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    SubjectRe: [PATCH RESEND 2/4] cpuset: simplify cpuset_node_allowed API
    On Mon, Oct 20, 2014 at 03:50:30PM +0400, Vladimir Davydov wrote:
    > Current cpuset API for checking if a zone/node is allowed to allocate
    > from looks rather awkward. We have hardwall and softwall versions of
    > cpuset_node_allowed with the softwall version doing literally the same
    > as the hardwall version if __GFP_HARDWALL is passed to it in gfp flags.
    > If it isn't, the softwall version may check the given node against the
    > enclosing hardwall cpuset, which it needs to take the callback lock to
    > do.
    >
    > Such a distinction was introduced by commit 02a0e53d8227 ("cpuset:
    > rework cpuset_zone_allowed api"). Before, we had the only version with
    > the __GFP_HARDWALL flag determining its behavior. The purpose of the
    > commit was to avoid sleep-in-atomic bugs when someone would mistakenly
    > call the function without the __GFP_HARDWALL flag for an atomic
    > allocation. The suffixes introduced were intended to make the callers
    > think before using the function.
    >
    > However, since the callback lock was converted from mutex to spinlock by
    > the previous patch, the softwall check function cannot sleep, and these
    > precautions are no longer necessary.
    >
    > So let's simplify the API back to the single check.
    >
    > Suggested-by: David Rientjes <rientjes@google.com>
    > Signed-off-by: Vladimir Davydov <vdavydov@parallels.com>
    > Acked-by: Christoph Lameter <cl@linux.com>
    > Acked-by: Zefan Li <lizefan@huawei.com>

    Applied 1-2 to cgroup/for-3.19-cpuset-api-simplification which
    contains only these two patches on top of v3.18-rc2 and will stay
    stable. sl[au]b trees can pull it in or I can take the other two
    patches too. Please let me know how the other two should be routed.

    Thanks.

    --
    tejun


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