From: Al Viro <viro@zeniv.linux.org.uk>
To: Dave Chinner <david@fromorbit.com>
Cc: linux-fsdevel@vger.kernel.org, linux-block@vger.kernel.org,
linux-cachefs@redhat.com, dhowells@redhat.com,
gfs2@lists.linux.dev, dm-devel@lists.linux.dev,
linux-security-module@vger.kernel.org, selinux@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 08/11] vfs: inode cache conversion to hash-bl
Date: Thu, 7 Dec 2023 06:42:00 +0000 [thread overview]
Message-ID: <20231207064200.GY1674809@ZenIV> (raw)
In-Reply-To: <20231206060629.2827226-9-david@fromorbit.com>
On Wed, Dec 06, 2023 at 05:05:37PM +1100, Dave Chinner wrote:
> + /*
> + * There are some callers that come through here without synchronisation
> + * and potentially with multiple references to the inode. Hence we have
> + * to handle the case that we might race with a remove and insert to a
> + * different list. Coda, in particular, seems to have a userspace API
> + * that can directly trigger "unhash/rehash to different list" behaviour
> + * without any serialisation at all.
> + *
> + * Hence we have to handle the situation where the inode->i_hash_head
> + * might point to a different list than what we expect, indicating that
> + * we raced with another unhash and potentially a new insertion. This
> + * means we have to retest the head once we have everything locked up
> + * and loop again if it doesn't match.
> + */
coda_replace_fid() is an old headache, but it's thankfully unique - nobody else
does that kind of shit (just rechecked).
Note that coda_replace_fid() is not going to have the sucker racing with
removal from another source, and I'm 100% sure that they really want
some serialization for handling those requests.
remove_inode_hash() is misused there - "in the middle of hash key change"
is not the same state as "unhashed".
Any races between insert and unhash are bugs, not something to support.
next prev parent reply other threads:[~2023-12-07 6:42 UTC|newest]
Thread overview: 34+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-06 6:05 [PATCH 0/11] vfs: inode cache scalability improvements Dave Chinner
2023-12-06 6:05 ` [PATCH 01/11] lib/dlock-list: Distributed and lock-protected lists Dave Chinner
2023-12-07 2:23 ` Al Viro
2023-12-06 6:05 ` [PATCH 02/11] vfs: Remove unnecessary list_for_each_entry_safe() variants Dave Chinner
2023-12-07 2:26 ` Al Viro
2023-12-07 4:18 ` Kent Overstreet
2023-12-06 6:05 ` [PATCH 03/11] vfs: Use dlock list for superblock's inode list Dave Chinner
2023-12-07 2:40 ` Al Viro
2023-12-07 4:59 ` Dave Chinner
2023-12-07 5:03 ` Kent Overstreet
2023-12-06 6:05 ` [PATCH 04/11] lib/dlock-list: Make sibling CPUs share the same linked list Dave Chinner
2023-12-07 4:31 ` Kent Overstreet
2023-12-07 5:42 ` Kent Overstreet
2023-12-07 6:25 ` Dave Chinner
2023-12-07 6:49 ` Al Viro
2023-12-06 6:05 ` [PATCH 05/11] selinux: use dlist for isec inode list Dave Chinner
2023-12-06 21:52 ` Paul Moore
2023-12-06 23:04 ` Dave Chinner
2023-12-07 0:36 ` Paul Moore
2023-12-06 6:05 ` [PATCH 06/11] vfs: factor out inode hash head calculation Dave Chinner
2023-12-07 3:02 ` Al Viro
2023-12-06 6:05 ` [PATCH 07/11] hlist-bl: add hlist_bl_fake() Dave Chinner
2023-12-07 3:05 ` Al Viro
2023-12-06 6:05 ` [PATCH 08/11] vfs: inode cache conversion to hash-bl Dave Chinner
2023-12-07 4:58 ` Kent Overstreet
2023-12-07 6:03 ` Dave Chinner
2023-12-07 6:42 ` Al Viro [this message]
2023-12-06 6:05 ` [PATCH 09/11] hash-bl: explicitly initialise hash-bl heads Dave Chinner
2023-12-07 3:15 ` Al Viro
2023-12-06 6:05 ` [PATCH 10/11] list_bl: don't use bit locks for PREEMPT_RT or lockdep Dave Chinner
2023-12-07 4:16 ` Kent Overstreet
2023-12-07 4:41 ` Dave Chinner
2023-12-06 6:05 ` [PATCH 11/11] hlist-bl: introduced nested locking for dm-snap Dave Chinner
2023-12-07 17:08 ` [PATCH 0/11] vfs: inode cache scalability improvements Kent Overstreet
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