linux-ext4 - Re: [PATCH] Revert "ext4: use ext4_write_inode() when fsyncing w/o a journal"

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Date:   Fri, 1 Feb 2019 23:08:11 -0500
From:   "Theodore Y. Ts'o" <tytso@....edu>
To:     Jan Kara <jack@...e.cz>
CC:     Ext4 Developers List <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH] Revert "ext4: use ext4_write_inode() when fsyncing w/o a
 journal"

On Fri, Feb 01, 2019 at 10:21:20PM +0100, Jan Kara wrote:
> On Thu 31-01-19 23:42:19, Theodore Ts'o wrote:
> > This reverts commit ad211f3e94b314a910d4af03178a0b52a7d1ee0a.
> > 
> > As Jan Kara pointed out, this change was unsafe since it means we lose
> > the call to sync_mapping_buffers() in the nojournal case.  The
> > original point of the commit was avoid taking the inode mutex (since
> > it causes a lockdep warning in generic/113); but we need the mutex in
> > order to call sync_mapping_buffers().
> 
> Actually, I don't think sync_mapping_buffers() needs inode mutex (i_rwsem
> these days). It uses blkdev_mapping->private_lock for synchronization of
> operations on the list of buffers and fsync_buffers_list() seems to be
> pretty careful about races with mark_buffer_dirty_inode(). So why do you
> think we need i_rwsem?

Hmm, I think you're right.  I wonder if we can therefore remove the
inode_lock() in __generic_file_fsync() then...   What do you think?

     			       		      	 - Ted