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Date:   Mon, 16 Jul 2018 19:57:01 +0300
From:   "Kirill A. Shutemov" <kirill@shutemov.name>
To:     Marcel Ziswiler <marcel.ziswiler@toradex.com>,
        "akpm@linux-foundation.org" <akpm@linux-foundation.org>
Cc:     "kirill.shutemov@linux.intel.com" <kirill.shutemov@linux.intel.com>,
        "linux-tegra@vger.kernel.org" <linux-tegra@vger.kernel.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "aarcange@redhat.com" <aarcange@redhat.com>,
        "dvyukov@google.com" <dvyukov@google.com>,
        "oleg@redhat.com" <oleg@redhat.com>
Subject: Re: REGRESSION: [PATCHv2 2/2] mm: Drop unneeded ->vm_ops checks
Message-ID: <20180716165701.2ssihyxqjvj4otqr@kshutemo-mobl1>
References: <20180712145626.41665-1-kirill.shutemov@linux.intel.com>
 <20180712145626.41665-3-kirill.shutemov@linux.intel.com>
 <1531747832.6547.7.camel@toradex.com>
 <20180716142049.ioa2irsd2d7sphn4@black.fi.intel.com>
 <1531757392.6547.28.camel@toradex.com>
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User-Agent: NeoMutt/20180622
Sender: linux-kernel-owner@vger.kernel.org
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On Mon, Jul 16, 2018 at 04:09:54PM +0000, Marcel Ziswiler wrote:
> On Mon, 2018-07-16 at 17:20 +0300, Kirill A. Shutemov wrote:
> > On Mon, Jul 16, 2018 at 01:30:34PM +0000, Marcel Ziswiler wrote:
> > > On Thu, 2018-07-12 at 17:56 +0300, Kirill A. Shutemov wrote:
> > > > We now have all VMAs with ->vm_ops set and don't need to check it
> > > > for
> > > > NULL everywhere.
> > > > 
> > > > Signed-off-by: Kirill A. Shutemov <kirill.shutemov@linux.intel.co
> > > > m>
> > > > ---
> > > >  fs/binfmt_elf.c      |  2 +-
> > > >  fs/kernfs/file.c     | 20 +-------------------
> > > >  fs/proc/task_mmu.c   |  2 +-
> > > >  kernel/events/core.c |  2 +-
> > > >  kernel/fork.c        |  2 +-
> > > >  mm/gup.c             |  2 +-
> > > >  mm/hugetlb.c         |  2 +-
> > > >  mm/memory.c          | 12 ++++++------
> > > >  mm/mempolicy.c       | 10 +++++-----
> > > >  mm/mmap.c            | 14 +++++++-------
> > > >  mm/mremap.c          |  2 +-
> > > >  mm/nommu.c           |  4 ++--
> > > >  12 files changed, 28 insertions(+), 46 deletions(-)
> > > > 
> > > > diff --git a/fs/binfmt_elf.c b/fs/binfmt_elf.c
> > > > index 0ac456b52bdd..4f171cf21bc2 100644
> > > > --- a/fs/binfmt_elf.c
> > > > +++ b/fs/binfmt_elf.c
> > > > @@ -1302,7 +1302,7 @@ static bool always_dump_vma(struct
> > > > vm_area_struct *vma)
> > > >  	 * Assume that all vmas with a .name op should always be
> > > > dumped.
> > > >  	 * If this changes, a new vm_ops field can easily be
> > > > added.
> > > >  	 */
> > > > -	if (vma->vm_ops && vma->vm_ops->name && vma->vm_ops-
> > > > > name(vma))
> > > > 
> > > > +	if (vma->vm_ops->name && vma->vm_ops->name(vma))
> > > >  		return true;
> > > >  
> > > >  	/*
> > > > diff --git a/fs/kernfs/file.c b/fs/kernfs/file.c
> > > > index 2015d8c45e4a..945c3d306d8f 100644
> > > > --- a/fs/kernfs/file.c
> > > > +++ b/fs/kernfs/file.c
> > > > @@ -336,9 +336,6 @@ static void kernfs_vma_open(struct
> > > > vm_area_struct
> > > > *vma)
> > > >  	struct file *file = vma->vm_file;
> > > >  	struct kernfs_open_file *of = kernfs_of(file);
> > > >  
> > > > -	if (!of->vm_ops)
> > > > -		return;
> > > > -
> > > >  	if (!kernfs_get_active(of->kn))
> > > >  		return;
> > > >  
> > > > @@ -354,9 +351,6 @@ static vm_fault_t kernfs_vma_fault(struct
> > > > vm_fault *vmf)
> > > >  	struct kernfs_open_file *of = kernfs_of(file);
> > > >  	vm_fault_t ret;
> > > >  
> > > > -	if (!of->vm_ops)
> > > > -		return VM_FAULT_SIGBUS;
> > > > -
> > > >  	if (!kernfs_get_active(of->kn))
> > > >  		return VM_FAULT_SIGBUS;
> > > >  
> > > > @@ -374,9 +368,6 @@ static vm_fault_t
> > > > kernfs_vma_page_mkwrite(struct
> > > > vm_fault *vmf)
> > > >  	struct kernfs_open_file *of = kernfs_of(file);
> > > >  	vm_fault_t ret;
> > > >  
> > > > -	if (!of->vm_ops)
> > > > -		return VM_FAULT_SIGBUS;
> > > > -
> > > >  	if (!kernfs_get_active(of->kn))
> > > >  		return VM_FAULT_SIGBUS;
> > > >  
> > > > @@ -397,9 +388,6 @@ static int kernfs_vma_access(struct
> > > > vm_area_struct *vma, unsigned long addr,
> > > >  	struct kernfs_open_file *of = kernfs_of(file);
> > > >  	int ret;
> > > >  
> > > > -	if (!of->vm_ops)
> > > > -		return -EINVAL;
> > > > -
> > > >  	if (!kernfs_get_active(of->kn))
> > > >  		return -EINVAL;
> > > >  
> > > > @@ -419,9 +407,6 @@ static int kernfs_vma_set_policy(struct
> > > > vm_area_struct *vma,
> > > >  	struct kernfs_open_file *of = kernfs_of(file);
> > > >  	int ret;
> > > >  
> > > > -	if (!of->vm_ops)
> > > > -		return 0;
> > > > -
> > > >  	if (!kernfs_get_active(of->kn))
> > > >  		return -EINVAL;
> > > >  
> > > > @@ -440,9 +425,6 @@ static struct mempolicy
> > > > *kernfs_vma_get_policy(struct vm_area_struct *vma,
> > > >  	struct kernfs_open_file *of = kernfs_of(file);
> > > >  	struct mempolicy *pol;
> > > >  
> > > > -	if (!of->vm_ops)
> > > > -		return vma->vm_policy;
> > > > -
> > > >  	if (!kernfs_get_active(of->kn))
> > > >  		return vma->vm_policy;
> > > >  
> > > > @@ -511,7 +493,7 @@ static int kernfs_fop_mmap(struct file *file,
> > > > struct vm_area_struct *vma)
> > > >  	 * So error if someone is trying to use close.
> > > >  	 */
> > > >  	rc = -EINVAL;
> > > > -	if (vma->vm_ops && vma->vm_ops->close)
> > > > +	if (vma->vm_ops->close)
> > > >  		goto out_put;
> > > >  
> > > >  	rc = 0;
> > > > diff --git a/fs/proc/task_mmu.c b/fs/proc/task_mmu.c
> > > > index e9679016271f..e959623123e4 100644
> > > > --- a/fs/proc/task_mmu.c
> > > > +++ b/fs/proc/task_mmu.c
> > > > @@ -326,7 +326,7 @@ show_map_vma(struct seq_file *m, struct
> > > > vm_area_struct *vma, int is_pid)
> > > >  		goto done;
> > > >  	}
> > > >  
> > > > -	if (vma->vm_ops && vma->vm_ops->name) {
> > > > +	if (vma->vm_ops->name) {
> > > >  		name = vma->vm_ops->name(vma);
> > > >  		if (name)
> > > >  			goto done;
> > > > diff --git a/kernel/events/core.c b/kernel/events/core.c
> > > > index 8f0434a9951a..2e35401a5c68 100644
> > > > --- a/kernel/events/core.c
> > > > +++ b/kernel/events/core.c
> > > > @@ -7269,7 +7269,7 @@ static void perf_event_mmap_event(struct
> > > > perf_mmap_event *mmap_event)
> > > >  
> > > >  		goto got_name;
> > > >  	} else {
> > > > -		if (vma->vm_ops && vma->vm_ops->name) {
> > > > +		if (vma->vm_ops->name) {
> > > >  			name = (char *) vma->vm_ops->name(vma);
> > > >  			if (name)
> > > >  				goto cpy_name;
> > > > diff --git a/kernel/fork.c b/kernel/fork.c
> > > > index 9440d61b925c..e5e7a220a124 100644
> > > > --- a/kernel/fork.c
> > > > +++ b/kernel/fork.c
> > > > @@ -519,7 +519,7 @@ static __latent_entropy int dup_mmap(struct
> > > > mm_struct *mm,
> > > >  		if (!(tmp->vm_flags & VM_WIPEONFORK))
> > > >  			retval = copy_page_range(mm, oldmm,
> > > > mpnt);
> > > >  
> > > > -		if (tmp->vm_ops && tmp->vm_ops->open)
> > > > +		if (tmp->vm_ops->open)
> > > >  			tmp->vm_ops->open(tmp);
> > > >  
> > > >  		if (retval)
> > > > diff --git a/mm/gup.c b/mm/gup.c
> > > > index b70d7ba7cc13..b732768ed3ac 100644
> > > > --- a/mm/gup.c
> > > > +++ b/mm/gup.c
> > > > @@ -31,7 +31,7 @@ static struct page *no_page_table(struct
> > > > vm_area_struct *vma,
> > > >  	 * But we can only make this optimization where a hole
> > > > would
> > > > surely
> > > >  	 * be zero-filled if handle_mm_fault() actually did
> > > > handle
> > > > it.
> > > >  	 */
> > > > -	if ((flags & FOLL_DUMP) && (!vma->vm_ops || !vma-
> > > > >vm_ops-
> > > > > fault))
> > > > 
> > > > +	if ((flags & FOLL_DUMP) && !vma->vm_ops->fault)
> > > >  		return ERR_PTR(-EFAULT);
> > > >  	return NULL;
> > > >  }
> > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > > > index 039ddbc574e9..2065acc5a6aa 100644
> > > > --- a/mm/hugetlb.c
> > > > +++ b/mm/hugetlb.c
> > > > @@ -637,7 +637,7 @@ EXPORT_SYMBOL_GPL(linear_hugepage_index);
> > > >   */
> > > >  unsigned long vma_kernel_pagesize(struct vm_area_struct *vma)
> > > >  {
> > > > -	if (vma->vm_ops && vma->vm_ops->pagesize)
> > > > +	if (vma->vm_ops->pagesize)
> > > >  		return vma->vm_ops->pagesize(vma);
> > > >  	return PAGE_SIZE;
> > > >  }
> > > > diff --git a/mm/memory.c b/mm/memory.c
> > > > index 7206a634270b..02fbef2bd024 100644
> > > > --- a/mm/memory.c
> > > > +++ b/mm/memory.c
> > > > @@ -768,7 +768,7 @@ static void print_bad_pte(struct
> > > > vm_area_struct
> > > > *vma, unsigned long addr,
> > > >  		 (void *)addr, vma->vm_flags, vma->anon_vma,
> > > > mapping, index);
> > > >  	pr_alert("file:%pD fault:%pf mmap:%pf readpage:%pf\n",
> > > >  		 vma->vm_file,
> > > > -		 vma->vm_ops ? vma->vm_ops->fault : NULL,
> > > > +		 vma->vm_ops->fault,
> > > >  		 vma->vm_file ? vma->vm_file->f_op->mmap : NULL,
> > > >  		 mapping ? mapping->a_ops->readpage : NULL);
> > > >  	dump_stack();
> > > > @@ -825,7 +825,7 @@ struct page *_vm_normal_page(struct
> > > > vm_area_struct *vma, unsigned long addr,
> > > >  	if (IS_ENABLED(CONFIG_ARCH_HAS_PTE_SPECIAL)) {
> > > >  		if (likely(!pte_special(pte)))
> > > >  			goto check_pfn;
> > > > -		if (vma->vm_ops && vma->vm_ops-
> > > > >find_special_page)
> > > > +		if (vma->vm_ops->find_special_page)
> > > >  			return vma->vm_ops-
> > > > >find_special_page(vma,
> > > > addr);
> > > >  		if (vma->vm_flags & (VM_PFNMAP | VM_MIXEDMAP))
> > > >  			return NULL;
> > > > @@ -2404,7 +2404,7 @@ static void fault_dirty_shared_page(struct
> > > > vm_area_struct *vma,
> > > >  {
> > > >  	struct address_space *mapping;
> > > >  	bool dirtied;
> > > > -	bool page_mkwrite = vma->vm_ops && vma->vm_ops-
> > > > > page_mkwrite;
> > > > 
> > > > +	bool page_mkwrite = vma->vm_ops->page_mkwrite;
> > > >  
> > > >  	dirtied = set_page_dirty(page);
> > > >  	VM_BUG_ON_PAGE(PageAnon(page), page);
> > > > @@ -2648,7 +2648,7 @@ static int wp_pfn_shared(struct vm_fault
> > > > *vmf)
> > > >  {
> > > >  	struct vm_area_struct *vma = vmf->vma;
> > > >  
> > > > -	if (vma->vm_ops && vma->vm_ops->pfn_mkwrite) {
> > > > +	if (vma->vm_ops->pfn_mkwrite) {
> > > >  		int ret;
> > > >  
> > > >  		pte_unmap_unlock(vmf->pte, vmf->ptl);
> > > > @@ -2669,7 +2669,7 @@ static int wp_page_shared(struct vm_fault
> > > > *vmf)
> > > >  
> > > >  	get_page(vmf->page);
> > > >  
> > > > -	if (vma->vm_ops && vma->vm_ops->page_mkwrite) {
> > > > +	if (vma->vm_ops->page_mkwrite) {
> > > >  		int tmp;
> > > >  
> > > >  		pte_unmap_unlock(vmf->pte, vmf->ptl);
> > > > @@ -4439,7 +4439,7 @@ int __access_remote_vm(struct task_struct
> > > > *tsk,
> > > > struct mm_struct *mm,
> > > >  			vma = find_vma(mm, addr);
> > > >  			if (!vma || vma->vm_start > addr)
> > > >  				break;
> > > > -			if (vma->vm_ops && vma->vm_ops->access)
> > > > +			if (vma->vm_ops->access)
> > > >  				ret = vma->vm_ops->access(vma,
> > > > addr,
> > > > buf,
> > > >  							  len,
> > > > write);
> > > >  			if (ret <= 0)
> > > > diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> > > > index 9ac49ef17b4e..f0fcf70bcec7 100644
> > > > --- a/mm/mempolicy.c
> > > > +++ b/mm/mempolicy.c
> > > > @@ -651,13 +651,13 @@ static int vma_replace_policy(struct
> > > > vm_area_struct *vma,
> > > >  	pr_debug("vma %lx-%lx/%lx vm_ops %p vm_file %p
> > > > set_policy
> > > > %p\n",
> > > >  		 vma->vm_start, vma->vm_end, vma->vm_pgoff,
> > > >  		 vma->vm_ops, vma->vm_file,
> > > > -		 vma->vm_ops ? vma->vm_ops->set_policy : NULL);
> > > > +		 vma->vm_ops->set_policy);
> > > >  
> > > >  	new = mpol_dup(pol);
> > > >  	if (IS_ERR(new))
> > > >  		return PTR_ERR(new);
> > > >  
> > > > -	if (vma->vm_ops && vma->vm_ops->set_policy) {
> > > > +	if (vma->vm_ops->set_policy) {
> > > >  		err = vma->vm_ops->set_policy(vma, new);
> > > >  		if (err)
> > > >  			goto err_out;
> > > > @@ -845,7 +845,7 @@ static long do_get_mempolicy(int *policy,
> > > > nodemask_t *nmask,
> > > >  			up_read(&mm->mmap_sem);
> > > >  			return -EFAULT;
> > > >  		}
> > > > -		if (vma->vm_ops && vma->vm_ops->get_policy)
> > > > +		if (vma->vm_ops->get_policy)
> > > >  			pol = vma->vm_ops->get_policy(vma,
> > > > addr);
> > > >  		else
> > > >  			pol = vma->vm_policy;
> > > > @@ -1617,7 +1617,7 @@ struct mempolicy *__get_vma_policy(struct
> > > > vm_area_struct *vma,
> > > >  	struct mempolicy *pol = NULL;
> > > >  
> > > >  	if (vma) {
> > > > -		if (vma->vm_ops && vma->vm_ops->get_policy) {
> > > > +		if (vma->vm_ops->get_policy) {
> > > >  			pol = vma->vm_ops->get_policy(vma,
> > > > addr);
> > > >  		} else if (vma->vm_policy) {
> > > >  			pol = vma->vm_policy;
> > > > @@ -1663,7 +1663,7 @@ bool vma_policy_mof(struct vm_area_struct
> > > > *vma)
> > > >  {
> > > >  	struct mempolicy *pol;
> > > >  
> > > > -	if (vma->vm_ops && vma->vm_ops->get_policy) {
> > > > +	if (vma->vm_ops->get_policy) {
> > > >  		bool ret = false;
> > > >  
> > > >  		pol = vma->vm_ops->get_policy(vma, vma-
> > > > >vm_start);
> > > > diff --git a/mm/mmap.c b/mm/mmap.c
> > > > index 527c17f31635..5adaf9f9b941 100644
> > > > --- a/mm/mmap.c
> > > > +++ b/mm/mmap.c
> > > > @@ -177,7 +177,7 @@ static struct vm_area_struct
> > > > *remove_vma(struct
> > > > vm_area_struct *vma)
> > > >  	struct vm_area_struct *next = vma->vm_next;
> > > >  
> > > >  	might_sleep();
> > > > -	if (vma->vm_ops && vma->vm_ops->close)
> > > > +	if (vma->vm_ops->close)
> > > >  		vma->vm_ops->close(vma);
> > > >  	if (vma->vm_file)
> > > >  		fput(vma->vm_file);
> > > > @@ -998,7 +998,7 @@ static inline int is_mergeable_vma(struct
> > > > vm_area_struct *vma,
> > > >  		return 0;
> > > >  	if (vma->vm_file != file)
> > > >  		return 0;
> > > > -	if (vma->vm_ops && vma->vm_ops->close)
> > > > +	if (vma->vm_ops->close)
> > > >  		return 0;
> > > >  	if (!is_mergeable_vm_userfaultfd_ctx(vma,
> > > > vm_userfaultfd_ctx))
> > > >  		return 0;
> > > > @@ -1638,7 +1638,7 @@ int vma_wants_writenotify(struct
> > > > vm_area_struct
> > > > *vma, pgprot_t vm_page_prot)
> > > >  		return 0;
> > > >  
> > > >  	/* The backer wishes to know when pages are first
> > > > written
> > > > to? */
> > > > -	if (vm_ops && (vm_ops->page_mkwrite || vm_ops-
> > > > >pfn_mkwrite))
> > > > +	if (vm_ops->page_mkwrite || vm_ops->pfn_mkwrite)
> > > >  		return 1;
> > > >  
> > > >  	/* The open routine did something to the protections
> > > > that
> > > > pgprot_modify
> > > > @@ -2624,7 +2624,7 @@ int __split_vma(struct mm_struct *mm,
> > > > struct
> > > > vm_area_struct *vma,
> > > >  	struct vm_area_struct *new;
> > > >  	int err;
> > > >  
> > > > -	if (vma->vm_ops && vma->vm_ops->split) {
> > > > +	if (vma->vm_ops->split) {
> > > >  		err = vma->vm_ops->split(vma, addr);
> > > >  		if (err)
> > > >  			return err;
> > > > @@ -2657,7 +2657,7 @@ int __split_vma(struct mm_struct *mm,
> > > > struct
> > > > vm_area_struct *vma,
> > > >  	if (new->vm_file)
> > > >  		get_file(new->vm_file);
> > > >  
> > > > -	if (new->vm_ops && new->vm_ops->open)
> > > > +	if (new->vm_ops->open)
> > > >  		new->vm_ops->open(new);
> > > >  
> > > >  	if (new_below)
> > > > @@ -2671,7 +2671,7 @@ int __split_vma(struct mm_struct *mm,
> > > > struct
> > > > vm_area_struct *vma,
> > > >  		return 0;
> > > >  
> > > >  	/* Clean everything up if vma_adjust failed. */
> > > > -	if (new->vm_ops && new->vm_ops->close)
> > > > +	if (new->vm_ops->close)
> > > >  		new->vm_ops->close(new);
> > > >  	if (new->vm_file)
> > > >  		fput(new->vm_file);
> > > > @@ -3232,7 +3232,7 @@ struct vm_area_struct *copy_vma(struct
> > > > vm_area_struct **vmap,
> > > >  			goto out_free_mempol;
> > > >  		if (new_vma->vm_file)
> > > >  			get_file(new_vma->vm_file);
> > > > -		if (new_vma->vm_ops && new_vma->vm_ops->open)
> > > > +		if (new_vma->vm_ops->open)
> > > >  			new_vma->vm_ops->open(new_vma);
> > > >  		vma_link(mm, new_vma, prev, rb_link, rb_parent);
> > > >  		*need_rmap_locks = false;
> > > > diff --git a/mm/mremap.c b/mm/mremap.c
> > > > index 5c2e18505f75..7ab222c283de 100644
> > > > --- a/mm/mremap.c
> > > > +++ b/mm/mremap.c
> > > > @@ -302,7 +302,7 @@ static unsigned long move_vma(struct
> > > > vm_area_struct *vma,
> > > >  				     need_rmap_locks);
> > > >  	if (moved_len < old_len) {
> > > >  		err = -ENOMEM;
> > > > -	} else if (vma->vm_ops && vma->vm_ops->mremap) {
> > > > +	} else if (vma->vm_ops->mremap) {
> > > >  		err = vma->vm_ops->mremap(new_vma);
> > > >  	}
> > > >  
> > > > diff --git a/mm/nommu.c b/mm/nommu.c
> > > > index f00f209833ab..73f66e81cfb0 100644
> > > > --- a/mm/nommu.c
> > > > +++ b/mm/nommu.c
> > > > @@ -764,7 +764,7 @@ static void delete_vma_from_mm(struct
> > > > vm_area_struct *vma)
> > > >   */
> > > >  static void delete_vma(struct mm_struct *mm, struct
> > > > vm_area_struct
> > > > *vma)
> > > >  {
> > > > -	if (vma->vm_ops && vma->vm_ops->close)
> > > > +	if (vma->vm_ops->close)
> > > >  		vma->vm_ops->close(vma);
> > > >  	if (vma->vm_file)
> > > >  		fput(vma->vm_file);
> > > > @@ -1496,7 +1496,7 @@ int split_vma(struct mm_struct *mm, struct
> > > > vm_area_struct *vma,
> > > >  		region->vm_pgoff = new->vm_pgoff += npages;
> > > >  	}
> > > >  
> > > > -	if (new->vm_ops && new->vm_ops->open)
> > > > +	if (new->vm_ops->open)
> > > >  		new->vm_ops->open(new);
> > > >  
> > > >  	delete_vma_from_mm(vma);
> > > 
> > > Today's -next on Apalis T30 [1] gives the following error upon
> > > boot:
> > > 
> > > [   16.147496] Unable to handle kernel NULL pointer dereference at
> > > virtual address 0000002c
> > > [   16.156152] pgd = 843045af
> > > [   16.158986] [0000002c] *pgd=facd9831
> > > [   16.162578] Internal error: Oops: 17 [#1] PREEMPT SMP ARM
> > > [   16.167970] Modules linked in:
> > > [   16.171034] CPU: 2 PID: 442 Comm: polkitd Not tainted 4.18.0-
> > > rc5-
> > > next-20180716-dirty #75
> > > [   16.179111] Hardware name: NVIDIA Tegra SoC (Flattened Device
> > > Tree)
> > > [   16.185382] PC is at show_map_vma.constprop.3+0xac/0x158
> > > [   16.190686] LR is at show_map_vma.constprop.3+0xa8/0x158
> > > [   16.195989] pc : [<c02c4900>]    lr : [<c02c48fc>]    psr:
> > > 800e0013
> > > [   16.202243] sp : ec02de60  ip : 000003ce  fp : c0f09a3c
> > > [   16.207457] r10: ec02df78  r9 : 00000000  r8 : 00000000
> > > [   16.212672] r7 : 00000000  r6 : eda8ec48  r5 : 00000000  r4 :
> > > c0f09a3c
> > > [   16.219188] r3 : 00000000  r2 : ed1df000  r1 : 00000020  r0 :
> > > eda8ec48
> > > [   16.225705] Flags: Nzcv  IRQs on  FIQs on  Mode SVC_32  ISA
> > > ARM  Segment none
> > > [   16.232829] Control: 10c5387d  Table: ac01804a  DAC: 00000051
> > > [   16.238573] Process polkitd (pid: 442, stack limit = 0xc0e83ce5)
> > > [   16.244572] Stack: (0xec02de60 to 0xec02e000)
> > > [   16.248928] de60: 00000000 00000000 00000000 00000000 eda8ec48
> > > eda8ec48 c0f09a3c 000003a6
> > > [   16.257097] de80: ecf46300 00000096 00000000 c02c4efc eda8ec48
> > > 00000000 000003a6 c0289908
> > > [   16.265287] dea0: 0000000c eda8ec78 ecf46300 000003f4 00081114
> > > eda8ec60 00000000 c0f04c48
> > > [   16.273482] dec0: c028956c 00000400 ec02df78 00000000 00081108
> > > 00000400 00000000 c0263b20
> > > [   16.281671] dee0: 5b4c9a7c 0ee6b280 000039ea 00000000 c0f04c48
> > > 8bb3ec56 c0f04c48 be8c7a00
> > > [   16.289853] df00: ecf46308 00000000 000007ff c0f04c48 00000001
> > > 00000000 00000000 00000000
> > > [   16.298037] df20: 00000000 8bb3ec56 000039ea 8bb3ec56 ecf46300
> > > 00081108 00000400 ec02df78
> > > [   16.306210] df40: 00000000 00081108 00000400 c0263cdc c0f04c48
> > > b686ac78 000005e8 c0f04c48
> > > [   16.314381] df60: ecf46303 00002400 00000000 ecf46300 00081108
> > > c02641c0 00002400 00000000
> > > [   16.322549] df80: 00000000 8bb3ec56 00022698 b686ac78 000005e8
> > > 00000003 c0101204 ec02c000
> > > [   16.330718] dfa0: 00000003 c0101000 00022698 b686ac78 00000009
> > > 00081108 00000400 000000c2
> > > [   16.338886] dfc0: 00022698 b686ac78 000005e8 00000003 0000004b
> > > be8c7af4 00000000 00000000
> > > [   16.347053] dfe0: 0004d1b2 be8c7a84 b686b94c b686ac98 000e0010
> > > 00000009 00000000 00000000
> > > [   16.355237] [<c02c4900>] (show_map_vma.constprop.3) from
> > > [<c02c4efc>] (show_pid_map+0x10/0x34)  
> > > [   16.363846] [<c02c4efc>] (show_pid_map) from [<c0289908>]
> > > (seq_read+0x39c/0x4f4)
> > > [   16.371264] [<c0289908>] (seq_read) from [<c0263b20>]
> > > (__vfs_read+0x2c/0x15c)
> > > [   16.378401] [<c0263b20>] (__vfs_read) from [<c0263cdc>]
> > > (vfs_read+0x8c/0x110)
> > > [   16.385546] [<c0263cdc>] (vfs_read) from [<c02641c0>]
> > > (ksys_read+0x4c/0xac)
> > > [   16.392519] [<c02641c0>] (ksys_read) from [<c0101000>]
> > > (ret_fast_syscall+0x0/0x54)
> > > [   16.400083] Exception stack(0xec02dfa8 to 0xec02dff0)
> > > [   16.405135] dfa0:                   00022698 b686ac78 00000009
> > > 00081108 00000400 000000c2
> > > [   16.413311] dfc0: 00022698 b686ac78 000005e8 00000003 0000004b
> > > be8c7af4 00000000 00000000
> > > [   16.421485] dfe0: 0004d1b2 be8c7a84 b686b94c b686ac98
> > > [   16.426542] Code: e1cd80f0 e5947020 ebfffb4f e5943048 (e593302c)
> > > [   16.432734] ---[ end trace 5dbf91c64da6bd91 ]---
> > > 
> > > Reverting this makes it behave as expected again. Anybody knows
> > > what is
> > > going on?
> > 
> > Could you check if this fixup helps?
> > 
> > diff --git a/arch/arm/kernel/process.c b/arch/arm/kernel/process.c
> > index 225d1c58d2de..553262999564 100644
> > --- a/arch/arm/kernel/process.c
> > +++ b/arch/arm/kernel/process.c
> > @@ -334,6 +334,7 @@ static struct vm_area_struct gate_vma = {
> >  	.vm_start	= 0xffff0000,
> >  	.vm_end		= 0xffff0000 + PAGE_SIZE,
> >  	.vm_flags	= VM_READ | VM_EXEC | VM_MAYREAD |
> > VM_MAYEXEC,
> > +	.vm_ops		= &dummy_vm_ops,
> >  };
> >  
> >  static int __init gate_vma_init(void)
> 
> Yep, that cuts it. Thanks!
> 
> I assume you will send a proper patch and/or do the needful?

Andrew, could you fold it into 1/2?

-- 
 Kirill A. Shutemov