From: Christoph Hellwig <hch@infradead.org>
To: Mateusz Guzik <mjguzik@gmail.com>
Cc: Bernd Schubert <bschubert@ddn.com>,
linux-fsdevel@vger.kernel.org, bernd.schubert@fastmail.fm,
miklos@szeredi.hu, dsingh@ddn.com,
Josef Bacik <josef@toxicpanda.com>,
linux-btrfs@vger.kernel.org,
Alexander Viro <viro@zeniv.linux.org.uk>,
Christian Brauner <brauner@kernel.org>
Subject: Re: [PATCH 0/2] Use exclusive lock for file_remove_privs
Date: Thu, 31 Aug 2023 23:49:20 -0700 [thread overview]
Message-ID: <ZPGJcMy+S2DjYutF@infradead.org> (raw)
In-Reply-To: <20230831101824.qdko4daizgh7phav@f>
On Thu, Aug 31, 2023 at 12:18:24PM +0200, Mateusz Guzik wrote:
> Turns out notify_change has the following:
> WARN_ON_ONCE(!inode_is_locked(inode));
>
> Which expands to:
> static inline int rwsem_is_locked(struct rw_semaphore *sem)
> {
> return atomic_long_read(&sem->count) != 0;
> }
>
> So it does check the lock, except it passes *any* locked state,
> including just readers.
>
> According to git blame this regressed from commit 5955102c9984
> ("wrappers for ->i_mutex access") by Al -- a bunch of mutex_is_locked
> were replaced with inode_is_locked, which unintentionally provides
> weaker guarantees.
>
> I don't see a rwsem helper for wlock check and I don't think it is all
> that beneficial to add. Instead, how about a bunch of lockdep, like so:
Yes, that's a good idea.
next prev parent reply other threads:[~2023-09-01 6:49 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-08-30 18:15 [PATCH 0/2] Use exclusive lock for file_remove_privs Bernd Schubert
2023-08-30 18:15 ` [PATCH 1/2] fs: Add and export file_needs_remove_privs Bernd Schubert
2023-09-01 6:48 ` Christoph Hellwig
2023-08-30 18:15 ` [PATCH 2/2] btrfs: file_remove_privs needs an exclusive lock Bernd Schubert
2023-08-31 7:40 ` [PATCH 0/2] Use exclusive lock for file_remove_privs Christoph Hellwig
2023-08-31 10:17 ` Bernd Schubert
2023-08-31 10:18 ` Mateusz Guzik
2023-08-31 14:41 ` Bernd Schubert
2023-09-01 6:49 ` Christoph Hellwig [this message]
2023-09-01 11:38 ` Matthew Wilcox
2023-09-01 11:47 ` Mateusz Guzik
2023-09-06 15:13 ` Matthew Wilcox
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=ZPGJcMy+S2DjYutF@infradead.org \
--to=hch@infradead.org \
--cc=bernd.schubert@fastmail.fm \
--cc=brauner@kernel.org \
--cc=bschubert@ddn.com \
--cc=dsingh@ddn.com \
--cc=josef@toxicpanda.com \
--cc=linux-btrfs@vger.kernel.org \
--cc=linux-fsdevel@vger.kernel.org \
--cc=miklos@szeredi.hu \
--cc=mjguzik@gmail.com \
--cc=viro@zeniv.linux.org.uk \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).