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Re: [PATCH] dax, pmem: add support for msync

From "Kirill A. Shutemov" <kirill@shutemov.name>
Newsgroups linux.kernel
Subject Re: [PATCH] dax, pmem: add support for msync
Date 2015-09-02 11:50 +0200
Message-ID <q4cQ2-1iy-9@gated-at.bofh.it> (permalink)
References (2 earlier) <q3QFT-3qt-83@gated-at.bofh.it> <q42xl-3mq-51@gated-at.bofh.it> <q4cn1-KF-23@gated-at.bofh.it> <q4cGo-17b-55@gated-at.bofh.it> <q4cQ1-1iy-1@gated-at.bofh.it>
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On Wed, Sep 02, 2015 at 12:41:44PM +0300, Boaz Harrosh wrote:
> On 09/02/2015 12:37 PM, Boaz Harrosh wrote:
> >>  
> >> +               /*
> >> +                * Make sure that for VM_MIXEDMAP VMA has both
> >> +                * vm_ops->page_mkwrite and vm_ops->pfn_mkwrite or has none.
> >> +                */
> >> +               if ((vma->vm_ops->page_mkwrite || vma->vm_ops->pfn_mkwrite) &&
> >> +                               vma->vm_flags & VM_MIXEDMAP) {
> >> +                       VM_BUG_ON_VMA(!vma->vm_ops->page_mkwrite, vma);
> >> +                       VM_BUG_ON_VMA(!vma->vm_ops->pfn_mkwrite, vma);
> > 
> > BTW: the page_mkwrite is used for reading of holes that put zero-pages at the radix tree.
> >      One can just map a single global zero-page in pfn-mode for that.
> > 
> > Kirill Hi. Please don't make these BUG_ONs its counter productive believe me.

This is VM_BUG_ON, not normal BUG_ON. VM_BUG_ON is under CONFIG_DEBUG_VM 
which is disabled on production kernels.

> > Please make them WARN_ON_ONCE() it is not a crashing bug to work like this.
> > (Actually it is not a bug at all in some cases, but we can relax that when a user
> >  comes up)
> > 
> > Thanks
> > Boaz
> > 
> 
> Second thought I do not like this patch. This is why we have xftests for, the fact of it
> is that test 080 catches this. For me this is enough.

I don't insist on applying the patch. And I worry about false-positives.

> An FS developer should test his code, and worst case we help him on ML, like we did
> in this case.
> 
> Thanks
> Boaz
> 
> >> +               }
> >>                 addr = vma->vm_start;
> >>                 vm_flags = vma->vm_flags;
> >>         } else if (vm_flags & VM_SHARED) {
> >>
> > 
> 

-- 
 Kirill A. Shutemov
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Thread

[PATCH] dax, pmem: add support for msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-08-31 21:10 +0200
  Re: [PATCH] dax, pmem: add support for msync Christoph Hellwig <hch@lst.de> - 2015-08-31 21:10 +0200
    Re: [PATCH] dax, pmem: add support for msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-08-31 21:30 +0200
      Re: [PATCH] dax, pmem: add support for msync Christoph Hellwig <hch@lst.de> - 2015-08-31 21:40 +0200
  Re: [PATCH] dax, pmem: add support for msync Dave Chinner <david@fromorbit.com> - 2015-09-01 01:40 +0200
    Re: [PATCH] dax, pmem: add support for msync Christoph Hellwig <hch@lst.de> - 2015-09-01 09:10 +0200
      Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-01 14:20 +0200
        Re: [PATCH] dax, pmem: add support for msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-09-02 21:10 +0200
          Re: [PATCH] dax, pmem: add support for msync "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-02 22:20 +0200
          Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-03 08:40 +0200
            Re: [PATCH] dax, pmem: add support for msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-09-03 18:50 +0200
      Re: [PATCH] dax, pmem: add support for msync Dave Chinner <david@fromorbit.com> - 2015-09-02 00:30 +0200
        Re: [PATCH] dax, pmem: add support for msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-09-02 05:20 +0200
          Re: [PATCH] dax, pmem: add support for msync Dave Chinner <david@fromorbit.com> - 2015-09-02 07:20 +0200
            Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-02 12:30 +0200
              Re: [PATCH] dax, pmem: add support for msync Dave Hansen <dave.hansen@linux.intel.com> - 2015-09-02 16:30 +0200
                Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-02 17:20 +0200
                Re: [PATCH] dax, pmem: add support for msync Dave Hansen <dave.hansen@linux.intel.com> - 2015-09-02 17:50 +0200
                Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-02 18:10 +0200
                Re: [PATCH] dax, pmem: add support for msync Dave Hansen <dave.hansen@linux.intel.com> - 2015-09-02 18:20 +0200
                Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-03 08:50 +0200
          Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-02 12:10 +0200
    Re: [PATCH] dax, pmem: add support for msync "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-01 12:10 +0200
      Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-01 13:30 +0200
      Re: [PATCH] dax, pmem: add support for msync Dave Chinner <david@fromorbit.com> - 2015-09-02 00:50 +0200
        Re: [PATCH] dax, pmem: add support for msync "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-02 11:20 +0200
          Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-02 11:40 +0200
            Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-02 11:50 +0200
              Re: [PATCH] dax, pmem: add support for msync "Kirill A. Shutemov" <kirill@shutemov.name> - 2015-09-02 11:50 +0200
                Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-02 12:30 +0200
          Re: [PATCH] dax, pmem: add support for msync Dave Chinner <david@fromorbit.com> - 2015-09-03 03:00 +0200
  Re: [PATCH] dax, pmem: add support for msync Boaz Harrosh <boaz@plexistor.com> - 2015-09-01 15:20 +0200
    Re: [PATCH] dax, pmem: add support for msync Ross Zwisler <ross.zwisler@linux.intel.com> - 2015-09-02 19:50 +0200

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