFsQoLmz-Lcg-7OgJOZDboJ+SGQ@mail.gmail.com/ CC: stable@vger.kernel.org # 6.0+ Signed-off-by: Filipe Manana Signed-off-by: David Sterba Signed-off-by: Greg Kroah-Hartman --- fs/btrfs/ctree.h | 5 ++++- fs/btrfs/file.c | 22 ++++++++++++++++------ fs/btrfs/inode.c | 14 +++++++++++--- 3 files changed, 31 insertions(+), 10 deletions(-) --- a/fs/btrfs/ctree.h +++ b/fs/btrfs/ctree.h @@ -3407,7 +3407,10 @@ ssize_t btrfs_encoded_read(struct kiocb ssize_t btrfs_do_encoded_write(struct kiocb *iocb, struct iov_iter *from, const struct btrfs_ioctl_encoded_io_args *encoded); -ssize_t btrfs_dio_rw(struct kiocb *iocb, struct iov_iter *iter, size_t done_before); +ssize_t btrfs_dio_read(struct kiocb *iocb, struct iov_iter *iter, + size_t done_before); +struct iomap_dio *btrfs_dio_write(struct kiocb *iocb, struct iov_iter *iter, + size_t done_before); extern const struct dentry_operations btrfs_dentry_operations; --- a/fs/btrfs/file.c +++ b/fs/btrfs/file.c @@ -1889,6 +1889,7 @@ static ssize_t btrfs_direct_write(struct loff_t endbyte; ssize_t err; unsigned int ilock_flags = 0; + struct iomap_dio *dio; if (iocb->ki_flags & IOCB_NOWAIT) ilock_flags |= BTRFS_ILOCK_TRY; @@ -1949,11 +1950,22 @@ relock: * So here we disable page faults in the iov_iter and then retry if we * got -EFAULT, faulting in the pages before the retry. */ -again: from->nofault = true; - err = btrfs_dio_rw(iocb, from, written); + dio = btrfs_dio_write(iocb, from, written); from->nofault = false; + /* + * iomap_dio_complete() will call btrfs_sync_file() if we have a dsync + * iocb, and that needs to lock the inode. So unlock it before calling + * iomap_dio_complete() to avoid a deadlock. + */ + btrfs_inode_unlock(inode, ilock_flags); + + if (IS_ERR_OR_NULL(dio)) + err = PTR_ERR_OR_ZERO(dio); + else + err = iomap_dio_complete(dio); + /* No increment (+=) because iomap returns a cumulative value. */ if (err > 0) written = err; @@ -1979,12 +1991,10 @@ again: } else { fault_in_iov_iter_readable(from, left); prev_left = left; - goto again; + goto relock; } } - btrfs_inode_unlock(inode, ilock_flags); - /* * If 'err' is -ENOTBLK or we have not written all data, then it means * we must fallback to buffered IO. @@ -3787,7 +3797,7 @@ again: */ pagefault_disable(); to->nofault = true; - ret = btrfs_dio_rw(iocb, to, read); + ret = btrfs_dio_read(iocb, to, read); to->nofault = false; pagefault_enable(); --- a/fs/btrfs/inode.c +++ b/fs/btrfs/inode.c @@ -8241,13 +8241,21 @@ static const struct iomap_dio_ops btrfs_ .bio_set = &btrfs_dio_bioset, }; -ssize_t btrfs_dio_rw(struct kiocb *iocb, struct iov_iter *iter, size_t done_before) +ssize_t btrfs_dio_read(struct kiocb *iocb, struct iov_iter *iter, size_t done_before) { struct btrfs_dio_data data; return iomap_dio_rw(iocb, iter, &btrfs_dio_iomap_ops, &btrfs_dio_ops, - IOMAP_DIO_PARTIAL | IOMAP_DIO_NOSYNC, - &data, done_before); + IOMAP_DIO_PARTIAL, &data, done_before); +} + +struct iomap_dio *btrfs_dio_write(struct kiocb *iocb, struct iov_iter *iter, + size_t done_before) +{ + struct btrfs_dio_data data; + + return __iomap_dio_rw(iocb, iter, &btrfs_dio_iomap_ops, &btrfs_dio_ops, + IOMAP_DIO_PARTIAL, &data, done_before); } static int btrfs_fiemap(struct inode *inode, struct fiemap_extent_info *fieinfo,