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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> Precedence: bulk X-Mailing-List: dm-devel@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <32bd9bed-a939-69c4-696d-f7f9a5fe31d8@redhat.com> 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