[PATCH 6/7] mm/slob: remove slob.c

Vlastimil Babka
2023-03-10T10:32:27Z

Remove the SLOB implementation.

RIP SLOB allocator (2006 - 2023)

Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
---
mm/slob.c | 757 ------------------------------------------------------
1 file changed, 757 deletions(-)
delete mode 100644 mm/slob.c

diff --git a/mm/slob.c b/mm/slob.c
deleted file mode 100644
index fe567fcfa3a3..000000000000
--- a/mm/slob.c
+++ /dev/null
@@ -1,757 +0,0 @@
-// SPDX-License-Identifier: GPL-2.0
-/*
- * SLOB Allocator: Simple List Of Blocks
- *
- * Matt Mackall <mpm@selenic.com> 12/30/03
- *
- * NUMA support by Paul Mundt, 2007.
- *
- * How SLOB works:
- *
- * The core of SLOB is a traditional K&R style heap allocator, with
- * support for returning aligned objects. The granularity of this
- * allocator is as little as 2 bytes, however typically most architectures
- * will require 4 bytes on 32-bit and 8 bytes on 64-bit.
- *
- * The slob heap is a set of linked list of pages from alloc_pages(),
- * and within each page, there is a singly-linked list of free blocks
- * (slob_t). The heap is grown on demand. To reduce fragmentation,
- * heap pages are segregated into three lists, with objects less than
- * 256 bytes, objects less than 1024 bytes, and all other objects.
- *
- * Allocation from heap involves first searching for a page with
- * sufficient free blocks (using a next-fit-like approach) followed by
- * a first-fit scan of the page. Deallocation inserts objects back
- * into the free list in address order, so this is effectively an
- * address-ordered first fit.
- *
- * Above this is an implementation of kmalloc/kfree. Blocks returned
- * from kmalloc are prepended with a 4-byte header with the kmalloc size.
- * If kmalloc is asked for objects of PAGE_SIZE or larger, it calls
- * alloc_pages() directly, allocating compound pages so the page order
- * does not have to be separately tracked.
- * These objects are detected in kfree() because folio_test_slab()
- * is false for them.
- *
- * SLAB is emulated on top of SLOB by simply calling constructors and
- * destructors for every SLAB allocation. Objects are returned with the
- * 4-byte alignment unless the SLAB_HWCACHE_ALIGN flag is set, in which
- * case the low-level allocator will fragment blocks to create the proper
- * alignment. Again, objects of page-size or greater are allocated by
- * calling alloc_pages(). As SLAB objects know their size, no separate
- * size bookkeeping is necessary and there is essentially no allocation
- * space overhead, and compound pages aren't needed for multi-page
- * allocations.
- *
- * NUMA support in SLOB is fairly simplistic, pushing most of the real
- * logic down to the page allocator, and simply doing the node accounting
- * on the upper levels. In the event that a node id is explicitly
- * provided, __alloc_pages_node() with the specified node id is used
- * instead. The common case (or when the node id isn't explicitly provided)
- * will default to the current node, as per numa_node_id().
- *
- * Node aware pages are still inserted in to the global freelist, and
- * these are scanned for by matching against the node id encoded in the
- * page flags. As a result, block allocations that can be satisfied from
- * the freelist will only be done so on pages residing on the same node,
- * in order to prevent random node placement.
- */
-
-#include <linux/kernel.h>
-#include <linux/slab.h>
-
-#include <linux/mm.h>
-#include <linux/swap.h> /* struct reclaim_state */
-#include <linux/cache.h>
-#include <linux/init.h>
-#include <linux/export.h>
-#include <linux/rcupdate.h>
-#include <linux/list.h>
-#include <linux/kmemleak.h>
-
-#include <trace/events/kmem.h>
-
-#include <linux/atomic.h>
-
-#include "slab.h"
-/*
- * slob_block has a field 'units', which indicates size of block if +ve,
- * or offset of next block if -ve (in SLOB_UNITs).
- *
- * Free blocks of size 1 unit simply contain the offset of the next block.
- * Those with larger size contain their size in the first SLOB_UNIT of
- * memory, and the offset of the next free block in the second SLOB_UNIT.
- */
-#if PAGE_SIZE <= (32767 * 2)
-typedef s16 slobidx_t;
-#else
-typedef s32 slobidx_t;
-#endif
-
-struct slob_block {
- slobidx_t units;
-};
-typedef struct slob_block slob_t;
-
-/*
- * All partially free slob pages go on these lists.
- */
-#define SLOB_BREAK1 256
-#define SLOB_BREAK2 1024
-static LIST_HEAD(free_slob_small);
-static LIST_HEAD(free_slob_medium);
-static LIST_HEAD(free_slob_large);
-
-/*
- * slob_page_free: true for pages on free_slob_pages list.
- */
-static inline int slob_page_free(struct slab *slab)
-{
- return PageSlobFree(slab_page(slab));
-}
-
-static void set_slob_page_free(struct slab *slab, struct list_head *list)
-{
- list_add(&slab->slab_list, list);
- __SetPageSlobFree(slab_page(slab));
-}
-
-static inline void clear_slob_page_free(struct slab *slab)
-{
- list_del(&slab->slab_list);
- __ClearPageSlobFree(slab_page(slab));
-}
-
-#define SLOB_UNIT sizeof(slob_t)
-#define SLOB_UNITS(size) DIV_ROUND_UP(size, SLOB_UNIT)
-
-/*
- * struct slob_rcu is inserted at the tail of allocated slob blocks, which
- * were created with a SLAB_TYPESAFE_BY_RCU slab. slob_rcu is used to free
- * the block using call_rcu.
- */
-struct slob_rcu {
- struct rcu_head head;
- int size;
-};
-
-/*
- * slob_lock protects all slob allocator structures.
- */
-static DEFINE_SPINLOCK(slob_lock);
-
-/*
- * Encode the given size and next info into a free slob block s.
- */
-static void set_slob(slob_t *s, slobidx_t size, slob_t *next)
-{
- slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
- slobidx_t offset = next - base;
-
- if (size > 1) {
- s[0].units = size;
- s[1].units = offset;
- } else
- s[0].units = -offset;
-}
-
-/*
- * Return the size of a slob block.
- */
-static slobidx_t slob_units(slob_t *s)
-{
- if (s->units > 0)
- return s->units;
- return 1;
-}
-
-/*
- * Return the next free slob block pointer after this one.
- */
-static slob_t *slob_next(slob_t *s)
-{
- slob_t *base = (slob_t *)((unsigned long)s & PAGE_MASK);
- slobidx_t next;
-
- if (s[0].units < 0)
- next = -s[0].units;
- else
- next = s[1].units;
- return base+next;
-}
-
-/*
- * Returns true if s is the last free block in its page.
- */
-static int slob_last(slob_t *s)
-{
- return !((unsigned long)slob_next(s) & ~PAGE_MASK);
-}
-
-static void *slob_new_pages(gfp_t gfp, int order, int node)
-{
- struct page *page;
-
-#ifdef CONFIG_NUMA
- if (node != NUMA_NO_NODE)
- page = __alloc_pages_node(node, gfp, order);
- else
-#endif
- page = alloc_pages(gfp, order);
-
- if (!page)
- return NULL;
-
- mod_node_page_state(page_pgdat(page), NR_SLAB_UNRECLAIMABLE_B,
- PAGE_SIZE << order);
- return page_address(page);
-}
-
-static void slob_free_pages(void *b, int order)
-{
- struct page *sp = virt_to_page(b);
-
- if (current->reclaim_state)
- current->reclaim_state->reclaimed_slab += 1 << order;
-
- mod_node_page_state(page_pgdat(sp), NR_SLAB_UNRECLAIMABLE_B,
- -(PAGE_SIZE << order));
- __free_pages(sp, order);
-}
-
-/*
- * slob_page_alloc() - Allocate a slob block within a given slob_page sp.
- * @sp: Page to look in.
- * @size: Size of the allocation.
- * @align: Allocation alignment.
- * @align_offset: Offset in the allocated block that will be aligned.
- * @page_removed_from_list: Return parameter.
- *
- * Tries to find a chunk of memory at least @size bytes big within @page.
- *
- * Return: Pointer to memory if allocated, %NULL otherwise. If the
- * allocation fills up @page then the page is removed from the
- * freelist, in this case @page_removed_from_list will be set to
- * true (set to false otherwise).
- */
-static void *slob_page_alloc(struct slab *sp, size_t size, int align,
- int align_offset, bool *page_removed_from_list)
-{
- slob_t *prev, *cur, *aligned = NULL;
- int delta = 0, units = SLOB_UNITS(size);
-
- *page_removed_from_list = false;
- for (prev = NULL, cur = sp->freelist; ; prev = cur, cur = slob_next(cur)) {
- slobidx_t avail = slob_units(cur);
-
- /*
- * 'aligned' will hold the address of the slob block so that the
- * address 'aligned'+'align_offset' is aligned according to the
- * 'align' parameter. This is for kmalloc() which prepends the
- * allocated block with its size, so that the block itself is
- * aligned when needed.
- */
- if (align) {
- aligned = (slob_t *)
- (ALIGN((unsigned long)cur + align_offset, align)
- - align_offset);
- delta = aligned - cur;
- }
- if (avail >= units + delta) { /* room enough? */
- slob_t *next;
-
- if (delta) { /* need to fragment head to align? */
- next = slob_next(cur);
- set_slob(aligned, avail - delta, next);
- set_slob(cur, delta, aligned);
- prev = cur;
- cur = aligned;
- avail = slob_units(cur);
- }
-
- next = slob_next(cur);
- if (avail == units) { /* exact fit? unlink. */
- if (prev)
- set_slob(prev, slob_units(prev), next);
- else
- sp->freelist = next;
- } else { /* fragment */
- if (prev)
- set_slob(prev, slob_units(prev), cur + units);
- else
- sp->freelist = cur + units;
- set_slob(cur + units, avail - units, next);
- }
-
- sp->units -= units;
- if (!sp->units) {
- clear_slob_page_free(sp);
- *page_removed_from_list = true;
- }
- return cur;
- }
- if (slob_last(cur))
- return NULL;
- }
-}
-
-/*
- * slob_alloc: entry point into the slob allocator.
- */
-static void *slob_alloc(size_t size, gfp_t gfp, int align, int node,
- int align_offset)
-{
- struct folio *folio;
- struct slab *sp;
- struct list_head *slob_list;
- slob_t *b = NULL;
- unsigned long flags;
- bool _unused;
-
- if (size < SLOB_BREAK1)
- slob_list = &free_slob_small;
- else if (size < SLOB_BREAK2)
- slob_list = &free_slob_medium;
- else
- slob_list = &free_slob_large;
-
- spin_lock_irqsave(&slob_lock, flags);
- /* Iterate through each partially free page, try to find room */
- list_for_each_entry(sp, slob_list, slab_list) {
- bool page_removed_from_list = false;
-#ifdef CONFIG_NUMA
- /*
- * If there's a node specification, search for a partial
- * page with a matching node id in the freelist.
- */
- if (node != NUMA_NO_NODE && slab_nid(sp) != node)
- continue;
-#endif
- /* Enough room on this page? */
- if (sp->units < SLOB_UNITS(size))
- continue;
-
- b = slob_page_alloc(sp, size, align, align_offset, &page_removed_from_list);
- if (!b)
- continue;
-
- /*
- * If slob_page_alloc() removed sp from the list then we
- * cannot call list functions on sp. If so allocation
- * did not fragment the page anyway so optimisation is
- * unnecessary.
- */
- if (!page_removed_from_list) {
- /*
- * Improve fragment distribution and reduce our average
- * search time by starting our next search here. (see
- * Knuth vol 1, sec 2.5, pg 449)
- */
- if (!list_is_first(&sp->slab_list, slob_list))
- list_rotate_to_front(&sp->slab_list, slob_list);
- }
- break;
- }
- spin_unlock_irqrestore(&slob_lock, flags);
-
- /* Not enough space: must allocate a new page */
- if (!b) {
- b = slob_new_pages(gfp & ~__GFP_ZERO, 0, node);
- if (!b)
- return NULL;
- folio = virt_to_folio(b);
- __folio_set_slab(folio);
- sp = folio_slab(folio);
-
- spin_lock_irqsave(&slob_lock, flags);
- sp->units = SLOB_UNITS(PAGE_SIZE);
- sp->freelist = b;
- INIT_LIST_HEAD(&sp->slab_list);
- set_slob(b, SLOB_UNITS(PAGE_SIZE), b + SLOB_UNITS(PAGE_SIZE));
- set_slob_page_free(sp, slob_list);
- b = slob_page_alloc(sp, size, align, align_offset, &_unused);
- BUG_ON(!b);
- spin_unlock_irqrestore(&slob_lock, flags);
- }
- if (unlikely(gfp & __GFP_ZERO))
- memset(b, 0, size);
- return b;
-}
-
-/*
- * slob_free: entry point into the slob allocator.
- */
-static void slob_free(void *block, int size)
-{
- struct slab *sp;
- slob_t *prev, *next, *b = (slob_t *)block;
- slobidx_t units;
- unsigned long flags;
- struct list_head *slob_list;
-
- if (unlikely(ZERO_OR_NULL_PTR(block)))
- return;
- BUG_ON(!size);
-
- sp = virt_to_slab(block);
- units = SLOB_UNITS(size);
-
- spin_lock_irqsave(&slob_lock, flags);
-
- if (sp->units + units == SLOB_UNITS(PAGE_SIZE)) {
- /* Go directly to page allocator. Do not pass slob allocator */
- if (slob_page_free(sp))
- clear_slob_page_free(sp);
- spin_unlock_irqrestore(&slob_lock, flags);
- __folio_clear_slab(slab_folio(sp));
- slob_free_pages(b, 0);
- return;
- }
-
- if (!slob_page_free(sp)) {
- /* This slob page is about to become partially free. Easy! */
- sp->units = units;
- sp->freelist = b;
- set_slob(b, units,
- (void *)((unsigned long)(b +
- SLOB_UNITS(PAGE_SIZE)) & PAGE_MASK));
- if (size < SLOB_BREAK1)
- slob_list = &free_slob_small;
- else if (size < SLOB_BREAK2)
- slob_list = &free_slob_medium;
- else
- slob_list = &free_slob_large;
- set_slob_page_free(sp, slob_list);
- goto out;
- }
-
- /*
- * Otherwise the page is already partially free, so find reinsertion
- * point.
- */
- sp->units += units;
-
- if (b < (slob_t *)sp->freelist) {
- if (b + units == sp->freelist) {
- units += slob_units(sp->freelist);
- sp->freelist = slob_next(sp->freelist);
- }
- set_slob(b, units, sp->freelist);
- sp->freelist = b;
- } else {
- prev = sp->freelist;
- next = slob_next(prev);
- while (b > next) {
- prev = next;
- next = slob_next(prev);
- }
-
- if (!slob_last(prev) && b + units == next) {
- units += slob_units(next);
- set_slob(b, units, slob_next(next));
- } else
- set_slob(b, units, next);
-
- if (prev + slob_units(prev) == b) {
- units = slob_units(b) + slob_units(prev);
- set_slob(prev, units, slob_next(b));
- } else
- set_slob(prev, slob_units(prev), b);
- }
-out:
- spin_unlock_irqrestore(&slob_lock, flags);
-}
-
-#ifdef CONFIG_PRINTK
-void __kmem_obj_info(struct kmem_obj_info *kpp, void *object, struct slab *slab)
-{
- kpp->kp_ptr = object;
- kpp->kp_slab = slab;
-}
-#endif
-
-/*
- * End of slob allocator proper. Begin kmem_cache_alloc and kmalloc frontend.
- */
-
-static __always_inline void *
-__do_kmalloc_node(size_t size, gfp_t gfp, int node, unsigned long caller)
-{
- unsigned int *m;
- unsigned int minalign;
- void *ret;
-
- minalign = max_t(unsigned int, ARCH_KMALLOC_MINALIGN,
- arch_slab_minalign());
- gfp &= gfp_allowed_mask;
-
- might_alloc(gfp);
-
- if (size < PAGE_SIZE - minalign) {
- int align = minalign;
-
- /*
- * For power of two sizes, guarantee natural alignment for
- * kmalloc()'d objects.
- */
- if (is_power_of_2(size))
- align = max_t(unsigned int, minalign, size);
-
- if (!size)
- return ZERO_SIZE_PTR;
-
- m = slob_alloc(size + minalign, gfp, align, node, minalign);
-
- if (!m)
- return NULL;
- *m = size;
- ret = (void *)m + minalign;
-
- trace_kmalloc(caller, ret, size, size + minalign, gfp, node);
- } else {
- unsigned int order = get_order(size);
-
- if (likely(order))
- gfp |= __GFP_COMP;
- ret = slob_new_pages(gfp, order, node);
-
- trace_kmalloc(caller, ret, size, PAGE_SIZE << order, gfp, node);
- }
-
- kmemleak_alloc(ret, size, 1, gfp);
- return ret;
-}
-
-void *__kmalloc(size_t size, gfp_t gfp)
-{
- return __do_kmalloc_node(size, gfp, NUMA_NO_NODE, _RET_IP_);
-}
-EXPORT_SYMBOL(__kmalloc);
-
-void *__kmalloc_node_track_caller(size_t size, gfp_t gfp,
- int node, unsigned long caller)
-{
- return __do_kmalloc_node(size, gfp, node, caller);
-}
-EXPORT_SYMBOL(__kmalloc_node_track_caller);
-
-void kfree(const void *block)
-{
- struct folio *sp;
-
- trace_kfree(_RET_IP_, block);
-
- if (unlikely(ZERO_OR_NULL_PTR(block)))
- return;
- kmemleak_free(block);
-
- sp = virt_to_folio(block);
- if (folio_test_slab(sp)) {
- unsigned int align = max_t(unsigned int,
- ARCH_KMALLOC_MINALIGN,
- arch_slab_minalign());
- unsigned int *m = (unsigned int *)(block - align);
-
- slob_free(m, *m + align);
- } else {
- unsigned int order = folio_order(sp);
-
- mod_node_page_state(folio_pgdat(sp), NR_SLAB_UNRECLAIMABLE_B,
- -(PAGE_SIZE << order));
- __free_pages(folio_page(sp, 0), order);
-
- }
-}
-EXPORT_SYMBOL(kfree);
-
-size_t kmalloc_size_roundup(size_t size)
-{
- /* Short-circuit the 0 size case. */
- if (unlikely(size == 0))
- return 0;
- /* Short-circuit saturated "too-large" case. */
- if (unlikely(size == SIZE_MAX))
- return SIZE_MAX;
-
- return ALIGN(size, ARCH_KMALLOC_MINALIGN);
-}
-
-EXPORT_SYMBOL(kmalloc_size_roundup);
-
-/* can't use ksize for kmem_cache_alloc memory, only kmalloc */
-size_t __ksize(const void *block)
-{
- struct folio *folio;
- unsigned int align;
- unsigned int *m;
-
- BUG_ON(!block);
- if (unlikely(block == ZERO_SIZE_PTR))
- return 0;
-
- folio = virt_to_folio(block);
- if (unlikely(!folio_test_slab(folio)))
- return folio_size(folio);
-
- align = max_t(unsigned int, ARCH_KMALLOC_MINALIGN,
- arch_slab_minalign());
- m = (unsigned int *)(block - align);
- return SLOB_UNITS(*m) * SLOB_UNIT;
-}
-
-int __kmem_cache_create(struct kmem_cache *c, slab_flags_t flags)
-{
- if (flags & SLAB_TYPESAFE_BY_RCU) {
- /* leave room for rcu footer at the end of object */
- c->size += sizeof(struct slob_rcu);
- }
-
- /* Actual size allocated */
- c->size = SLOB_UNITS(c->size) * SLOB_UNIT;
- c->flags = flags;
- return 0;
-}
-
-static void *slob_alloc_node(struct kmem_cache *c, gfp_t flags, int node)
-{
- void *b;
-
- flags &= gfp_allowed_mask;
-
- might_alloc(flags);
-
- if (c->size < PAGE_SIZE) {
- b = slob_alloc(c->size, flags, c->align, node, 0);
- trace_kmem_cache_alloc(_RET_IP_, b, c, flags, node);
- } else {
- b = slob_new_pages(flags, get_order(c->size), node);
- trace_kmem_cache_alloc(_RET_IP_, b, c, flags, node);
- }
-
- if (b && c->ctor) {
- WARN_ON_ONCE(flags & __GFP_ZERO);
- c->ctor(b);
- }
-
- kmemleak_alloc_recursive(b, c->size, 1, c->flags, flags);
- return b;
-}
-
-void *kmem_cache_alloc(struct kmem_cache *cachep, gfp_t flags)
-{
- return slob_alloc_node(cachep, flags, NUMA_NO_NODE);
-}
-EXPORT_SYMBOL(kmem_cache_alloc);
-
-
-void *kmem_cache_alloc_lru(struct kmem_cache *cachep, struct list_lru *lru, gfp_t flags)
-{
- return slob_alloc_node(cachep, flags, NUMA_NO_NODE);
-}
-EXPORT_SYMBOL(kmem_cache_alloc_lru);
-
-void *__kmalloc_node(size_t size, gfp_t gfp, int node)
-{
- return __do_kmalloc_node(size, gfp, node, _RET_IP_);
-}
-EXPORT_SYMBOL(__kmalloc_node);
-
-void *kmem_cache_alloc_node(struct kmem_cache *cachep, gfp_t gfp, int node)
-{
- return slob_alloc_node(cachep, gfp, node);
-}
-EXPORT_SYMBOL(kmem_cache_alloc_node);
-
-static void __kmem_cache_free(void *b, int size)
-{
- if (size < PAGE_SIZE)
- slob_free(b, size);
- else
- slob_free_pages(b, get_order(size));
-}
-
-static void kmem_rcu_free(struct rcu_head *head)
-{
- struct slob_rcu *slob_rcu = (struct slob_rcu *)head;
- void *b = (void *)slob_rcu - (slob_rcu->size - sizeof(struct slob_rcu));
-
- __kmem_cache_free(b, slob_rcu->size);
-}
-
-void kmem_cache_free(struct kmem_cache *c, void *b)
-{
- kmemleak_free_recursive(b, c->flags);
- trace_kmem_cache_free(_RET_IP_, b, c);
- if (unlikely(c->flags & SLAB_TYPESAFE_BY_RCU)) {
- struct slob_rcu *slob_rcu;
- slob_rcu = b + (c->size - sizeof(struct slob_rcu));
- slob_rcu->size = c->size;
- call_rcu(&slob_rcu->head, kmem_rcu_free);
- } else {
- __kmem_cache_free(b, c->size);
- }
-}
-EXPORT_SYMBOL(kmem_cache_free);
-
-void kmem_cache_free_bulk(struct kmem_cache *s, size_t nr, void **p)
-{
- size_t i;
-
- for (i = 0; i < nr; i++) {
- if (s)
- kmem_cache_free(s, p[i]);
- else
- kfree(p[i]);
- }
-}
-EXPORT_SYMBOL(kmem_cache_free_bulk);
-
-int kmem_cache_alloc_bulk(struct kmem_cache *s, gfp_t flags, size_t nr,
- void **p)
-{
- size_t i;
-
- for (i = 0; i < nr; i++) {
- void *x = p[i] = kmem_cache_alloc(s, flags);
-
- if (!x) {
- kmem_cache_free_bulk(s, i, p);
- return 0;
- }
- }
- return i;
-}
-EXPORT_SYMBOL(kmem_cache_alloc_bulk);
-
-int __kmem_cache_shutdown(struct kmem_cache *c)
-{
- /* No way to check for remaining objects */
- return 0;
-}
-
-void __kmem_cache_release(struct kmem_cache *c)
-{
-}
-
-int __kmem_cache_shrink(struct kmem_cache *d)
-{
- return 0;
-}
-
-static struct kmem_cache kmem_cache_boot = {
- .name = "kmem_cache",
- .size = sizeof(struct kmem_cache),
- .flags = SLAB_PANIC,
- .align = ARCH_KMALLOC_MINALIGN,
-};
-
-void __init kmem_cache_init(void)
-{
- kmem_cache = &kmem_cache_boot;
- slab_state = UP;
-}
-
-void __init kmem_cache_init_late(void)
-{
- slab_state = FULL;
-}
--
2.39.2