Re: [PATCHv5 2/9] fs/buffer.c: Add generic_buffer_fsync implementation

[Jan Kara <jack@suse.cz>]

On Mon 17-04-23 13:01:49, Jan Kara wrote:
> On Sun 16-04-23 15:38:37, Ritesh Harjani (IBM) wrote:
> > Some of the higher layers like iomap takes inode_lock() when calling
> > generic_write_sync().
> > Also writeback already happens from other paths without inode lock,
> > so it's difficult to say that we really need sync_mapping_buffers() to
> > take any inode locking here. Having said that, let's add
> > generic_buffer_fsync() implementation in buffer.c with no
> > inode_lock/unlock() for now so that filesystems like ext2 and
> > ext4's nojournal mode can use it.
> > 
> > Ext4 when got converted to iomap for direct-io already copied it's own
> > variant of __generic_file_fsync() without lock. Hence let's add a helper
> > API and use it both in ext2 and ext4.
> > 
> > Later we can review other filesystems as well to see if we can make
> > generic_buffer_fsync() which does not take any inode_lock() as the
> > default path.
> > 
> > Tested-by: Disha Goel <disgoel@linux.ibm.com>
> > Reviewed-by: Christoph Hellwig <hch@lst.de>
> > Signed-off-by: Ritesh Harjani (IBM) <ritesh.list@gmail.com>
> 
> There is a problem with generic_buffer_fsync() that it does not call
> blkdev_issue_flush() so the caller is responsible for doing that. That's
> necessary for ext2 & ext4 so fine for now.

Actually a slight correction: ext2 could use a variant of
generic_buffer_fsync() that flushes disk caches.

								Honza

-- 
Jan Kara <jack@suse.com>
SUSE Labs, CR