On 10/28/19 4:23 PM, Matthew Bobrowski wrote:
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 <mbobrowski@xxxxxxxxxxxxxx>
Thanks for the patch. Looks good to me.
You may add:
Reviewed-by: Ritesh Harjani <riteshh@xxxxxxxxxxxxx>
---
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;
