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Mon, 07 Apr 2025 11:33:58 -0700 (PDT) Received: from localhost ([196.207.164.177]) by smtp.gmail.com with UTF8SMTPSA id 5b1f17b1804b1-43ec364cb9asm137138975e9.31.2025.04.07.11.33.57 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Apr 2025 11:33:57 -0700 (PDT) Date: Mon, 7 Apr 2025 21:33:54 +0300 From: Dan Carpenter To: Ingo Molnar Cc: David Hildenbrand , linux-kernel@vger.kernel.org, linux-mm@kvack.org, x86@kernel.org, kernel test robot , Dan Carpenter , Andrew Morton , Lorenzo Stoakes , Dave Hansen , Andy Lutomirski , Peter Zijlstra , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Rik van Riel , "H. Peter Anvin" , Linus Torvalds Subject: Re: [PATCH v1] x86/mm/pat: (un)track_pfn_copy() fix + improvements Message-ID: <4961949a-75db-4071-a478-fdc543c1dd28@stanley.mountain> References: <20250404124931.2255618-1-david@redhat.com> <630caa8e-2ee2-4895-9e4e-8bf2fa079100@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Queue-Id: EDB5E40008 X-Stat-Signature: j3yorpqkcommp77za4eodyix1ys7fk6t X-Rspam-User: X-Rspamd-Server: rspam12 X-HE-Tag: 1744050839-768286 X-HE-Meta: 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 ueTyolMH sK1w/gZs+FHIC/h2kCv+XuuNJ0+VHmmScMjAbG0roTOQBGsJi+lR5O2iSfaZ+mocCyt+CGIDLFOUQ7CRy7SdVrGrM43G28qGd+nvXuHHEadNDiPi3mg9nO9o/TqDHfsCLqjyTzgy49Sp6+4JF7Cm0dWER5nHejpg8VM6H1GGx/QNoLPb38xxBXfSePVR2eG6BoxaIwlWEr+PmefjoK0UDOAN/Lg7r1l/0iSzvOOt/PCJGsLqeXgrnlaldQFg9C5oKSMnJ2HQ8icyo98RQSTRtENljOJH74iQ5alzPmJuJk18ZQcwyul4pnfKBAmVv4bCnxYeTeHb5jHOp1Ig= 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, Apr 07, 2025 at 06:50:43PM +0200, Ingo Molnar wrote: > > diff --git a/mm/memory.c b/mm/memory.c > > index 2d8c265fc7d60..1a35165622e1c 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -1361,7 +1361,7 @@ copy_page_range(struct vm_area_struct *dst_vma, struct vm_area_struct *src_vma) > > struct mm_struct *dst_mm = dst_vma->vm_mm; > > struct mm_struct *src_mm = src_vma->vm_mm; > > struct mmu_notifier_range range; > > - unsigned long next, pfn; > > + unsigned long next, pfn = 0; > > Ack. > > I hate it how uninitialized variables are even a thing in C, and why > there's no compiler switch to turn it off for the kernel. (At least for > non-struct variables. Even for structs I would zero-initialize and > *maybe* allow a non-initialized opt-in for cases where it matters. It > matters in very few cases in praxis. And don't get me started about the > stupidity that is to not initialize holes in struct members ...) Everyone sane uses CONFIG_INIT_STACK_ALL_ZERO these days. regards, dan carpenter