From: Dan Williams <dan.j.williams-ral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
To: "Kirill A. Shutemov" <kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org>
Cc: Jan Kara <jack-AlSwsSmVLrQ@public.gmane.org>,
Arnd Bergmann <arnd-r2nGTMty4D4@public.gmane.org>,
"linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org"
<linux-nvdimm-hn68Rpc1hR1g9hUCZPvPmw@public.gmane.org>,
Linux API <linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
"linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org"
<linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
linux-xfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
Linux MM <linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org>,
Andy Lutomirski <luto-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
linux-fsdevel
<linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org>,
Andrew Morton
<akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>
Subject: Re: [PATCH v5 3/5] mm: introduce mmap3 for safely defining new mmap flags
Date: Wed, 16 Aug 2017 09:52:16 -0700 [thread overview]
Message-ID: <CAPcyv4hGP19iaqvMTUDm6Gu5Tiacm1LFDV7qE-KFnR7pmYK-wg@mail.gmail.com> (raw)
In-Reply-To: <20170816164717.xjbtbdjtwnhvzukg-sVvlyX1904swdBt8bTSxpkEMvNT87kid@public.gmane.org>
On Wed, Aug 16, 2017 at 9:47 AM, Kirill A. Shutemov
<kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org> wrote:
> On Wed, Aug 16, 2017 at 09:35:11AM -0700, Dan Williams wrote:
>> On Wed, Aug 16, 2017 at 4:15 AM, Kirill A. Shutemov
>> <kirill-oKw7cIdHH8eLwutG50LtGA@public.gmane.org> wrote:
>> > On Wed, Aug 16, 2017 at 12:44:22AM -0700, Dan Williams wrote:
>> >> diff --git a/include/linux/mman.h b/include/linux/mman.h
>> >> index c8367041fafd..0e1de42c836f 100644
>> >> --- a/include/linux/mman.h
>> >> +++ b/include/linux/mman.h
>> >> @@ -7,6 +7,40 @@
>> >> #include <linux/atomic.h>
>> >> #include <uapi/linux/mman.h>
>> >>
>> >> +#ifndef MAP_32BIT
>> >> +#define MAP_32BIT 0
>> >> +#endif
>> >> +#ifndef MAP_HUGE_2MB
>> >> +#define MAP_HUGE_2MB 0
>> >> +#endif
>> >> +#ifndef MAP_HUGE_1GB
>> >> +#define MAP_HUGE_1GB 0
>> >> +#endif
>> >> +
>> >> +/*
>> >> + * The historical set of flags that all mmap implementations implicitly
>> >> + * support when file_operations.mmap_supported_mask is zero.
>> >> + */
>> >> +#define LEGACY_MAP_SUPPORTED_MASK (MAP_SHARED \
>> >> + | MAP_PRIVATE \
>> >> + | MAP_FIXED \
>> >> + | MAP_ANONYMOUS \
>> >> + | MAP_UNINITIALIZED \
>> >> + | MAP_GROWSDOWN \
>> >> + | MAP_DENYWRITE \
>> >> + | MAP_EXECUTABLE \
>> >> + | MAP_LOCKED \
>> >> + | MAP_NORESERVE \
>> >> + | MAP_POPULATE \
>> >> + | MAP_NONBLOCK \
>> >> + | MAP_STACK \
>> >> + | MAP_HUGETLB \
>> >> + | MAP_32BIT \
>> >> + | MAP_HUGE_2MB \
>> >> + | MAP_HUGE_1GB)
>> >> +
>> >> +#define MAP_SUPPORTED_MASK (LEGACY_MAP_SUPPORTED_MASK)
>> >> +
>> >> extern int sysctl_overcommit_memory;
>> >> extern int sysctl_overcommit_ratio;
>> >> extern unsigned long sysctl_overcommit_kbytes;
>> >
>> > Since we looking into mmap(2) ABI, maybe we should consider re-defining
>> > MAP_DENYWRITE and MAP_EXECUTABLE as 0 in hope that we would be able to
>> > re-use these bits in the future? These flags are ignored now anyway.
>>
>> Yes, we can make these -EOPNOTSUPP in the new syscall.
>
> You cannot detect them, if we would redefine them as 0. :)
Yes, we can, there will now be missing bits in
LEGACY_MAP_SUPPORTED_MASK that will fail those bit values until we
re-define them. Everything else is a an exercise for libc about what
it wants to do when it sees those values.
next prev parent reply other threads:[~2017-08-16 16:52 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-16 7:44 [PATCH v5 0/5] MAP_DIRECT and block-map-atomic files Dan Williams
[not found] ` <150286944610.8837.9513410258028246174.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-08-16 7:44 ` [PATCH v5 1/5] vfs: add flags parameter to ->mmap() in 'struct file_operations' Dan Williams
2017-08-16 7:44 ` [PATCH v5 4/5] fs, xfs: introduce MAP_DIRECT for creating block-map-atomic file ranges Dan Williams
[not found] ` <150286946864.8837.17147962029964281564.stgit-p8uTFz9XbKj2zm6wflaqv1nYeNYlB/vhral2JQCrhuEAvxtiuMwx3w@public.gmane.org>
2017-08-16 11:12 ` Kirill A. Shutemov
2017-08-16 16:29 ` Dan Williams
2017-08-16 16:32 ` Dan Williams
2017-08-16 17:28 ` Dan Williams
2017-08-16 7:44 ` [PATCH v5 2/5] fs, xfs: introduce S_IOMAP_SEALED Dan Williams
2017-08-16 7:44 ` [PATCH v5 3/5] mm: introduce mmap3 for safely defining new mmap flags Dan Williams
2017-08-16 11:15 ` Kirill A. Shutemov
2017-08-16 16:35 ` Dan Williams
[not found] ` <CAPcyv4gB1JycB_1k6mKe-_OwjZv1a7vPV6Hh393-U_HQ15RWEw-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2017-08-16 16:47 ` Kirill A. Shutemov
[not found] ` <20170816164717.xjbtbdjtwnhvzukg-sVvlyX1904swdBt8bTSxpkEMvNT87kid@public.gmane.org>
2017-08-16 16:52 ` Dan Williams [this message]
2017-08-16 7:44 ` [PATCH v5 5/5] fs, fcntl: add F_MAP_DIRECT Dan Williams
2017-08-16 23:42 ` [PATCH v5 0/5] MAP_DIRECT and block-map-atomic files Dan Williams
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