linux-ext4 - Re: [PATCHSET v3.1 0/7] data integrity: Stabilize pages during writeback for various fses

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Date:	Wed, 11 May 2011 00:24:58 +0900
From:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
To:	Jan Kara <jack@...e.cz>
Cc:	Christoph Hellwig <hch@...radead.org>,
	"Darrick J. Wong" <djwong@...ibm.com>,
	Theodore Tso <tytso@....edu>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	Jens Axboe <axboe@...nel.dk>,
	"Martin K. Petersen" <martin.petersen@...cle.com>,
	Jeff Layton <jlayton@...hat.com>,
	Dave Chinner <david@...morbit.com>,
	linux-kernel <linux-kernel@...r.kernel.org>,
	Dave Hansen <dave@...ux.vnet.ibm.com>, linux-mm@...ck.org,
	Chris Mason <chris.mason@...cle.com>,
	Joel Becker <jlbec@...lplan.org>,
	linux-scsi <linux-scsi@...r.kernel.org>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	linux-ext4@...r.kernel.org, Mingming Cao <mcao@...ibm.com>
Subject: Re: [PATCHSET v3.1 0/7] data integrity: Stabilize pages during writeback for various fses

Jan Kara <jack@...e.cz> writes:

>> Isn't it reallocated blocks too, and metadata too?
>   Reallocated blocks - not really. For a block to be freed it cannot be
> under writeback and when it's freed no writeback is started.

Sure for data -> data reallocated case. metadata -> data/metadata is
still there.

> For metadata - yes. But ext3, ext4, xfs, btrfs have to avoid modifying
> metadata under writeback anyway (because of journalling / COW
> constraints) and thus they don't care.

Yes. Those would use better way than just blocking.

> For ext2 or vfat it's a different story. But as I wrote to Darrick,
> I'm not sure about vfat but for ext2 and similar legacy filesystems,
> I'd rather let them live with their unstable pages under IO ;) because
> I see a limited use for that.

If this patches was not going to tackle it, I have no argument here ;)
It would be simply FS specific approach/fixes anymore like journal.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
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