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Howlett" , Vlastimil Babka , Shakeel Butt , Jann Horn , Pedro Falcato Subject: Re: [PATCH v2 2/2] mm: Use vma_start_write_killable() in dup_mmap() Message-ID: References: <20251110203204.1454057-1-willy@infradead.org> <20251110203204.1454057-3-willy@infradead.org> <01ab3958-8a3d-457f-86de-2c7959b01d10@lucifer.local> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <01ab3958-8a3d-457f-86de-2c7959b01d10@lucifer.local> X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 83E6440020 X-Stat-Signature: smx8ztke81agokfptm3gnq4wxaxb1kkd X-Rspam-User: X-HE-Tag: 1763044260-132022 X-HE-Meta: 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 n9hWlnuD K2AhqPGQUxtVabHdKwARv4V9kpUhBVyri4OFN712WwjwdOU11OrSsd7VlRLE8ZqFZ08Fzd2rd/h7X5M+ENsCLS1QI+wpIazKkwAVRXK+p2m2qtBdgkg2QpfqJvk1l3qZKMB2Kjsz/YAQwLrLjWYhFJBYYtJ/2EDZYHqlgRXeYX704jugvsJoAZr9dBVDcoMbZpfaZKkt9VQ/N7BE55nT8vziXZFqYSNBWFUzAgp3w2VGGX2Wiq6GcNTG+0x4aFWSpEr9egdNRiPK8/wIfxEPMWg3f0MsjlfdV2Is4Xd6Pp/GG+Gxw01QfErDvBH9vkslOjohn 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 Thu, Nov 13, 2025 at 01:25:40PM +0000, Lorenzo Stoakes wrote: > On Mon, Nov 10, 2025 at 08:32:02PM +0000, Matthew Wilcox (Oracle) wrote: > > Allow waiting for the VMA write lock to be interrupted by fatal signals. > > The explicit check for fatal_signal_pending() can be removed as it > > is checked during vma_start_write_killable(). Improves the latency > > of killing the task as we do not wait for the reader to finish before > > checking for signals. > > Does this fix Chris's issues or is a forthcoming series required for that? > I'm guessing not, as his issue was w.r.t. reclaim right rather than at the > point of forking? > > If it does we should say so I think. If not then obviously not! No, it won't fix Chris's issue. I just wanted to have one user in tree (which was a good idea because syzbot promptly caught the lockdep bug). This one is an obvious one which already has a good fallback path. Most of the other places need a fallback path written, which requires more time and attention than I can devote to the task right now. > Reviewed-by: Lorenzo Stoakes Thanks! > > - vma_start_write(mpnt); > > + retval = vma_start_write_killable(mpnt); > > Maybe worth explicitly adding a comment to say we handle fatal signals > here? I guess it is implied but still maybe useful? I think that would be over-commenting, tbh.