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Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Rik van Riel , Harry Yoo , Johannes Weiner , Shakeel Butt , Baolin Wang , "Darrick J. Wong" , Dave Chinner , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Kiryl Shutsemau Subject: Re: [PATCHv2 1/2] mm/memory: Do not populate page table entries beyond i_size Message-Id: <20251023134929.b72ab75a8c132a17ae68a582@linux-foundation.org> In-Reply-To: <20251023093251.54146-2-kirill@shutemov.name> References: <20251023093251.54146-1-kirill@shutemov.name> <20251023093251.54146-2-kirill@shutemov.name> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam01 X-Stat-Signature: z5t8omb5ugorebnxqsu83g1dw4adcxp6 X-Rspam-User: X-Rspamd-Queue-Id: BEA214000D X-HE-Tag: 1761252571-559120 X-HE-Meta: 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 6I/QTenD amZLoxuw/bcjWhgUCnW+yXm26KId9rewyj1WJ39xoTcLIb50iU8PsbrcL7SY8Xz0saZRZQ0694R+7196W+1XXwv0edNfC0NfNOF62XS56oSiL28AOm/BRTzgYSDoiY9esIaRoAdPjlmmVsSiKB65jnnjzoyr6RCoVewWhEAw0rYWLbUqw8k+9wIO20/HdaxqHfGd9koxtJc/HPDDeUxY66D3WmTcrRNfWOfp22qfQZuSinhOblYW+tyBX5mhtpQdBjk/4YFnMfPeXtsj8/+ZecTXauC78w+KphQ3gxo9oGASksQfXlhpTLHBQ8pXv3pap37bL 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, 23 Oct 2025 10:32:50 +0100 Kiryl Shutsemau wrote: > From: Kiryl Shutsemau > > Accesses within VMA, but beyond i_size rounded up to PAGE_SIZE are > supposed to generate SIGBUS. > > Recent changes attempted to fault in full folio where possible. They did > not respect i_size, which led to populating PTEs beyond i_size and > breaking SIGBUS semantics. > > Darrick reported generic/749 breakage because of this. > > However, the problem existed before the recent changes. With huge=always > tmpfs, any write to a file leads to PMD-size allocation. Following the > fault-in of the folio will install PMD mapping regardless of i_size. > > Fix filemap_map_pages() and finish_fault() to not install: > - PTEs beyond i_size; > - PMD mappings across i_size; > > Signed-off-by: Kiryl Shutsemau > Fixes: 19773df031bc ("mm/fault: try to map the entire file folio in finish_fault()") Sep 28 2025 > Fixes: 357b92761d94 ("mm/filemap: map entire large folio faultaround") Sep 28 2025 > Fixes: 800d8c63b2e9 ("shmem: add huge pages support") Jul 26 2016 eek, what's this one doing here? Are we asking -stable maintainers to backport this patch into nine years worth of kernels? I'll remove this Fixes: line for now...