linux-kernel - Re: [PATCH v3 0/3] data integrity: Stabilize pages during writeback for ext4

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Date:	Wed, 04 May 2011 15:21:55 -0400
From:	Chris Mason <chris.mason@...cle.com>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	"Darrick J. Wong" <djwong@...ibm.com>,
	"Theodore Ts'o" <tytso@....edu>, Jeff Layton <jlayton@...hat.com>,
	Jan Kara <jack@...e.cz>, Dave Chinner <david@...morbit.com>,
	Joel Becker <jlbec@...lplan.org>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Jens Axboe <axboe@...nel.dk>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	Mingming Cao <mcao@...ibm.com>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	linux-mm <linux-mm@...ck.org>
Subject: Re: [PATCH v3 0/3] data integrity: Stabilize pages during writeback for ext4

Excerpts from Christoph Hellwig's message of 2011-05-04 14:46:44 -0400:
> This seems to miss out on a lot of the generic functionality like
> write_cache_pages and block_page_mkwrite and just patch it into
> the ext4 copy & paste variants.  Please make sure your patches also
> work for filesystem that use more of the generic functionality like
> xfs or ext2 (the latter one might be fun for the mmap case).

Probably after the block_commit_write in block_page_mkwrite()
Another question is, do we want to introduce a wait_on_stable_page_writeback()?

This would allow us to add a check against the bdi requesting stable
pages.

> 
> Also what's the status of btrfs?  I remembered there was one or two
> bits missing despite doing the right thing in most areas.

As far as I know btrfs is getting it right.  The only bit missing is the
one Nick Piggin pointed out where it is possible to change mmap'd O_DIRECT
memory in flight while a DIO is in progress.  Josef has a test case that
demonstrates this.

Nick had a plan to fix it, but it involved redoing the get_user_pages
api.

-chris
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