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b=eFQls6H27sn4CofrScIUPfBadO+TKU2V5axepFAdJ80Gzjvm3C9T1JDus1G4zUBRu DxUkDf1LMbllvkJHHQ5IBaITKDeWKnsryUKlrmdtZ8CO2NFK+uYtx6yKFQAZ7Bj1hp /CzwRcPIMpVFozsFAxuTpOCbBpGBDl5NpgS24uT9dCuDrGAnrYyhzI46OZkH+b8uQ6 IAkTr63W9fzOEXhr/smBXxRz0ZZ1LVjyc3NkKCS5sDTPa0XelVZDrGUJLQLNUfOe4D LV7S+/zc6IP0kOZvBjuNNQ7ChYxbof6mIWb6VY4pKdLLxrwnreBbaqktfIG0gMvv3A fTddIO4KLZq/Q== Message-ID: Date: Fri, 31 Jul 2026 16:52:59 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3 19/26] mm/page_alloc: rename ALLOC_NON_BLOCK back to _HARDER Content-Language: en-US To: Brendan Jackman , Borislav Petkov , Dave Hansen , Peter Zijlstra , Andrew Morton , David Hildenbrand , Mike Rapoport , Wei Xu , Johannes Weiner , Zi Yan , Lorenzo Stoakes Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, x86@kernel.org, Sumit Garg , Will Deacon , rientjes@google.com, "Kalyazin, Nikita" , patrick.roy@linux.dev, "Itazuri, Takahiro" , Andy Lutomirski , David Kaplan , Thomas Gleixner , Yosry Ahmed , Patrick Bellasi , Reiji Watanabe , Sean Christopherson References: <20260726-page_alloc-unmapped-v3-0-6f5729aa9832@google.com> <20260726-page_alloc-unmapped-v3-19-6f5729aa9832@google.com> From: "Vlastimil Babka (SUSE)" Autocrypt: addr=vbabka@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: CDCF0C0013 X-Stat-Signature: efeujo39rqykpfnomnyfmspt1q944suj X-HE-Tag: 1785509587-700672 X-HE-Meta: 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 jyGDejxL vQVD0dW8jRopZqDpcyJFwG0z1VMEFK8zMKHNaoyEYEaQeOJsQyRKdEbjMUxRecZqXn8DFNaCJ4hCQ/lGfCcwL+8uTQgqUuvXaNGoGHKKK3wEcR10fzwp945OJ2wT7vXhGETkqol5jGYFNnHl8bpX8ITM6PXrJG3kmCTSRg8j+Oumm503yEYGhh2iVhN/CGUcj6lMnHofKCySCUa3ihaWNK//uRgnMsLcvNffRn/oIkO5v0NUuXld2ZzLbTTeUoET0AYIZc5Wi9PXLuUgwr7tDqHKHiiTFR/sPLuqxYueS+k2u4Ubb4jrsvL+Fk/PfWF7bpfytcKnEC4TV8Q4= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/27/26 00:22, Brendan Jackman wrote: > Commit 1ebbb21811b7 ("mm/page_alloc: explicitly define how __GFP_HIGH > non-blocking allocations accesses reserves") renamed ALLOC_HARDER to > ALLOC_NON_BLOCK because the former is "a vague description". > > However, vagueness is accurate here, this is a vague flag. It is not set > for __GFP_NOMEMALLOC. It doesn't really mean "allocate without blocking" > but rather "allow dipping into atomic reserves, _because_ of the need > not to block". > > A later commit will need an alloc flag that really means "don't block > here", so go back to the flag's old name and update the commentary > to try and give it a slightly clearer meaning. > > Signed-off-by: Brendan Jackman I wonder if we need to do this, and instead we could repurpose ALLOC_NON_BLOCK directly. AFAIU it's about removing the side-effect of gfp_allowed_mask in the next patch. But what would happen if we did that using the existing ALLOC_NON_BLOCK (or maybe just renamed to ALLOC_NOBLOCK?). - in __zone_watermark_ok(), ALLOC_NON_BLOCK could now be *not* set in situations where previously it was set due to gfp_allowed_mask masking out __GFP_DIRECT_RECLAIM. But it only has an effect on top of __GFP_HIGH (thus ALLOC_MIN_RESERVE... which seems contradicting the ALLOC_NON_BLOCK description comment btw). Also __GFP_DIRECT_RECLAIM is only masked out by GFP_BOOT_MASK when all memory is free, so it's kinda moot? - in rmqueue_buddy() we allow access to highatomic reserves since 281dd25c1a018. That commit describes GFP_ATOMIC so we could have been checking ALLOC_MIN_RESERVE. But we can also leave this alone because it doesn't actually matter when GFP_BOOT_MASK is set, as above. > --- > mm/page_alloc.c | 8 ++++---- > mm/page_alloc.h | 9 +++++---- > 2 files changed, 9 insertions(+), 8 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 30ba61c20209c..fb522a09f2e60 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -3431,7 +3431,7 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone, > * reserves as failing now is worse than failing a > * high-order atomic allocation in the future. > */ > - if (!page && (alloc_flags & (ALLOC_OOM|ALLOC_NON_BLOCK))) > + if (!page && (alloc_flags & (ALLOC_OOM|ALLOC_HARDER))) > page = __rmqueue_smallest(zone, order, ft_high); > > if (!page) { > @@ -3811,7 +3811,7 @@ bool __zone_watermark_ok(struct zone *z, unsigned int order, unsigned long mark, > * or (GFP_KERNEL & ~__GFP_DIRECT_RECLAIM) do not get > * access to the min reserve. > */ > - if (alloc_flags & ALLOC_NON_BLOCK) > + if (alloc_flags & ALLOC_HARDER) > min -= min / 4; > } > > @@ -4733,7 +4733,7 @@ alloc_flags_nonblocking(gfp_t gfp_mask, unsigned int order) > if (gfp_mask & __GFP_NOMEMALLOC) > return 0; > > - alloc_flags |= ALLOC_NON_BLOCK; > + alloc_flags |= ALLOC_HARDER; > > if (order > 0 && (gfp_mask & __GFP_HIGH)) > alloc_flags |= ALLOC_HIGHATOMIC; > @@ -4750,7 +4750,7 @@ alloc_flags_slowpath(gfp_t gfp_mask, unsigned int order) > * The caller may dip into page reserves a bit more if the caller > * cannot run direct reclaim, or if the caller has realtime scheduling > * policy or is asking for __GFP_HIGH memory. GFP_ATOMIC requests will > - * set both ALLOC_NON_BLOCK and ALLOC_MIN_RESERVE(__GFP_HIGH). > + * set both ALLOC_HARDER and ALLOC_MIN_RESERVE(__GFP_HIGH). > */ > if (gfp_mask & __GFP_HIGH) > alloc_flags |= ALLOC_MIN_RESERVE; > diff --git a/mm/page_alloc.h b/mm/page_alloc.h > index fac8e5304bb03..2307b173a459f 100644 > --- a/mm/page_alloc.h > +++ b/mm/page_alloc.h > @@ -32,9 +32,10 @@ > #define ALLOC_OOM ALLOC_NO_WATERMARKS > #endif > > -#define ALLOC_NON_BLOCK 0x10 /* Caller cannot block. Allow access > - * to 25% of the min watermark or > - * 62.5% if __GFP_HIGH is set. > +#define ALLOC_HARDER 0x10 /* Because the caller cannot block, > + * allow access to 25% of the min > + * watermark or 62.5% if __GFP_HIGH is > + * set. > */ > #define ALLOC_MIN_RESERVE 0x20 /* __GFP_HIGH set. Allow access to 50% > * of the min watermark. > @@ -76,7 +77,7 @@ > #endif > > /* Flags that allow allocations below the min watermark. */ > -#define ALLOC_RESERVES (ALLOC_NON_BLOCK|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM) > +#define ALLOC_RESERVES (ALLOC_HARDER|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM) > > /* > * Structure for holding the mostly immutable allocation parameters passed >