From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-wm1-f73.google.com (mail-wm1-f73.google.com [209.85.128.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id D39D739EF0F for ; Mon, 22 Jun 2026 10:01:46 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.128.73 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782122508; cv=none; b=H+AkAxafSre7u0xTmTqbWxR/obz7+WhC94UgY6eiUzCdLVi+8eQkfbciIZQ4apSEBfUhXdT2ielJvxRBpeHN1vbowDWJgQ9XJ1KHBOfLyTFfppO4rqFJTpmjp6OMbwKU+F8u5fLK4bkuNVWqAo/fd+iwhJyG/6jYRdmHaoO70QA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782122508; c=relaxed/simple; bh=cXyjb3bcJTlei9Rk2BBBpTGW3mbF5qZX6kIvUhjfXA8=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=VY3sy3sS2E82rwflj4g8FtbYfJ3rUa1DRrBT9DoqQWiSvtToHqlCcZEXN8uAtbL1ww3zGz2ZPPJJB9ytTgbHwMF5zdPMscvFlN9cnekhZA0zthvCujHIfAAu0w+91YumAbQxq4OF6fvtmuMbsfPYcfp6xfU1A/9paRVCzEwcSso= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=nmeOsk3S; arc=none smtp.client-ip=209.85.128.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jackmanb.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="nmeOsk3S" Received: by mail-wm1-f73.google.com with SMTP id 5b1f17b1804b1-490b9cd54f3so27566085e9.2 for ; Mon, 22 Jun 2026 03:01:46 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1782122505; x=1782727305; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=acHa8qzGpYOuvZT+OpZqGrTA/yeCpJyZkBIOAz883N8=; b=nmeOsk3ShNAVnN/VMX9sNQ97Rz/OAXCDnKgljmO7QAxDOnDRaiAdHLokD3g0A5E3Ma Ppxl+2xFzuLs0K1UR7buICitjs7OPhOZPFN458AOlqLEGoT0G1nPxGc41x5YJu/jOzDJ 42sLR8mb6Ogp4vHdhApxLYhPEt+jvVShT8YQsnJzlb/e/O2AY3HTXsulp3XOj0CUk1XK r8FgQ6DQOtakxRR74ZGN9z90VmvdikI5Ffm9LiYOutTunLMQI6ukLm6x6Aw+PVriwxti RKgPHau9C/bBLcr0/zqkmDnCPT0MqmjtNiYioMQQLglrioqBhfXkFDpDPC+FM5zywtWL IYhQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1782122505; x=1782727305; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=acHa8qzGpYOuvZT+OpZqGrTA/yeCpJyZkBIOAz883N8=; b=FlbMI1pmgqU5exPbYMqNqqAHIzeg5h3zk1nHSaAUGnXRgZEoID10IXLvblPPDsMIl9 PUznNQCXyMSaItwzTvybpiVhdeE7v7r4RMIct0biDOoGog4Wet/fzAdw3f2V+DWZwXzO UrGZEbTF0HsyL1cUbJmMd8Nx7kr/AFYdwm7fEnKNdYLbBuExgSy9AtB/YWck0pS7nsEn Sx0UMnF3svIgr+x7Vezl67hUynem2n4QfU27aAUTf1xbCW6wveeGt99+FTo4qxzQMDSO 5mkJm+eogYMOQRcAfGCTCqtn8EIpip9FSur0SelHPXEewd4FKk16EfQ7YjK6CeRrSlbL LFuQ== X-Forwarded-Encrypted: i=1; AFNElJ9j1rjI0zyAjvhStW+rScgy53PGhdQYGm+9ok/8CVNPpwb9jEKTT3wh2Qwh1+qjgOAklh9PoVneCH2NmMY=@vger.kernel.org X-Gm-Message-State: AOJu0YxymU/1oBuslkd3US8Y2/qtd+hq7LV8tE/uupEttCQWxxbwK8GC SDmym8nPo9SntdgyszUY7QcSftgcQ5qCqvjkUsPOB5EH5m4lbeN2NdnDP7Ecet0U1Fthz8kkpQY s6UUFqlMr144j5A== X-Received: from wmbgx8.prod.google.com ([2002:a05:600c:8588:b0:490:b195:62b3]) (user=jackmanb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:c088:b0:492:2f3c:d0ed with SMTP id 5b1f17b1804b1-4923f594511mr211459175e9.30.1782122504907; Mon, 22 Jun 2026 03:01:44 -0700 (PDT) Date: Mon, 22 Jun 2026 10:01:30 +0000 In-Reply-To: <20260622-alloc-trylock-v2-0-31f31367d420@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260622-alloc-trylock-v2-0-31f31367d420@google.com> X-Mailer: b4 0.15.2 Message-ID: <20260622-alloc-trylock-v2-3-31f31367d420@google.com> Subject: [PATCH v2 03/13] mm/page_alloc: unify __alloc_frozen_pages[_nolock]_noprof() From: Brendan Jackman To: Andrew Morton , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , Johannes Weiner , Zi Yan , Muchun Song , Oscar Salvador , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Matthew Brost , Joshua Hahn , Rakie Kim , Byungchul Park , Ying Huang , Alistair Popple , Hao Li , Christoph Lameter , David Rientjes , Roman Gushchin , Sebastian Andrzej Siewior , Clark Williams , Steven Rostedt Cc: "Harry Yoo (Oracle)" , Gregory Price , Johannes Weiner , Alexei Starovoitov , Matthew Wilcox , linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-rt-devel@lists.linux.dev, Brendan Jackman Content-Type: text/plain; charset="utf-8" Currently the core allocator code is controlled by ALLOC_NOLOCK, but the main entry point function is significantly different from the normal __alloc_frozen_pages_nolock(), this is tiring when reading the code. Plumb the ALLOC_NOLOCK control one layer up in the call stack: create an alloc_flags argument to __alloc_frozen_pages_nolock() (which is only exposed to mm/) and then turn the nolock variant into a thin wrapper that just sets that flag (as well as handling NUMA_NO_NODE, similar to how some of the wrappers in gfp.h do). Rationale that this doesn't change anything: 1. Simple bits: A bunch of the nolock-specific handling is just moved to the new alloc_order_allowed(), alloc_trylock_allowed() and gfp_trylock. 2. __alloc_frozen_pages_noprof() has some extra logic that wasn't previously in the nolock variant: a. Application of gfp_allowed_mask; this only affects early boot, and only flags that affect the slowpath get changed here. b. Application of current_gfp_context() - also only affects the slowpath 3. The slowpath itself: this is now just explicitly skipped under !ALLOC_TRYLOCK. Ulterior motive: adding an alloc_flags arg to the allocator's mm-internal entrypoint can later be used to do more allocation customisation without needing to create new GFP flags. While adding this flag to a bunch of places, create ALLOC_DEFAULT to avoid a mysterious literal 0 in most places. alloc_frozen_pages_noprof() is defined above the alloc flags so just leave that as a slightly messy exception instead of trying to fully reorder mm/internal.h for that one case. No functional change intended. Signed-off-by: Brendan Jackman --- mm/hugetlb.c | 3 +- mm/internal.h | 8 ++- mm/mempolicy.c | 10 ++-- mm/page_alloc.c | 178 +++++++++++++++++++++++++++++--------------------------- mm/slub.c | 6 +- 5 files changed, 110 insertions(+), 95 deletions(-) diff --git a/mm/hugetlb.c b/mm/hugetlb.c index 571212b80835e..2ce6169ca0dfd 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -1806,7 +1806,8 @@ static struct folio *alloc_buddy_frozen_folio(int order, gfp_t gfp_mask, if (alloc_try_hard) gfp_mask |= __GFP_RETRY_MAYFAIL; - folio = (struct folio *)__alloc_frozen_pages(gfp_mask, order, nid, nmask); + folio = (struct folio *)__alloc_frozen_pages(gfp_mask, order, nid, nmask, + ALLOC_DEFAULT); /* * If we did not specify __GFP_RETRY_MAYFAIL, but still got a diff --git a/mm/internal.h b/mm/internal.h index 1483a4fcdfce1..6bc89ec62e527 100644 --- a/mm/internal.h +++ b/mm/internal.h @@ -913,7 +913,7 @@ extern bool free_pages_prepare(struct page *page, unsigned int order); extern int user_min_free_kbytes; struct page *__alloc_frozen_pages_noprof(gfp_t, unsigned int order, int nid, - nodemask_t *); + nodemask_t *, unsigned int alloc_flags); #define __alloc_frozen_pages(...) \ alloc_hooks(__alloc_frozen_pages_noprof(__VA_ARGS__)) void free_frozen_pages(struct page *page, unsigned int order); @@ -924,7 +924,8 @@ struct page *alloc_frozen_pages_noprof(gfp_t, unsigned int order); #else static inline struct page *alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order) { - return __alloc_frozen_pages_noprof(gfp, order, numa_node_id(), NULL); + return __alloc_frozen_pages_noprof(gfp, order, numa_node_id(), NULL, + 0 /* ALLOC_DEFAULT */); } #endif @@ -1440,6 +1441,9 @@ extern void set_pageblock_order(void); unsigned long reclaim_pages(struct list_head *folio_list); unsigned int reclaim_clean_pages_from_list(struct zone *zone, struct list_head *folio_list); + + +#define ALLOC_DEFAULT 0 /* The ALLOC_WMARK bits are used as an index to zone->watermark */ #define ALLOC_WMARK_MIN WMARK_MIN #define ALLOC_WMARK_LOW WMARK_LOW diff --git a/mm/mempolicy.c b/mm/mempolicy.c index 36699fabd3c22..40bbea614aced 100644 --- a/mm/mempolicy.c +++ b/mm/mempolicy.c @@ -2425,9 +2425,11 @@ static struct page *alloc_pages_preferred_many(gfp_t gfp, unsigned int order, */ preferred_gfp = gfp | __GFP_NOWARN; preferred_gfp &= ~(__GFP_DIRECT_RECLAIM | __GFP_NOFAIL); - page = __alloc_frozen_pages_noprof(preferred_gfp, order, nid, nodemask); + page = __alloc_frozen_pages_noprof(preferred_gfp, order, nid, nodemask, + ALLOC_DEFAULT); if (!page) - page = __alloc_frozen_pages_noprof(gfp, order, nid, NULL); + page = __alloc_frozen_pages_noprof(gfp, order, nid, NULL, + ALLOC_DEFAULT); return page; } @@ -2475,7 +2477,7 @@ static struct page *alloc_pages_mpol(gfp_t gfp, unsigned int order, */ page = __alloc_frozen_pages_noprof( gfp | __GFP_THISNODE | __GFP_NORETRY, order, - nid, NULL); + nid, NULL, ALLOC_DEFAULT); if (page || !(gfp & __GFP_DIRECT_RECLAIM)) return page; /* @@ -2487,7 +2489,7 @@ static struct page *alloc_pages_mpol(gfp_t gfp, unsigned int order, } } - page = __alloc_frozen_pages_noprof(gfp, order, nid, nodemask); + page = __alloc_frozen_pages_noprof(gfp, order, nid, nodemask, ALLOC_DEFAULT); if (unlikely(pol->mode == MPOL_INTERLEAVE || pol->mode == MPOL_WEIGHTED_INTERLEAVE) && page) { diff --git a/mm/page_alloc.c b/mm/page_alloc.c index bc05d75a41627..e31babe2181a1 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -5204,7 +5204,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid, } nr_account++; - prep_new_page(page, 0, gfp, 0); + prep_new_page(page, 0, gfp, ALLOC_DEFAULT); set_page_refcounted(page); page_array[nr_populated++] = page; } @@ -5253,24 +5253,98 @@ void free_pages_bulk(struct page **page_array, unsigned long nr_pages) } } -/* - * This is the 'heart' of the zoned buddy allocator. - */ -struct page *__alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order, - int preferred_nid, nodemask_t *nodemask) +static inline bool alloc_order_allowed(gfp_t gfp, unsigned int order, + unsigned int alloc_flags) { - struct page *page; - unsigned int fastpath_alloc_flags = ALLOC_WMARK_LOW; - gfp_t alloc_gfp; /* The gfp_t that was actually used for allocation */ - struct alloc_context ac = { }; + if (alloc_flags & ALLOC_NOLOCK) + return pcp_allowed_order(order); /* * There are several places where we assume that the order value is sane * so bail out early if the request is out of bound. */ - if (WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp)) + return !(WARN_ON_ONCE_GFP(order > MAX_PAGE_ORDER, gfp)); +} + +static inline bool alloc_trylock_allowed(void) +{ + /* + * In PREEMPT_RT spin_trylock() will call raw_spin_lock() which is + * unsafe in NMI. If spin_trylock() is called from hard IRQ the current + * task may be waiting for one rt_spin_lock, but rt_spin_trylock() will + * mark the task as the owner of another rt_spin_lock which will + * confuse PI logic, so return immediately if called from hard IRQ or + * NMI. + * + * Note, irqs_disabled() case is ok. This function can be called + * from raw_spin_lock_irqsave region. + */ + if (IS_ENABLED(CONFIG_PREEMPT_RT) && (in_nmi() || in_hardirq())) + return false; + + /* On UP, spin_trylock() always succeeds even when it is locked */ + if (!IS_ENABLED(CONFIG_SMP) && in_nmi()) + return false; + + /* Bailout, since _deferred_grow_zone() needs to take a lock */ + if (deferred_pages_enabled()) + return false; + + return true; +} + +/* + * GFP flags to set for ALLOC_NOLOCK i.e. alloc_pages_nolock(). + * + * Do not specify __GFP_DIRECT_RECLAIM, since direct claim is not allowed. + * Do not specify __GFP_KSWAPD_RECLAIM either, since wake up of kswapd + * is not safe in arbitrary context. + * + * These two are the conditions for gfpflags_allow_spinning() being true. + * + * Specify __GFP_NOWARN since failing alloc_pages_nolock() is not a reason + * to warn. Also warn would trigger printk() which is unsafe from + * various contexts. We cannot use printk_deferred_enter() to mitigate, + * since the running context is unknown. + * + * Specify __GFP_ZERO to make sure that call to kmsan_alloc_page() below + * is safe in any context. Also zeroing the page is mandatory for + * BPF use cases. + * + * Though __GFP_NOMEMALLOC is not checked in the code path below, + * specify it here to highlight that alloc_pages_nolock() + * doesn't want to deplete reserves. + */ +static const gfp_t gfp_nolock = __GFP_NOWARN | __GFP_ZERO | __GFP_NOMEMALLOC | + __GFP_COMP; + +/* + * This is the 'heart' of the zoned buddy allocator. + */ +struct page *__alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order, + int preferred_nid, nodemask_t *nodemask, unsigned int alloc_flags) +{ + struct page *page; + gfp_t alloc_gfp; /* The gfp_t that was actually used for allocation */ + struct alloc_context ac = { }; + unsigned int fastpath_alloc_flags = alloc_flags; + + /* Other flags could be supported later if needed. */ + if (WARN_ON(alloc_flags & ~ALLOC_NOLOCK)) return NULL; + if (!alloc_order_allowed(gfp, order, alloc_flags)) + return NULL; + + if (alloc_flags & ALLOC_NOLOCK) { + VM_WARN_ON_ONCE(gfp & ~__GFP_ACCOUNT); + if (!alloc_trylock_allowed()) + return NULL; + gfp |= gfp_nolock; + } else { + fastpath_alloc_flags |= ALLOC_WMARK_LOW; + } + gfp &= gfp_allowed_mask; /* * Apply scoped allocation constraints. This is mainly about GFP_NOFS @@ -5291,9 +5365,9 @@ struct page *__alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order, */ fastpath_alloc_flags |= alloc_flags_nofragment(zonelist_zone(ac.preferred_zoneref), gfp); - /* First allocation attempt */ + /* First allocation attempt (or, for nolock, only attempt) */ page = get_page_from_freelist(alloc_gfp, order, fastpath_alloc_flags, &ac); - if (likely(page)) + if (likely(page) || (alloc_flags & ALLOC_NOLOCK)) goto out; alloc_gfp = gfp; @@ -5310,7 +5384,8 @@ struct page *__alloc_frozen_pages_noprof(gfp_t gfp, unsigned int order, out: if (memcg_kmem_online() && (gfp & __GFP_ACCOUNT) && page && unlikely(__memcg_kmem_charge_page(page, gfp, order) != 0)) { - free_frozen_pages(page, order); + __free_frozen_pages(page, order, + alloc_flags & ALLOC_NOLOCK ? FPI_TRYLOCK : 0); page = NULL; } @@ -5326,7 +5401,8 @@ struct page *__alloc_pages_noprof(gfp_t gfp, unsigned int order, { struct page *page; - page = __alloc_frozen_pages_noprof(gfp, order, preferred_nid, nodemask); + page = __alloc_frozen_pages_noprof(gfp, order, preferred_nid, nodemask, + ALLOC_DEFAULT); if (page) set_page_refcounted(page); return page; @@ -7856,80 +7932,10 @@ static bool __free_unaccepted(struct page *page) struct page *alloc_frozen_pages_nolock_noprof(gfp_t gfp_flags, int nid, unsigned int order) { - /* - * Do not specify __GFP_DIRECT_RECLAIM, since direct claim is not allowed. - * Do not specify __GFP_KSWAPD_RECLAIM either, since wake up of kswapd - * is not safe in arbitrary context. - * - * These two are the conditions for gfpflags_allow_spinning() being true. - * - * Specify __GFP_NOWARN since failing alloc_pages_nolock() is not a reason - * to warn. Also warn would trigger printk() which is unsafe from - * various contexts. We cannot use printk_deferred_enter() to mitigate, - * since the running context is unknown. - * - * Specify __GFP_ZERO to make sure that call to kmsan_alloc_page() below - * is safe in any context. Also zeroing the page is mandatory for - * BPF use cases. - * - * Though __GFP_NOMEMALLOC is not checked in the code path below, - * specify it here to highlight that alloc_pages_nolock() - * doesn't want to deplete reserves. - */ - gfp_t alloc_gfp = __GFP_NOWARN | __GFP_ZERO | __GFP_NOMEMALLOC | __GFP_COMP - | gfp_flags; - unsigned int alloc_flags = ALLOC_NOLOCK; - struct alloc_context ac = { }; - struct page *page; - - VM_WARN_ON_ONCE(gfp_flags & ~__GFP_ACCOUNT); - /* - * In PREEMPT_RT spin_trylock() will call raw_spin_lock() which is - * unsafe in NMI. If spin_trylock() is called from hard IRQ the current - * task may be waiting for one rt_spin_lock, but rt_spin_trylock() will - * mark the task as the owner of another rt_spin_lock which will - * confuse PI logic, so return immediately if called from hard IRQ or - * NMI. - * - * Note, irqs_disabled() case is ok. This function can be called - * from raw_spin_lock_irqsave region. - */ - if (IS_ENABLED(CONFIG_PREEMPT_RT) && (in_nmi() || in_hardirq())) - return NULL; - - /* On UP, spin_trylock() always succeeds even when it is locked */ - if (!IS_ENABLED(CONFIG_SMP) && in_nmi()) - return NULL; - - if (!pcp_allowed_order(order)) - return NULL; - - /* Bailout, since _deferred_grow_zone() needs to take a lock */ - if (deferred_pages_enabled()) - return NULL; - if (nid == NUMA_NO_NODE) nid = numa_node_id(); - prepare_alloc_pages(alloc_gfp, order, nid, NULL, &ac, - &alloc_gfp, &alloc_flags); - - /* - * Best effort allocation from percpu free list. - * If it's empty attempt to spin_trylock zone->lock. - */ - page = get_page_from_freelist(alloc_gfp, order, alloc_flags, &ac); - - /* Unlike regular alloc_pages() there is no __alloc_pages_slowpath(). */ - - if (memcg_kmem_online() && page && (gfp_flags & __GFP_ACCOUNT) && - unlikely(__memcg_kmem_charge_page(page, alloc_gfp, order) != 0)) { - __free_frozen_pages(page, order, FPI_TRYLOCK); - page = NULL; - } - trace_mm_page_alloc(page, order, alloc_gfp, ac.migratetype); - kmsan_alloc_page(page, order, alloc_gfp); - return page; + return __alloc_frozen_pages_noprof(gfp_flags, order, nid, NULL, ALLOC_NOLOCK); } /** * alloc_pages_nolock - opportunistic reentrant allocation from any context diff --git a/mm/slub.c b/mm/slub.c index a2bf3756ca7d0..b9c1284844a0a 100644 --- a/mm/slub.c +++ b/mm/slub.c @@ -3275,7 +3275,8 @@ static inline struct slab *alloc_slab_page(gfp_t flags, int node, else if (node == NUMA_NO_NODE) page = alloc_frozen_pages(flags, order); else - page = __alloc_frozen_pages(flags, order, node, NULL); + page = __alloc_frozen_pages(flags, order, node, NULL, + ALLOC_DEFAULT); if (!page) return NULL; @@ -5236,7 +5237,8 @@ static void *___kmalloc_large_node(size_t size, gfp_t flags, int node) if (node == NUMA_NO_NODE) page = alloc_frozen_pages_noprof(flags, order); else - page = __alloc_frozen_pages_noprof(flags, order, node, NULL); + page = __alloc_frozen_pages_noprof(flags, order, node, NULL, + ALLOC_DEFAULT); if (page) { ptr = page_address(page); -- 2.54.0