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[99.254.144.39]) by smtp.gmail.com with ESMTPSA id h17-20020ae9ec11000000b0074def53eca5sm240162qkg.53.2023.06.19.12.18.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 19 Jun 2023 12:18:14 -0700 (PDT) Date: Mon, 19 Jun 2023 15:18:13 -0400 From: Peter Xu To: Lorenzo Stoakes Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, Matthew Wilcox , Andrea Arcangeli , John Hubbard , Mike Rapoport , David Hildenbrand , Vlastimil Babka , "Kirill A . Shutemov" , Andrew Morton , Mike Kravetz , James Houghton , Hugh Dickins Subject: Re: [PATCH 5/7] mm/gup: Cleanup next_page handling Message-ID: References: <20230613215346.1022773-1-peterx@redhat.com> <20230613215346.1022773-6-peterx@redhat.com> <5886f78c-3ff8-4b64-9aa6-027c22e7d5fc@lucifer.local> MIME-Version: 1.0 In-Reply-To: <5886f78c-3ff8-4b64-9aa6-027c22e7d5fc@lucifer.local> X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: F23BFC0016 X-Stat-Signature: is35pziqhnmssam6sq7ti4zpy13exgrq X-Rspam-User: X-HE-Tag: 1687202297-354704 X-HE-Meta: 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 zHcwp/Z5 CdjKwrL5NHTDprD9EXhEP101Jnpcouedr3C9O8QTgU2Uji2tvRhbi3gC+M81zZGKi1YJFqsFTqPlEJJj7O6rtfOfgQFWvU4KgaihtVWklXBfufEO1QWDK9Ji6aDkMUUGu50Z9uX1ArLk5qzyzEu5YRHEWZR+A25UuWn+zGw8jgNEl6gOy5KJGtC4tMJGLodPZM02KoSpg9A0/UCTXkWiEzkBNK99GHudhVMW88xb+h1FHkTgTZua8EdLDYnwe3ZdIaeB7Sd9o1lZ71DHRwHi8PvSg1C3dznG4/g/3fTSxjby5PChJzexAKvpGQ1jiGRKH+dKt+eap7JwemIiVsMU6gW4cvrWvnCKc+97LzAJkgpCWS6DTnuIKP3PN7B1yG0cLpsfh13BAkLjaDZlmE/4MVCZ+90K3dAsncTc3oj+M1oct34ujOqAYBqi6ied6DpnLrH+YfCkDBE6QaDc= 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: On Sat, Jun 17, 2023 at 09:00:34PM +0100, Lorenzo Stoakes wrote: > On Sat, Jun 17, 2023 at 08:48:38PM +0100, Lorenzo Stoakes wrote: > > On Tue, Jun 13, 2023 at 05:53:44PM -0400, Peter Xu wrote: > > > The only path that doesn't use generic "**pages" handling is the gate vma. > > > Make it use the same path, meanwhile tune the next_page label upper to > > > cover "**pages" handling. This prepares for THP handling for "**pages". > > > > > > Signed-off-by: Peter Xu > > > --- > > > mm/gup.c | 7 +++---- > > > 1 file changed, 3 insertions(+), 4 deletions(-) > > > > > > diff --git a/mm/gup.c b/mm/gup.c > > > index 8d59ae4554e7..a2d1b3c4b104 100644 > > > --- a/mm/gup.c > > > +++ b/mm/gup.c > > > @@ -1135,7 +1135,7 @@ static long __get_user_pages(struct mm_struct *mm, > > > if (!vma && in_gate_area(mm, start)) { > > > ret = get_gate_page(mm, start & PAGE_MASK, > > > gup_flags, &vma, > > > - pages ? &pages[i] : NULL); > > > + pages ? &page : NULL); > > > > Good spot... ugh that we handled this differently. > > > > > if (ret) > > > goto out; > > > ctx.page_mask = 0; > > > > We can drop this line now right? As the new next_page block will duplicate > > this. > > OK I can see why you left this in given the last patch in the series :) > Please disregard. Yes the other "page_mask=0" will be removed in the next (not last) patch. > > > > > > @@ -1205,19 +1205,18 @@ static long __get_user_pages(struct mm_struct *mm, > > > ret = PTR_ERR(page); > > > goto out; > > > } > > > - > > > - goto next_page; > > > > This is neat, we've already checked if pages != NULL so the if (pages) > > block at the new next_page label will not be run. Yes. > > > > > } else if (IS_ERR(page)) { > > > ret = PTR_ERR(page); > > > goto out; > > > } > > > +next_page: > > > if (pages) { > > > pages[i] = page; > > > flush_anon_page(vma, page, start); > > > flush_dcache_page(page); > > > > I guess there's no harm that we now flush here, though it seems to me to be > > superfluous, it's not a big deal I don't think. I'd say GUP on gate vma page should be so rare so yeah I think it shouldn't be a big deal. Even iiuc vsyscall=xonly should be the default, so gup may have already failed on a gate vma page even trying to read-only.. > > > > > ctx.page_mask = 0; > > > } > > > -next_page: > > > + > > > page_increm = 1 + (~(start >> PAGE_SHIFT) & ctx.page_mask); > > > if (page_increm > nr_pages) > > > page_increm = nr_pages; > > > -- > > > 2.40.1 > > > > > > > Other than that, LGTM, > > > > Reviewed-by: Lorenzo Stoakes Thanks for looking! -- Peter Xu