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 PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 12 Sep 2022 08:54:25 -0400 From: bfields@...ldses.org (J. Bruce Fields) To: Jeff Layton <jlayton@...nel.org> Cc: Theodore Ts'o <tytso@....edu>, Jan Kara <jack@...e.cz>, NeilBrown <neilb@...e.de>, adilger.kernel@...ger.ca, djwong@...nel.org, david@...morbit.com, trondmy@...merspace.com, viro@...iv.linux.org.uk, zohar@...ux.ibm.com, xiubli@...hat.com, chuck.lever@...cle.com, lczerner@...hat.com, brauner@...nel.org, fweimer@...hat.com, linux-man@...r.kernel.org, linux-api@...r.kernel.org, linux-btrfs@...r.kernel.org, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, ceph-devel@...r.kernel.org, linux-ext4@...r.kernel.org, linux-nfs@...r.kernel.org, linux-xfs@...r.kernel.org Subject: Re: [man-pages RFC PATCH v4] statx, inode: document the new STATX_INO_VERSION field On Mon, Sep 12, 2022 at 07:42:16AM -0400, Jeff Layton wrote: > A scheme like that could work. It might be hard to do it without a > spinlock or something, but maybe that's ok. Thinking more about how we'd > implement this in the underlying filesystems: > > To do this we'd need 2 64-bit fields in the on-disk and in-memory > superblocks for ext4, xfs and btrfs. On the first mount after a crash, > the filesystem would need to bump s_version_max by the significant > increment (2^40 bits or whatever). On a "clean" mount, it wouldn't need > to do that. > > Would there be a way to ensure that the new s_version_max value has made > it to disk? Bumping it by a large value and hoping for the best might be > ok for most cases, but there are always outliers, so it might be > worthwhile to make an i_version increment wait on that if necessary. I was imagining that when you recognize you're getting close, you kick off something which writes s_version_max+2^40 to disk, and then updates s_version_max to that new value on success of the write. The code that increments i_version checks to make sure it wouldn't exceed s_version_max. If it would, something has gone wrong--a write has failed or taken a long time--so it waits or errors out or something, depending on desired filesystem behavior in that case. No locking required in the normal case? --b.
Powered by blists - more mailing lists