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Groups > linux.kernel > #1720041
| From | Christoph Hellwig <hch@infradead.org> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags |
| Date | 2017-08-25 15:10 +0200 |
| Message-ID | <uimx3-4tc-7@gated-at.bofh.it> (permalink) |
| References | <uhNIZ-78j-1@gated-at.bofh.it> <uhNJ0-78j-21@gated-at.bofh.it> <ui3E6-Db-23@gated-at.bofh.it> <ui4gP-17m-33@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
On Thu, Aug 24, 2017 at 10:36:02AM -0700, Dan Williams wrote:
> I'll let Andy and Kirill restate their concerns, but one of the
> arguments that swayed me is that any new mmap flag with this hack must
> be documented to only work with MAP_SHARED and that MAP_PRIVATE is
> silently ignored. I agree with the mess and delays it causes for other
> archs and libc, but at the same time this is for new applications and
> libraries that know to look for the new flag, so they need to do the
> extra work to check for the new syscall.
True. That is for the original hack, but I spent some more time
looking at the mmap code, and there is one thing I noticed:
include/uapi/asm-generic/mman-common.h:
#define MAP_SHARED 0x01 /* Share changes */
#define MAP_PRIVATE 0x02 /* Changes are private */
#define MAP_TYPE 0x0f /* Mask for type of mapping */
mm/mmap.c:
if (file) {
struct inode *inode = file_inode(file);
switch (flags & MAP_TYPE) {
case MAP_SHARED:
...
case MAP_PRIVATE:
...
default:
return -EINVAL;
}
and very similar for the anonymous and nommu cases.
So if we pick e.g. 0x4 as the valid bit we don't even need to overload
the MAP_SHARED and MAP_PRIVATE meaning.
>
> However, if the fcntl lease approach works for the DMA cases then we
> only have the one mmap flag to add for now, so maybe the weird
> MAP_{SHARED|PRIVATE} semantics are tolerable.
---end quoted text---
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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
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags Christoph Hellwig <hch@infradead.org> - 2017-08-25 15:10 +0200
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-08-25 18:00 +0200
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags Christoph Hellwig <hch@infradead.org> - 2017-08-25 18:10 +0200
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-08-25 18:20 +0200
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags Helge Deller <deller@gmx.de> - 2017-08-25 18:30 +0200
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com> - 2017-08-25 19:00 +0200
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags Dan Williams <dan.j.williams@intel.com> - 2017-08-25 22:30 +0200
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags Helge Deller <deller@gmx.de> - 2017-08-26 09:50 +0200
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags Dan Williams <dan.j.williams@intel.com> - 2017-08-26 17:20 +0200
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags Helge Deller <deller@gmx.de> - 2017-08-26 22:00 +0200
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags Dan Williams <dan.j.williams@intel.com> - 2017-08-27 00:50 +0200
Re: [PATCH v6 3/5] mm: introduce mmap3 for safely defining new mmap flags "Kirill A. Shutemov" <kirill@shutemov.name> - 2017-08-27 02:00 +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 2/5] fs, xfs: introduce S_IOMAP_SEALED Dan Williams <dan.j.williams@intel.com> - 2017-08-25 21:50 +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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