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From: Hao Li To: "Vlastimil Babka (SUSE)" Cc: Harry Yoo , Christoph Lameter , David Rientjes , Roman Gushchin , Suren Baghdasaryan , Alexei Starovoitov , Andrew Morton , Johannes Weiner , Michal Hocko , Shakeel Butt , Alexander Potapenko , Marco Elver , Dmitry Vyukov , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, cgroups@vger.kernel.org Subject: Re: [PATCH v2 05/16] mm/slab: introduce alloc_flags and SLAB_ALLOC_TRYLOCK Message-ID: References: <20260610-slab_alloc_flags-v2-0-7190909db118@kernel.org> <20260610-slab_alloc_flags-v2-5-7190909db118@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260610-slab_alloc_flags-v2-5-7190909db118@kernel.org> X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 22707C0002 X-Stat-Signature: qndoztx3dpwekznjre9jkmpuzkdpcbok X-Rspam-User: X-HE-Tag: 1781236192-454796 X-HE-Meta: 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 UV6EyarH t/S1lSQ1NAnCzlFsZtjpritcxuZ3EIyxDga73PkqrWGbginQohGyEJo39kvlbBUpwATzJyaH8k6kM9s83S+EQdlYq+Ij3TnHt09KkvFcrNMaT5noGjCVXHPkUPUXhJ+4PMbBnBl17C6YNUafEOZ4L2jqxRqr57tpdXWUCrZeW4NeILBtWTFCFwraYviQ6F5LmHhb5vPRk1Y021yfCOTWtAVKWuwSejueOPP+53Z3jJvlNUCBUlSMfv961Wgw/NV2NPV0hxh9EgB1I8GWkv+t9oTaX+Q== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Jun 10, 2026 at 05:40:07PM +0200, Vlastimil Babka (SUSE) wrote: > Similarly to the page allocators, introduce slab-allocator specific > alloc flags that internally control allocation behavior in addition to > gfp_flags, without occupying the limited gfp flags space. > > Introduce the first flag SLAB_ALLOC_TRYLOCK that behaves similarly to > page allocator's ALLOC_TRYLOCK and will be used to reimplement > kmalloc_nolock()'s "!allow_spin" behavior. That currently relies on > gfpflags_allow_spinning() and thus the lack of both __GFP_RECLAIM flags, > importantly __GFP_KSWAPD_RECLAIM. This can give false-positive results > e.g. in early boot with a restricted gfp_allowed_mask. > > Also introduce alloc_flags_allow_spinning() to replace the usage of > gfpflags_allow_spinning(). > > Start using alloc_flags and the new check first in alloc_from_pcs() and > __pcs_replace_empty_main(). This means some slab allocations that were > falsely treated as kmalloc_nolock() due to their gfp flags will now have > higher chances of succeed, and this will further increase with followup > changes. > > Remove a WARN_ON_ONCE() from refill_objects() as it's now legitimate to > reach it from a slab allocation that's not _nolock() and yet lacks > __GFP_KSWAPD_RECLAIM for other reasons. > > Signed-off-by: Vlastimil Babka (SUSE) > --- Reviewed-by: Hao Li -- Thanks, Hao