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Re: [PATCH v6 1/5] vfs: add flags parameter to ->mmap() in 'struct file_operations'

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On Thu, Aug 24, 2017 at 9:58 AM, Christoph Hellwig <hch@infradead.org> wrote:
> On Wed, Aug 23, 2017 at 04:48:40PM -0700, Dan Williams wrote:
>> We are running running short of vma->vm_flags. We can avoid needing a
>> new VM_* flag in some cases if the original @flags submitted to mmap(2)
>> is made available to the ->mmap() 'struct file_operations'
>> implementation. For example, the proposed addition of MAP_DIRECT can be
>> implemented without taking up a new vm_flags bit. Another motivation to
>> avoid vm_flags is that they appear in /proc/$pid/smaps, and we have seen
>> software that tries to dangerously (TOCTOU) read smaps to infer the
>> behavior of a virtual address range.
>>
>> This conversion was performed by the following semantic patch. There
>> were a few manual edits for oddities like proc_reg_mmap.
>>
>> Thanks to Julia for helping me with coccinelle iteration to cover cases
>> where the mmap routine is defined in a separate file from the 'struct
>> file_operations' instance that consumes it.
>
> How are we going to check that an instance actually supports any
> of those flags?

In patch 3 I validate the flags by introducing an
"mmap_supported_mask" field to 'struct file_operations'. It will be
zero by default for almost all implementations and zero means "support
the legacy mmap flags".

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[PATCH v6 0/5] MAP_DIRECT and block-map-atomic files Dan Williams <dan.j.williams@intel.com> - 2017-08-24 02:00 +0200
  [PATCH v6 4/5] fs,  xfs: introduce MAP_DIRECT for creating block-map-atomic file ranges Dan Williams <dan.j.williams@intel.com> - 2017-08-24 02:00 +0200
    Re: [PATCH v6 4/5] fs, xfs: introduce MAP_DIRECT for creating         block-map-atomic file ranges Christoph Hellwig <hch@lst.de> - 2017-08-24 18:20 +0200
      Re: [PATCH v6 4/5] fs, xfs: introduce MAP_DIRECT for creating         block-map-atomic file ranges Christoph Hellwig <hch@lst.de> - 2017-08-24 18:40 +0200
        Re: [PATCH v6 4/5] fs, xfs: introduce MAP_DIRECT for creating  block-map-atomic file ranges Dan Williams <dan.j.williams@intel.com> - 2017-08-24 22:30 +0200
      Re: [PATCH v6 4/5] fs, xfs: introduce MAP_DIRECT for creating  block-map-atomic file ranges Dan Williams <dan.j.williams@intel.com> - 2017-08-24 18:40 +0200
  [PATCH v6 5/5] fs, fcntl: add F_MAP_DIRECT Dan Williams <dan.j.williams@intel.com> - 2017-08-24 02:00 +0200
  [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap  flags Dan Williams <dan.j.williams@intel.com> - 2017-08-24 02:00 +0200
    Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap  flags Jan Kara <jack@suse.cz> - 2017-08-24 15:10 +0200
    Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap  flags Christoph Hellwig <hch@infradead.org> - 2017-08-24 19:00 +0200
      Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags Dan Williams <dan.j.williams@intel.com> - 2017-08-24 19:40 +0200
  [PATCH v6 2/5] fs, xfs: introduce S_IOMAP_SEALED Dan Williams <dan.j.williams@intel.com> - 2017-08-24 02:00 +0200
    Re: [PATCH v6 2/5] fs, xfs: introduce S_IOMAP_SEALED Christoph Hellwig <hch@lst.de> - 2017-08-24 18:20 +0200
      Re: [PATCH v6 2/5] fs, xfs: introduce S_IOMAP_SEALED Dan Williams <dan.j.williams@intel.com> - 2017-08-25 08:10 +0200
  Re: [PATCH v6 0/5] MAP_DIRECT and block-map-atomic files Christoph Hellwig <hch@lst.de> - 2017-08-24 18:10 +0200
    Re: [PATCH v6 0/5] MAP_DIRECT and block-map-atomic files Dan Williams <dan.j.williams@intel.com> - 2017-08-24 18:30 +0200
  Re: [PATCH v6 1/5] vfs: add flags parameter to ->mmap() in 'struct  file_operations' Christoph Hellwig <hch@infradead.org> - 2017-08-24 19:00 +0200
    Re: [PATCH v6 1/5] vfs: add flags parameter to ->mmap() in 'struct file_operations' Dan Williams <dan.j.williams@intel.com> - 2017-08-24 19:50 +0200

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