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b=hXRHhmrB9NhcEkiy7kvByZxgQdF2vfg2sXL63KJyiVDOAbH4giWC3rrE1BYeZx3P8 GlMqexvqR1BEnxX+bIlseBFGTRMIe8avCCI/W/HCZEHmRS403M3NHZup7vuVRAhUgx yxoCQJLQTVrxDmhTe5J9/i5t41chXhheoL4AJO/45XmGvDvFOOPQYIguBWMOgbYttC 2ZKj2ODVAjDOEoM3VdCfDZ6XfoXNCkjd+NalL3o1/A5G10ZWYUqS4JVQddQlZkKM6W TLZIQ7Tlh7ff/pR8nFPrWCKUQ69LPN2/R7Ai7w2iOuavHVf8r0TKz6k9uKpIQ6ZX4u BjFAQ7dvmSCVg== Message-ID: <80206444-d0c3-4dab-a5e3-a2909e58ea33@kernel.org> Date: Wed, 23 Sep 2026 08:32:29 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/page_alloc: let the bulk and folio allocators carry alloc_flags To: Gregory Price , Lance Yang Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel-team@meta.com, akpm@linux-foundation.org, surenb@google.com, mhocko@suse.com, brendan.jackman@linux.dev, hannes@cmpxchg.org, ziy@nvidia.com, david@kernel.org, ljs@kernel.org, liam@infradead.org, rppt@kernel.org, baolin.wang@linux.alibaba.com, nico.pache@linux.dev, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, usama.arif@linux.dev, kas@kernel.org, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, ying.huang@linux.alibaba.com, apopple@nvidia.com References: <20260914155115.439742-1-gourry@gourry.net> <20260922130558.48402-1-lance.yang@linux.dev> From: "Vlastimil Babka (SUSE)" Content-Language: en-US Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Stat-Signature: cr5z7hpmi6shrejhybnxhobqbf8jpgio X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: ED6D7120008 X-HE-Tag: 1790145158-368405 X-HE-Meta: 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 MVFl6q+c 40Ay317HPtR3cs/eVdLau+RlMvLdDZ7QNfI6/RM3pjQcAQPINGW/7rJ9cIXxw0R33ZJEUn1SDNC2VOc0u9tqO2RMLSS7dINspoT8zEAhO6DhH+lyzyHRoRRuRdA2nWfs01XCVYsPI5BTYfynflOKCIBKkZI5/s2KzN2ufomgAw9qAl1ZLo4UCmjnH4DYgzQhdZNy2gjF02X2e/P/h7HFm90mc/jVtzJQOawA35rZH2Qj5njqME9akCt2Se5Y4dA6amRAF1UKR5kDXS3vKVbdSaYtjbB+TMtAr9f7oRnGp1hO2BRC3WUu0lPgHjX5nhB6hUJIkD0jp1P3NKtZK+Lvm4ASUI/FAHSDCeFtjkmNm464r0cl0x8T9bArlB2fK4sVvmLhA Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/23/26 03:59, Gregory Price wrote: > On Tue, Sep 22, 2026 at 09:05:58PM +0800, Lance Yang wrote: >> >> On Mon, Sep 14, 2026 at 11:51:14AM -0400, Gregory Price wrote: >> >__alloc_pages_noprof() takes an explicit alloc_flags, but the bulk and >> >folio entry points do not, so callers cannot select allocator behaviour >> >(e.g. an alternate zonelist) through them. >> > >> >Thread alloc_flags through both, matching __alloc_pages_noprof(), and >> >keep the flag-carrying primitives mm-internal (page_alloc.h) so the >> >public gfp.h wrappers stay flag-free: >> > >> > - add __alloc_pages_bulk_noprof(gfp, ..., alloc_flags) in page_alloc.h >> > alloc_pages_bulk_noprof() becomes a wrapper passing ALLOC_DEFAULT >> > >> > - give __folio_alloc_noprof() an alloc_flags parameter and moves >> > __folio_alloc_node_noprof() moves into page_alloc.h >> > __folio_alloc_noprof() is no longer exported >> > >> >No functional change: every caller passes ALLOC_DEFAULT. >> >> Yeah, but what if a caller passes ALLOC_NOLOCK in the future? >> >> __alloc_pages_noprof() checks alloc_nolock_allowed() first, but >> __alloc_pages_bulk_noprof() can enter its fast path without that check. >> >> That fast path can reach _deferred_grow_zone() or pcp_spin_trylock(). >> Shouldn't we do the same check first? >> >> Or am I missing something? >> >> Cheers, Lance > > There is some concern around NOLOCK here yes, in fact sashiko picked > this issue up and I've been poking at it. It's possible to document it as unsupported, add a VM_WARN_ON_ONCE etc. It's not necessary for bulk alloc to support ALLOC_NOLOCK just because it takes flags. e.g. kmalloc_nolock() supports a subset of gfp flags as well. > I've actually been reworking this patch and pulled in changes from the > ALLOC_UNMAPPED series to address this all at once. I've been developing > a page allocator unit-testing harness to help validate some assumptions > before I post it. > > ~Gregory