[PATCH] ext4: Reduce i_mutex usage in ext4_file_sync()

From: Jan Kara
Date: Tue Nov 20 2012 - 19:46:51 EST


ext4_file_sync() needs i_mutex only to avoid livelocks of
ext4_flush_unwritten_io() all other code doesn't need it. In particular
syncing of inode & metadata in non-journal case is safe (writeback doesn't
hold i_mutex either) and forcing of transaction commits doesn't need i_mutex
either (there's nothing inode specific in that code apart from grabbing
transaction ids from the inode). So shorten the span where i_mutex is held.

Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/ext4/fsync.c | 6 ++----
1 files changed, 2 insertions(+), 4 deletions(-)

diff --git a/fs/ext4/fsync.c b/fs/ext4/fsync.c
index be1d89f..2268114 100644
--- a/fs/ext4/fsync.c
+++ b/fs/ext4/fsync.c
@@ -113,8 +113,6 @@ static int __sync_inode(struct inode *inode, int datasync)
*
* What we do is just kick off a commit and wait on it. This will snapshot the
* inode to disk.
- *
- * i_mutex lock is held when entering and exiting this function
*/

int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
@@ -133,12 +131,13 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
ret = filemap_write_and_wait_range(inode->i_mapping, start, end);
if (ret)
return ret;
- mutex_lock(&inode->i_mutex);

if (inode->i_sb->s_flags & MS_RDONLY)
goto out;

+ mutex_lock(&inode->i_mutex);
ret = ext4_flush_unwritten_io(inode);
+ mutex_unlock(&inode->i_mutex);
if (ret < 0)
goto out;

@@ -180,7 +179,6 @@ int ext4_sync_file(struct file *file, loff_t start, loff_t end, int datasync)
ret = err;
}
out:
- mutex_unlock(&inode->i_mutex);
trace_ext4_sync_file_exit(inode, ret);
return ret;
}
--
1.7.1


--k+w/mQv8wyuph6w0--
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