From: Matthew Wilcox <willy@infradead.org>
To: Wenjie Qi <qwjhust@gmail.com>
Cc: akpm@linux-foundation.org, jack@suse.cz,
linux-fsdevel@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, baohua@kernel.org,
Wenjie Qi <qiwenjie@xiaomi.com>
Subject: Re: [PATCH] mm: filemap: tighten dropbehind completion context check
Date: Thu, 20 Aug 2026 15:34:25 +0100 [thread overview]
Message-ID: <aocQcaMMU7-rfn3e@casper.infradead.org> (raw)
In-Reply-To: <20260820142956.1414337-1-qiwenjie@xiaomi.com>
On Thu, Aug 20, 2026 at 10:29:56PM +0800, Wenjie Qi wrote:
> folio_end_dropbehind() uses in_task() to keep folio invalidation out of
> interrupt context. Task context alone is not sufficient: preemption can
> still be disabled, or the task can be in a preemptible RCU read-side
> critical section, while filemap_end_dropbehind() may reach
> folio_unmap_invalidate() and sleep.
>
> Use the established conservative three-part atomic-context test: reject
> preemptible RCU read-side sections, reject configurations without
> PREEMPT_COUNT, and otherwise require a preemptible context. Unsafe
> completions retain the existing best-effort behavior and skip invalidation.
Have you seen this happen in practice, or is this based on code
examination?
next prev parent reply other threads:[~2026-08-20 14:34 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-20 14:29 [PATCH] mm: filemap: tighten dropbehind completion context check Wenjie Qi
2026-08-20 14:34 ` Matthew Wilcox [this message]
2026-08-21 1:23 ` Wenjie Qi
2026-08-21 3:30 ` Matthew Wilcox
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