From: Al Viro <viro@zeniv.linux.org.uk>
To: NeilBrown <neil@brown.name>
Cc: Christian Brauner <brauner@kernel.org>, Jan Kara <jack@suse.cz>,
David Howells <dhowells@redhat.com>,
Tyler Hicks <code@tyhicks.com>,
Chuck Lever <chuck.lever@oracle.com>,
Jeff Layton <jlayton@kernel.org>,
Miklos Szeredi <miklos@szeredi.hu>,
Amir Goldstein <amir73il@gmail.com>, Kees Cook <kees@kernel.org>,
Joel Granados <joel.granados@kernel.org>,
Namjae Jeon <linkinjeon@kernel.org>,
Steve French <smfrench@gmail.com>,
Sergey Senozhatsky <senozhatsky@chromium.org>,
netfs@lists.linux.dev, linux-kernel@vger.kernel.org,
ecryptfs@vger.kernel.org, linux-fsdevel@vger.kernel.org,
linux-nfs@vger.kernel.org, linux-unionfs@vger.kernel.org,
linux-cifs@vger.kernel.org
Subject: Re: [PATCH 2/2] fs/proc: take rcu_read_lock() in proc_sys_compare()
Date: Thu, 12 Jun 2025 00:33:06 +0100 [thread overview]
Message-ID: <20250611233306.GA1647736@ZenIV> (raw)
In-Reply-To: <20250611225848.1374929-3-neil@brown.name>
On Thu, Jun 12, 2025 at 08:57:03AM +1000, NeilBrown wrote:
> However there is no guarantee that this lock is held by d_same_name()
> (the caller of ->d_compare). In particularly d_alloc_parallel() calls
> d_same_name() after rcu_read_unlock().
d_alloc_parallel() calls d_same_name() with dentry being pinned;
if it's positive, nothing's going to happen to its inode,
rcu_read_lock() or not. It can go from negative to positive,
but that's it.
Why is it needed? We do care about possibly NULL inode (basically,
when RCU dcache lookup runs into a dentry getting evicted right
under it), but that's not relevant here.
next prev parent reply other threads:[~2025-06-11 23:33 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-11 22:57 [PATCH 0/2] Minor VFS-related cleanups NeilBrown
2025-06-11 22:57 ` [PATCH 1/2] VFS: change old_dir and new_dir in struct renamedata to dentrys NeilBrown
2025-06-11 23:38 ` Al Viro
2025-06-12 6:10 ` Miklos Szeredi
2025-06-13 7:08 ` NeilBrown
2025-06-12 6:20 ` Amir Goldstein
2025-06-12 23:22 ` NeilBrown
2025-06-12 13:03 ` Chuck Lever
2025-06-12 22:52 ` Namjae Jeon
2025-06-11 22:57 ` [PATCH 2/2] fs/proc: take rcu_read_lock() in proc_sys_compare() NeilBrown
2025-06-11 23:33 ` Al Viro [this message]
2025-06-12 4:30 ` NeilBrown
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