From: Christoph Hellwig <hch@infradead.org>
To: Eric Biggers <ebiggers@kernel.org>
Cc: Christoph Hellwig <hch@infradead.org>,
linux-block@vger.kernel.org, linux-mm@kvack.org,
linux-kernel@vger.kernel.org, Jens Axboe <axboe@kernel.dk>,
Vlastimil Babka <vbabka@kernel.org>, Harry Yoo <harry@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>,
Hao Li <hao.li@linux.dev>, Christoph Lameter <cl@gentwo.org>,
David Rientjes <rientjes@google.com>,
Roman Gushchin <roman.gushchin@linux.dev>
Subject: Re: [PATCH 2/3] mm: support fallible mempool_alloc_bulk()
Date: Mon, 10 Aug 2026 10:21:15 -0700 [thread overview]
Message-ID: <anoIiy0V-m-05yZc@infradead.org> (raw)
In-Reply-To: <20260810161404.GA1930@sol>
On Mon, Aug 10, 2026 at 09:14:04AM -0700, Eric Biggers wrote:
> On Mon, Aug 10, 2026 at 09:00:11AM -0700, Christoph Hellwig wrote:
> > On Thu, Aug 06, 2026 at 03:10:30PM -0700, Eric Biggers wrote:
> > > To fix a deadlock, blk-crypto-fallback needs to be able to make fallible
> > > mempool_alloc_bulk() allocations.
> >
> > It doesn't. fallible mempool allocations are a concept that doesn't
> > make much sense. Please just go straight to the backing page allocator
> > instead for callers that do not need the mempool guarantees.
>
> It does make sense. When alloc_pages_bulk() doesn't completely succeed,
> there still might be pages available in the mempool.
But they should not go to a caller that does not need the mempool.
> blk_crypto_alloc_enc_bio() should try to take them before falling back
> to scheduling the rescuer kworker. The rescuer encounters scheduling
> overhead and is single-threaded, so it's slow and should be used only
> when absolutely necessary.
No, it should just try a regular non-bulk alloc_pages (and eventually
alloc_pages_bulk should do that fallback for the callers, but that's
a separate discussion).
next prev parent reply other threads:[~2026-08-10 17:21 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-06 22:10 [PATCH 0/3] Fix a deadlock in blk-crypto-fallback Eric Biggers
2026-08-06 22:10 ` [PATCH 1/3] mm: make mempool_alloc_from_pool() return bool Eric Biggers
2026-08-10 15:59 ` Christoph Hellwig
2026-08-06 22:10 ` [PATCH 2/3] mm: support fallible mempool_alloc_bulk() Eric Biggers
2026-08-10 16:00 ` Christoph Hellwig
2026-08-10 16:14 ` Eric Biggers
2026-08-10 17:21 ` Christoph Hellwig [this message]
2026-08-10 18:22 ` Eric Biggers
2026-08-06 22:10 ` [PATCH 3/3] blk-crypto-fallback: Fix deadlock when encrypting large bio in dm layer Eric Biggers
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