Re: [PATCH 0/12] make ->sync_fs mandatory

[Al Viro <viro@ZenIV.linux.org.uk>]

On Mon, Jun 08, 2009 at 10:02:52AM +0200, Christoph Hellwig wrote:
> Currently the superblock methods are a bit confusing.  There is the
> newer ->sync_fs method which is unconditionally called from
> __sync_filesystem for data integrity writebacks.  And there is the older
> ->write_super which is called from pdflush for the periodic superblock
> writeback, but also from __sync_filesystem just before calling
> ->sync_fs. (And still from file_fsync, but that is about to go away).
> 
> This series makes sure all filesystems that need superblock writeouts
> define a ->sync_fs so we can stop calling ->write_super for the data
> integrity writeback.  This means the presence of ->write_super indicates
> a filesystem does want periodic superblock writeback and can implement
> these independently from the data integrity writeback. It also means
> we don't need to bother with possible s_dirt races for the data
> integrity syncs.
> 
> This patch series first adds ->sync_fs methods to all filesystems having
> ->write_super, often refactoring the code in that are (and also
> preparing the ->write_super instances for moving MS_RDONLY checking into
> the caller), then it makes sure the existing ->sync_fs instaces cover
> the work previously done in ->write_super for the two cases where they
> differed widely, and lastly removes the call to ->write_super from
> __sync_filesystem.

Applied.  FWIW, file_fsync() is nearly gone; the last remnants are exofs,
hfs and hfsplus.  Is there any sane way to keep track of dirty metadata
blocks there?  Or is "just flush all dirty buffer_head for the device"
really the best we can do?