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Fri, 20 Mar 2026 10:55:16 -0400 (EDT) Date: Fri, 20 Mar 2026 14:55:14 +0000 From: Kiryl Shutsemau To: Usama Arif Cc: Andrew Morton , david@kernel.org, willy@infradead.org, ryan.roberts@arm.com, linux-mm@kvack.org, r@hev.cc, jack@suse.cz, ajd@linux.ibm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, brauner@kernel.org, catalin.marinas@arm.com, dev.jain@arm.com, kees@kernel.org, kevin.brodsky@arm.com, lance.yang@linux.dev, Liam.Howlett@oracle.com, linux-arm-kernel@lists.infradead.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, mhocko@suse.com, npache@redhat.com, pasha.tatashin@soleen.com, rmclure@linux.ibm.com, rppt@kernel.org, surenb@google.com, vbabka@kernel.org, Al Viro , wilts@infradead.org, ziy@nvidia.com, hannes@cmpxchg.org, shakeel.butt@linux.dev, kernel-team@meta.com Subject: Re: [PATCH v2 3/4] elf: align ET_DYN base to max folio size for PTE coalescing Message-ID: References: <20260320140315.979307-1-usama.arif@linux.dev> <20260320140315.979307-4-usama.arif@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260320140315.979307-4-usama.arif@linux.dev> X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: ABBBE14000A X-Stat-Signature: sifcr3cxzi5whnpebdebcway3gznh5sx X-Rspam-User: X-HE-Tag: 1774018520-134433 X-HE-Meta: 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 CO/+7Exc Adw/3DPGGgDd6CrGNgd/eSTfEPYI/SsasQV5BH0TRgi4CLbZMjAeRQXryamFBzhrkhXgIhlG8QA4ZcP1MsxL4NSDNba4M7epp/06MleJx/9Pt9EgaiERQRe8mXNjRjCnNV7bwZcGqE5jGTbKgptSd81sjGLbWIMHUgSB4N0VFQ3R/XKaaxh/OOFrlCkhOUd+uksSLeU6Tl0szeRTZ3AK9vZrk9bAhsoMGcWNUmHBALpJ1fI0Sc7RLeTAkQv0ayj40YXN3tqWRF5Tp0lmQBKzcXSV8fvdLQtG75VdbBSAhvz/XRVe1CbgdU9L/yY9UpZDfDo/GfHyhKpZPGWkUCOYbZBWRf8HNtg5yjF1H Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Mar 20, 2026 at 06:58:53AM -0700, Usama Arif wrote: > For PIE binaries (ET_DYN), the load address is randomized at PAGE_SIZE > granularity via arch_mmap_rnd(). On arm64 with 64K base pages, this > means the binary is 64K-aligned, but contpte mapping requires 2M > (CONT_PTE_SIZE) alignment. > > Without proper virtual address alignment, readahead patches that > allocate 2M folios with 2M-aligned file offsets and physical addresses > cannot benefit from contpte mapping, as the contpte fold check in > contpte_set_ptes() requires the virtual address to be CONT_PTE_SIZE- > aligned. > > Fix this by extending maximum_alignment() to consider the maximum folio > size supported by the page cache (via mapping_max_folio_size()). For > each PT_LOAD segment, the alignment is bumped to the largest > power-of-2 that fits within the segment size, capped by the max folio > size the filesystem will allocate, if: > > - Both p_vaddr and p_offset are aligned to that size > - The segment is large enough (p_filesz >= size) > > This ensures load_bias is folio-aligned so that file-offset-aligned > folios map to properly aligned virtual addresses, enabling hardware PTE > coalescing (e.g. arm64 contpte) and PMD mappings for large folios. > > The segment size check avoids reducing ASLR entropy for small binaries > that cannot benefit from large folio alignment. > > Signed-off-by: Usama Arif Reviewed-by: Kiryl Shutsemau (Meta) -- Kiryl Shutsemau / Kirill A. Shutemov