From: Christoph Hellwig <hch@lst.de>
To: Ming Lei <ming.lei@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, Christoph Hellwig <hch@lst.de>
Subject: Re: [PATCH 1/2] block: avoid to hold q->limits_lock across APIs for atomic update queue limits
Date: Mon, 16 Dec 2024 16:49:01 +0100 [thread overview]
Message-ID: <20241216154901.GA23786@lst.de> (raw)
In-Reply-To: <20241216080206.2850773-2-ming.lei@redhat.com>
On Mon, Dec 16, 2024 at 04:02:03PM +0800, Ming Lei wrote:
> More importantly, queue_limits_start_update() returns one local copy of
> q->limits, then the API user overwrites the local copy, and commit the
> copy by queue_limits_commit_update() finally.
>
> So holding q->limits_lock protects nothing for the local copy, and not see
> any real help by preventing new update & commit from happening, cause
> what matters is that we do validation & commit atomically.
It protects against someone else changing the copy in the queue while
the current thread is updating the local copy, and thus incoherent
updates. So no, we can't just remove it.
next prev parent reply other threads:[~2024-12-16 15:49 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-12-16 8:02 [PATCH 0/2] block: fix deadlock caused by atomic limits update Ming Lei
2024-12-16 8:02 ` [PATCH 1/2] block: avoid to hold q->limits_lock across APIs for atomic update queue limits Ming Lei
2024-12-16 15:49 ` Christoph Hellwig [this message]
2024-12-17 1:52 ` Ming Lei
2024-12-17 4:40 ` Christoph Hellwig
2024-12-17 7:05 ` Ming Lei
2024-12-17 7:19 ` Christoph Hellwig
2024-12-17 7:30 ` Ming Lei
2024-12-17 16:07 ` Damien Le Moal
2024-12-18 2:09 ` Ming Lei
2024-12-18 11:33 ` Nilay Shroff
2024-12-18 13:40 ` Ming Lei
2024-12-18 14:05 ` Nilay Shroff
2024-12-18 14:57 ` Damien Le Moal
2024-12-19 6:20 ` Christoph Hellwig
2024-12-19 7:16 ` Nilay Shroff
2024-12-21 13:03 ` Nilay Shroff
2024-12-30 9:02 ` Ming Lei
2024-12-30 23:29 ` Damien Le Moal
2025-01-01 11:17 ` Nilay Shroff
2024-12-19 6:17 ` Christoph Hellwig
2024-12-19 6:15 ` Christoph Hellwig
2024-12-16 8:02 ` [PATCH 2/2] block: remove queue_limits_cancel_update() Ming Lei
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