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Fri, 07 Apr 2023 00:24:06 -0700 (PDT) MIME-Version: 1.0 References: <20230406074005.1784728-1-usama.anjum@collabora.com> <20230406074005.1784728-3-usama.anjum@collabora.com> In-Reply-To: From: =?UTF-8?B?TWljaGHFgiBNaXJvc8WCYXc=?= Date: Fri, 7 Apr 2023 09:23:55 +0200 Message-ID: Subject: Re: [PATCH v12 2/5] fs/proc/task_mmu: Implement IOCTL to get and optionally clear info about PTEs To: Muhammad Usama Anjum Cc: Peter Xu , David Hildenbrand , Andrew Morton , Andrei Vagin , Danylo Mocherniuk , Paul Gofman , Cyrill Gorcunov , Mike Rapoport , Nadav Amit , Alexander Viro , Shuah Khan , Christian Brauner , Yang Shi , Vlastimil Babka , "Liam R . Howlett" , Yun Zhou , Suren Baghdasaryan , Alex Sierra , Matthew Wilcox , Pasha Tatashin , Axel Rasmussen , "Gustavo A . R . Silva" , Dan Williams , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, Greg KH , kernel@collabora.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 67F4E160002 X-Stat-Signature: twydj3seeh64esnfs1rzt5gdisb5pcpx X-HE-Tag: 1680852259-228181 X-HE-Meta: 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 9gFvN7fB dzX2K9ltEuT9hQbaevrlfA4CHpX4lj+0sfp0HsuSp6y5flF57AyBSZUL3EYJbSi/ILe8/JJQkeiT5hZc4zfRkD+hQhx3vElTEBDLMd/FaovZQUzOM4TMixWzN8Tdc8kar/00fCnj/MH7bfitZGZ3tZ4aGKR27buD1nIHSgcuidZ9s/k9UntaVgNvIyq0r2pVT7irW8pmIcazKI2NWFe61qobM8wqAupT7YoyUtfcRsanbUhmMb1bJHUgFK/A56X3vv5CUGk8mheDozB87m2x4SmvZ6+8C+/xqVz0I+E88YCvyvjtfEdhqrh+htQLnVmxd6wOGxmRURkXO93Z7rhfChLeC+tP8j7hlX1Hw2CCD9cg7ngrbvMmP1sgZ8scRzFUkrKTG0i2Z+f2uoewOHFuoatOnNN7FsFfK8c0vISiPv5nZa6rl/XY2BUPOHg== 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 Thu, 6 Apr 2023 at 23:12, Muhammad Usama Anjum wrote: > On 4/7/23 1:12=E2=80=AFAM, Micha=C5=82 Miros=C5=82aw wrote: > > On Thu, 6 Apr 2023 at 09:40, Muhammad Usama Anjum > > wrote: > > [...] > >> --- a/fs/proc/task_mmu.c > >> +++ b/fs/proc/task_mmu.c > > [...] > >> +static int pagemap_scan_pmd_entry(pmd_t *pmd, unsigned long start, > >> + unsigned long end, struct mm_walk *w= alk) > >> +{ [...] > >> +#ifdef CONFIG_TRANSPARENT_HUGEPAGE > >> + ptl =3D pmd_trans_huge_lock(pmd, vma); > >> + if (ptl) { > > [...] > >> + return ret; > >> + } > >> +process_smaller_pages: > >> + if (pmd_trans_unstable(pmd)) > >> + return 0; > > > > Why pmd_trans_unstable() is needed here and not only after split_huge_p= md()? > I'm not entirely sure. But the idea is if THP is unstable, we should > return. As it doesn't seem like after splitting THP can be unstable, we > should not check it. Do you agree with the following? The description of pmd_trans_unstable() [1] seems to indicate that it is needed only after split_huge_pmd(). [1] https://elixir.bootlin.com/linux/v6.3-rc5/source/include/linux/pgtable.= h#L1394 Best Regards Micha=C5=82 Miros=C5=82aw