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
| ||
|
Message-ID: <20080709005254.GQ11558@disturbed> Date: Wed, 9 Jul 2008 10:52:54 +1000 From: Dave Chinner <david@...morbit.com> To: Pavel Machek <pavel@...e.cz> Cc: Christoph Hellwig <hch@...radead.org>, Takashi Sato <t-sato@...jp.nec.com>, akpm@...ux-foundation.org, viro@...IV.linux.org.uk, "linux-ext4@...r.kernel.org" <linux-ext4@...r.kernel.org>, "xfs@....sgi.com" <xfs@....sgi.com>, "dm-devel@...hat.com" <dm-devel@...hat.com>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, axboe@...nel.dk, mtk.manpages@...glemail.com Subject: Re: [PATCH 3/3] Add timeout feature On Wed, Jul 09, 2008 at 01:20:31AM +0200, Pavel Machek wrote: > On Wed 2008-07-09 09:10:27, Dave Chinner wrote: > > On Mon, Jul 07, 2008 at 01:07:31PM +0200, Pavel Machek wrote: > > > Hi! > > > > > > > I still disagree with this whole patch. There is not reason to let > > > > the freeze request timeout - an auto-unfreezing will only confuse the > > > > hell out of the caller. The only reason where the current XFS freeze > > > > call can hang and this would be theoretically useful is when the > > > > > > What happens when someone dirties so much data that vm swaps out > > > whatever process that frozen the filesystem? > > > > a) you can't dirty a frozen filesystem - by definition a frozen > > filesystem is a *clean filesystem* and *cannot be dirtied*. > > Can you stop me? > > mmap("/some/huge_file", MAP_SHARED); > > then write to memory mapping? Sure - we can put a hook in ->page_mkwrite() to prevent it. We don't right now because nobody in the real world really cares if one half of a concurrent user data change is in the old snapshot or the new one...... > > b) Swap doesn't write through the filesystem > > c) you can still read from a frozen filesystem to page your > > executable?? in. > > atime modification should mean dirty data, right? Metadata, not data. If that's really a problem (and it never has been for XFS because we always allow in memory changes to atime) then touch_atime could be easily changed to avoid this... > And dirty data mean > memory pressure, right? If you walk enough inodes while the filesystem is frozen, it theoretically could happen. Typically a filesystem is only for a few seconds at a time so in the real world this has never, ever been a problem. Cheers, Dave. -- Dave Chinner david@...morbit.com -- 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
Powered by blists - more mailing lists