From: Al Viro <viro@zeniv.linux.org.uk>
To: NeilBrown <neilb@suse.de>
Cc: Miklos Szeredi <mszeredi@redhat.com>,
Xavier Roche <xavier.roche@algolia.com>,
linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v2] vfs: fix link vs. rename race
Date: Wed, 14 Sep 2022 01:13:31 +0100 [thread overview]
Message-ID: <YyEcqxthoso9SGI2@ZenIV> (raw)
In-Reply-To: <166311315747.20483.5039023553379547679@noble.neil.brown.name>
On Wed, Sep 14, 2022 at 09:52:37AM +1000, NeilBrown wrote:
> - lookup the parents of both paths.
> - lock the "to" directory.
> - if the "from" directory is the same, or if a trylock of the from
> directory succeeds, then we have the locks and can perform the
> last component lookup and perform the link without racing with
> rename.
> - if the trylock fails, we drop the lock on "to" and use lock_rename().
> We drop the s_vfs_rename_mutex immediately after lock_rename()
> so after the vfs_link() we just unlock both parent directories.
Umm... Care to put together an update of deadlock avoidance proof?
The one in D/f/directory-locking.rst, that is. I'm not saying it's
not a usable approach - it might very well work...
BTW, one testcase worth profiling would be something like
for i in `seq 100`; do
cp -al linux.git linux.git-$i &
done
next prev parent reply other threads:[~2022-09-14 0:13 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-02-21 8:20 [PATCH v2] vfs: fix link vs. rename race Miklos Szeredi
2022-02-21 8:56 ` Xavier Roche
2022-09-13 2:04 ` Al Viro
2022-09-13 4:29 ` Al Viro
2022-09-13 8:02 ` Amir Goldstein
2022-09-13 10:03 ` Miklos Szeredi
2022-09-13 4:41 ` NeilBrown
2022-09-13 5:20 ` Al Viro
2022-09-13 5:40 ` Al Viro
2022-09-14 0:14 ` NeilBrown
2022-09-14 1:30 ` Al Viro
2022-09-13 23:52 ` NeilBrown
2022-09-14 0:13 ` Al Viro [this message]
2022-09-16 6:13 ` [PATCH RFC] VFS: lock source directory for link to avoid " NeilBrown
2022-09-16 6:28 ` Miklos Szeredi
2022-09-16 6:45 ` NeilBrown
2022-09-16 6:49 ` Al Viro
2022-09-16 14:32 ` Amir Goldstein
2022-09-19 8:28 ` Christian Brauner
2022-09-19 22:56 ` NeilBrown
2022-09-23 3:02 ` [VFS] 3fb4ec6faa: ltp.linkat02.fail kernel test robot
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