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[114.78.127.22]) by smtp.gmail.com with ESMTPSA id v1sm11626385pjd.22.2019.10.28.03.53.55 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 28 Oct 2019 03:53:58 -0700 (PDT) Date: Mon, 28 Oct 2019 21:53:52 +1100 From: Matthew Bobrowski To: tytso@mit.edu, jack@suse.cz, adilger.kernel@dilger.ca Cc: linux-ext4@vger.kernel.org, linux-fsdevel@vger.kernel.org, hch@infradead.org, david@fromorbit.com, darrick.wong@oracle.com Subject: [PATCH v6 10/11] ext4: update ext4_sync_file() to not use __generic_file_fsync() Message-ID: References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-fsdevel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org When the filesystem is created without a journal, we eventually call into __generic_file_fsync() in order to write out all the modified in-core data to the permanent storage device. This function happens to try and obtain an inode_lock() while synchronizing the files buffer and it's associated metadata. Generally, this is fine, however it becomes a problem when there is higher level code that has already obtained an inode_lock() as this leads to a recursive lock situation. This case is especially true when porting across direct I/O to iomap infrastructure as we obtain an inode_lock() early on in the I/O within ext4_dio_write_iter() and hold it until the I/O has been completed. Consequently, to not run into this specific issue, we move away from calling into __generic_file_fsync() and perform the necessary synchronization tasks within ext4_sync_file(). Signed-off-by: Matthew Bobrowski --- Thanks Jan and Christoph for the suggestion on this one, highly appreciated. fs/ext4/fsync.c | 72 ++++++++++++++++++++++++++++++++----------------- 1 file changed, 47 insertions(+), 25 deletions(-) diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c index 5508baa11bb6..e10206e7f4bb 100644 --- a/fs/ext4/fsync.c +++ b/fs/ext4/fsync.c @@ -80,6 +80,43 @@ static int ext4_sync_parent(struct inode *inode) return ret; } +static int ext4_fsync_nojournal(struct inode *inode, bool datasync, + bool *needs_barrier) +{ + int ret, err; + + ret = sync_mapping_buffers(inode->i_mapping); + if (!(inode->i_state & I_DIRTY_ALL)) + return ret; + if (datasync && !(inode->i_state & I_DIRTY_DATASYNC)) + return ret; + + err = sync_inode_metadata(inode, 1); + if (!ret) + ret = err; + + if (!ret) + ret = ext4_sync_parent(inode); + if (test_opt(inode->i_sb, BARRIER)) + *needs_barrier = true; + + return ret; +} + +static int ext4_fsync_journal(struct inode *inode, bool datasync, + bool *needs_barrier) +{ + struct ext4_inode_info *ei = EXT4_I(inode); + journal_t *journal = EXT4_SB(inode->i_sb)->s_journal; + tid_t commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid; + + if (journal->j_flags & JBD2_BARRIER && + !jbd2_trans_will_send_data_barrier(journal, commit_tid)) + *needs_barrier = true; + + return jbd2_complete_transaction(journal, commit_tid); +} + /* * akpm: A new design for ext4_sync_file(). * @@ -91,17 +128,14 @@ static int ext4_sync_parent(struct inode *inode) * What we do is just kick off a commit and wait on it. This will snapshot the * inode to disk. */ - int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync) { - struct inode *inode = file->f_mapping->host; - struct ext4_inode_info *ei = EXT4_I(inode); - journal_t *journal = EXT4_SB(inode->i_sb)->s_journal; int ret = 0, err; - tid_t commit_tid; bool needs_barrier = false; + struct inode *inode = file->f_mapping->host; + struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb); - if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb)))) + if (unlikely(ext4_forced_shutdown(sbi))) return -EIO; J_ASSERT(ext4_journal_current_handle() == NULL); @@ -111,23 +145,15 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync) if (sb_rdonly(inode->i_sb)) { /* Make sure that we read updated s_mount_flags value */ smp_rmb(); - if (EXT4_SB(inode->i_sb)->s_mount_flags & EXT4_MF_FS_ABORTED) + if (sbi->s_mount_flags & EXT4_MF_FS_ABORTED) ret = -EROFS; goto out; } - if (!journal) { - ret = __generic_file_fsync(file, start, end, datasync); - if (!ret) - ret = ext4_sync_parent(inode); - if (test_opt(inode->i_sb, BARRIER)) - goto issue_flush; - goto out; - } - ret = file_write_and_wait_range(file, start, end); if (ret) return ret; + /* * data=writeback,ordered: * The caller's filemap_fdatawrite()/wait will sync the data. @@ -142,18 +168,14 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync) * (they were dirtied by commit). But that's OK - the blocks are * safe in-journal, which is all fsync() needs to ensure. */ - if (ext4_should_journal_data(inode)) { + if (!sbi->s_journal) + ret = ext4_fsync_nojournal(inode, datasync, &needs_barrier); + else if (ext4_should_journal_data(inode)) ret = ext4_force_commit(inode->i_sb); - goto out; - } + else + ret = ext4_fsync_journal(inode, datasync, &needs_barrier); - commit_tid = datasync ? ei->i_datasync_tid : ei->i_sync_tid; - if (journal->j_flags & JBD2_BARRIER && - !jbd2_trans_will_send_data_barrier(journal, commit_tid)) - needs_barrier = true; - ret = jbd2_complete_transaction(journal, commit_tid); if (needs_barrier) { - issue_flush: err = blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL); if (!ret) ret = err; -- 2.20.1