mm: introduce common struct mm_slot

Patch series "add common struct mm_slot and use it in THP and KSM", v2.

At present, both THP and KSM module have similar structures mm_slot for
organizing and recording the information required for scanning mm, and
each defines the following exactly the same operation functions:

 - alloc_mm_slot
 - free_mm_slot
 - get_mm_slot
 - insert_to_mm_slots_hash

In order to de-duplicate these codes, this patchset introduces a common
struct mm_slot, and lets THP and KSM to use it.

This patch (of 7):

At present, both THP and KSM module have similar structures mm_slot for
organizing and recording the information required for scanning mm, and
each defines the following exactly the same operation functions:

 - alloc_mm_slot
 - free_mm_slot
 - get_mm_slot
 - insert_to_mm_slots_hash

In order to de-duplicate these codes, this patch introduces a common
struct mm_slot, and subsequent patches will let THP and KSM to use it.

Link: https://lkml.kernel.org/r/20220831031951.43152-1-zhengqi.arch@bytedance.com
Link: https://lkml.kernel.org/r/20220831031951.43152-2-zhengqi.arch@bytedance.com
Signed-off-by: Qi Zheng <zhengqi.arch@bytedance.com>
Cc: Johannes Weiner <hannes@cmpxchg.org>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Mike Rapoport <rppt@kernel.org>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Yang Shi <shy828301@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/mm_slot.h b/mm/mm_slot.h
new file mode 100644 (file)
index 0000000..83f18ed
--- /dev/null
+++ b/mm/mm_slot.h
@@ -0,0 +1,55 @@
+// SPDX-License-Identifier: GPL-2.0
+
+#ifndef _LINUX_MM_SLOT_H
+#define _LINUX_MM_SLOT_H
+
+#include <linux/hashtable.h>
+#include <linux/slab.h>
+
+/*
+ * struct mm_slot - hash lookup from mm to mm_slot
+ * @hash: link to the mm_slots hash list
+ * @mm_node: link into the mm_slots list
+ * @mm: the mm that this information is valid for
+ */
+struct mm_slot {
+       struct hlist_node hash;
+       struct list_head mm_node;
+       struct mm_struct *mm;
+};
+
+#define mm_slot_entry(ptr, type, member) \
+       container_of(ptr, type, member)
+
+static inline void *mm_slot_alloc(struct kmem_cache *cache)
+{
+       if (!cache)     /* initialization failed */
+               return NULL;
+       return kmem_cache_zalloc(cache, GFP_KERNEL);
+}
+
+static inline void mm_slot_free(struct kmem_cache *cache, void *objp)
+{
+       kmem_cache_free(cache, objp);
+}
+
+#define mm_slot_lookup(_hashtable, _mm)                                       \
+({                                                                            \
+       struct mm_slot *tmp_slot, *mm_slot = NULL;                             \
+                                                                              \
+       hash_for_each_possible(_hashtable, tmp_slot, hash, (unsigned long)_mm) \
+               if (_mm == tmp_slot->mm) {                                     \
+                       mm_slot = tmp_slot;                                    \
+                       break;                                                 \
+               }                                                              \
+                                                                              \
+       mm_slot;                                                               \
+})
+
+#define mm_slot_insert(_hashtable, _mm, _mm_slot)                             \
+({                                                                            \
+       _mm_slot->mm = _mm;                                                    \
+       hash_add(_hashtable, &_mm_slot->hash, (unsigned long)_mm);             \
+})
+
+#endif /* _LINUX_MM_SLOT_H */