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AJvYcCWr+9MGSASx+Xq9+xzsmg6xpNNaktMHSUgkdnGWya7qquQx5dG+BrOYaRB1rhsCSJwvu466UP9LjA==@kvack.org X-Gm-Message-State: AOJu0YwWh4t/ayGvzhD590OmxFlAmGDcigDpcmiBfXWiWXMimNhMG/P9 2XC+m1tvH9G87QVv6kn4ESngkiVU9TuM2nFnRz9eF50Rm3U6fCLOpIpY3tjjTK8d9xptdsmFh23 RP6O1V9+QlYYmTw== X-Google-Smtp-Source: AGHT+IHCnkhtu+erinZRjzHU08DdBwFzraMet61P9UwT8esvB8HjyL7gPlKocQZ3b3SJKLvMZ7snSMNitdCnUA== X-Received: from edbek6.prod.google.com ([2002:a05:6402:3706:b0:647:5ed5:87dd]) (user=jackmanb job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6402:2816:b0:647:57e7:472e with SMTP id 4fb4d7f45d1cf-6491abf2749mr7780459a12.22.1765262212352; Mon, 08 Dec 2025 22:36:52 -0800 (PST) Date: Tue, 09 Dec 2025 06:36:51 +0000 In-Reply-To: <20251209-b4-vmalloc-might_alloc-v2-1-2462ba26ead1@google.com> Mime-Version: 1.0 References: <20251209-b4-vmalloc-might_alloc-v2-1-2462ba26ead1@google.com> X-Mailer: aerc 0.21.0 Message-ID: Subject: Re: [PATCH v2] mm/vmalloc: clarify why vmap_range_noflush() might sleep From: Brendan Jackman To: Brendan Jackman , Andrew Morton , Uladzislau Rezki Cc: Anshuman Khandual , , Content-Type: text/plain; charset="UTF-8" X-Rspam-User: X-Rspamd-Queue-Id: 43F63180002 X-Rspamd-Server: rspam10 X-Stat-Signature: p4ymqn5sqc5ynpbgoigir89z95w7ii9h X-HE-Tag: 1765262214-859960 X-HE-Meta: U2FsdGVkX194M+EucU8uzPBjlKDyD03WpvARBa6fLNy0CiP0OheCsef1wnBnru5Z/C+bhbBjly3DtLMBCQP1ZyZ8gw/Az6OqpS6ncKw04GRT36rd4rJzyZKNz55bkyuVy+C+aa23qikqa/fMt6x+haPyQWOTQpuIDw2TauDKgzYsXeJQIyhZqpFuKnzlHBuipO4jyTFQqrZgkgOgEZDXDRGvt6PwN1NBoBRyS7V9+OqUF0K5bm2QdB2o6v7MyShRAxmHlbXkBIz7es4s0MIYG0PKpKQQqsxqtJSFQr7qNcnHjDFXB7YNLKlWG/tKmPuFV1fyF2oBv/YolrpHwna9+PVuTLtuPBKsbW3aHp7sjZLTc3RqfAz+qq9gmhhmKKbbuVTmuLq6oexgifLDb8PWD09Ni+qexhDsiCjuUCDZW7tnE/1w34BsUv3zg/v809QTIrgzTuZbaQpO6J2QrIcj7cIyHezj/7t5lPN3mLTHwqukB/prfl5voT6XlbX2B40JhIR6lGpBWdbeExDYa/zIBbB4U39J/to1ns2tbbC//xKLxZL6y8zsPJnU2UWAcogGwnf2FMigZoIey4R4tc6bU3N1yGO+AgsQXZ3HzPKfumKg1WC4WIFqAp9h03u7D6+sN6Q/PUevl912mcy6MpeJDfQMD432MJ4O4WTvAKXof5PpZEDSQ7s+bDibnoZOGB8WE69ZzMVgLnVWNJqq0K8nXIrfqhoeBwlFGBjtg3S0G/ivGbS8MBmsnzKpXkGZUIRlf8PQ/9iGr46o86VMz9d8xFjeO7RPqGTbfAwR31jY6/gCIkam4Jnh+yufqARfSU7XU5UFGbkIQPGX1Zy23jrxrAIGuzZ6j4MFXhS/uCy1XLgE0w9EyUjkXNgsymCdMWOWPHS3hZShBqd5sCTX57t2zkJdJ0IqCMSIeD9mffHMCNFv2Ux9IwHAPAE0pc2Tn7Gra2XCdykPhLAgHbIJgH8 j9AznmC9 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue Dec 9, 2025 at 5:44 AM UTC, Brendan Jackman wrote: > The only reason vmap_range_noflush() can sleep is because of pagetable > allocations. > > The actual allocation mechanism is arch-specific so might_alloc() > doesn't work here (what GFP flags would be used?). Hence, just add a > comment. > > Signed-off-by: Brendan Jackman > --- > Changes in v2: > - Switched from might_alloc() to keeping might_sleep() + comment > - Link to v1: https://lore.kernel.org/r/20251208-b4-vmalloc-might_alloc-v1-1-94a9bb8ecb08@google.com > --- > mm/vmalloc.c | 1 + > 1 file changed, 1 insertion(+) > > diff --git a/mm/vmalloc.c b/mm/vmalloc.c > index a53c7462671bdd896f95712af71398ffbe22fb80..c23d378dd4446e2784505ec3d5bb9568fb0d3c9a 100644 > --- a/mm/vmalloc.c > +++ b/mm/vmalloc.c > @@ -305,6 +305,7 @@ static int vmap_range_noflush(unsigned long addr, unsigned long end, > int err; > pgtbl_mod_mask mask = 0; > > + /* Might allocate pagetables. */ I just realised that for x86, there's also TLB shootdowns in pud_free_pmd_page() etc. So I guess this is also a might_ for the the lockdep_assert_irqs_enabled() in smp_call_function_many_cond(). Should probably mention that too. Anything else I missed, before I send v3? > might_sleep(); > BUG_ON(addr >= end);