From 23fa022a07555a9cd2dcfe827c769a89c4c2e21e Mon Sep 17 00:00:00 2001 From: "Kirill A. Shutemov" Date: Tue, 6 May 2025 14:25:08 +0300 Subject: [PATCH] mm/page_alloc: ensure try_alloc_pages() plays well with unaccepted memory try_alloc_pages() will not attempt to allocate memory if the system has *any* unaccepted memory. Memory is accepted as needed and can remain in the system indefinitely, causing the interface to always fail. Rather than immediately giving up, attempt to use already accepted memory on free lists. Pass 'alloc_flags' to cond_accept_memory() and do not accept new memory for ALLOC_TRYLOCK requests. Found via code inspection - only BPF uses this at present and the runtime effects are unclear. Link: https://lkml.kernel.org/r/20250506112509.905147-2-kirill.shutemov@linux.intel.com Signed-off-by: Kirill A. Shutemov Fixes: 97769a53f117 ("mm, bpf: Introduce try_alloc_pages() for opportunistic page allocation") Cc: Alexei Starovoitov Cc: Vlastimil Babka Cc: Suren Baghdasaryan Cc: Michal Hocko Cc: Brendan Jackman Cc: Johannes Weiner Cc: Signed-off-by: Andrew Morton --- mm/page_alloc.c | 28 +++++++++++++++------------- 1 file changed, 15 insertions(+), 13 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1b00e14a9780..7248e300d36e 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -290,7 +290,8 @@ EXPORT_SYMBOL(nr_online_nodes); #endif static bool page_contains_unaccepted(struct page *page, unsigned int order); -static bool cond_accept_memory(struct zone *zone, unsigned int order); +static bool cond_accept_memory(struct zone *zone, unsigned int order, + int alloc_flags); static bool __free_unaccepted(struct page *page); int page_group_by_mobility_disabled __read_mostly; @@ -3611,7 +3612,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, } } - cond_accept_memory(zone, order); + cond_accept_memory(zone, order, alloc_flags); /* * Detect whether the number of free pages is below high @@ -3638,7 +3639,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, gfp_mask)) { int ret; - if (cond_accept_memory(zone, order)) + if (cond_accept_memory(zone, order, alloc_flags)) goto try_this_zone; /* @@ -3691,7 +3692,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags, return page; } else { - if (cond_accept_memory(zone, order)) + if (cond_accept_memory(zone, order, alloc_flags)) goto try_this_zone; /* Try again if zone has deferred pages */ @@ -4844,7 +4845,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid, goto failed; } - cond_accept_memory(zone, 0); + cond_accept_memory(zone, 0, alloc_flags); retry_this_zone: mark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK) + nr_pages; if (zone_watermark_fast(zone, 0, mark, @@ -4853,7 +4854,7 @@ unsigned long alloc_pages_bulk_noprof(gfp_t gfp, int preferred_nid, break; } - if (cond_accept_memory(zone, 0)) + if (cond_accept_memory(zone, 0, alloc_flags)) goto retry_this_zone; /* Try again if zone has deferred pages */ @@ -7281,7 +7282,8 @@ static inline bool has_unaccepted_memory(void) return static_branch_unlikely(&zones_with_unaccepted_pages); } -static bool cond_accept_memory(struct zone *zone, unsigned int order) +static bool cond_accept_memory(struct zone *zone, unsigned int order, + int alloc_flags) { long to_accept, wmark; bool ret = false; @@ -7292,6 +7294,10 @@ static bool cond_accept_memory(struct zone *zone, unsigned int order) if (list_empty(&zone->unaccepted_pages)) return false; + /* Bailout, since try_to_accept_memory_one() needs to take a lock */ + if (alloc_flags & ALLOC_TRYLOCK) + return false; + wmark = promo_wmark_pages(zone); /* @@ -7348,7 +7354,8 @@ static bool page_contains_unaccepted(struct page *page, unsigned int order) return false; } -static bool cond_accept_memory(struct zone *zone, unsigned int order) +static bool cond_accept_memory(struct zone *zone, unsigned int order, + int alloc_flags) { return false; } @@ -7419,11 +7426,6 @@ struct page *try_alloc_pages_noprof(int nid, unsigned int order) if (!pcp_allowed_order(order)) return NULL; -#ifdef CONFIG_UNACCEPTED_MEMORY - /* Bailout, since try_to_accept_memory_one() needs to take a lock */ - if (has_unaccepted_memory()) - return NULL; -#endif /* Bailout, since _deferred_grow_zone() needs to take a lock */ if (deferred_pages_enabled()) return NULL;