linux-kernel - Re: [patch 3/6] fs: dcache remove d

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:	Thu, 15 Oct 2009 18:37:09 +0800
From:	Ian Kent <raven@...maw.net>
To:	npiggin@...e.de
Cc:	Al Viro <viro@...iv.linux.org.uk>, linux-fsdevel@...r.kernel.org,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 3/6] fs: dcache remove d_mounted

On Thu, Oct 15, 2009 at 03:40:29PM +1100, npiggin@...e.de wrote:
> Rather than keep a d_mounted count in the dentry (which is only used to
> speculatively take a look in the mount hash table if it is non-zero), set a
> dentry flag instead. The flag can be cleared by checking the hash table to see
> if there are any mounts left. It is not time critical because it is performed
> at detach time.
> 
> This saves 4 bytes on 32-bit, nothing on 64-bit but it does provide a hole I
> might use later (and some configs have larger than 32-bit spinlocks which might
> make use of the hole).
> 
> Autofs4 conversion and changelog by Ian Kent <raven@...maw.net>:
> In autofs4, when expring direct (or offset) mounts we need to ensure that we
> block user path walks into the autofs mount, which is covered by another mount.
> To do this we clear the mounted status so that follows stop before walking into
> the mount and are essentially blocked until the expire is completed. The
> automount daemon still finds the correct dentry for the umount due to the
> follow mount logic in fs/autofs4/root.c:autofs4_follow_link(), which is set as
> an inode operation for direct and offset mounts only and is called following
> the lookup that stopped at the covered mount.
> 
> At the end of the expire the covering mount probably has gone away so the
> mounted status need not be restored. But we need to check this and only restore
> the mounted status if the expire failed.
> 
> Signed-off-by: Nick Piggin <npiggin@...e.de>

For the autofs4 bits.

Acked-by: Ian Kent <raven@...maw.net>

--
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/