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From: Christoph Hellwig <hch@infradead.org>
To: Kuan-Wei Chiu <visitorckw@gmail.com>
Cc: Richard Weinberger <richard@nod.at>,
	Andrew Morton <akpm@linux-foundation.org>,
	chengzhihao1 <chengzhihao1@huawei.com>,
	jserv@ccns.ncku.edu.tw, eleanor15x@gmail.com,
	marscheng@google.com, linux-mtd <linux-mtd@lists.infradead.org>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] lib/list_sort: introduce list_sort_nonatomic() and remove dummy cmp() calls
Date: Tue, 17 Mar 2026 07:22:12 -0700	[thread overview]
Message-ID: <abljlKim3-hPngCG@infradead.org> (raw)
In-Reply-To: <abhGF65wCbI7CsTm@google.com>

On Tue, Mar 17, 2026 at 02:04:07AM +0800, Kuan-Wei Chiu wrote:
> I tried to dig into the history. It turns out this mechanism was
> introduced 16 years ago in commit 835cc0c8477f ("lib: more scalable
> list_sort()"). The commit message explicitly mentioned both XFS and
> UBIFS as the intended users for this long-list workaround. However,
> looking at the tree back then, XFS never actually put a cond_resched()
> in their cmp() function. It seems UBIFS has been the sole user of this
> trick ever since. Given that it has been this way for 16 years, it
> seems other subsystems haven't really encountered any practical issues
> with it.

.. or it wasn't even needed in the first place.

> For UBIFS, this patch doesn't alter the frequency, timing, or behavior
> of the cond_resched() calls at all, so I am confident that this won't
> introduce any regressions.

I'd be tempted to drop the workaround and remove the cond_resched
from ubifs given that entirely non-preemptible scheduling models are
on their way out.


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http://lists.infradead.org/mailman/listinfo/linux-mtd/

WARNING: multiple messages have this Message-ID (diff)
From: Christoph Hellwig <hch@infradead.org>
To: Kuan-Wei Chiu <visitorckw@gmail.com>
Cc: Richard Weinberger <richard@nod.at>,
	Andrew Morton <akpm@linux-foundation.org>,
	chengzhihao1 <chengzhihao1@huawei.com>,
	jserv@ccns.ncku.edu.tw, eleanor15x@gmail.com,
	marscheng@google.com, linux-mtd <linux-mtd@lists.infradead.org>,
	linux-kernel <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] lib/list_sort: introduce list_sort_nonatomic() and remove dummy cmp() calls
Date: Tue, 17 Mar 2026 07:22:12 -0700	[thread overview]
Message-ID: <abljlKim3-hPngCG@infradead.org> (raw)
In-Reply-To: <abhGF65wCbI7CsTm@google.com>

On Tue, Mar 17, 2026 at 02:04:07AM +0800, Kuan-Wei Chiu wrote:
> I tried to dig into the history. It turns out this mechanism was
> introduced 16 years ago in commit 835cc0c8477f ("lib: more scalable
> list_sort()"). The commit message explicitly mentioned both XFS and
> UBIFS as the intended users for this long-list workaround. However,
> looking at the tree back then, XFS never actually put a cond_resched()
> in their cmp() function. It seems UBIFS has been the sole user of this
> trick ever since. Given that it has been this way for 16 years, it
> seems other subsystems haven't really encountered any practical issues
> with it.

.. or it wasn't even needed in the first place.

> For UBIFS, this patch doesn't alter the frequency, timing, or behavior
> of the cond_resched() calls at all, so I am confident that this won't
> introduce any regressions.

I'd be tempted to drop the workaround and remove the cond_resched
from ubifs given that entirely non-preemptible scheduling models are
on their way out.


  parent reply	other threads:[~2026-03-17 14:22 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-03-15 19:39 [PATCH] lib/list_sort: introduce list_sort_nonatomic() and remove dummy cmp() calls Kuan-Wei Chiu
2026-03-15 19:39 ` Kuan-Wei Chiu
2026-03-16  7:25 ` Richard Weinberger
2026-03-16  7:25   ` Richard Weinberger
2026-03-16 18:04   ` Kuan-Wei Chiu
2026-03-16 18:04     ` Kuan-Wei Chiu
2026-03-16 21:49     ` Richard Weinberger
2026-03-16 21:49       ` Richard Weinberger
2026-03-17 14:22     ` Christoph Hellwig [this message]
2026-03-17 14:22       ` Christoph Hellwig
2026-03-17 14:38       ` Richard Weinberger
2026-03-17 14:38         ` Richard Weinberger
2026-03-17 14:40         ` Christoph Hellwig
2026-03-17 14:40           ` Christoph Hellwig
2026-03-17 16:08           ` Kuan-Wei Chiu
2026-03-17 16:08             ` Kuan-Wei Chiu
2026-03-17  4:05 ` Zhihao Cheng
2026-03-17  4:05   ` Zhihao Cheng
2026-03-17 12:32   ` Kuan-Wei Chiu
2026-03-17 12:32     ` Kuan-Wei Chiu
2026-03-17 13:22     ` Zhihao Cheng
2026-03-17 13:22       ` Zhihao Cheng
2026-03-17 14:15       ` Kuan-Wei Chiu
2026-03-17 14:15         ` Kuan-Wei Chiu

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