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-rw-r--r--mm/page_cgroup.c34
1 files changed, 32 insertions, 2 deletions
diff --git a/mm/page_cgroup.c b/mm/page_cgroup.c
index 3d535d594826..3dd88539a0e6 100644
--- a/mm/page_cgroup.c
+++ b/mm/page_cgroup.c
@@ -335,6 +335,37 @@ not_enough_page:
}
/**
+ * swap_cgroup_cmpxchg - cmpxchg mem_cgroup's id for this swp_entry.
+ * @end: swap entry to be cmpxchged
+ * @old: old id
+ * @new: new id
+ *
+ * Returns old id at success, 0 at failure.
+ * (There is no mem_cgroup useing 0 as its id)
+ */
+unsigned short swap_cgroup_cmpxchg(swp_entry_t ent,
+ unsigned short old, unsigned short new)
+{
+ int type = swp_type(ent);
+ unsigned long offset = swp_offset(ent);
+ unsigned long idx = offset / SC_PER_PAGE;
+ unsigned long pos = offset & SC_POS_MASK;
+ struct swap_cgroup_ctrl *ctrl;
+ struct page *mappage;
+ struct swap_cgroup *sc;
+
+ ctrl = &swap_cgroup_ctrl[type];
+
+ mappage = ctrl->map[idx];
+ sc = page_address(mappage);
+ sc += pos;
+ if (cmpxchg(&sc->id, old, new) == old)
+ return old;
+ else
+ return 0;
+}
+
+/**
* swap_cgroup_record - record mem_cgroup for this swp_entry.
* @ent: swap entry to be recorded into
* @mem: mem_cgroup to be recorded
@@ -358,8 +389,7 @@ unsigned short swap_cgroup_record(swp_entry_t ent, unsigned short id)
mappage = ctrl->map[idx];
sc = page_address(mappage);
sc += pos;
- old = sc->id;
- sc->id = id;
+ old = xchg(&sc->id, id);
return old;
}