From 312fcae227037619dc858c9ccd362c7b847730a2 Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan@kernel.org>
Date: Wed, 15 Apr 2015 16:15:30 -0700
Subject: [PATCH] zsmalloc: support compaction

This patch provides core functions for migration of zsmalloc.  Migraion
policy is simple as follows.

for each size class {
        while {
                src_page = get zs_page from ZS_ALMOST_EMPTY
                if (!src_page)
                        break;
                dst_page = get zs_page from ZS_ALMOST_FULL
                if (!dst_page)
                        dst_page = get zs_page from ZS_ALMOST_EMPTY
                if (!dst_page)
                        break;
                migrate(from src_page, to dst_page);
        }
}

For migration, we need to identify which objects in zspage are allocated
to migrate them out.  We could know it by iterating of freed objects in a
zspage because first_page of zspage keeps free objects singly-linked list
but it's not efficient.  Instead, this patch adds a tag(ie,
OBJ_ALLOCATED_TAG) in header of each object(ie, handle) so we could check
whether the object is allocated easily.

This patch adds another status bit in handle to synchronize between user
access through zs_map_object and migration.  During migration, we cannot
move objects user are using due to data coherency between old object and
new object.

[akpm@linux-foundation.org: zsmalloc.c needs sched.h for cond_resched()]
Signed-off-by: Minchan Kim <minchan@kernel.org>
Cc: Juneho Choi <juno.choi@lge.com>
Cc: Gunho Lee <gunho.lee@lge.com>
Cc: Luigi Semenzato <semenzato@google.com>
Cc: Dan Streetman <ddstreet@ieee.org>
Cc: Seth Jennings <sjennings@variantweb.net>
Cc: Nitin Gupta <ngupta@vflare.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Mel Gorman <mel@csn.ul.ie>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
---
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