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Howlett" , Lorenzo Stoakes , Vlastimil Babka , Jann Horn , "xe-linux-external(mailer list)" , "linux-kernel@vger.kernel.org" , "linux-trace-kernel@vger.kernel.org" , "linux-perf-users@vger.kernel.org" , "linux-mm@kvack.org" Subject: Re: [PATCH] mm/madvise: preserve uprobe breakpoints across MADV_DONTNEED Message-ID: References: <20260429131522.4049054-1-dtominac@cisco.com> <889e4186-9f75-45d3-bd9a-1c90b218a635@kernel.org> <2d815203-a81e-40b4-92ba-31832c84c20b@kernel.org> MIME-Version: 1.0 In-Reply-To: <2d815203-a81e-40b4-92ba-31832c84c20b@kernel.org> X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 X-Mimecast-MFC-PROC-ID: MwN1jZfmN0SBx38u39lwrbZefqzoXoEoiYENPV7Qmq0_1777574815 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: B226DA000B X-Stat-Signature: d1siptswmzzct9967yzmtqdpphpk7xs4 X-Rspam-User: X-HE-Tag: 1777574824-596536 X-HE-Meta: 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 vupLFnN1 BbbXQkawLN3uWTw0PI3yPA7nfhkewEBRghdmfDxhwwwNzZewWKG+4MARYOdKKBISb76ncGOcztZX+Ny+MDb4nx54Dj0AAckhv4indXq3Y/XMJ+5BtxokWwUnMTnCrQQQ5xnOvrRxtpxC/fuAPlratvabJDg44VMZ9S9WyfpPBEZ1L2/Y/Lrc0vVypO6vePIGjxAEzjjN65923lypXl9Ovjqq2/9hk/nqZv1e0Wf0AwymQuv/sIZb0FMoFaqy5WtnZyz5cvJpdwQJoAD/7nFFCb7adBy0qd5lgMLZ9qIxIqMplgZZlJ69U/CJu49Z2FCZJpO+40HWpzI1y7h9okOE7baDWTbxHft6btTVDMIbYC8hl/Di38506CQ5Wk7i36gPVvCecakMgCmFLPE0S+tlx0q3CAHLW2kTJqVFQzqu3wPbISTqDVxdbVfenrtv/0QvbCIu9 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: David, et al, I am sorry for the unnecessary spam but I can't resist... On 04/30, David Hildenbrand (Arm) wrote: > > On 4/30/26 11:16, Oleg Nesterov wrote: > > > > But may be MADV_DONTNEED should not set zap_details.even_cows == true > > by default ? > > It should. If you do mmap(MAP_PRIVATE, fd), and modify some pages, MADV_DONTNEED > must zap these pages. [... snip the correct explanation ...] Ah. Sorry for the confusion, I should not have said "by default". Of course you are right, and I understand this. At least I hope ;) Let me try to explain what I tried to say. First of all, I still agree with your "It shouldn't do that on a MAP_PRIVATE file-backed VMA". I also agree with Jann who suggests to make the manpage more clear about uprobes/bps. But, lets suppose that this "problem" is raised again, and we come to conclusion that it should be fixed/mitigated. ("we" actually meaning you and other mm experts ;) _In that case_. Instead of this patch (which, rightly or not, I personally dislike in any case), can't MADV_DONTNEED paths check MMF_HAS_UPROBES or vma_has_uprobes() to decide whether .even_cows should be true? At least when madvise_behavior.mm != current->mm ? Oleg.