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    Subject[PATCH 27/45] mm: add kernel_mbind() helper; remove in-kernel call to syscall
    Date
    Using the mm-internal kernel_mbind() helper allows us to get rid of the
    mm-internal call to the sys_mbind() syscall.

    This patch is part of a series which tries to remove in-kernel calls to
    syscalls. On this basis, the syscall entry path can be streamlined.

    Cc: Al Viro <viro@zeniv.linux.org.uk>
    Cc: linux-mm@kvack.org
    Cc: Andrew Morton <akpm@linux-foundation.org>
    Signed-off-by: Dominik Brodowski <linux@dominikbrodowski.net>
    ---
    mm/mempolicy.c | 15 +++++++++++----
    1 file changed, 11 insertions(+), 4 deletions(-)

    diff --git a/mm/mempolicy.c b/mm/mempolicy.c
    index 7399ede02b5f..e4d7d4c0b253 100644
    --- a/mm/mempolicy.c
    +++ b/mm/mempolicy.c
    @@ -1336,9 +1336,9 @@ static int copy_nodes_to_user(unsigned long __user *mask, unsigned long maxnode,
    return copy_to_user(mask, nodes_addr(*nodes), copy) ? -EFAULT : 0;
    }

    -SYSCALL_DEFINE6(mbind, unsigned long, start, unsigned long, len,
    - unsigned long, mode, const unsigned long __user *, nmask,
    - unsigned long, maxnode, unsigned, flags)
    +static long kernel_mbind(unsigned long start, unsigned long len,
    + unsigned long mode, const unsigned long __user *nmask,
    + unsigned long maxnode, unsigned int flags)
    {
    nodemask_t nodes;
    int err;
    @@ -1357,6 +1357,13 @@ SYSCALL_DEFINE6(mbind, unsigned long, start, unsigned long, len,
    return do_mbind(start, len, mode, mode_flags, &nodes, flags);
    }

    +SYSCALL_DEFINE6(mbind, unsigned long, start, unsigned long, len,
    + unsigned long, mode, const unsigned long __user *, nmask,
    + unsigned long, maxnode, unsigned int, flags)
    +{
    + return kernel_mbind(start, len, mode, nmask, maxnode, flags);
    +}
    +
    /* Set the process memory policy */
    SYSCALL_DEFINE3(set_mempolicy, int, mode, const unsigned long __user *, nmask,
    unsigned long, maxnode)
    @@ -1575,7 +1582,7 @@ COMPAT_SYSCALL_DEFINE6(mbind, compat_ulong_t, start, compat_ulong_t, len,
    return -EFAULT;
    }

    - return sys_mbind(start, len, mode, nm, nr_bits+1, flags);
    + return kernel_mbind(start, len, mode, nm, nr_bits+1, flags);
    }

    COMPAT_SYSCALL_DEFINE4(migrate_pages, compat_pid_t, pid,
    --
    2.16.2
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