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b=dFW0x7S7mNWIQoARVeWzcpBEbSVee/D78573Rn20SoA7QdQg5VWRYHZnXXTnlI2Ns 4dF0/tF11libYL2OiyoLWM+d5UIYem7jje89glD+BfzhyG5pQz4+C6Ur9VPRt8atl/ cwMw7GsBr0A9G630qeNkvmiTkA37sdkINghyA1YI= Date: Tue, 11 Jun 2024 11:06:22 -0700 From: Andrew Morton To: David Hildenbrand Cc: Andrew Bresticker , linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2] mm/memory: Don't require head page for do_set_pmd() Message-Id: <20240611110622.8e9892e92618ddc36bca11b7@linux-foundation.org> In-Reply-To: <8040793f-e9e9-4a2e-807c-afcb310a48f5@redhat.com> References: <20240611153216.2794513-1-abrestic@rivosinc.com> <8040793f-e9e9-4a2e-807c-afcb310a48f5@redhat.com> 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-Rspam-User: X-Rspamd-Queue-Id: 9FA1BA0008 X-Rspamd-Server: rspam01 X-Stat-Signature: 96zuqxrjo3zi1xhua6phejjef3pwsgqh X-HE-Tag: 1718129187-495984 X-HE-Meta: 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 oZ5J7R0Y oaKwKXfRW2f/58Xa3gmmR5MS/R0KEJ9Nyheg0YZlkS/YSwItfpUq1kxsTkAidmAaflPEonYi0Cx5GPLNwjkEXrUxGypXtfy2RNNpzVX0PDndhLGB74/gysThd3CzWjKiz2y4JktYEroYSUCFKVsoFepnRiWxLNU2KtPX2i1xW7LWWKTVGmXkb59C306KiF+/Pg6R9oxDOaDaCDYraZrjak+IMMoBMAlnJmVke+zfjfNETMxtHyz3XqAZph+zlzQBTgwuOO6iIxH7+Tf45OOEJtjx4oizr6S8NULxpnyxGIViNF5Q2k9LsxPmhynMSoeGBvT3gtLvxADErvb2L3lWzkJRZ+TiHbqlCE01a 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 Tue, 11 Jun 2024 17:33:17 +0200 David Hildenbrand wrote: > On 11.06.24 17:32, Andrew Bresticker wrote: > > The requirement that the head page be passed to do_set_pmd() was added > > in commit ef37b2ea08ac ("mm/memory: page_add_file_rmap() -> > > folio_add_file_rmap_[pte|pmd]()") and prevents pmd-mapping in the > > finish_fault() and filemap_map_pages() paths if the page to be inserted > > is anything but the head page for an otherwise suitable vma and pmd-sized > > page. > > > > Fixes: ef37b2ea08ac ("mm/memory: page_add_file_rmap() -> folio_add_file_rmap_[pte|pmd]()") > > Signed-off-by: Andrew Bresticker > > --- > > mm/memory.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/mm/memory.c b/mm/memory.c > > index 0f47a533014e..a1fce5ddacb3 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -4614,8 +4614,9 @@ vm_fault_t do_set_pmd(struct vm_fault *vmf, struct page *page) > > if (!thp_vma_suitable_order(vma, haddr, PMD_ORDER)) > > return ret; > > > > - if (page != &folio->page || folio_order(folio) != HPAGE_PMD_ORDER) > > + if (folio_order(folio) != HPAGE_PMD_ORDER) > > return ret; > > + page = &folio->page; > > > > /* > > * Just backoff if any subpage of a THP is corrupted otherwise > > Acked-by: David Hildenbrand You know what I'm going to ask ;) I'm assuming that the runtime effects are "small performance optimization" and that "should we backport the fix" is "no".