linux-kernel - Re: [PATCH] writeback: Don't wait for completion in writeback_inodes_sb

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]

Message-ID: <20110630121558.GF28475@quack.suse.cz>
Date:	Thu, 30 Jun 2011 14:15:58 +0200
From:	Jan Kara <jack@...e.cz>
To:	Christoph Hellwig <hch@...radead.org>
Cc:	Jan Kara <jack@...e.cz>, Curt Wohlgemuth <curtw@...gle.com>,
	Al Viro <viro@...iv.linux.org.uk>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	fengguang.wu@...el.com
Subject: Re: [PATCH] writeback: Don't wait for completion in
 writeback_inodes_sb_nr

On Wed 29-06-11 16:12:34, Christoph Hellwig wrote:
> On Wed, Jun 29, 2011 at 09:15:18PM +0200, Jan Kara wrote:
> >   True but writeback_single_inode() has in it:
> >         if (wbc->sync_mode == WB_SYNC_ALL) {
> >                 int err = filemap_fdatawait(mapping);
> >                 if (ret == 0)
> >                         ret = err;
> >         }
> >   So we end up waiting much earlier. Probably we should remove this wait
> > but that will need some audit I guess.
> 
> Uhh, indeed.  We'll need this wait for things like sync_inode, though.
  Yes. Actually, specifically for filesystems like XFS which update inode
after IO completion we would need more passes to be efficient and correct:
  for all inodes
    fdatawrite
  for all inodes
    fdatawait
  for all inodes
    write_inode
  for all inodes
    wait for inode IO

  But maybe this could be handled by having new WB_SYNC_ mode indicating
that writeback_single_inode() should not bother waiting (thus we'd really
end up waiting in sync_inodes_sb()) and then XFS and other filesystems that
need it would writeout inodes in their sync_fs() implementation (possibly
using a generic helper)?
								Honza
-- 
Jan Kara <jack@...e.cz>
SUSE Labs, CR
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/