From: NeilBrown <neilb@suse.com>
To: Ian Kent <raven@themaw.net>, Al Viro <viro@zeniv.linux.org.uk>,
Jonathan Corbet <corbet@lwn.net>
Cc: "Tobin C. Harding" <tobin@kernel.org>,
Mauro Carvalho Chehab <mchehab@s-opensource.com>,
Randy Dunlap <rdunlap@infradead.org>,
linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 00/24] Convert vfs.txt to vfs.rst
Date: Wed, 03 Apr 2019 11:55:01 +1100 [thread overview]
Message-ID: <87ftqz29i2.fsf@notabene.neil.brown.name> (raw)
In-Reply-To: <5c5e02f8b8add4aa2fc24ba2a0880652529588af.camel@themaw.net>
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On Wed, Apr 03 2019, Ian Kent wrote:
> On Tue, 2019-04-02 at 20:08 +0100, Al Viro wrote:
>> On Tue, Apr 02, 2019 at 06:54:01PM +0100, Al Viro wrote:
>> > static void autofs_dentry_release(struct dentry *de)
>> > {
>> > struct autofs_info *ino = autofs_dentry_ino(de);
>> > struct autofs_sb_info *sbi = autofs_sbi(de->d_sb);
>> >
>> > pr_debug("releasing %p\n", de);
>> >
>> > if (!ino)
>> > return;
>> > ...
>> > autofs_free_ino(ino);
>> > }
>> > with autofs_free_ino() being straight kfree(). Which means
>> > that the lockless case of autofs_d_manage() can run into
>> > autofs_dentry_ino(dentry) getting freed right under it.
>> >
>> > And there we do have this reachable:
>> > int autofs_expire_wait(const struct path *path, int rcu_walk)
>> > {
>> > struct dentry *dentry = path->dentry;
>> > struct autofs_sb_info *sbi = autofs_sbi(dentry->d_sb);
>> > struct autofs_info *ino = autofs_dentry_ino(dentry);
>> > int status;
>> > int state;
>> >
>> > /* Block on any pending expire */
>> > if (!(ino->flags & AUTOFS_INF_WANT_EXPIRE))
>
> Oh yes, this is saying the dentry hasn't been selected
> for expire on the first pass, there's a second pass at
> expire selection so there's a delay there and both flags
> (this one and the expiring flag) are kept throughout the
> expire operation if dentry is selected.
>
> That might be partly why an oops has never been seen but
> path walks can occur at any time so it's a bit puzzling.
>
> LOL, and Neil probably can't remember the deeper detail
> on what he did there now either.
It seems very likely that this was just a subtlety that I missed.
I doesn't help that "ino" isn't actually and inode and isn't freed like
an inode, but that is no excuse.
When we add the rcu_head linkage to 'struct autofs_info', we might as
well remove the 'struct inode' from there - it doesn't seem to have been
used for years.
Thanks,
NeilBrown
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next prev parent reply other threads:[~2019-04-03 0:55 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-27 5:16 [PATCH v3 00/24] Convert vfs.txt to vfs.rst Tobin C. Harding
2019-03-27 5:16 ` [PATCH v3 01/24] vfs: Remove trailing whitespace Tobin C. Harding
2019-03-27 5:16 ` [PATCH v3 02/24] vfs: Clean up VFS data structure declarations Tobin C. Harding
2019-03-27 5:16 ` [PATCH v3 03/24] fs: Update function docstring for dio_complete() Tobin C. Harding
2019-03-27 5:16 ` [PATCH v3 04/24] fs: Add docstrings to exported functions Tobin C. Harding
2019-03-27 5:16 ` [PATCH v3 05/24] fs: Guard unusual text with backticks Tobin C. Harding
2019-03-27 5:16 ` [PATCH v3 06/24] fs: Update function docstring for simple_write_end() Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 07/24] fs: Fix function docstring for posix_acl_update_mode() Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 08/24] dcache: Remove trailing whitespace Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 09/24] dcache: Fix i.e. usage in coments Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 10/24] dcache: Fix e.g. usage in comment Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 11/24] dcache: Fix docstring comment for d_drop() Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 12/24] dcache: Fix non-docstring comments Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 13/24] dcache: Clean up function docstrings Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 14/24] dcache: Clean up function docstring members Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 15/24] docs: filesystems: vfs: Remove space before tab Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 16/24] docs: filesystems: vfs: Use uniform space after period Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 17/24] docs: filesystems: vfs: Use 72 character column width Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 18/24] docs: filesystems: vfs: Use uniform spacing around headings Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 19/24] docs: filesystems: vfs: Use correct initial heading Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 20/24] docs: filesystems: vfs: Use SPDX identifier Tobin C. Harding
2019-04-01 5:43 ` Mukesh Ojha
2019-03-27 5:17 ` [PATCH v3 21/24] docs: filesystems: vfs: Fix pre-amble indentation Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 22/24] fs: Copy documentation to struct declarations Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 23/24] dcache: Copy documentation to struct declaration Tobin C. Harding
2019-03-27 5:17 ` [PATCH v3 24/24] docs: Convert vfs.txt to reStructuredText format Tobin C. Harding
2019-03-27 5:24 ` [PATCH v3 00/24] Convert vfs.txt to vfs.rst Joe Perches
2019-03-27 6:26 ` Tobin C. Harding
2019-04-02 15:49 ` Jonathan Corbet
2019-04-02 16:48 ` Al Viro
2019-04-02 17:54 ` Al Viro
2019-04-02 19:08 ` Al Viro
2019-04-02 23:36 ` Ian Kent
2019-04-02 23:56 ` Ian Kent
2019-04-03 0:55 ` NeilBrown [this message]
2019-04-03 19:35 ` Al Viro
2019-04-04 6:30 ` Ian Kent
2019-04-03 23:28 ` Ian Kent
2019-04-02 19:25 ` Tobin C. Harding
2019-04-03 19:47 ` Al Viro
2019-04-03 20:59 ` Tobin C. Harding
2019-04-03 1:00 ` NeilBrown
2019-04-03 1:44 ` Al Viro
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