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Tue, 31 Mar 2026 10:38:59 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 9B0EFC19423; Tue, 31 Mar 2026 10:38:58 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1774953539; bh=ns25mF2UrLHOJDvx/LnwaHuyB+Hf+Nyj2xT98c2l78k=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Kj7mU3zJLCNNKhIQIiBnX3/r4iNBlU6v60RiEgsOF7hVhyKpPx7fHySOX/1HcZ6HT g46QUG/QO0DvQW1+pKythy1s52UNDgvTjrWLTdj5d7spmSO1LFbNQUyRArY7Mj37Z3 7GHfGdvFSXRLtrA12eblkVnS0sp8uYMAOeilRIccIqfzkyfaGXDubOLNifxNz+z1EL JmAWQ1FY+eJeiMxXzo4jYsxtkMZYa6oPg7TWrLWfmhPzaBZ1DhSvnKuYoSeP9/E2Xm kG8zGjdKyVcdRF/Y9LgYk7Ghn6/jZmqo2vQFXc8thsNIf/gxryTLdUM9GwUrpEdsQe Zc/hNO6wMpYBA== Date: Tue, 31 Mar 2026 11:38:57 +0100 From: "Lorenzo Stoakes (Oracle)" To: Suren Baghdasaryan Cc: akpm@linux-foundation.org, willy@infradead.org, david@kernel.org, ziy@nvidia.com, matthew.brost@intel.com, joshua.hahnjy@gmail.com, rakie.kim@sk.com, byungchul@sk.com, gourry@gourry.net, ying.huang@linux.alibaba.com, apopple@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, vbabka@suse.cz, jannh@google.com, rppt@kernel.org, mhocko@suse.com, pfalcato@suse.de, kees@kernel.org, maddy@linux.ibm.com, npiggin@gmail.com, mpe@ellerman.id.au, chleroy@kernel.org, borntraeger@linux.ibm.com, frankja@linux.ibm.com, imbrenda@linux.ibm.com, hca@linux.ibm.com, gor@linux.ibm.com, agordeev@linux.ibm.com, svens@linux.ibm.com, gerald.schaefer@linux.ibm.com, linux-mm@kvack.org, linuxppc-dev@lists.ozlabs.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, linux-s390@vger.kernel.org Subject: Re: [PATCH v6 5/6] mm: use vma_start_write_killable() in process_vma_walk_lock() Message-ID: <4e1c47a9-77a2-4f29-8de5-37f9958f5885@lucifer.local> References: <20260327205457.604224-1-surenb@google.com> <20260327205457.604224-6-surenb@google.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260327205457.604224-6-surenb@google.com> On Fri, Mar 27, 2026 at 01:54:56PM -0700, Suren Baghdasaryan wrote: > Replace vma_start_write() with vma_start_write_killable() when > process_vma_walk_lock() is used with PGWALK_WRLOCK option. > Adjust its direct and indirect users to check for a possible error > and handle it. Ensure users handle EINTR correctly and do not ignore > it. When queue_pages_range() fails, check whether it failed due to > a fatal signal or some other reason and return appropriate error. > > Suggested-by: Matthew Wilcox > Signed-off-by: Suren Baghdasaryan > --- > fs/proc/task_mmu.c | 12 ++++++------ > mm/mempolicy.c | 10 +++++++++- > mm/pagewalk.c | 22 +++++++++++++++------- > 3 files changed, 30 insertions(+), 14 deletions(-) > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c > index e091931d7ca1..33e5094a7842 100644 > --- a/fs/proc/task_mmu.c > +++ b/fs/proc/task_mmu.c > @@ -1774,15 +1774,15 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, > struct vm_area_struct *vma; > enum clear_refs_types type; > int itype; > - int rv; > + int err; > > if (count > sizeof(buffer) - 1) > count = sizeof(buffer) - 1; > if (copy_from_user(buffer, buf, count)) > return -EFAULT; > - rv = kstrtoint(strstrip(buffer), 10, &itype); > - if (rv < 0) > - return rv; > + err = kstrtoint(strstrip(buffer), 10, &itype); > + if (err) > + return err; > type = (enum clear_refs_types)itype; > if (type < CLEAR_REFS_ALL || type >= CLEAR_REFS_LAST) > return -EINVAL; > @@ -1824,7 +1824,7 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, > 0, mm, 0, -1UL); > mmu_notifier_invalidate_range_start(&range); > } > - walk_page_range(mm, 0, -1, &clear_refs_walk_ops, &cp); > + err = walk_page_range(mm, 0, -1, &clear_refs_walk_ops, &cp); > if (type == CLEAR_REFS_SOFT_DIRTY) { > mmu_notifier_invalidate_range_end(&range); > flush_tlb_mm(mm); > @@ -1837,7 +1837,7 @@ static ssize_t clear_refs_write(struct file *file, const char __user *buf, > } > put_task_struct(task); > > - return count; > + return err ? : count; > } > > const struct file_operations proc_clear_refs_operations = { > diff --git a/mm/mempolicy.c b/mm/mempolicy.c > index c38a90487531..51f298cfc33b 100644 > --- a/mm/mempolicy.c > +++ b/mm/mempolicy.c > @@ -969,6 +969,7 @@ static const struct mm_walk_ops queue_pages_lock_vma_walk_ops = { > * (a hugetlbfs page or a transparent huge page being counted as 1). > * -EIO - a misplaced page found, when MPOL_MF_STRICT specified without MOVEs. > * -EFAULT - a hole in the memory range, when MPOL_MF_DISCONTIG_OK unspecified. > + * -EINTR - walk got terminated due to pending fatal signal. > */ > static long > queue_pages_range(struct mm_struct *mm, unsigned long start, unsigned long end, > @@ -1545,7 +1546,14 @@ static long do_mbind(unsigned long start, unsigned long len, > flags | MPOL_MF_INVERT | MPOL_MF_WRLOCK, &pagelist); > > if (nr_failed < 0) { > - err = nr_failed; > + /* > + * queue_pages_range() might override the original error with -EFAULT. > + * Confirm that fatal signals are still treated correctly. > + */ > + if (fatal_signal_pending(current)) > + err = -EINTR; > + else > + err = nr_failed; Is that really a big deal? Does it really matter if the caller doesn't get -EINTR in this case? This feels like another sashiko nitpick and is adding a bunch of additional complexity here. I mean if you 'filter' error messages you might always end up with an error that's different than the original... > nr_failed = 0; > } else { > vma_iter_init(&vmi, mm, start); > diff --git a/mm/pagewalk.c b/mm/pagewalk.c > index 3ae2586ff45b..eca7bc711617 100644 > --- a/mm/pagewalk.c > +++ b/mm/pagewalk.c > @@ -443,14 +443,13 @@ static inline void process_mm_walk_lock(struct mm_struct *mm, > mmap_assert_write_locked(mm); > } > > -static inline void process_vma_walk_lock(struct vm_area_struct *vma, > - enum page_walk_lock walk_lock) > +static int process_vma_walk_lock(struct vm_area_struct *vma, > + enum page_walk_lock walk_lock) > { > #ifdef CONFIG_PER_VMA_LOCK > switch (walk_lock) { > case PGWALK_WRLOCK: > - vma_start_write(vma); > - break; > + return vma_start_write_killable(vma); > case PGWALK_WRLOCK_VERIFY: > vma_assert_write_locked(vma); > break; > @@ -462,6 +461,7 @@ static inline void process_vma_walk_lock(struct vm_area_struct *vma, > break; > } > #endif > + return 0; > } > > /* > @@ -505,7 +505,9 @@ int walk_page_range_mm_unsafe(struct mm_struct *mm, unsigned long start, > if (ops->pte_hole) > err = ops->pte_hole(start, next, -1, &walk); > } else { /* inside vma */ > - process_vma_walk_lock(vma, ops->walk_lock); > + err = process_vma_walk_lock(vma, ops->walk_lock); > + if (err) > + break; > walk.vma = vma; > next = min(end, vma->vm_end); > vma = find_vma(mm, vma->vm_end); > @@ -722,6 +724,7 @@ int walk_page_range_vma_unsafe(struct vm_area_struct *vma, unsigned long start, > .vma = vma, > .private = private, > }; > + int err; > > if (start >= end || !walk.mm) > return -EINVAL; > @@ -729,7 +732,9 @@ int walk_page_range_vma_unsafe(struct vm_area_struct *vma, unsigned long start, > return -EINVAL; > > process_mm_walk_lock(walk.mm, ops->walk_lock); > - process_vma_walk_lock(vma, ops->walk_lock); > + err = process_vma_walk_lock(vma, ops->walk_lock); > + if (err) > + return err; > return __walk_page_range(start, end, &walk); > } > > @@ -752,6 +757,7 @@ int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops, > .vma = vma, > .private = private, > }; > + int err; > > if (!walk.mm) > return -EINVAL; > @@ -759,7 +765,9 @@ int walk_page_vma(struct vm_area_struct *vma, const struct mm_walk_ops *ops, > return -EINVAL; > > process_mm_walk_lock(walk.mm, ops->walk_lock); > - process_vma_walk_lock(vma, ops->walk_lock); > + err = process_vma_walk_lock(vma, ops->walk_lock); > + if (err) > + return err; > return __walk_page_range(vma->vm_start, vma->vm_end, &walk); > } > > -- > 2.53.0.1018.g2bb0e51243-goog >