From: Christoph Hellwig <hch@lst.de>
To: "Darrick J. Wong" <djwong@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>, Brian Foster <bfoster@redhat.com>,
Carlos Maiolino <cem@kernel.org>,
linux-xfs@vger.kernel.org
Subject: Re: [PATCH 02/12] xfs: consolidate buffer locking in xfs_buf_get_map
Date: Tue, 28 Jul 2026 06:38:38 +0200 [thread overview]
Message-ID: <20260728043838.GA20064@lst.de> (raw)
In-Reply-To: <20260724164218.GP2901224@frogsfrogsfrogs>
On Fri, Jul 24, 2026 at 09:42:18AM -0700, Darrick J. Wong wrote:
> It could emphasize that b_lockref is used to make rcu lookups safe
> against a freed buffer whereas b_sema is used to prevent racing threads
> from doing anything non-trivial with the buffer once they've gotten
> themselves a lockref, and that's why the comment is obsolete and can go
> away.
>
> Or modify the comment?
I've picked up a slight variant of this, thanks.
> Is there a subtlety here that the buffer creator might not be the one to
> read the buffer contents in from disk if another thread happens to find
> the buffer in the cache, take b_sema, notice that it's not XBF_DONE, and
> start the read on its own?
Yes, but it doesn't really matter.
next prev parent reply other threads:[~2026-07-28 4:38 UTC|newest]
Thread overview: 36+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-07-15 14:50 misc buffer cache improvements Christoph Hellwig
2026-07-15 14:50 ` [PATCH 01/12] xfs: don't get a pag reference in xfs_buf_get_map Christoph Hellwig
2026-07-24 16:32 ` Darrick J. Wong
2026-07-15 14:50 ` [PATCH 02/12] xfs: consolidate buffer locking " Christoph Hellwig
2026-07-16 13:12 ` Brian Foster
2026-07-17 8:59 ` Christoph Hellwig
2026-07-17 14:13 ` Brian Foster
2026-07-20 7:59 ` Christoph Hellwig
2026-07-24 16:42 ` Darrick J. Wong
2026-07-28 4:38 ` Christoph Hellwig [this message]
2026-07-15 14:50 ` [PATCH 03/12] xfs: split out a lower-level xfs_buf_get_map helper from xfs_find_get_buf Christoph Hellwig
2026-07-24 16:44 ` Darrick J. Wong
2026-07-28 4:39 ` Christoph Hellwig
2026-07-15 14:50 ` [PATCH 04/12] xfs: remove spurious XBF_DONE clearing on readahead validation failure Christoph Hellwig
2026-07-24 16:45 ` Darrick J. Wong
2026-07-15 14:50 ` [PATCH 05/12] xfs: remove _XBF_LOGRECOVERY Christoph Hellwig
2026-07-24 16:49 ` Darrick J. Wong
2026-07-28 4:39 ` Christoph Hellwig
2026-07-15 14:50 ` [PATCH 06/12] xfs: hide b_flags manipulation from code outside of xfs_buf.c Christoph Hellwig
2026-07-24 16:49 ` Darrick J. Wong
2026-07-15 14:51 ` [PATCH 07/12] xfs: use WRITE_ONCE to update b_flags Christoph Hellwig
2026-07-24 16:53 ` Darrick J. Wong
2026-07-28 4:40 ` Christoph Hellwig
2026-07-15 14:51 ` [PATCH 08/12] xfs: don't reverify buffers in xfs_buf_readahead_map Christoph Hellwig
2026-07-24 16:56 ` Darrick J. Wong
2026-07-15 14:51 ` [PATCH 09/12] xfs: use goto based error unwinding in xfs_buf_read_map Christoph Hellwig
2026-07-24 16:57 ` Darrick J. Wong
2026-07-15 14:51 ` [PATCH 10/12] xfs: merge xfs_buf_reverify into xfs_buf_read_map Christoph Hellwig
2026-07-17 14:13 ` Brian Foster
2026-07-24 16:58 ` Darrick J. Wong
2026-07-15 14:51 ` [PATCH 11/12] xfs: move buffer locking out of xfs_find_get_buf Christoph Hellwig
2026-07-24 16:59 ` Darrick J. Wong
2026-07-15 14:51 ` [PATCH 12/12] xfs: add lockless xfs_buf_readahead_map fast path Christoph Hellwig
2026-07-24 17:03 ` Darrick J. Wong
2026-07-28 4:41 ` Christoph Hellwig
-- strict thread matches above, loose matches on Subject: below --
2026-07-28 8:11 misc buffer cache improvements v2 Christoph Hellwig
2026-07-28 8:11 ` [PATCH 02/12] xfs: consolidate buffer locking in xfs_buf_get_map Christoph Hellwig
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