From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id ECCE417F38D for ; Tue, 14 May 2024 16:09:38 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715702979; cv=none; b=ILiEULXdy+9UcrzZh5gslwfshYy1ui0dqHao9k7IiBMsPdw1DerJpuM3+0MzMtL62Smsi4ynP5RS5qGfK84Wo/dAc5RRB1L8xzTqp3hvdQWlH3zEQlZbylfrsNVlwRw3GgNO3VgsGWvrr6rPAPIe1hMClMlxfq6IYbG+1vlfENI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1715702979; c=relaxed/simple; bh=vhQydVTRtjxkPaHb5KfVHAR+hCQTbKZ2234Oroi1hkk=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=i43dumGAen2Ct/Hbb+dm1iNSU5rLohPsuAasSWK6w7TzotUjLq8ReCIpM1reGU3RLUSHqXFGcqzHDLGfdAsAfQ18rSnz+hSsZPWVgJwGmVk9bqezeRZMX55dqsQzF7Gj5MZpCRD7DqBlCmBcVDLqEqhVI6qMQW4P6yk5SY4YocE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=f+/wsULA; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="f+/wsULA" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 3D778C2BD10; Tue, 14 May 2024 16:09:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1715702978; bh=vhQydVTRtjxkPaHb5KfVHAR+hCQTbKZ2234Oroi1hkk=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=f+/wsULAYEK1/fTo01gH+G2dGG4b99QqEId2LHiohLXde5DsJCjgTWg/AWDm66LfM EaCqJK35ynrCMgWiTpia/h1/YK0KGoGRRJgR2OmX/t2VOr6wleU9WSFt2kc8PCbvpZ 4RJyETwgviu8wbqQ2KJzUjsMUTr7fYvM37QVJ6/WI1YfBhU8QuzHeLFMvpCSsJFIKa xwCIEy/2W2/BDleGrj1+E65oHoUV15Tovptz9a/UkfegFFqPfTVdFB5+xK1jgj9JQ8 A4SgFBJ1lYT4nO28IeV3Xx/j7/66yzEHqZOyv861ONTGQ8o8B4uVPRsAYpiAQTSy+T dKUE0VN0ZRAVA== Date: Tue, 14 May 2024 16:09:36 +0000 From: Jaegeuk Kim To: Chao Yu Cc: linux-f2fs-devel@lists.sourceforge.net, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] f2fs: fix to avoid racing in between read and OPU dio write Message-ID: References: <20240510023906.281700-1-chao@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20240510023906.281700-1-chao@kernel.org> On 05/10, Chao Yu wrote: > If lfs mode is on, buffered read may race w/ OPU dio write as below, > it may cause buffered read hits unwritten data unexpectly, and for > dio read, the race condition exists as well. > > Thread A Thread B > - f2fs_file_write_iter > - f2fs_dio_write_iter > - __iomap_dio_rw > - f2fs_iomap_begin > - f2fs_map_blocks > - __allocate_data_block > - allocated blkaddr #x > - iomap_dio_submit_bio > - f2fs_file_read_iter > - filemap_read > - f2fs_read_data_folio > - f2fs_mpage_readpages > - f2fs_map_blocks > : get blkaddr #x > - f2fs_submit_read_bio > IRQ > - f2fs_read_end_io > : read IO on blkaddr #x complete > IRQ > - iomap_dio_bio_end_io > : direct write IO on blkaddr #x complete > > This patch introduces a new per-inode i_opu_rwsem lock to avoid > such race condition. Wasn't this supposed to be managed by user-land? > > Fixes: f847c699cff3 ("f2fs: allow out-place-update for direct IO in LFS mode") > Signed-off-by: Chao Yu > --- > v2: > - fix to cover dio read path w/ i_opu_rwsem as well. > fs/f2fs/f2fs.h | 1 + > fs/f2fs/file.c | 28 ++++++++++++++++++++++++++-- > fs/f2fs/super.c | 1 + > 3 files changed, 28 insertions(+), 2 deletions(-) > > diff --git a/fs/f2fs/f2fs.h b/fs/f2fs/f2fs.h > index 30058e16a5d0..91cf4b3d6bc6 100644 > --- a/fs/f2fs/f2fs.h > +++ b/fs/f2fs/f2fs.h > @@ -847,6 +847,7 @@ struct f2fs_inode_info { > /* avoid racing between foreground op and gc */ > struct f2fs_rwsem i_gc_rwsem[2]; > struct f2fs_rwsem i_xattr_sem; /* avoid racing between reading and changing EAs */ > + struct f2fs_rwsem i_opu_rwsem; /* avoid racing between buf read and opu dio write */ > > int i_extra_isize; /* size of extra space located in i_addr */ > kprojid_t i_projid; /* id for project quota */ > diff --git a/fs/f2fs/file.c b/fs/f2fs/file.c > index 72ce1a522fb2..4ec260af321f 100644 > --- a/fs/f2fs/file.c > +++ b/fs/f2fs/file.c > @@ -4445,6 +4445,7 @@ static ssize_t f2fs_dio_read_iter(struct kiocb *iocb, struct iov_iter *to) > const loff_t pos = iocb->ki_pos; > const size_t count = iov_iter_count(to); > struct iomap_dio *dio; > + bool do_opu = f2fs_lfs_mode(sbi); > ssize_t ret; > > if (count == 0) > @@ -4457,8 +4458,14 @@ static ssize_t f2fs_dio_read_iter(struct kiocb *iocb, struct iov_iter *to) > ret = -EAGAIN; > goto out; > } > + if (do_opu && !f2fs_down_read_trylock(&fi->i_opu_rwsem)) { > + f2fs_up_read(&fi->i_gc_rwsem[READ]); > + ret = -EAGAIN; > + goto out; > + } > } else { > f2fs_down_read(&fi->i_gc_rwsem[READ]); > + f2fs_down_read(&fi->i_opu_rwsem); > } > > /* > @@ -4477,6 +4484,7 @@ static ssize_t f2fs_dio_read_iter(struct kiocb *iocb, struct iov_iter *to) > ret = iomap_dio_complete(dio); > } > > + f2fs_up_read(&fi->i_opu_rwsem); > f2fs_up_read(&fi->i_gc_rwsem[READ]); > > file_accessed(file); > @@ -4523,7 +4531,13 @@ static ssize_t f2fs_file_read_iter(struct kiocb *iocb, struct iov_iter *to) > if (f2fs_should_use_dio(inode, iocb, to)) { > ret = f2fs_dio_read_iter(iocb, to); > } else { > + bool do_opu = f2fs_lfs_mode(F2FS_I_SB(inode)); > + > + if (do_opu) > + f2fs_down_read(&F2FS_I(inode)->i_opu_rwsem); > ret = filemap_read(iocb, to, 0); > + if (do_opu) > + f2fs_up_read(&F2FS_I(inode)->i_opu_rwsem); > if (ret > 0) > f2fs_update_iostat(F2FS_I_SB(inode), inode, > APP_BUFFERED_READ_IO, ret); > @@ -4748,14 +4762,22 @@ static ssize_t f2fs_dio_write_iter(struct kiocb *iocb, struct iov_iter *from, > ret = -EAGAIN; > goto out; > } > + if (do_opu && !f2fs_down_write_trylock(&fi->i_opu_rwsem)) { > + f2fs_up_read(&fi->i_gc_rwsem[READ]); > + f2fs_up_read(&fi->i_gc_rwsem[WRITE]); > + ret = -EAGAIN; > + goto out; > + } > } else { > ret = f2fs_convert_inline_inode(inode); > if (ret) > goto out; > > f2fs_down_read(&fi->i_gc_rwsem[WRITE]); > - if (do_opu) > + if (do_opu) { > f2fs_down_read(&fi->i_gc_rwsem[READ]); > + f2fs_down_write(&fi->i_opu_rwsem); > + } > } > > /* > @@ -4779,8 +4801,10 @@ static ssize_t f2fs_dio_write_iter(struct kiocb *iocb, struct iov_iter *from, > ret = iomap_dio_complete(dio); > } > > - if (do_opu) > + if (do_opu) { > + f2fs_up_write(&fi->i_opu_rwsem); > f2fs_up_read(&fi->i_gc_rwsem[READ]); > + } > f2fs_up_read(&fi->i_gc_rwsem[WRITE]); > > if (ret < 0) > diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c > index daf2c4dbe150..b4ed3b094366 100644 > --- a/fs/f2fs/super.c > +++ b/fs/f2fs/super.c > @@ -1428,6 +1428,7 @@ static struct inode *f2fs_alloc_inode(struct super_block *sb) > init_f2fs_rwsem(&fi->i_gc_rwsem[READ]); > init_f2fs_rwsem(&fi->i_gc_rwsem[WRITE]); > init_f2fs_rwsem(&fi->i_xattr_sem); > + init_f2fs_rwsem(&fi->i_opu_rwsem); > > /* Will be used by directory only */ > fi->i_dir_level = F2FS_SB(sb)->dir_level; > -- > 2.40.1