* [PATCH v2 1/2] mm: z3fold: remove z3fold
2025-01-29 18:06 [PATCH v2 0/2] mm: zswap: remove z3fold and zbud Yosry Ahmed
@ 2025-01-29 18:06 ` Yosry Ahmed
2025-01-29 18:06 ` [PATCH v2 2/2] mm: zbud: remove zbud Yosry Ahmed
1 sibling, 0 replies; 6+ messages in thread
From: Yosry Ahmed @ 2025-01-29 18:06 UTC (permalink / raw)
To: Andrew Morton
Cc: Vitaly Wool, Seth Jennings, Dan Streetman, Miaohe Lin,
Johannes Weiner, Nhat Pham, Chengming Zhou, Huacai Chen,
WANG Xuerui, Heiko Carstens, Vasily Gorbik, Alexander Gordeev,
Christian Borntraeger, Sven Schnelle, Shakeel Butt,
Vlastimil Babka, linux-mm, linux-kernel, loongarch, linux-s390,
linux-doc
Z3fold has been marked as deprecated for 2 cycles and no one complained,
as expected. As there are no known users, remove the code now.
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Acked-by: Nhat Pham <nphamcs@gmail.com>
---
CREDITS | 1 +
Documentation/mm/index.rst | 1 -
Documentation/mm/z3fold.rst | 28 -
Documentation/translations/zh_CN/mm/index.rst | 1 -
.../translations/zh_CN/mm/z3fold.rst | 31 -
MAINTAINERS | 7 -
mm/Kconfig | 29 -
mm/Makefile | 1 -
mm/z3fold.c | 1447 -----------------
9 files changed, 1 insertion(+), 1545 deletions(-)
delete mode 100644 Documentation/mm/z3fold.rst
delete mode 100644 Documentation/translations/zh_CN/mm/z3fold.rst
delete mode 100644 mm/z3fold.c
diff --git a/CREDITS b/CREDITS
index 1f9f0f078b4ae..324428ad37e83 100644
--- a/CREDITS
+++ b/CREDITS
@@ -4313,6 +4313,7 @@ S: England
N: Vitaly Wool
E: vitaly.wool@konsulko.com
D: Maintenance and development of zswap
+D: Maintenance and development of z3fold
N: Chris Wright
E: chrisw@sous-sol.org
diff --git a/Documentation/mm/index.rst b/Documentation/mm/index.rst
index 0be1c7503a010..d3ada3e45e103 100644
--- a/Documentation/mm/index.rst
+++ b/Documentation/mm/index.rst
@@ -62,5 +62,4 @@ documentation, or deleted if it has served its purpose.
unevictable-lru
vmalloced-kernel-stacks
vmemmap_dedup
- z3fold
zsmalloc
diff --git a/Documentation/mm/z3fold.rst b/Documentation/mm/z3fold.rst
deleted file mode 100644
index 25b5935d06c7d..0000000000000
--- a/Documentation/mm/z3fold.rst
+++ /dev/null
@@ -1,28 +0,0 @@
-======
-z3fold
-======
-
-z3fold is a special purpose allocator for storing compressed pages.
-It is designed to store up to three compressed pages per physical page.
-It is a zbud derivative which allows for higher compression
-ratio keeping the simplicity and determinism of its predecessor.
-
-The main differences between z3fold and zbud are:
-
-* unlike zbud, z3fold allows for up to PAGE_SIZE allocations
-* z3fold can hold up to 3 compressed pages in its page
-* z3fold doesn't export any API itself and is thus intended to be used
- via the zpool API.
-
-To keep the determinism and simplicity, z3fold, just like zbud, always
-stores an integral number of compressed pages per page, but it can store
-up to 3 pages unlike zbud which can store at most 2. Therefore the
-compression ratio goes to around 2.7x while zbud's one is around 1.7x.
-
-Unlike zbud (but like zsmalloc for that matter) z3fold_alloc() does not
-return a dereferenceable pointer. Instead, it returns an unsigned long
-handle which encodes actual location of the allocated object.
-
-Keeping effective compression ratio close to zsmalloc's, z3fold doesn't
-depend on MMU enabled and provides more predictable reclaim behavior
-which makes it a better fit for small and response-critical systems.
diff --git a/Documentation/translations/zh_CN/mm/index.rst b/Documentation/translations/zh_CN/mm/index.rst
index c8726bce8f745..a71116be058fd 100644
--- a/Documentation/translations/zh_CN/mm/index.rst
+++ b/Documentation/translations/zh_CN/mm/index.rst
@@ -58,7 +58,6 @@ Linux内存管理文档
remap_file_pages
split_page_table_lock
vmalloced-kernel-stacks
- z3fold
zsmalloc
TODOLIST:
diff --git a/Documentation/translations/zh_CN/mm/z3fold.rst b/Documentation/translations/zh_CN/mm/z3fold.rst
deleted file mode 100644
index 9569a6d882700..0000000000000
--- a/Documentation/translations/zh_CN/mm/z3fold.rst
+++ /dev/null
@@ -1,31 +0,0 @@
-:Original: Documentation/mm/z3fold.rst
-
-:翻译:
-
- 司延腾 Yanteng Si <siyanteng@loongson.cn>
-
-:校译:
-
-
-======
-z3fold
-======
-
-z3fold是一个专门用于存储压缩页的分配器。它被设计为每个物理页最多可以存储三个压缩页。
-它是zbud的衍生物，允许更高的压缩率，保持其前辈的简单性和确定性。
-
-z3fold和zbud的主要区别是:
-
-* 与zbud不同的是，z3fold允许最大的PAGE_SIZE分配。
-* z3fold在其页面中最多可以容纳3个压缩页面
-* z3fold本身没有输出任何API，因此打算通过zpool的API来使用
-
-为了保持确定性和简单性，z3fold，就像zbud一样，总是在每页存储一个整数的压缩页，但是
-它最多可以存储3页，不像zbud最多可以存储2页。因此压缩率达到2.7倍左右，而zbud的压缩
-率是1.7倍左右。
-
-不像zbud（但也像zsmalloc），z3fold_alloc()那样不返回一个可重复引用的指针。相反，它
-返回一个无符号长句柄，它编码了被分配对象的实际位置。
-
-保持有效的压缩率接近于zsmalloc，z3fold不依赖于MMU的启用，并提供更可预测的回收行
-为，这使得它更适合于小型和反应迅速的系统。
diff --git a/MAINTAINERS b/MAINTAINERS
index feed152470f68..1583bb8eee587 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -26055,13 +26055,6 @@ S: Maintained
F: Documentation/input/devices/yealink.rst
F: drivers/input/misc/yealink.*
-Z3FOLD COMPRESSED PAGE ALLOCATOR
-M: Vitaly Wool <vitaly.wool@konsulko.com>
-R: Miaohe Lin <linmiaohe@huawei.com>
-L: linux-mm@kvack.org
-S: Maintained
-F: mm/z3fold.c
-
Z8530 DRIVER FOR AX.25
M: Joerg Reuter <jreuter@yaina.de>
L: linux-hams@vger.kernel.org
diff --git a/mm/Kconfig b/mm/Kconfig
index 1b501db064172..6fa19022c09b8 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -146,15 +146,6 @@ config ZSWAP_ZPOOL_DEFAULT_ZBUD
help
Use the zbud allocator as the default allocator.
-config ZSWAP_ZPOOL_DEFAULT_Z3FOLD_DEPRECATED
- bool "z3foldi (DEPRECATED)"
- select Z3FOLD_DEPRECATED
- help
- Use the z3fold allocator as the default allocator.
-
- Deprecated and scheduled for removal in a few cycles,
- see CONFIG_Z3FOLD_DEPRECATED.
-
config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
bool "zsmalloc"
select ZSMALLOC
@@ -166,7 +157,6 @@ config ZSWAP_ZPOOL_DEFAULT
string
depends on ZSWAP
default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
- default "z3fold" if ZSWAP_ZPOOL_DEFAULT_Z3FOLD_DEPRECATED
default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
default ""
@@ -180,25 +170,6 @@ config ZBUD
deterministic reclaim properties that make it preferable to a higher
density approach when reclaim will be used.
-config Z3FOLD_DEPRECATED
- tristate "3:1 compression allocator (z3fold) (DEPRECATED)"
- depends on ZSWAP
- help
- Deprecated and scheduled for removal in a few cycles. If you have
- a good reason for using Z3FOLD over ZSMALLOC, please contact
- linux-mm@kvack.org and the zswap maintainers.
-
- A special purpose allocator for storing compressed pages.
- It is designed to store up to three compressed pages per physical
- page. It is a ZBUD derivative so the simplicity and determinism are
- still there.
-
-config Z3FOLD
- tristate
- default y if Z3FOLD_DEPRECATED=y
- default m if Z3FOLD_DEPRECATED=m
- depends on Z3FOLD_DEPRECATED
-
config ZSMALLOC
tristate
prompt "N:1 compression allocator (zsmalloc)" if (ZSWAP || ZRAM)
diff --git a/mm/Makefile b/mm/Makefile
index 850386a67b3e0..e4c03da3c0846 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -115,7 +115,6 @@ obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
obj-$(CONFIG_ZPOOL) += zpool.o
obj-$(CONFIG_ZBUD) += zbud.o
obj-$(CONFIG_ZSMALLOC) += zsmalloc.o
-obj-$(CONFIG_Z3FOLD) += z3fold.o
obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
obj-$(CONFIG_CMA) += cma.o
obj-$(CONFIG_NUMA) += numa.o
diff --git a/mm/z3fold.c b/mm/z3fold.c
deleted file mode 100644
index 379d24b4fef99..0000000000000
--- a/mm/z3fold.c
+++ /dev/null
@@ -1,1447 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * z3fold.c
- *
- * Author: Vitaly Wool <vitaly.wool@konsulko.com>
- * Copyright (C) 2016, Sony Mobile Communications Inc.
- *
- * This implementation is based on zbud written by Seth Jennings.
- *
- * z3fold is an special purpose allocator for storing compressed pages. It
- * can store up to three compressed pages per page which improves the
- * compression ratio of zbud while retaining its main concepts (e. g. always
- * storing an integral number of objects per page) and simplicity.
- * It still has simple and deterministic reclaim properties that make it
- * preferable to a higher density approach (with no requirement on integral
- * number of object per page) when reclaim is used.
- *
- * As in zbud, pages are divided into "chunks". The size of the chunks is
- * fixed at compile time and is determined by NCHUNKS_ORDER below.
- *
- * z3fold doesn't export any API and is meant to be used via zpool API.
- */
-
-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-
-#include <linux/atomic.h>
-#include <linux/sched.h>
-#include <linux/cpumask.h>
-#include <linux/list.h>
-#include <linux/mm.h>
-#include <linux/module.h>
-#include <linux/page-flags.h>
-#include <linux/migrate.h>
-#include <linux/node.h>
-#include <linux/compaction.h>
-#include <linux/percpu.h>
-#include <linux/preempt.h>
-#include <linux/workqueue.h>
-#include <linux/slab.h>
-#include <linux/spinlock.h>
-#include <linux/zpool.h>
-#include <linux/kmemleak.h>
-
-/*
- * NCHUNKS_ORDER determines the internal allocation granularity, effectively
- * adjusting internal fragmentation. It also determines the number of
- * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
- * allocation granularity will be in chunks of size PAGE_SIZE/64. Some chunks
- * in the beginning of an allocated page are occupied by z3fold header, so
- * NCHUNKS will be calculated to 63 (or 62 in case CONFIG_DEBUG_SPINLOCK=y),
- * which shows the max number of free chunks in z3fold page, also there will
- * be 63, or 62, respectively, freelists per pool.
- */
-#define NCHUNKS_ORDER 6
-
-#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
-#define CHUNK_SIZE (1 << CHUNK_SHIFT)
-#define ZHDR_SIZE_ALIGNED round_up(sizeof(struct z3fold_header), CHUNK_SIZE)
-#define ZHDR_CHUNKS (ZHDR_SIZE_ALIGNED >> CHUNK_SHIFT)
-#define TOTAL_CHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
-#define NCHUNKS (TOTAL_CHUNKS - ZHDR_CHUNKS)
-
-#define BUDDY_MASK (0x3)
-#define BUDDY_SHIFT 2
-#define SLOTS_ALIGN (0x40)
-
-/*****************
- * Structures
-*****************/
-struct z3fold_pool;
-
-enum buddy {
- HEADLESS = 0,
- FIRST,
- MIDDLE,
- LAST,
- BUDDIES_MAX = LAST
-};
-
-struct z3fold_buddy_slots {
- /*
- * we are using BUDDY_MASK in handle_to_buddy etc. so there should
- * be enough slots to hold all possible variants
- */
- unsigned long slot[BUDDY_MASK + 1];
- unsigned long pool; /* back link */
- rwlock_t lock;
-};
-#define HANDLE_FLAG_MASK (0x03)
-
-/*
- * struct z3fold_header - z3fold page metadata occupying first chunks of each
- * z3fold page, except for HEADLESS pages
- * @buddy: links the z3fold page into the relevant list in the
- * pool
- * @page_lock: per-page lock
- * @refcount: reference count for the z3fold page
- * @work: work_struct for page layout optimization
- * @slots: pointer to the structure holding buddy slots
- * @pool: pointer to the containing pool
- * @cpu: CPU which this page "belongs" to
- * @first_chunks: the size of the first buddy in chunks, 0 if free
- * @middle_chunks: the size of the middle buddy in chunks, 0 if free
- * @last_chunks: the size of the last buddy in chunks, 0 if free
- * @first_num: the starting number (for the first handle)
- * @mapped_count: the number of objects currently mapped
- */
-struct z3fold_header {
- struct list_head buddy;
- spinlock_t page_lock;
- struct kref refcount;
- struct work_struct work;
- struct z3fold_buddy_slots *slots;
- struct z3fold_pool *pool;
- short cpu;
- unsigned short first_chunks;
- unsigned short middle_chunks;
- unsigned short last_chunks;
- unsigned short start_middle;
- unsigned short first_num:2;
- unsigned short mapped_count:2;
- unsigned short foreign_handles:2;
-};
-
-/**
- * struct z3fold_pool - stores metadata for each z3fold pool
- * @name: pool name
- * @lock: protects pool unbuddied lists
- * @stale_lock: protects pool stale page list
- * @unbuddied: per-cpu array of lists tracking z3fold pages that contain 2-
- * buddies; the list each z3fold page is added to depends on
- * the size of its free region.
- * @stale: list of pages marked for freeing
- * @pages_nr: number of z3fold pages in the pool.
- * @c_handle: cache for z3fold_buddy_slots allocation
- * @compact_wq: workqueue for page layout background optimization
- * @release_wq: workqueue for safe page release
- * @work: work_struct for safe page release
- *
- * This structure is allocated at pool creation time and maintains metadata
- * pertaining to a particular z3fold pool.
- */
-struct z3fold_pool {
- const char *name;
- spinlock_t lock;
- spinlock_t stale_lock;
- struct list_head __percpu *unbuddied;
- struct list_head stale;
- atomic64_t pages_nr;
- struct kmem_cache *c_handle;
- struct workqueue_struct *compact_wq;
- struct workqueue_struct *release_wq;
- struct work_struct work;
-};
-
-/*
- * Internal z3fold page flags
- */
-enum z3fold_page_flags {
- PAGE_HEADLESS = 0,
- MIDDLE_CHUNK_MAPPED,
- NEEDS_COMPACTING,
- PAGE_STALE,
- PAGE_CLAIMED, /* by either reclaim or free */
- PAGE_MIGRATED, /* page is migrated and soon to be released */
-};
-
-/*
- * handle flags, go under HANDLE_FLAG_MASK
- */
-enum z3fold_handle_flags {
- HANDLES_NOFREE = 0,
-};
-
-/*
- * Forward declarations
- */
-static struct z3fold_header *__z3fold_alloc(struct z3fold_pool *, size_t, bool);
-static void compact_page_work(struct work_struct *w);
-
-/*****************
- * Helpers
-*****************/
-
-/* Converts an allocation size in bytes to size in z3fold chunks */
-static int size_to_chunks(size_t size)
-{
- return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
-}
-
-#define for_each_unbuddied_list(_iter, _begin) \
- for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
-
-static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
- gfp_t gfp)
-{
- struct z3fold_buddy_slots *slots = kmem_cache_zalloc(pool->c_handle,
- gfp);
-
- if (slots) {
- /* It will be freed separately in free_handle(). */
- kmemleak_not_leak(slots);
- slots->pool = (unsigned long)pool;
- rwlock_init(&slots->lock);
- }
-
- return slots;
-}
-
-static inline struct z3fold_pool *slots_to_pool(struct z3fold_buddy_slots *s)
-{
- return (struct z3fold_pool *)(s->pool & ~HANDLE_FLAG_MASK);
-}
-
-static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
-{
- return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
-}
-
-/* Lock a z3fold page */
-static inline void z3fold_page_lock(struct z3fold_header *zhdr)
-{
- spin_lock(&zhdr->page_lock);
-}
-
-/* Try to lock a z3fold page */
-static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
-{
- return spin_trylock(&zhdr->page_lock);
-}
-
-/* Unlock a z3fold page */
-static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
-{
- spin_unlock(&zhdr->page_lock);
-}
-
-/* return locked z3fold page if it's not headless */
-static inline struct z3fold_header *get_z3fold_header(unsigned long handle)
-{
- struct z3fold_buddy_slots *slots;
- struct z3fold_header *zhdr;
- int locked = 0;
-
- if (!(handle & (1 << PAGE_HEADLESS))) {
- slots = handle_to_slots(handle);
- do {
- unsigned long addr;
-
- read_lock(&slots->lock);
- addr = *(unsigned long *)handle;
- zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
- locked = z3fold_page_trylock(zhdr);
- read_unlock(&slots->lock);
- if (locked) {
- struct page *page = virt_to_page(zhdr);
-
- if (!test_bit(PAGE_MIGRATED, &page->private))
- break;
- z3fold_page_unlock(zhdr);
- }
- cpu_relax();
- } while (true);
- } else {
- zhdr = (struct z3fold_header *)(handle & PAGE_MASK);
- }
-
- return zhdr;
-}
-
-static inline void put_z3fold_header(struct z3fold_header *zhdr)
-{
- struct page *page = virt_to_page(zhdr);
-
- if (!test_bit(PAGE_HEADLESS, &page->private))
- z3fold_page_unlock(zhdr);
-}
-
-static inline void free_handle(unsigned long handle, struct z3fold_header *zhdr)
-{
- struct z3fold_buddy_slots *slots;
- int i;
- bool is_free;
-
- if (WARN_ON(*(unsigned long *)handle == 0))
- return;
-
- slots = handle_to_slots(handle);
- write_lock(&slots->lock);
- *(unsigned long *)handle = 0;
-
- if (test_bit(HANDLES_NOFREE, &slots->pool)) {
- write_unlock(&slots->lock);
- return; /* simple case, nothing else to do */
- }
-
- if (zhdr->slots != slots)
- zhdr->foreign_handles--;
-
- is_free = true;
- for (i = 0; i <= BUDDY_MASK; i++) {
- if (slots->slot[i]) {
- is_free = false;
- break;
- }
- }
- write_unlock(&slots->lock);
-
- if (is_free) {
- struct z3fold_pool *pool = slots_to_pool(slots);
-
- if (zhdr->slots == slots)
- zhdr->slots = NULL;
- kmem_cache_free(pool->c_handle, slots);
- }
-}
-
-/* Initializes the z3fold header of a newly allocated z3fold page */
-static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
- struct z3fold_pool *pool, gfp_t gfp)
-{
- struct z3fold_header *zhdr = page_address(page);
- struct z3fold_buddy_slots *slots;
-
- clear_bit(PAGE_HEADLESS, &page->private);
- clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
- clear_bit(NEEDS_COMPACTING, &page->private);
- clear_bit(PAGE_STALE, &page->private);
- clear_bit(PAGE_CLAIMED, &page->private);
- clear_bit(PAGE_MIGRATED, &page->private);
- if (headless)
- return zhdr;
-
- slots = alloc_slots(pool, gfp);
- if (!slots)
- return NULL;
-
- memset(zhdr, 0, sizeof(*zhdr));
- spin_lock_init(&zhdr->page_lock);
- kref_init(&zhdr->refcount);
- zhdr->cpu = -1;
- zhdr->slots = slots;
- zhdr->pool = pool;
- INIT_LIST_HEAD(&zhdr->buddy);
- INIT_WORK(&zhdr->work, compact_page_work);
- return zhdr;
-}
-
-/* Resets the struct page fields and frees the page */
-static void free_z3fold_page(struct page *page, bool headless)
-{
- if (!headless) {
- lock_page(page);
- __ClearPageMovable(page);
- unlock_page(page);
- }
- __free_page(page);
-}
-
-/* Helper function to build the index */
-static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
-{
- return (bud + zhdr->first_num) & BUDDY_MASK;
-}
-
-/*
- * Encodes the handle of a particular buddy within a z3fold page.
- * Zhdr->page_lock should be held as this function accesses first_num
- * if bud != HEADLESS.
- */
-static unsigned long __encode_handle(struct z3fold_header *zhdr,
- struct z3fold_buddy_slots *slots,
- enum buddy bud)
-{
- unsigned long h = (unsigned long)zhdr;
- int idx = 0;
-
- /*
- * For a headless page, its handle is its pointer with the extra
- * PAGE_HEADLESS bit set
- */
- if (bud == HEADLESS)
- return h | (1 << PAGE_HEADLESS);
-
- /* otherwise, return pointer to encoded handle */
- idx = __idx(zhdr, bud);
- h += idx;
- if (bud == LAST)
- h |= (zhdr->last_chunks << BUDDY_SHIFT);
-
- write_lock(&slots->lock);
- slots->slot[idx] = h;
- write_unlock(&slots->lock);
- return (unsigned long)&slots->slot[idx];
-}
-
-static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
-{
- return __encode_handle(zhdr, zhdr->slots, bud);
-}
-
-/* only for LAST bud, returns zero otherwise */
-static unsigned short handle_to_chunks(unsigned long handle)
-{
- struct z3fold_buddy_slots *slots = handle_to_slots(handle);
- unsigned long addr;
-
- read_lock(&slots->lock);
- addr = *(unsigned long *)handle;
- read_unlock(&slots->lock);
- return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
-}
-
-/*
- * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
- * but that doesn't matter. because the masking will result in the
- * correct buddy number.
- */
-static enum buddy handle_to_buddy(unsigned long handle)
-{
- struct z3fold_header *zhdr;
- struct z3fold_buddy_slots *slots = handle_to_slots(handle);
- unsigned long addr;
-
- read_lock(&slots->lock);
- WARN_ON(handle & (1 << PAGE_HEADLESS));
- addr = *(unsigned long *)handle;
- read_unlock(&slots->lock);
- zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
- return (addr - zhdr->first_num) & BUDDY_MASK;
-}
-
-static inline struct z3fold_pool *zhdr_to_pool(struct z3fold_header *zhdr)
-{
- return zhdr->pool;
-}
-
-static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
-{
- struct page *page = virt_to_page(zhdr);
- struct z3fold_pool *pool = zhdr_to_pool(zhdr);
-
- WARN_ON(!list_empty(&zhdr->buddy));
- set_bit(PAGE_STALE, &page->private);
- clear_bit(NEEDS_COMPACTING, &page->private);
- spin_lock(&pool->lock);
- spin_unlock(&pool->lock);
-
- if (locked)
- z3fold_page_unlock(zhdr);
-
- spin_lock(&pool->stale_lock);
- list_add(&zhdr->buddy, &pool->stale);
- queue_work(pool->release_wq, &pool->work);
- spin_unlock(&pool->stale_lock);
-
- atomic64_dec(&pool->pages_nr);
-}
-
-static void release_z3fold_page_locked(struct kref *ref)
-{
- struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
- refcount);
- WARN_ON(z3fold_page_trylock(zhdr));
- __release_z3fold_page(zhdr, true);
-}
-
-static void release_z3fold_page_locked_list(struct kref *ref)
-{
- struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
- refcount);
- struct z3fold_pool *pool = zhdr_to_pool(zhdr);
-
- spin_lock(&pool->lock);
- list_del_init(&zhdr->buddy);
- spin_unlock(&pool->lock);
-
- WARN_ON(z3fold_page_trylock(zhdr));
- __release_z3fold_page(zhdr, true);
-}
-
-static inline int put_z3fold_locked(struct z3fold_header *zhdr)
-{
- return kref_put(&zhdr->refcount, release_z3fold_page_locked);
-}
-
-static inline int put_z3fold_locked_list(struct z3fold_header *zhdr)
-{
- return kref_put(&zhdr->refcount, release_z3fold_page_locked_list);
-}
-
-static void free_pages_work(struct work_struct *w)
-{
- struct z3fold_pool *pool = container_of(w, struct z3fold_pool, work);
-
- spin_lock(&pool->stale_lock);
- while (!list_empty(&pool->stale)) {
- struct z3fold_header *zhdr = list_first_entry(&pool->stale,
- struct z3fold_header, buddy);
- struct page *page = virt_to_page(zhdr);
-
- list_del(&zhdr->buddy);
- if (WARN_ON(!test_bit(PAGE_STALE, &page->private)))
- continue;
- spin_unlock(&pool->stale_lock);
- cancel_work_sync(&zhdr->work);
- free_z3fold_page(page, false);
- cond_resched();
- spin_lock(&pool->stale_lock);
- }
- spin_unlock(&pool->stale_lock);
-}
-
-/*
- * Returns the number of free chunks in a z3fold page.
- * NB: can't be used with HEADLESS pages.
- */
-static int num_free_chunks(struct z3fold_header *zhdr)
-{
- int nfree;
- /*
- * If there is a middle object, pick up the bigger free space
- * either before or after it. Otherwise just subtract the number
- * of chunks occupied by the first and the last objects.
- */
- if (zhdr->middle_chunks != 0) {
- int nfree_before = zhdr->first_chunks ?
- 0 : zhdr->start_middle - ZHDR_CHUNKS;
- int nfree_after = zhdr->last_chunks ?
- 0 : TOTAL_CHUNKS -
- (zhdr->start_middle + zhdr->middle_chunks);
- nfree = max(nfree_before, nfree_after);
- } else
- nfree = NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
- return nfree;
-}
-
-/* Add to the appropriate unbuddied list */
-static inline void add_to_unbuddied(struct z3fold_pool *pool,
- struct z3fold_header *zhdr)
-{
- if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0 ||
- zhdr->middle_chunks == 0) {
- struct list_head *unbuddied;
- int freechunks = num_free_chunks(zhdr);
-
- migrate_disable();
- unbuddied = this_cpu_ptr(pool->unbuddied);
- spin_lock(&pool->lock);
- list_add(&zhdr->buddy, &unbuddied[freechunks]);
- spin_unlock(&pool->lock);
- zhdr->cpu = smp_processor_id();
- migrate_enable();
- }
-}
-
-static inline enum buddy get_free_buddy(struct z3fold_header *zhdr, int chunks)
-{
- enum buddy bud = HEADLESS;
-
- if (zhdr->middle_chunks) {
- if (!zhdr->first_chunks &&
- chunks <= zhdr->start_middle - ZHDR_CHUNKS)
- bud = FIRST;
- else if (!zhdr->last_chunks)
- bud = LAST;
- } else {
- if (!zhdr->first_chunks)
- bud = FIRST;
- else if (!zhdr->last_chunks)
- bud = LAST;
- else
- bud = MIDDLE;
- }
-
- return bud;
-}
-
-static inline void *mchunk_memmove(struct z3fold_header *zhdr,
- unsigned short dst_chunk)
-{
- void *beg = zhdr;
- return memmove(beg + (dst_chunk << CHUNK_SHIFT),
- beg + (zhdr->start_middle << CHUNK_SHIFT),
- zhdr->middle_chunks << CHUNK_SHIFT);
-}
-
-static inline bool buddy_single(struct z3fold_header *zhdr)
-{
- return !((zhdr->first_chunks && zhdr->middle_chunks) ||
- (zhdr->first_chunks && zhdr->last_chunks) ||
- (zhdr->middle_chunks && zhdr->last_chunks));
-}
-
-static struct z3fold_header *compact_single_buddy(struct z3fold_header *zhdr)
-{
- struct z3fold_pool *pool = zhdr_to_pool(zhdr);
- void *p = zhdr;
- unsigned long old_handle = 0;
- size_t sz = 0;
- struct z3fold_header *new_zhdr = NULL;
- int first_idx = __idx(zhdr, FIRST);
- int middle_idx = __idx(zhdr, MIDDLE);
- int last_idx = __idx(zhdr, LAST);
- unsigned short *moved_chunks = NULL;
-
- /*
- * No need to protect slots here -- all the slots are "local" and
- * the page lock is already taken
- */
- if (zhdr->first_chunks && zhdr->slots->slot[first_idx]) {
- p += ZHDR_SIZE_ALIGNED;
- sz = zhdr->first_chunks << CHUNK_SHIFT;
- old_handle = (unsigned long)&zhdr->slots->slot[first_idx];
- moved_chunks = &zhdr->first_chunks;
- } else if (zhdr->middle_chunks && zhdr->slots->slot[middle_idx]) {
- p += zhdr->start_middle << CHUNK_SHIFT;
- sz = zhdr->middle_chunks << CHUNK_SHIFT;
- old_handle = (unsigned long)&zhdr->slots->slot[middle_idx];
- moved_chunks = &zhdr->middle_chunks;
- } else if (zhdr->last_chunks && zhdr->slots->slot[last_idx]) {
- p += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
- sz = zhdr->last_chunks << CHUNK_SHIFT;
- old_handle = (unsigned long)&zhdr->slots->slot[last_idx];
- moved_chunks = &zhdr->last_chunks;
- }
-
- if (sz > 0) {
- enum buddy new_bud = HEADLESS;
- short chunks = size_to_chunks(sz);
- void *q;
-
- new_zhdr = __z3fold_alloc(pool, sz, false);
- if (!new_zhdr)
- return NULL;
-
- if (WARN_ON(new_zhdr == zhdr))
- goto out_fail;
-
- new_bud = get_free_buddy(new_zhdr, chunks);
- q = new_zhdr;
- switch (new_bud) {
- case FIRST:
- new_zhdr->first_chunks = chunks;
- q += ZHDR_SIZE_ALIGNED;
- break;
- case MIDDLE:
- new_zhdr->middle_chunks = chunks;
- new_zhdr->start_middle =
- new_zhdr->first_chunks + ZHDR_CHUNKS;
- q += new_zhdr->start_middle << CHUNK_SHIFT;
- break;
- case LAST:
- new_zhdr->last_chunks = chunks;
- q += PAGE_SIZE - (new_zhdr->last_chunks << CHUNK_SHIFT);
- break;
- default:
- goto out_fail;
- }
- new_zhdr->foreign_handles++;
- memcpy(q, p, sz);
- write_lock(&zhdr->slots->lock);
- *(unsigned long *)old_handle = (unsigned long)new_zhdr +
- __idx(new_zhdr, new_bud);
- if (new_bud == LAST)
- *(unsigned long *)old_handle |=
- (new_zhdr->last_chunks << BUDDY_SHIFT);
- write_unlock(&zhdr->slots->lock);
- add_to_unbuddied(pool, new_zhdr);
- z3fold_page_unlock(new_zhdr);
-
- *moved_chunks = 0;
- }
-
- return new_zhdr;
-
-out_fail:
- if (new_zhdr && !put_z3fold_locked(new_zhdr)) {
- add_to_unbuddied(pool, new_zhdr);
- z3fold_page_unlock(new_zhdr);
- }
- return NULL;
-
-}
-
-#define BIG_CHUNK_GAP 3
-/* Has to be called with lock held */
-static int z3fold_compact_page(struct z3fold_header *zhdr)
-{
- struct page *page = virt_to_page(zhdr);
-
- if (test_bit(MIDDLE_CHUNK_MAPPED, &page->private))
- return 0; /* can't move middle chunk, it's used */
-
- if (unlikely(PageIsolated(page)))
- return 0;
-
- if (zhdr->middle_chunks == 0)
- return 0; /* nothing to compact */
-
- if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
- /* move to the beginning */
- mchunk_memmove(zhdr, ZHDR_CHUNKS);
- zhdr->first_chunks = zhdr->middle_chunks;
- zhdr->middle_chunks = 0;
- zhdr->start_middle = 0;
- zhdr->first_num++;
- return 1;
- }
-
- /*
- * moving data is expensive, so let's only do that if
- * there's substantial gain (at least BIG_CHUNK_GAP chunks)
- */
- if (zhdr->first_chunks != 0 && zhdr->last_chunks == 0 &&
- zhdr->start_middle - (zhdr->first_chunks + ZHDR_CHUNKS) >=
- BIG_CHUNK_GAP) {
- mchunk_memmove(zhdr, zhdr->first_chunks + ZHDR_CHUNKS);
- zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
- return 1;
- } else if (zhdr->last_chunks != 0 && zhdr->first_chunks == 0 &&
- TOTAL_CHUNKS - (zhdr->last_chunks + zhdr->start_middle
- + zhdr->middle_chunks) >=
- BIG_CHUNK_GAP) {
- unsigned short new_start = TOTAL_CHUNKS - zhdr->last_chunks -
- zhdr->middle_chunks;
- mchunk_memmove(zhdr, new_start);
- zhdr->start_middle = new_start;
- return 1;
- }
-
- return 0;
-}
-
-static void do_compact_page(struct z3fold_header *zhdr, bool locked)
-{
- struct z3fold_pool *pool = zhdr_to_pool(zhdr);
- struct page *page;
-
- page = virt_to_page(zhdr);
- if (locked)
- WARN_ON(z3fold_page_trylock(zhdr));
- else
- z3fold_page_lock(zhdr);
- if (WARN_ON(!test_and_clear_bit(NEEDS_COMPACTING, &page->private))) {
- z3fold_page_unlock(zhdr);
- return;
- }
- spin_lock(&pool->lock);
- list_del_init(&zhdr->buddy);
- spin_unlock(&pool->lock);
-
- if (put_z3fold_locked(zhdr))
- return;
-
- if (test_bit(PAGE_STALE, &page->private) ||
- test_and_set_bit(PAGE_CLAIMED, &page->private)) {
- z3fold_page_unlock(zhdr);
- return;
- }
-
- if (!zhdr->foreign_handles && buddy_single(zhdr) &&
- zhdr->mapped_count == 0 && compact_single_buddy(zhdr)) {
- if (!put_z3fold_locked(zhdr)) {
- clear_bit(PAGE_CLAIMED, &page->private);
- z3fold_page_unlock(zhdr);
- }
- return;
- }
-
- z3fold_compact_page(zhdr);
- add_to_unbuddied(pool, zhdr);
- clear_bit(PAGE_CLAIMED, &page->private);
- z3fold_page_unlock(zhdr);
-}
-
-static void compact_page_work(struct work_struct *w)
-{
- struct z3fold_header *zhdr = container_of(w, struct z3fold_header,
- work);
-
- do_compact_page(zhdr, false);
-}
-
-/* returns _locked_ z3fold page header or NULL */
-static inline struct z3fold_header *__z3fold_alloc(struct z3fold_pool *pool,
- size_t size, bool can_sleep)
-{
- struct z3fold_header *zhdr = NULL;
- struct page *page;
- struct list_head *unbuddied;
- int chunks = size_to_chunks(size), i;
-
-lookup:
- migrate_disable();
- /* First, try to find an unbuddied z3fold page. */
- unbuddied = this_cpu_ptr(pool->unbuddied);
- for_each_unbuddied_list(i, chunks) {
- struct list_head *l = &unbuddied[i];
-
- zhdr = list_first_entry_or_null(READ_ONCE(l),
- struct z3fold_header, buddy);
-
- if (!zhdr)
- continue;
-
- /* Re-check under lock. */
- spin_lock(&pool->lock);
- if (unlikely(zhdr != list_first_entry(READ_ONCE(l),
- struct z3fold_header, buddy)) ||
- !z3fold_page_trylock(zhdr)) {
- spin_unlock(&pool->lock);
- zhdr = NULL;
- migrate_enable();
- if (can_sleep)
- cond_resched();
- goto lookup;
- }
- list_del_init(&zhdr->buddy);
- zhdr->cpu = -1;
- spin_unlock(&pool->lock);
-
- page = virt_to_page(zhdr);
- if (test_bit(NEEDS_COMPACTING, &page->private) ||
- test_bit(PAGE_CLAIMED, &page->private)) {
- z3fold_page_unlock(zhdr);
- zhdr = NULL;
- migrate_enable();
- if (can_sleep)
- cond_resched();
- goto lookup;
- }
-
- /*
- * this page could not be removed from its unbuddied
- * list while pool lock was held, and then we've taken
- * page lock so kref_put could not be called before
- * we got here, so it's safe to just call kref_get()
- */
- kref_get(&zhdr->refcount);
- break;
- }
- migrate_enable();
-
- if (!zhdr) {
- int cpu;
-
- /* look for _exact_ match on other cpus' lists */
- for_each_online_cpu(cpu) {
- struct list_head *l;
-
- unbuddied = per_cpu_ptr(pool->unbuddied, cpu);
- spin_lock(&pool->lock);
- l = &unbuddied[chunks];
-
- zhdr = list_first_entry_or_null(READ_ONCE(l),
- struct z3fold_header, buddy);
-
- if (!zhdr || !z3fold_page_trylock(zhdr)) {
- spin_unlock(&pool->lock);
- zhdr = NULL;
- continue;
- }
- list_del_init(&zhdr->buddy);
- zhdr->cpu = -1;
- spin_unlock(&pool->lock);
-
- page = virt_to_page(zhdr);
- if (test_bit(NEEDS_COMPACTING, &page->private) ||
- test_bit(PAGE_CLAIMED, &page->private)) {
- z3fold_page_unlock(zhdr);
- zhdr = NULL;
- if (can_sleep)
- cond_resched();
- continue;
- }
- kref_get(&zhdr->refcount);
- break;
- }
- }
-
- if (zhdr && !zhdr->slots) {
- zhdr->slots = alloc_slots(pool, GFP_ATOMIC);
- if (!zhdr->slots)
- goto out_fail;
- }
- return zhdr;
-
-out_fail:
- if (!put_z3fold_locked(zhdr)) {
- add_to_unbuddied(pool, zhdr);
- z3fold_page_unlock(zhdr);
- }
- return NULL;
-}
-
-/*
- * API Functions
- */
-
-/**
- * z3fold_create_pool() - create a new z3fold pool
- * @name: pool name
- * @gfp: gfp flags when allocating the z3fold pool structure
- *
- * Return: pointer to the new z3fold pool or NULL if the metadata allocation
- * failed.
- */
-static struct z3fold_pool *z3fold_create_pool(const char *name, gfp_t gfp)
-{
- struct z3fold_pool *pool = NULL;
- int i, cpu;
-
- pool = kzalloc(sizeof(struct z3fold_pool), gfp);
- if (!pool)
- goto out;
- pool->c_handle = kmem_cache_create("z3fold_handle",
- sizeof(struct z3fold_buddy_slots),
- SLOTS_ALIGN, 0, NULL);
- if (!pool->c_handle)
- goto out_c;
- spin_lock_init(&pool->lock);
- spin_lock_init(&pool->stale_lock);
- pool->unbuddied = __alloc_percpu(sizeof(struct list_head) * NCHUNKS,
- __alignof__(struct list_head));
- if (!pool->unbuddied)
- goto out_pool;
- for_each_possible_cpu(cpu) {
- struct list_head *unbuddied =
- per_cpu_ptr(pool->unbuddied, cpu);
- for_each_unbuddied_list(i, 0)
- INIT_LIST_HEAD(&unbuddied[i]);
- }
- INIT_LIST_HEAD(&pool->stale);
- atomic64_set(&pool->pages_nr, 0);
- pool->name = name;
- pool->compact_wq = create_singlethread_workqueue(pool->name);
- if (!pool->compact_wq)
- goto out_unbuddied;
- pool->release_wq = create_singlethread_workqueue(pool->name);
- if (!pool->release_wq)
- goto out_wq;
- INIT_WORK(&pool->work, free_pages_work);
- return pool;
-
-out_wq:
- destroy_workqueue(pool->compact_wq);
-out_unbuddied:
- free_percpu(pool->unbuddied);
-out_pool:
- kmem_cache_destroy(pool->c_handle);
-out_c:
- kfree(pool);
-out:
- return NULL;
-}
-
-/**
- * z3fold_destroy_pool() - destroys an existing z3fold pool
- * @pool: the z3fold pool to be destroyed
- *
- * The pool should be emptied before this function is called.
- */
-static void z3fold_destroy_pool(struct z3fold_pool *pool)
-{
- kmem_cache_destroy(pool->c_handle);
-
- /*
- * We need to destroy pool->compact_wq before pool->release_wq,
- * as any pending work on pool->compact_wq will call
- * queue_work(pool->release_wq, &pool->work).
- *
- * There are still outstanding pages until both workqueues are drained,
- * so we cannot unregister migration until then.
- */
-
- destroy_workqueue(pool->compact_wq);
- destroy_workqueue(pool->release_wq);
- free_percpu(pool->unbuddied);
- kfree(pool);
-}
-
-static const struct movable_operations z3fold_mops;
-
-/**
- * z3fold_alloc() - allocates a region of a given size
- * @pool: z3fold pool from which to allocate
- * @size: size in bytes of the desired allocation
- * @gfp: gfp flags used if the pool needs to grow
- * @handle: handle of the new allocation
- *
- * This function will attempt to find a free region in the pool large enough to
- * satisfy the allocation request. A search of the unbuddied lists is
- * performed first. If no suitable free region is found, then a new page is
- * allocated and added to the pool to satisfy the request.
- *
- * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
- * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
- * a new page.
- */
-static int z3fold_alloc(struct z3fold_pool *pool, size_t size, gfp_t gfp,
- unsigned long *handle)
-{
- int chunks = size_to_chunks(size);
- struct z3fold_header *zhdr = NULL;
- struct page *page = NULL;
- enum buddy bud;
- bool can_sleep = gfpflags_allow_blocking(gfp);
-
- if (!size || (gfp & __GFP_HIGHMEM))
- return -EINVAL;
-
- if (size > PAGE_SIZE)
- return -ENOSPC;
-
- if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
- bud = HEADLESS;
- else {
-retry:
- zhdr = __z3fold_alloc(pool, size, can_sleep);
- if (zhdr) {
- bud = get_free_buddy(zhdr, chunks);
- if (bud == HEADLESS) {
- if (!put_z3fold_locked(zhdr))
- z3fold_page_unlock(zhdr);
- pr_err("No free chunks in unbuddied\n");
- WARN_ON(1);
- goto retry;
- }
- page = virt_to_page(zhdr);
- goto found;
- }
- bud = FIRST;
- }
-
- page = alloc_page(gfp);
- if (!page)
- return -ENOMEM;
-
- zhdr = init_z3fold_page(page, bud == HEADLESS, pool, gfp);
- if (!zhdr) {
- __free_page(page);
- return -ENOMEM;
- }
- atomic64_inc(&pool->pages_nr);
-
- if (bud == HEADLESS) {
- set_bit(PAGE_HEADLESS, &page->private);
- goto headless;
- }
- if (can_sleep) {
- lock_page(page);
- __SetPageMovable(page, &z3fold_mops);
- unlock_page(page);
- } else {
- WARN_ON(!trylock_page(page));
- __SetPageMovable(page, &z3fold_mops);
- unlock_page(page);
- }
- z3fold_page_lock(zhdr);
-
-found:
- if (bud == FIRST)
- zhdr->first_chunks = chunks;
- else if (bud == LAST)
- zhdr->last_chunks = chunks;
- else {
- zhdr->middle_chunks = chunks;
- zhdr->start_middle = zhdr->first_chunks + ZHDR_CHUNKS;
- }
- add_to_unbuddied(pool, zhdr);
-
-headless:
- spin_lock(&pool->lock);
- *handle = encode_handle(zhdr, bud);
- spin_unlock(&pool->lock);
- if (bud != HEADLESS)
- z3fold_page_unlock(zhdr);
-
- return 0;
-}
-
-/**
- * z3fold_free() - frees the allocation associated with the given handle
- * @pool: pool in which the allocation resided
- * @handle: handle associated with the allocation returned by z3fold_alloc()
- *
- * In the case that the z3fold page in which the allocation resides is under
- * reclaim, as indicated by the PAGE_CLAIMED flag being set, this function
- * only sets the first|middle|last_chunks to 0. The page is actually freed
- * once all buddies are evicted (see z3fold_reclaim_page() below).
- */
-static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
-{
- struct z3fold_header *zhdr;
- struct page *page;
- enum buddy bud;
- bool page_claimed;
-
- zhdr = get_z3fold_header(handle);
- page = virt_to_page(zhdr);
- page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
-
- if (test_bit(PAGE_HEADLESS, &page->private)) {
- /* if a headless page is under reclaim, just leave.
- * NB: we use test_and_set_bit for a reason: if the bit
- * has not been set before, we release this page
- * immediately so we don't care about its value any more.
- */
- if (!page_claimed) {
- put_z3fold_header(zhdr);
- free_z3fold_page(page, true);
- atomic64_dec(&pool->pages_nr);
- }
- return;
- }
-
- /* Non-headless case */
- bud = handle_to_buddy(handle);
-
- switch (bud) {
- case FIRST:
- zhdr->first_chunks = 0;
- break;
- case MIDDLE:
- zhdr->middle_chunks = 0;
- break;
- case LAST:
- zhdr->last_chunks = 0;
- break;
- default:
- pr_err("%s: unknown bud %d\n", __func__, bud);
- WARN_ON(1);
- put_z3fold_header(zhdr);
- return;
- }
-
- if (!page_claimed)
- free_handle(handle, zhdr);
- if (put_z3fold_locked_list(zhdr))
- return;
- if (page_claimed) {
- /* the page has not been claimed by us */
- put_z3fold_header(zhdr);
- return;
- }
- if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
- clear_bit(PAGE_CLAIMED, &page->private);
- put_z3fold_header(zhdr);
- return;
- }
- if (zhdr->cpu < 0 || !cpu_online(zhdr->cpu)) {
- zhdr->cpu = -1;
- kref_get(&zhdr->refcount);
- clear_bit(PAGE_CLAIMED, &page->private);
- do_compact_page(zhdr, true);
- return;
- }
- kref_get(&zhdr->refcount);
- clear_bit(PAGE_CLAIMED, &page->private);
- queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
- put_z3fold_header(zhdr);
-}
-
-/**
- * z3fold_map() - maps the allocation associated with the given handle
- * @pool: pool in which the allocation resides
- * @handle: handle associated with the allocation to be mapped
- *
- * Extracts the buddy number from handle and constructs the pointer to the
- * correct starting chunk within the page.
- *
- * Returns: a pointer to the mapped allocation
- */
-static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
-{
- struct z3fold_header *zhdr;
- struct page *page;
- void *addr;
- enum buddy buddy;
-
- zhdr = get_z3fold_header(handle);
- addr = zhdr;
- page = virt_to_page(zhdr);
-
- if (test_bit(PAGE_HEADLESS, &page->private))
- goto out;
-
- buddy = handle_to_buddy(handle);
- switch (buddy) {
- case FIRST:
- addr += ZHDR_SIZE_ALIGNED;
- break;
- case MIDDLE:
- addr += zhdr->start_middle << CHUNK_SHIFT;
- set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
- break;
- case LAST:
- addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
- break;
- default:
- pr_err("unknown buddy id %d\n", buddy);
- WARN_ON(1);
- addr = NULL;
- break;
- }
-
- if (addr)
- zhdr->mapped_count++;
-out:
- put_z3fold_header(zhdr);
- return addr;
-}
-
-/**
- * z3fold_unmap() - unmaps the allocation associated with the given handle
- * @pool: pool in which the allocation resides
- * @handle: handle associated with the allocation to be unmapped
- */
-static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
-{
- struct z3fold_header *zhdr;
- struct page *page;
- enum buddy buddy;
-
- zhdr = get_z3fold_header(handle);
- page = virt_to_page(zhdr);
-
- if (test_bit(PAGE_HEADLESS, &page->private))
- return;
-
- buddy = handle_to_buddy(handle);
- if (buddy == MIDDLE)
- clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
- zhdr->mapped_count--;
- put_z3fold_header(zhdr);
-}
-
-/**
- * z3fold_get_pool_pages() - gets the z3fold pool size in pages
- * @pool: pool whose size is being queried
- *
- * Returns: size in pages of the given pool.
- */
-static u64 z3fold_get_pool_pages(struct z3fold_pool *pool)
-{
- return atomic64_read(&pool->pages_nr);
-}
-
-static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
-{
- struct z3fold_header *zhdr;
- struct z3fold_pool *pool;
-
- VM_BUG_ON_PAGE(PageIsolated(page), page);
-
- if (test_bit(PAGE_HEADLESS, &page->private))
- return false;
-
- zhdr = page_address(page);
- z3fold_page_lock(zhdr);
- if (test_bit(NEEDS_COMPACTING, &page->private) ||
- test_bit(PAGE_STALE, &page->private))
- goto out;
-
- if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0)
- goto out;
-
- if (test_and_set_bit(PAGE_CLAIMED, &page->private))
- goto out;
- pool = zhdr_to_pool(zhdr);
- spin_lock(&pool->lock);
- if (!list_empty(&zhdr->buddy))
- list_del_init(&zhdr->buddy);
- spin_unlock(&pool->lock);
-
- kref_get(&zhdr->refcount);
- z3fold_page_unlock(zhdr);
- return true;
-
-out:
- z3fold_page_unlock(zhdr);
- return false;
-}
-
-static int z3fold_page_migrate(struct page *newpage, struct page *page,
- enum migrate_mode mode)
-{
- struct z3fold_header *zhdr, *new_zhdr;
- struct z3fold_pool *pool;
-
- VM_BUG_ON_PAGE(!PageIsolated(page), page);
- VM_BUG_ON_PAGE(!test_bit(PAGE_CLAIMED, &page->private), page);
- VM_BUG_ON_PAGE(!PageLocked(newpage), newpage);
-
- zhdr = page_address(page);
- pool = zhdr_to_pool(zhdr);
-
- if (!z3fold_page_trylock(zhdr))
- return -EAGAIN;
- if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
- clear_bit(PAGE_CLAIMED, &page->private);
- z3fold_page_unlock(zhdr);
- return -EBUSY;
- }
- if (work_pending(&zhdr->work)) {
- z3fold_page_unlock(zhdr);
- return -EAGAIN;
- }
- new_zhdr = page_address(newpage);
- memcpy(new_zhdr, zhdr, PAGE_SIZE);
- newpage->private = page->private;
- set_bit(PAGE_MIGRATED, &page->private);
- z3fold_page_unlock(zhdr);
- spin_lock_init(&new_zhdr->page_lock);
- INIT_WORK(&new_zhdr->work, compact_page_work);
- /*
- * z3fold_page_isolate() ensures that new_zhdr->buddy is empty,
- * so we only have to reinitialize it.
- */
- INIT_LIST_HEAD(&new_zhdr->buddy);
- __ClearPageMovable(page);
-
- get_page(newpage);
- z3fold_page_lock(new_zhdr);
- if (new_zhdr->first_chunks)
- encode_handle(new_zhdr, FIRST);
- if (new_zhdr->last_chunks)
- encode_handle(new_zhdr, LAST);
- if (new_zhdr->middle_chunks)
- encode_handle(new_zhdr, MIDDLE);
- set_bit(NEEDS_COMPACTING, &newpage->private);
- new_zhdr->cpu = smp_processor_id();
- __SetPageMovable(newpage, &z3fold_mops);
- z3fold_page_unlock(new_zhdr);
-
- queue_work_on(new_zhdr->cpu, pool->compact_wq, &new_zhdr->work);
-
- /* PAGE_CLAIMED and PAGE_MIGRATED are cleared now. */
- page->private = 0;
- put_page(page);
- return 0;
-}
-
-static void z3fold_page_putback(struct page *page)
-{
- struct z3fold_header *zhdr;
- struct z3fold_pool *pool;
-
- zhdr = page_address(page);
- pool = zhdr_to_pool(zhdr);
-
- z3fold_page_lock(zhdr);
- if (!list_empty(&zhdr->buddy))
- list_del_init(&zhdr->buddy);
- INIT_LIST_HEAD(&page->lru);
- if (put_z3fold_locked(zhdr))
- return;
- if (list_empty(&zhdr->buddy))
- add_to_unbuddied(pool, zhdr);
- clear_bit(PAGE_CLAIMED, &page->private);
- z3fold_page_unlock(zhdr);
-}
-
-static const struct movable_operations z3fold_mops = {
- .isolate_page = z3fold_page_isolate,
- .migrate_page = z3fold_page_migrate,
- .putback_page = z3fold_page_putback,
-};
-
-/*****************
- * zpool
- ****************/
-
-static void *z3fold_zpool_create(const char *name, gfp_t gfp)
-{
- return z3fold_create_pool(name, gfp);
-}
-
-static void z3fold_zpool_destroy(void *pool)
-{
- z3fold_destroy_pool(pool);
-}
-
-static int z3fold_zpool_malloc(void *pool, size_t size, gfp_t gfp,
- unsigned long *handle)
-{
- return z3fold_alloc(pool, size, gfp, handle);
-}
-static void z3fold_zpool_free(void *pool, unsigned long handle)
-{
- z3fold_free(pool, handle);
-}
-
-static void *z3fold_zpool_map(void *pool, unsigned long handle,
- enum zpool_mapmode mm)
-{
- return z3fold_map(pool, handle);
-}
-static void z3fold_zpool_unmap(void *pool, unsigned long handle)
-{
- z3fold_unmap(pool, handle);
-}
-
-static u64 z3fold_zpool_total_pages(void *pool)
-{
- return z3fold_get_pool_pages(pool);
-}
-
-static struct zpool_driver z3fold_zpool_driver = {
- .type = "z3fold",
- .sleep_mapped = true,
- .owner = THIS_MODULE,
- .create = z3fold_zpool_create,
- .destroy = z3fold_zpool_destroy,
- .malloc = z3fold_zpool_malloc,
- .free = z3fold_zpool_free,
- .map = z3fold_zpool_map,
- .unmap = z3fold_zpool_unmap,
- .total_pages = z3fold_zpool_total_pages,
-};
-
-MODULE_ALIAS("zpool-z3fold");
-
-static int __init init_z3fold(void)
-{
- /*
- * Make sure the z3fold header is not larger than the page size and
- * there has remaining spaces for its buddy.
- */
- BUILD_BUG_ON(ZHDR_SIZE_ALIGNED > PAGE_SIZE - CHUNK_SIZE);
- zpool_register_driver(&z3fold_zpool_driver);
-
- return 0;
-}
-
-static void __exit exit_z3fold(void)
-{
- zpool_unregister_driver(&z3fold_zpool_driver);
-}
-
-module_init(init_z3fold);
-module_exit(exit_z3fold);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Vitaly Wool <vitalywool@gmail.com>");
-MODULE_DESCRIPTION("3-Fold Allocator for Compressed Pages");
--
2.48.1.262.g85cc9f2d1e-goog
^ permalink raw reply [flat|nested] 6+ messages in thread* [PATCH v2 2/2] mm: zbud: remove zbud
2025-01-29 18:06 [PATCH v2 0/2] mm: zswap: remove z3fold and zbud Yosry Ahmed
2025-01-29 18:06 ` [PATCH v2 1/2] mm: z3fold: remove z3fold Yosry Ahmed
@ 2025-01-29 18:06 ` Yosry Ahmed
2025-01-29 19:26 ` Shakeel Butt
` (2 more replies)
1 sibling, 3 replies; 6+ messages in thread
From: Yosry Ahmed @ 2025-01-29 18:06 UTC (permalink / raw)
To: Andrew Morton
Cc: Vitaly Wool, Seth Jennings, Dan Streetman, Miaohe Lin,
Johannes Weiner, Nhat Pham, Chengming Zhou, Huacai Chen,
WANG Xuerui, Heiko Carstens, Vasily Gorbik, Alexander Gordeev,
Christian Borntraeger, Sven Schnelle, Shakeel Butt,
Vlastimil Babka, linux-mm, linux-kernel, loongarch, linux-s390,
linux-doc
The zbud compressed pages allocator is rarely used, most users use
zsmalloc. zbud consumes much more memory (only stores 1 or 2 compressed
pages per physical page). The only advantage of zbud is a marginal
performance improvement that by no means justify the memory overhead.
Historically, zsmalloc had significantly worse latency than zbud and
z3fold but offered better memory savings. This is no longer the case as
shown by a simple recent analysis [1]. In a kernel build test on tmpfs
in a limited cgroup, zbud 2-3% less time than zsmalloc, but at the cost
of using ~32% more memory (1.5G vs 1.13G). The tradeoff does not make
sense for zbud in any practical scenario.
The only alleged advantage of zbud is not having the dependency on
CONFIG_MMU, but CONFIG_SWAP already depends on CONFIG_MMU anyway, and
zbud is only used by zswap.
Remove zbud after z3fold's removal, leaving zsmalloc as the one and only
zpool allocator. Leave the removal of the zpool API (and its associated
config options) to a followup cleanup after no more allocators show up.
Deprecating zbud for a few cycles before removing it was initially
proposed [2], like z3fold was marked as deprecated for 2 cycles [3].
However, Johannes rightfully pointed out that the 2 cycles is too short
for most downstream consumers, and z3fold was deprecated first only as a
courtesy anyway.
[1]https://lore.kernel.org/lkml/CAJD7tkbRF6od-2x_L8-A1QL3=2Ww13sCj4S3i4bNndqF+3+_Vg@mail.gmail.com/
[2]https://lore.kernel.org/lkml/Z5gdnSX5Lv-nfjQL@google.com/
[3]https://lore.kernel.org/lkml/20240904233343.933462-1-yosryahmed@google.com/
Signed-off-by: Yosry Ahmed <yosry.ahmed@linux.dev>
---
CREDITS | 2 +
Documentation/admin-guide/mm/zswap.rst | 10 +-
MAINTAINERS | 7 -
arch/loongarch/configs/loongson3_defconfig | 3 +-
arch/s390/configs/debug_defconfig | 2 +-
arch/s390/configs/defconfig | 2 +-
include/linux/zpool.h | 5 +-
mm/Kconfig | 18 -
mm/Makefile | 1 -
mm/zbud.c | 455 ---------------------
mm/zpool.c | 4 +-
11 files changed, 13 insertions(+), 496 deletions(-)
delete mode 100644 mm/zbud.c
diff --git a/CREDITS b/CREDITS
index 324428ad37e83..7d1f554238d65 100644
--- a/CREDITS
+++ b/CREDITS
@@ -1895,6 +1895,7 @@ S: Czech Republic
N: Seth Jennings
E: sjenning@redhat.com
D: Creation and maintenance of zswap
+D: Creation and maintenace of the zbud allocator
N: Jeremy Kerr
D: Maintainer of SPU File System
@@ -3790,6 +3791,7 @@ N: Dan Streetman
E: ddstreet@ieee.org
D: Maintenance and development of zswap
D: Creation and maintenance of the zpool API
+D: Maintenace of the zbud allocator
N: Drew Sullivan
E: drew@ss.org
diff --git a/Documentation/admin-guide/mm/zswap.rst b/Documentation/admin-guide/mm/zswap.rst
index 3598dcd7dbe7e..fd3370aa43fe8 100644
--- a/Documentation/admin-guide/mm/zswap.rst
+++ b/Documentation/admin-guide/mm/zswap.rst
@@ -60,15 +60,13 @@ accessed. The compressed memory pool grows on demand and shrinks as compressed
pages are freed. The pool is not preallocated. By default, a zpool
of type selected in ``CONFIG_ZSWAP_ZPOOL_DEFAULT`` Kconfig option is created,
but it can be overridden at boot time by setting the ``zpool`` attribute,
-e.g. ``zswap.zpool=zbud``. It can also be changed at runtime using the sysfs
+e.g. ``zswap.zpool=zsmalloc``. It can also be changed at runtime using the sysfs
``zpool`` attribute, e.g.::
- echo zbud > /sys/module/zswap/parameters/zpool
+ echo zsmalloc > /sys/module/zswap/parameters/zpool
-The zbud type zpool allocates exactly 1 page to store 2 compressed pages, which
-means the compression ratio will always be 2:1 or worse (because of half-full
-zbud pages). The zsmalloc type zpool has a more complex compressed page
-storage method, and it can achieve greater storage densities.
+The zsmalloc type zpool has a complex compressed page storage method, and it
+can achieve great storage densities.
When a swap page is passed from swapout to zswap, zswap maintains a mapping
of the swap entry, a combination of the swap type and swap offset, to the zpool
diff --git a/MAINTAINERS b/MAINTAINERS
index 1583bb8eee587..6460fd94a986e 100644
--- a/MAINTAINERS
+++ b/MAINTAINERS
@@ -26065,13 +26065,6 @@ F: Documentation/networking/device_drivers/hamradio/z8530drv.rst
F: drivers/net/hamradio/*scc.c
F: drivers/net/hamradio/z8530.h
-ZBUD COMPRESSED PAGE ALLOCATOR
-M: Seth Jennings <sjenning@redhat.com>
-M: Dan Streetman <ddstreet@ieee.org>
-L: linux-mm@kvack.org
-S: Maintained
-F: mm/zbud.c
-
ZD1211RW WIRELESS DRIVER
L: linux-wireless@vger.kernel.org
S: Orphan
diff --git a/arch/loongarch/configs/loongson3_defconfig b/arch/loongarch/configs/loongson3_defconfig
index 73c77500ac467..7ce5beb3cbf34 100644
--- a/arch/loongarch/configs/loongson3_defconfig
+++ b/arch/loongarch/configs/loongson3_defconfig
@@ -109,8 +109,7 @@ CONFIG_BINFMT_MISC=m
CONFIG_ZPOOL=y
CONFIG_ZSWAP=y
CONFIG_ZSWAP_COMPRESSOR_DEFAULT_ZSTD=y
-CONFIG_ZBUD=y
-CONFIG_ZSMALLOC=m
+CONFIG_ZSMALLOC=y
# CONFIG_COMPAT_BRK is not set
CONFIG_MEMORY_HOTPLUG=y
# CONFIG_MHP_DEFAULT_ONLINE_TYPE_OFFLINE is not set
diff --git a/arch/s390/configs/debug_defconfig b/arch/s390/configs/debug_defconfig
index d6beec5292a00..9bf540aee8277 100644
--- a/arch/s390/configs/debug_defconfig
+++ b/arch/s390/configs/debug_defconfig
@@ -92,7 +92,7 @@ CONFIG_UNIXWARE_DISKLABEL=y
CONFIG_IOSCHED_BFQ=y
CONFIG_BINFMT_MISC=m
CONFIG_ZSWAP=y
-CONFIG_ZSWAP_ZPOOL_DEFAULT_ZBUD=y
+CONFIG_ZSMALLOC=y
CONFIG_ZSMALLOC_STAT=y
CONFIG_SLAB_BUCKETS=y
CONFIG_SLUB_STATS=y
diff --git a/arch/s390/configs/defconfig b/arch/s390/configs/defconfig
index 8cfbfb10bba8c..2918635d8e55a 100644
--- a/arch/s390/configs/defconfig
+++ b/arch/s390/configs/defconfig
@@ -86,7 +86,7 @@ CONFIG_UNIXWARE_DISKLABEL=y
CONFIG_IOSCHED_BFQ=y
CONFIG_BINFMT_MISC=m
CONFIG_ZSWAP=y
-CONFIG_ZSWAP_ZPOOL_DEFAULT_ZBUD=y
+CONFIG_ZSMALLOC=y
CONFIG_ZSMALLOC_STAT=y
CONFIG_SLAB_BUCKETS=y
# CONFIG_COMPAT_BRK is not set
diff --git a/include/linux/zpool.h b/include/linux/zpool.h
index a67d62b796980..5e6dc46b8cc4c 100644
--- a/include/linux/zpool.h
+++ b/include/linux/zpool.h
@@ -4,9 +4,8 @@
*
* Copyright (C) 2014 Dan Streetman
*
- * This is a common frontend for the zbud and zsmalloc memory
- * storage pool implementations. Typically, this is used to
- * store compressed memory.
+ * This is a common frontend for the zswap compressed memory storage
+ * implementations.
*/
#ifndef _ZPOOL_H_
diff --git a/mm/Kconfig b/mm/Kconfig
index 6fa19022c09b8..fba9757e58147 100644
--- a/mm/Kconfig
+++ b/mm/Kconfig
@@ -129,7 +129,6 @@ choice
prompt "Default allocator"
depends on ZSWAP
default ZSWAP_ZPOOL_DEFAULT_ZSMALLOC if MMU
- default ZSWAP_ZPOOL_DEFAULT_ZBUD
help
Selects the default allocator for the compressed cache for
swap pages.
@@ -140,12 +139,6 @@ choice
The selection made here can be overridden by using the kernel
command line 'zswap.zpool=' option.
-config ZSWAP_ZPOOL_DEFAULT_ZBUD
- bool "zbud"
- select ZBUD
- help
- Use the zbud allocator as the default allocator.
-
config ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
bool "zsmalloc"
select ZSMALLOC
@@ -156,20 +149,9 @@ endchoice
config ZSWAP_ZPOOL_DEFAULT
string
depends on ZSWAP
- default "zbud" if ZSWAP_ZPOOL_DEFAULT_ZBUD
default "zsmalloc" if ZSWAP_ZPOOL_DEFAULT_ZSMALLOC
default ""
-config ZBUD
- tristate "2:1 compression allocator (zbud)"
- depends on ZSWAP
- help
- A special purpose allocator for storing compressed pages.
- It is designed to store up to two compressed pages per physical
- page. While this design limits storage density, it has simple and
- deterministic reclaim properties that make it preferable to a higher
- density approach when reclaim will be used.
-
config ZSMALLOC
tristate
prompt "N:1 compression allocator (zsmalloc)" if (ZSWAP || ZRAM)
diff --git a/mm/Makefile b/mm/Makefile
index e4c03da3c0846..53392d2af3a58 100644
--- a/mm/Makefile
+++ b/mm/Makefile
@@ -113,7 +113,6 @@ obj-$(CONFIG_DEBUG_VM_PGTABLE) += debug_vm_pgtable.o
obj-$(CONFIG_PAGE_OWNER) += page_owner.o
obj-$(CONFIG_MEMORY_ISOLATION) += page_isolation.o
obj-$(CONFIG_ZPOOL) += zpool.o
-obj-$(CONFIG_ZBUD) += zbud.o
obj-$(CONFIG_ZSMALLOC) += zsmalloc.o
obj-$(CONFIG_GENERIC_EARLY_IOREMAP) += early_ioremap.o
obj-$(CONFIG_CMA) += cma.o
diff --git a/mm/zbud.c b/mm/zbud.c
deleted file mode 100644
index e9836fff94381..0000000000000
--- a/mm/zbud.c
+++ /dev/null
@@ -1,455 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0-only
-/*
- * zbud.c
- *
- * Copyright (C) 2013, Seth Jennings, IBM
- *
- * Concepts based on zcache internal zbud allocator by Dan Magenheimer.
- *
- * zbud is an special purpose allocator for storing compressed pages. Contrary
- * to what its name may suggest, zbud is not a buddy allocator, but rather an
- * allocator that "buddies" two compressed pages together in a single memory
- * page.
- *
- * While this design limits storage density, it has simple and deterministic
- * reclaim properties that make it preferable to a higher density approach when
- * reclaim will be used.
- *
- * zbud works by storing compressed pages, or "zpages", together in pairs in a
- * single memory page called a "zbud page". The first buddy is "left
- * justified" at the beginning of the zbud page, and the last buddy is "right
- * justified" at the end of the zbud page. The benefit is that if either
- * buddy is freed, the freed buddy space, coalesced with whatever slack space
- * that existed between the buddies, results in the largest possible free region
- * within the zbud page.
- *
- * zbud also provides an attractive lower bound on density. The ratio of zpages
- * to zbud pages can not be less than 1. This ensures that zbud can never "do
- * harm" by using more pages to store zpages than the uncompressed zpages would
- * have used on their own.
- *
- * zbud pages are divided into "chunks". The size of the chunks is fixed at
- * compile time and determined by NCHUNKS_ORDER below. Dividing zbud pages
- * into chunks allows organizing unbuddied zbud pages into a manageable number
- * of unbuddied lists according to the number of free chunks available in the
- * zbud page.
- *
- * The zbud API differs from that of conventional allocators in that the
- * allocation function, zbud_alloc(), returns an opaque handle to the user,
- * not a dereferenceable pointer. The user must map the handle using
- * zbud_map() in order to get a usable pointer by which to access the
- * allocation data and unmap the handle with zbud_unmap() when operations
- * on the allocation data are complete.
- */
-
-#define pr_fmt(fmt) KBUILD_MODNAME ": " fmt
-
-#include <linux/atomic.h>
-#include <linux/list.h>
-#include <linux/mm.h>
-#include <linux/module.h>
-#include <linux/preempt.h>
-#include <linux/slab.h>
-#include <linux/spinlock.h>
-#include <linux/zpool.h>
-
-/*****************
- * Structures
-*****************/
-/*
- * NCHUNKS_ORDER determines the internal allocation granularity, effectively
- * adjusting internal fragmentation. It also determines the number of
- * freelists maintained in each pool. NCHUNKS_ORDER of 6 means that the
- * allocation granularity will be in chunks of size PAGE_SIZE/64. As one chunk
- * in allocated page is occupied by zbud header, NCHUNKS will be calculated to
- * 63 which shows the max number of free chunks in zbud page, also there will be
- * 63 freelists per pool.
- */
-#define NCHUNKS_ORDER 6
-
-#define CHUNK_SHIFT (PAGE_SHIFT - NCHUNKS_ORDER)
-#define CHUNK_SIZE (1 << CHUNK_SHIFT)
-#define ZHDR_SIZE_ALIGNED CHUNK_SIZE
-#define NCHUNKS ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
-
-struct zbud_pool;
-
-/**
- * struct zbud_pool - stores metadata for each zbud pool
- * @lock: protects all pool fields and first|last_chunk fields of any
- * zbud page in the pool
- * @unbuddied: array of lists tracking zbud pages that only contain one buddy;
- * the lists each zbud page is added to depends on the size of
- * its free region.
- * @buddied: list tracking the zbud pages that contain two buddies;
- * these zbud pages are full
- * @pages_nr: number of zbud pages in the pool.
- *
- * This structure is allocated at pool creation time and maintains metadata
- * pertaining to a particular zbud pool.
- */
-struct zbud_pool {
- spinlock_t lock;
- union {
- /*
- * Reuse unbuddied[0] as buddied on the ground that
- * unbuddied[0] is unused.
- */
- struct list_head buddied;
- struct list_head unbuddied[NCHUNKS];
- };
- u64 pages_nr;
-};
-
-/*
- * struct zbud_header - zbud page metadata occupying the first chunk of each
- * zbud page.
- * @buddy: links the zbud page into the unbuddied/buddied lists in the pool
- * @first_chunks: the size of the first buddy in chunks, 0 if free
- * @last_chunks: the size of the last buddy in chunks, 0 if free
- */
-struct zbud_header {
- struct list_head buddy;
- unsigned int first_chunks;
- unsigned int last_chunks;
-};
-
-/*****************
- * Helpers
-*****************/
-/* Just to make the code easier to read */
-enum buddy {
- FIRST,
- LAST
-};
-
-/* Converts an allocation size in bytes to size in zbud chunks */
-static int size_to_chunks(size_t size)
-{
- return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
-}
-
-#define for_each_unbuddied_list(_iter, _begin) \
- for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
-
-/* Initializes the zbud header of a newly allocated zbud page */
-static struct zbud_header *init_zbud_page(struct page *page)
-{
- struct zbud_header *zhdr = page_address(page);
- zhdr->first_chunks = 0;
- zhdr->last_chunks = 0;
- INIT_LIST_HEAD(&zhdr->buddy);
- return zhdr;
-}
-
-/* Resets the struct page fields and frees the page */
-static void free_zbud_page(struct zbud_header *zhdr)
-{
- __free_page(virt_to_page(zhdr));
-}
-
-/*
- * Encodes the handle of a particular buddy within a zbud page
- * Pool lock should be held as this function accesses first|last_chunks
- */
-static unsigned long encode_handle(struct zbud_header *zhdr, enum buddy bud)
-{
- unsigned long handle;
-
- /*
- * For now, the encoded handle is actually just the pointer to the data
- * but this might not always be the case. A little information hiding.
- * Add CHUNK_SIZE to the handle if it is the first allocation to jump
- * over the zbud header in the first chunk.
- */
- handle = (unsigned long)zhdr;
- if (bud == FIRST)
- /* skip over zbud header */
- handle += ZHDR_SIZE_ALIGNED;
- else /* bud == LAST */
- handle += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
- return handle;
-}
-
-/* Returns the zbud page where a given handle is stored */
-static struct zbud_header *handle_to_zbud_header(unsigned long handle)
-{
- return (struct zbud_header *)(handle & PAGE_MASK);
-}
-
-/* Returns the number of free chunks in a zbud page */
-static int num_free_chunks(struct zbud_header *zhdr)
-{
- /*
- * Rather than branch for different situations, just use the fact that
- * free buddies have a length of zero to simplify everything.
- */
- return NCHUNKS - zhdr->first_chunks - zhdr->last_chunks;
-}
-
-/*****************
- * API Functions
-*****************/
-/**
- * zbud_create_pool() - create a new zbud pool
- * @gfp: gfp flags when allocating the zbud pool structure
- *
- * Return: pointer to the new zbud pool or NULL if the metadata allocation
- * failed.
- */
-static struct zbud_pool *zbud_create_pool(gfp_t gfp)
-{
- struct zbud_pool *pool;
- int i;
-
- pool = kzalloc(sizeof(struct zbud_pool), gfp);
- if (!pool)
- return NULL;
- spin_lock_init(&pool->lock);
- for_each_unbuddied_list(i, 0)
- INIT_LIST_HEAD(&pool->unbuddied[i]);
- INIT_LIST_HEAD(&pool->buddied);
- pool->pages_nr = 0;
- return pool;
-}
-
-/**
- * zbud_destroy_pool() - destroys an existing zbud pool
- * @pool: the zbud pool to be destroyed
- *
- * The pool should be emptied before this function is called.
- */
-static void zbud_destroy_pool(struct zbud_pool *pool)
-{
- kfree(pool);
-}
-
-/**
- * zbud_alloc() - allocates a region of a given size
- * @pool: zbud pool from which to allocate
- * @size: size in bytes of the desired allocation
- * @gfp: gfp flags used if the pool needs to grow
- * @handle: handle of the new allocation
- *
- * This function will attempt to find a free region in the pool large enough to
- * satisfy the allocation request. A search of the unbuddied lists is
- * performed first. If no suitable free region is found, then a new page is
- * allocated and added to the pool to satisfy the request.
- *
- * gfp should not set __GFP_HIGHMEM as highmem pages cannot be used
- * as zbud pool pages.
- *
- * Return: 0 if success and handle is set, otherwise -EINVAL if the size or
- * gfp arguments are invalid or -ENOMEM if the pool was unable to allocate
- * a new page.
- */
-static int zbud_alloc(struct zbud_pool *pool, size_t size, gfp_t gfp,
- unsigned long *handle)
-{
- int chunks, i, freechunks;
- struct zbud_header *zhdr = NULL;
- enum buddy bud;
- struct page *page;
-
- if (!size || (gfp & __GFP_HIGHMEM))
- return -EINVAL;
- if (size > PAGE_SIZE - ZHDR_SIZE_ALIGNED - CHUNK_SIZE)
- return -ENOSPC;
- chunks = size_to_chunks(size);
- spin_lock(&pool->lock);
-
- /* First, try to find an unbuddied zbud page. */
- for_each_unbuddied_list(i, chunks) {
- if (!list_empty(&pool->unbuddied[i])) {
- zhdr = list_first_entry(&pool->unbuddied[i],
- struct zbud_header, buddy);
- list_del(&zhdr->buddy);
- if (zhdr->first_chunks == 0)
- bud = FIRST;
- else
- bud = LAST;
- goto found;
- }
- }
-
- /* Couldn't find unbuddied zbud page, create new one */
- spin_unlock(&pool->lock);
- page = alloc_page(gfp);
- if (!page)
- return -ENOMEM;
- spin_lock(&pool->lock);
- pool->pages_nr++;
- zhdr = init_zbud_page(page);
- bud = FIRST;
-
-found:
- if (bud == FIRST)
- zhdr->first_chunks = chunks;
- else
- zhdr->last_chunks = chunks;
-
- if (zhdr->first_chunks == 0 || zhdr->last_chunks == 0) {
- /* Add to unbuddied list */
- freechunks = num_free_chunks(zhdr);
- list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
- } else {
- /* Add to buddied list */
- list_add(&zhdr->buddy, &pool->buddied);
- }
-
- *handle = encode_handle(zhdr, bud);
- spin_unlock(&pool->lock);
-
- return 0;
-}
-
-/**
- * zbud_free() - frees the allocation associated with the given handle
- * @pool: pool in which the allocation resided
- * @handle: handle associated with the allocation returned by zbud_alloc()
- */
-static void zbud_free(struct zbud_pool *pool, unsigned long handle)
-{
- struct zbud_header *zhdr;
- int freechunks;
-
- spin_lock(&pool->lock);
- zhdr = handle_to_zbud_header(handle);
-
- /* If first buddy, handle will be page aligned */
- if ((handle - ZHDR_SIZE_ALIGNED) & ~PAGE_MASK)
- zhdr->last_chunks = 0;
- else
- zhdr->first_chunks = 0;
-
- /* Remove from existing buddy list */
- list_del(&zhdr->buddy);
-
- if (zhdr->first_chunks == 0 && zhdr->last_chunks == 0) {
- /* zbud page is empty, free */
- free_zbud_page(zhdr);
- pool->pages_nr--;
- } else {
- /* Add to unbuddied list */
- freechunks = num_free_chunks(zhdr);
- list_add(&zhdr->buddy, &pool->unbuddied[freechunks]);
- }
-
- spin_unlock(&pool->lock);
-}
-
-/**
- * zbud_map() - maps the allocation associated with the given handle
- * @pool: pool in which the allocation resides
- * @handle: handle associated with the allocation to be mapped
- *
- * While trivial for zbud, the mapping functions for others allocators
- * implementing this allocation API could have more complex information encoded
- * in the handle and could create temporary mappings to make the data
- * accessible to the user.
- *
- * Returns: a pointer to the mapped allocation
- */
-static void *zbud_map(struct zbud_pool *pool, unsigned long handle)
-{
- return (void *)(handle);
-}
-
-/**
- * zbud_unmap() - maps the allocation associated with the given handle
- * @pool: pool in which the allocation resides
- * @handle: handle associated with the allocation to be unmapped
- */
-static void zbud_unmap(struct zbud_pool *pool, unsigned long handle)
-{
-}
-
-/**
- * zbud_get_pool_pages() - gets the zbud pool size in pages
- * @pool: pool whose size is being queried
- *
- * Returns: size in pages of the given pool. The pool lock need not be
- * taken to access pages_nr.
- */
-static u64 zbud_get_pool_pages(struct zbud_pool *pool)
-{
- return pool->pages_nr;
-}
-
-/*****************
- * zpool
- ****************/
-
-static void *zbud_zpool_create(const char *name, gfp_t gfp)
-{
- return zbud_create_pool(gfp);
-}
-
-static void zbud_zpool_destroy(void *pool)
-{
- zbud_destroy_pool(pool);
-}
-
-static int zbud_zpool_malloc(void *pool, size_t size, gfp_t gfp,
- unsigned long *handle)
-{
- return zbud_alloc(pool, size, gfp, handle);
-}
-static void zbud_zpool_free(void *pool, unsigned long handle)
-{
- zbud_free(pool, handle);
-}
-
-static void *zbud_zpool_map(void *pool, unsigned long handle,
- enum zpool_mapmode mm)
-{
- return zbud_map(pool, handle);
-}
-static void zbud_zpool_unmap(void *pool, unsigned long handle)
-{
- zbud_unmap(pool, handle);
-}
-
-static u64 zbud_zpool_total_pages(void *pool)
-{
- return zbud_get_pool_pages(pool);
-}
-
-static struct zpool_driver zbud_zpool_driver = {
- .type = "zbud",
- .sleep_mapped = true,
- .owner = THIS_MODULE,
- .create = zbud_zpool_create,
- .destroy = zbud_zpool_destroy,
- .malloc = zbud_zpool_malloc,
- .free = zbud_zpool_free,
- .map = zbud_zpool_map,
- .unmap = zbud_zpool_unmap,
- .total_pages = zbud_zpool_total_pages,
-};
-
-MODULE_ALIAS("zpool-zbud");
-
-static int __init init_zbud(void)
-{
- /* Make sure the zbud header will fit in one chunk */
- BUILD_BUG_ON(sizeof(struct zbud_header) > ZHDR_SIZE_ALIGNED);
- pr_info("loaded\n");
-
- zpool_register_driver(&zbud_zpool_driver);
-
- return 0;
-}
-
-static void __exit exit_zbud(void)
-{
- zpool_unregister_driver(&zbud_zpool_driver);
- pr_info("unloaded\n");
-}
-
-module_init(init_zbud);
-module_exit(exit_zbud);
-
-MODULE_LICENSE("GPL");
-MODULE_AUTHOR("Seth Jennings <sjennings@variantweb.net>");
-MODULE_DESCRIPTION("Buddy Allocator for Compressed Pages");
diff --git a/mm/zpool.c b/mm/zpool.c
index b9fda1fa857da..4bbd12d4b6599 100644
--- a/mm/zpool.c
+++ b/mm/zpool.c
@@ -95,7 +95,7 @@ static void zpool_put_driver(struct zpool_driver *driver)
/**
* zpool_has_pool() - Check if the pool driver is available
- * @type: The type of the zpool to check (e.g. zbud, zsmalloc)
+ * @type: The type of the zpool to check (e.g. zsmalloc)
*
* This checks if the @type pool driver is available. This will try to load
* the requested module, if needed, but there is no guarantee the module will
@@ -130,7 +130,7 @@ EXPORT_SYMBOL(zpool_has_pool);
/**
* zpool_create_pool() - Create a new zpool
- * @type: The type of the zpool to create (e.g. zbud, zsmalloc)
+ * @type: The type of the zpool to create (e.g. zsmalloc)
* @name: The name of the zpool (e.g. zram0, zswap)
* @gfp: The GFP flags to use when allocating the pool.
*
--
2.48.1.262.g85cc9f2d1e-goog
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