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[2003:cb:c703:fe00:10fe:298:6bf1:d163]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-422874e6b63sm53141465e9.39.2024.06.13.01.30.15 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 13 Jun 2024 01:30:16 -0700 (PDT) Message-ID: Date: Thu, 13 Jun 2024 10:30:15 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v7 2/4] mm/rmap: add helper to restart pgtable walk on changes To: Lance Yang , akpm@linux-foundation.org Cc: willy@infradead.org, sj@kernel.org, baolin.wang@linux.alibaba.com, maskray@google.com, ziy@nvidia.com, ryan.roberts@arm.com, 21cnbao@gmail.com, mhocko@suse.com, fengwei.yin@intel.com, zokeefe@google.com, shy828301@gmail.com, xiehuan09@gmail.com, libang.li@antgroup.com, wangkefeng.wang@huawei.com, songmuchun@bytedance.com, peterx@redhat.com, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20240610120209.66311-1-ioworker0@gmail.com> <20240610120209.66311-3-ioworker0@gmail.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 55F3E140007 X-Stat-Signature: 3a16cpiu1ntm1bc93g9ww8pcx8bp3amr X-Rspam-User: X-HE-Tag: 1718267421-729299 X-HE-Meta: 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 fZNwqcRq rW545u/IBe57SRkHsu7esNVZiMQcLDRBmXuDRDxj6KdYbr2aCHFgL3Brd4zXjEgFDB1zvisswQINT2v/O6WHeYqa5YkyubHuubhwB/6x5yphMu95YErzz6Kc1fl9M9GlwjpIixRrEmJXrql2qchWLfbXPp1e47s9zryHLbXbXBEJFpWQVV25ffPKTHH7nFPrOeItpWWlq9CIt0uTFjPXqt1um5pAUBNZajEyEY0WDuPmKb4i79cjd3b75fdaFPgAU/pzYP5xJ1RxwUsZ7y+Wb9W+zQewvM+4nn9q5zhgBwLE7flJNWL2ME4udC5Qg0SsAAeJ+BFQODrVvdVUY7Li92zyFleQCEK7oASAepy8ccneeEqBlTgwmULo61NCyTRgDQwplT4S90+P8bAmSnaWNqjIRVAYdQPM1XFHP 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 10.06.24 14:02, Lance Yang wrote: > Introduce the page_vma_mapped_walk_restart() helper to handle scenarios > where the page table walk needs to be restarted due to changes in the page > table, such as when a PMD is split. It releases the PTL held during the > previous walk and resets the state, allowing a new walk to start at the > current address stored in pvmw->address. > > Suggested-by: David Hildenbrand > Signed-off-by: Lance Yang > --- > include/linux/rmap.h | 22 ++++++++++++++++++++++ > 1 file changed, 22 insertions(+) > > diff --git a/include/linux/rmap.h b/include/linux/rmap.h > index 7229b9baf20d..5f18509610cc 100644 > --- a/include/linux/rmap.h > +++ b/include/linux/rmap.h > @@ -710,6 +710,28 @@ static inline void page_vma_mapped_walk_done(struct page_vma_mapped_walk *pvmw) > spin_unlock(pvmw->ptl); > } > > +/** > + * page_vma_mapped_walk_restart - Restart the page table walk. > + * @pvmw: Pointer to struct page_vma_mapped_walk. > + * > + * It restarts the page table walk when changes occur in the page > + * table, such as splitting a PMD. Ensures that the PTL held during > + * the previous walk is released and resets the state to allow for > + * a new walk starting at the current address stored in pvmw->address. > + */ > +static inline void > +page_vma_mapped_walk_restart(struct page_vma_mapped_walk *pvmw) > +{ > + WARN_ON_ONCE(!pvmw->pmd); Can we have this more general, like WARN_ON_ONCE(!pvmw->pmd && !pvmw->pte); And then setting both to NULL below? > + WARN_ON_ONCE(!pvmw->ptl); This is confusing: you check for ptl below. What would be clearer is if (likely(pvmw->ptl)) spin_unlock(pvmw->ptl); else WARN_ON_ONCE(1); > + > + if (pvmw->ptl) > + spin_unlock(pvmw->ptl); > + > + pvmw->ptl = NULL; > + pvmw->pmd = NULL; > +} > + > bool page_vma_mapped_walk(struct page_vma_mapped_walk *pvmw); > > /* I'd suggest squashing that into the next patch. -- Cheers, David / dhildenb