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Mon, 23 Feb 2026 12:07:50 -0800 (PST) Received: from pc636 ([2001:9b1:d5a0:a500::800]) by smtp.gmail.com with ESMTPSA id 38308e7fff4ca-389a7a201fbsm17562561fa.22.2026.02.23.12.07.50 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 23 Feb 2026 12:07:50 -0800 (PST) From: Uladzislau Rezki X-Google-Original-From: Uladzislau Rezki Date: Mon, 23 Feb 2026 21:07:48 +0100 To: Mikulas Patocka Cc: "Vishal Moola (Oracle)" , Michal Hocko , Christoph Hellwig , "Uladzislau Rezki (Sony)" , SeongJae Park , Andrew Morton , zkabelac@redhat.com, Matthew Sakai , linux-mm@kvack.org, dm-devel@lists.linux.dev Subject: Re: [PATCH] mm: allow __GFP_RETRY_MAYFAIL in vmalloc Message-ID: References: <32bd9bed-a939-69c4-696d-f7f9a5fe31d8@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <32bd9bed-a939-69c4-696d-f7f9a5fe31d8@redhat.com> X-Rspam-User: X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 3FEFB1A000D X-Stat-Signature: ox41e9s1x5xg86ros5td8he9ar83quba X-HE-Tag: 1771877273-355998 X-HE-Meta: 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 U/wPbLbx 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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 Mon, Feb 23, 2026 at 08:25:38PM +0100, Mikulas Patocka wrote: > > > On Mon, 23 Feb 2026, Vishal Moola (Oracle) wrote: > > > On Thu, Feb 12, 2026 at 05:33:30PM +0100, Mikulas Patocka wrote: > > > The commit 07003531e03c8 ("mm/vmalloc: warn on invalid vmalloc gfp > > > flags") breaks the device mapper VDO target. The VDO target calls vmalloc > > > with __GFP_RETRY_MAYFAIL and this flag is not in the mask of allowed > > > flags. > > > > > > There is no reason why vmalloc couldn't support __GFP_RETRY_MAYFAIL, so > > > let's add this flag to GFP_VMALLOC_SUPPORTED. > > > > My only skepticism about this comes from the line in the > > vmalloc_node_range() doc: > > "and %__GFP_RETRY_MAYFAIL are not supported." > > > > I myself don't know why that may be. Could you elaborate on if/why the > > doc is wrong please? > > This statement was added by Michal Hocko in the commit > b7d90e7a5ea8d64e668d5685925900d33d3884d5. Michal, could you explain why do > you think that __GFP_RETRY_MAYFAIL is not supported? > > The VDO module needs to allocate large amounts of memory and it doesn't > want to trigger the OOM killer (which would kill some innocent task and > wouldn't solve the out of memory condition at all), so I think that > __GFP_RETRY_MAYFAIL is appropriate. > I do not see any problems using this with vmalloc from the first glance. KASAN path was hard-coded when it comes to GFP but it is not anymore. -- Uladzislau Rezki