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Howlett" Cc: "Vlastimil Babka (SUSE)" , syzbot , akpm@linux-foundation.org, jannh@google.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org, ljs@kernel.org, pfalcato@suse.de, syzkaller-bugs@googlegroups.com Subject: Re: [syzbot] [mm?] WARNING in mas_nomem Message-ID: <20260807192622.GK200537@ziepe.ca> References: <6a6c4f18.b1a781d0.210f9.001f.GAE@google.com> <6yf7k4fmg4tkbmli6t4qzrk2eiyuuynoc2oimbgaebught2yh5@dspb7xile3kj> <20260805004619.GA28508@ziepe.ca> <5cf3542f-fca7-44d0-8a17-8aa316b1fb12@kernel.org> <20260806154845.GF28508@ziepe.ca> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: On Fri, Aug 07, 2026 at 03:24:24PM -0400, Liam R. Howlett wrote: > On 26/08/07 09:19AM, Liam R. Howlett wrote: > > On 26/08/06 12:48PM, Jason Gunthorpe wrote: > > > On Thu, Aug 06, 2026 at 10:29:27AM -0400, Liam R. Howlett wrote: > > > > > > > @@ -5609,8 +5612,7 @@ void *mas_store(struct ma_state *mas, void *entry) > > > > goto store; > > > > > > > > mas_alloc_nodes(mas, GFP_NOWAIT); > > > > - if (mas_is_err(mas)) > > > > - return NULL; > > > > + mas_nomem(mas, GFP_KERNEL | __GFP_NOFAIL); > > > > > > It still feels really weird to ignore the return code from mas_nomem.. > > > > > > void mas_nomem_nofail() > > > > Sure, that's fair. > > > > > > > > ? and maybe it can have a WARN_ON > > > > > > The warning would never trigger. If the allocation fails with nofail, > > then you'd never reach the warning. > > Upon rereading my reply, I don't think it was clear what's going to > happen here. > > If there's really no memory and no reserves, then we're going to panic > on trying to allocate. So, even if I rewrite this to have a void > function to print a warning, it will never trigger, at that point why > have another function? Are you looking to document what's happening in > the code with this? If so, maybe a comment would be better. Yeah, it is clearer to document it with a function that can't be called wrong, IMHO Jason