mm: Serialize access to min_free_kbytes
mm: Serialize access to min_free_kbytes

There is a race between the min_free_kbytes sysctl, memory hotplug
and transparent hugepage support enablement.  Memory hotplug uses a
zonelists_mutex to avoid a race when building zonelists. Reuse it to
serialise watermark updates.

[a.p.zijlstra@chello.nl: Older patch fixed the race with spinlock]
Signed-off-by: Mel Gorman <39ea6a09710987173e32e37c86918024a0f441c1@suse.de>
Signed-off-by: Marek Szyprowski <2a0259761cc3e88db42be5300c1579a67c77e65e@samsung.com>
Reviewed-by: KAMEZAWA Hiroyuki <634f508bd7c47cf0ee4126243675c3e598920fbc@jp.fujitsu.com>
Tested-by: Barry Song <a856445693a373abed3e477bd705f7011cbd8a1d@csr.com>

KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas