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b=PoyOKEVNRy4VXTHA+NBiLBYDZc6Sblto8Kaz7UsiOV0QrOkd+U6KphTUovSDNjhCz q7m+nudOTVg3uWbyUbQ1K/0rmRM9xZxyvl43eHr+m/KaV8/+Bt+iJP1qA+qLRmwqhY kfkrd57WJ4utnJF9Yh+A7rU8ghy9VxqBexyWkFemv+rw9RK9Yx+kL/BjPy8/0iVJlH fxK3oXlu/CBuDfkAR/y75njkvq7DNeDTYUABFhtRrfHzBERdZHQzIwGgUnsJnZN8fb r6NYrwXxiUhaMsRCpUBMelI1o26+9ocIx7No45lfOZwm841rcd19HgskuKzFteika5 sC5hUTUEN4gvA== Date: Mon, 7 Sep 2026 12:05:04 +0100 From: "Lorenzo Stoakes (ARM)" To: Ye Liu Cc: Miaohe Lin , Andrew Morton , Ye Liu , Michal Hocko , peterz@infradead.org, paulmck@kernel.org, mingo@redhat.com, rostedt@goodmis.org, jpoimboe@kernel.org, mic@digikod.net, oleg@redhat.com, tglx@kernel.org, david@kernel.org, nao.horiguchi@gmail.com, rafael@kernel.org, gnoack3000@gmail.com, sj@kernel.org, rientjes@google.com, shakeel.butt@linux.dev, xu.xin16@zte.com.cn, chengming.zhou@linux.dev, will@kernel.org, boqun@kernel.org, frederic@kernel.org, neeraj.upadhyay@kernel.org, joelagnelf@nvidia.com, josh@joshtriplett.org, urezki@gmail.com, juri.lelli@redhat.com, vincent.guittot@linaro.org, tony.luck@intel.com, reinette.chatre@intel.com, x86@kernel.org, paul@paul-moore.com, jmorris@namei.org, serge@hallyn.com, pavel@kernel.org, lance.yang@linux.dev, mhiramat@kernel.org, pmladek@suse.com, longman@redhat.com, mathieu.desnoyers@efficios.com, jiangshanlai@gmail.com, qiang.zhang@linux.dev, dietmar.eggemann@arm.com, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, mark.rutland@arm.com, Dave.Martin@arm.com, james.morse@arm.com, babu.moger@amd.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-pm@vger.kernel.org, rcu@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-security-module@vger.kernel.org Subject: Re: [PATCH v2 4/8] mm/memory-failure: convert process iterator to for_each_process_rculock Message-ID: References: <20260907081334.1152889-1-ye.liu@linux.dev> <20260907081334.1152889-5-ye.liu@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260907081334.1152889-5-ye.liu@linux.dev> X-Stat-Signature: ghh1kh8ijwk84jqqdgtspbds8ncci1ce X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: ACB9D1C000C X-Rspam-User: X-HE-Tag: 1788779120-894910 X-HE-Meta: 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 +UmPtPZO 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Mon, Sep 07, 2026 at 04:13:30PM +0800, Ye Liu wrote: > From: Ye Liu > > Replace the manual rcu_read_lock()/rcu_read_unlock() pairs combined > with for_each_process() loop in mm/memory-failure.c with > for_each_process_rculock(), which scopes the RCU read lock to the > loop body via scoped_guard(rcu). > > In collect_procs_file(), the page_pgoff() call now falls outside the > RCU read-side critical section. This is safe because page_pgoff() > only reads folio->index and does not traverse any RCU-protected > structures. > > Signed-off-by: Ye Liu > Acked-by: Michal Hocko > Acked-by: Miaohe Lin LGTM so: Reviewed-by: Lorenzo Stoakes (ARM) > --- > Changes in v2: > - Rename *_rcu to *_rculock > - Clarify page_pgoff() safety outside RCU lock (SJ Park) > mm/memory-failure.c | 16 ++++------------ > 1 file changed, 4 insertions(+), 12 deletions(-) > > diff --git a/mm/memory-failure.c b/mm/memory-failure.c > index a8b03e2920ba..7d93deb1f7b3 100644 > --- a/mm/memory-failure.c > +++ b/mm/memory-failure.c > @@ -555,8 +555,7 @@ static void collect_procs_anon(const struct folio *folio, > return; > > pgoff = page_pgoff(folio, page); > - rcu_read_lock(); > - for_each_process(tsk) { > + for_each_process_rculock(tsk) { > struct vm_area_struct *vma; > struct anon_vma_chain *vmac; > struct task_struct *t = task_early_kill(tsk, force_early); > @@ -572,7 +571,6 @@ static void collect_procs_anon(const struct folio *folio, > add_to_kill_anon_file(t, page, vma, to_kill, addr); > } > } > - rcu_read_unlock(); > anon_vma_unlock_read(av); > } > > @@ -589,9 +587,8 @@ static void collect_procs_file(const struct folio *folio, > pgoff_t pgoff; > > i_mmap_lock_read(mapping); > - rcu_read_lock(); > pgoff = page_pgoff(folio, page); > - for_each_process(tsk) { > + for_each_process_rculock(tsk) { > struct task_struct *t = task_early_kill(tsk, force_early); > unsigned long addr; > > @@ -611,7 +608,6 @@ static void collect_procs_file(const struct folio *folio, > add_to_kill_anon_file(t, page, vma, to_kill, addr); > } > } > - rcu_read_unlock(); > i_mmap_unlock_read(mapping); > } > > @@ -635,8 +631,7 @@ static void collect_procs_fsdax(const struct page *page, > struct task_struct *tsk; > > i_mmap_lock_read(mapping); > - rcu_read_lock(); > - for_each_process(tsk) { > + for_each_process_rculock(tsk) { > struct task_struct *t = tsk; > > /* > @@ -653,7 +648,6 @@ static void collect_procs_fsdax(const struct page *page, > add_to_kill_fsdax(t, page, vma, to_kill, pgoff); > } > } > - rcu_read_unlock(); > i_mmap_unlock_read(mapping); > } > #endif /* CONFIG_FS_DAX */ > @@ -2288,8 +2282,7 @@ static void collect_procs_pfn(struct pfn_address_space *pfn_space, > struct address_space *mapping = pfn_space->mapping; > > i_mmap_lock_read(mapping); > - rcu_read_lock(); > - for_each_process(tsk) { > + for_each_process_rculock(tsk) { > struct task_struct *t = tsk; > > t = task_early_kill(tsk, true); > @@ -2303,7 +2296,6 @@ static void collect_procs_pfn(struct pfn_address_space *pfn_space, > add_to_kill_pgoff(t, vma, to_kill, pgoff); > } > } > - rcu_read_unlock(); > i_mmap_unlock_read(mapping); > } > > -- > 2.25.1 > -- Cheers, Lorenzo