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

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Tue, 10 May 2011 16:49:39 +0200
From:	Jan Kara <jack@...e.cz>
To:	OGAWA Hirofumi <hirofumi@...l.parknet.co.jp>
Cc:	Christoph Hellwig <hch@...radead.org>,
	"Darrick J. Wong" <djwong@...ibm.com>,
	Theodore Tso <tytso@....edu>, Jan Kara <jack@...e.cz>,
	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

On Tue 10-05-11 22:52:10, OGAWA Hirofumi wrote:
> Christoph Hellwig <hch@...radead.org> writes:
> 
> > On Tue, May 10, 2011 at 10:59:15AM +0900, OGAWA Hirofumi wrote:
> >> I'd like to know those patches are on what state. Waiting in writeback
> >> page makes slower, like you mentioned it (I guess it would more
> >> noticeable if device was slower that like FAT uses). And I think
> >> currently it doesn't help anything others for blk-integrity stuff
> >> (without other technic, it doesn't help FS consistency)?
> >
> > It only makes things slower if we rewrite a region in a file that is
> > currently undergoing writeback. I'd be interested to know about real
> > life applications doing that, and if they really are badly affect we
> > should help them to work around that in userspace, e.g. by adding a
> > fadvice will rewrite call that might be used to never write back that
> > regions without an explicit fsync call.
> 
> 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. 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. 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.

								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-ext4" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html