linux-ext4 - Re: [PATCH v3 12/13] docs: Add fast commit documentation

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 for Android: free password hash cracker in your pocket

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

Message-Id: <9DF0D322-3ACC-4094-976B-CF8F4A06F655@dilger.ca>
Date:   Thu, 31 Oct 2019 12:53:10 -0600
From:   Andreas Dilger <adilger@...ger.ca>
To:     "Theodore Y. Ts'o" <tytso@....EDU>
Cc:     Harshad Shirwadkar <harshadshirwadkar@...il.com>,
        linux-ext4@...r.kernel.org
Subject: Re: [PATCH v3 12/13] docs: Add fast commit documentation

On Oct 18, 2019, at 7:28 AM, Theodore Y. Ts'o <tytso@....EDU> wrote:
> 
> On Fri, Oct 18, 2019 at 01:51:56PM +0900, Andreas Dilger wrote:
>> What about rename or hard link?
> 
> Neither is currently handled by the fast commit patches, but each
> operation can fit inside a single block, so it could be handled as a
> update to a single inode.  In the case of rename, we will need to add
> some tags to indicate the desintation directory and directory enrty
> name, and whether or not there is a destination inode which needs to
> have its refcount dropped and possibly deleted.
> 
> Harshad, we probably should handle them, since in order to support
> NFS, the nfs server will send the rename or hard link request,
> followed by a commit metadata request, and that commit metadata
> request needs to persist the rename or link.  So for the purposes of
> accelerating NFS, we should handle these commands.
> 
> If we don't handle these commands, we will need to declare the inode
> as fast commit ineligible, so that we force a full journal commit when
> the commit metadata request is received.

As a simplifying assumption, you could limit the case of rename/link
within a single directory?  That handles the common case of "create
temp file, write contents there, sync, rename over original file"
used by most editors, rsync, etc.  The case of cross-directory rename
is much less common in my experience, so it is less important to
optimize that case (if this makes it easier to add to fast commits).

Cheers, Andreas






Download attachment "signature.asc" of type "application/pgp-signature" (874 bytes)