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Message-ID: <YzGxuZ8jQ2sO4ZML@dhcp22.suse.cz> Date: Mon, 26 Sep 2022 16:05:45 +0200 From: Michal Hocko <mhocko@...e.com> To: Florian Westphal <fw@...len.de> Cc: linux-mm@...ck.org, linux-kernel@...r.kernel.org, vbabka@...e.cz, akpm@...ux-foundation.org, urezki@...il.com, netdev@...r.kernel.org, netfilter-devel@...r.kernel.org, Martin Zaharinov <micron10@...il.com> Subject: Re: [PATCH mm] mm: fix BUG with kvzalloc+GFP_ATOMIC On Mon 26-09-22 15:08:08, Florian Westphal wrote: [...] > To the best of my knowledge there are users of this interface that > invoke it with rcu read lock held, and since those always nest, the > rcu_read_unlock() won't move us to GFP_KERNEL territory. Fiar point. I can see a comment above rhashtable_insert_fast which is supposed to be used by drivers and explicitly documented to be compatible with an atomic context. So the above is clearly a no-go In that case I would propose to go with the patch going http://lkml.kernel.org/r/YzFplwSxwwsLpzzX@dhcp22.suse.cz direction. For that we could use an alternative implementation for the vmalloc fallback for non-sleeping request in the future. A single branch for an unlikely event is not nice but acceptable I would say. Especially if we want to go in line with Linus' original "prevent hack for gfp_mask in callers". -- Michal Hocko SUSE Labs
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