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    SubjectRe: [PATCH 01/18] mm: Make mmap_sem for write waits killable for mm syscalls
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    On 02/29/2016 02:26 PM, Michal Hocko wrote:
    > From: Michal Hocko <mhocko@suse.com>
    >
    > This is the first step in making mmap_sem write holders killable. It

    s/holders/waiters/?

    > focuses on the trivial ones which are taking the lock early after
    > entering the syscall and they are not changing state before.
    >
    > Therefore it is very easy to change them to use down_write_killable
    > and immediately return with -EINTR. This will allow the waiter to
    > pass away without blocking the mmap_sem which might be required to
    > make a forward progress. E.g. the oom reaper will need the lock for
    > reading to dismantle the OOM victim address space.
    >
    > The only tricky function in this patch is vm_mmap_pgoff which has many
    > call sites via vm_mmap. To reduce the risk keep vm_mmap with the
    > original non-killable semantic for now.
    >
    > vm_munmap callers do not bother checking the return value so open code
    > it into the munmap syscall path for now for simplicity.
    >
    > Cc: Mel Gorman <mgorman@suse.de>
    > Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
    > Cc: Konstantin Khlebnikov <koct9i@gmail.com>
    > Cc: Hugh Dickins <hughd@google.com>
    > Cc: Andrea Arcangeli <aarcange@redhat.com>
    > Cc: David Rientjes <rientjes@google.com>
    > Cc: Dave Hansen <dave.hansen@linux.intel.com>
    > Cc: Johannes Weiner <hannes@cmpxchg.org>
    > Signed-off-by: Michal Hocko <mhocko@suse.com>

    Acked-by: Vlastimil Babka <vbabka@suse.cz>


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