blob: a7c436127aa121064a195936979ca01eada57733 [file] [log] [blame]
/*
* zbud.c - Compression buddies allocator
*
* Copyright (c) 2010-2012, Dan Magenheimer, Oracle Corp.
*
* Compression buddies ("zbud") provides for efficiently packing two
* (or, possibly in the future, more) compressed pages ("zpages") into
* a single "raw" pageframe and for tracking both zpages and pageframes
* so that whole pageframes can be easily reclaimed in LRU-like order.
* It is designed to be used in conjunction with transcendent memory
* ("tmem"); for example separate LRU lists are maintained for persistent
* vs. ephemeral pages.
*
* A zbudpage is an overlay for a struct page and thus each zbudpage
* refers to a physical pageframe of RAM. When the caller passes a
* struct page from the kernel's page allocator, zbud "transforms" it
* to a zbudpage which sets/uses a different set of fields than the
* struct-page and thus must "untransform" it back by reinitializing
* certain fields before the struct-page can be freed. The fields
* of a zbudpage include a page lock for controlling access to the
* corresponding pageframe, and there is a size field for each zpage.
* Each zbudpage also lives on two linked lists: a "budlist" which is
* used to support efficient buddying of zpages; and an "lru" which
* is used for reclaiming pageframes in approximately least-recently-used
* order.
*
* A zbudpageframe is a pageframe divided up into aligned 64-byte "chunks"
* which contain the compressed data for zero, one, or two zbuds. Contained
* with the compressed data is a tmem_handle which is a key to allow
* the same data to be found via the tmem interface so the zpage can
* be invalidated (for ephemeral pages) or repatriated to the swap cache
* (for persistent pages). The contents of a zbudpageframe must never
* be accessed without holding the page lock for the corresponding
* zbudpage and, to accomodate highmem machines, the contents may
* only be examined or changes when kmapped. Thus, when in use, a
* kmapped zbudpageframe is referred to in the zbud code as "void *zbpg".
*
* Note that the term "zbud" refers to the combination of a zpage and
* a tmem_handle that is stored as one of possibly two "buddied" zpages;
* it also generically refers to this allocator... sorry for any confusion.
*
* A zbudref is a pointer to a struct zbudpage (which can be cast to a
* struct page), with the LSB either cleared or set to indicate, respectively,
* the first or second zpage in the zbudpageframe. Since a zbudref can be
* cast to a pointer, it is used as the tmem "pampd" pointer and uniquely
* references a stored tmem page and so is the only zbud data structure
* externally visible to zbud.c/zbud.h.
*
* Since we wish to reclaim entire pageframes but zpages may be randomly
* added and deleted to any given pageframe, we approximate LRU by
* promoting a pageframe to MRU when a zpage is added to it, but
* leaving it at the current place in the list when a zpage is deleted
* from it. As a side effect, zpages that are difficult to buddy (e.g.
* very large paages) will be reclaimed faster than average, which seems
* reasonable.
*
* In the current implementation, no more than two zpages may be stored in
* any pageframe and no zpage ever crosses a pageframe boundary. While
* other zpage allocation mechanisms may allow greater density, this two
* zpage-per-pageframe limit both ensures simple reclaim of pageframes
* (including garbage collection of references to the contents of those
* pageframes from tmem data structures) AND avoids the need for compaction.
* With additional complexity, zbud could be modified to support storing
* up to three zpages per pageframe or, to handle larger average zpages,
* up to three zpages per pair of pageframes, but it is not clear if the
* additional complexity would be worth it. So consider it an exercise
* for future developers.
*
* Note also that zbud does no page allocation or freeing. This is so
* that the caller has complete control over and, for accounting, visibility
* into if/when pages are allocated and freed.
*
* Finally, note that zbud limits the size of zpages it can store; the
* caller must check the zpage size with zbud_max_buddy_size before
* storing it, else BUGs will result. User beware.
*/
#include <linux/module.h>
#include <linux/highmem.h>
#include <linux/list.h>
#include <linux/spinlock.h>
#include <linux/pagemap.h>
#include <linux/atomic.h>
#include <linux/bug.h>
#include "tmem.h"
#include "zcache.h"
#include "zbud.h"
/*
* We need to ensure that a struct zbudpage is never larger than a
* struct page. This is checked with a BUG_ON in zbud_init.
*
* The unevictable field indicates that a zbud is being added to the
* zbudpage. Since this is a two-phase process (due to tmem locking),
* this field locks the zbudpage against eviction when a zbud match
* or creation is in process. Since this addition process may occur
* in parallel for two zbuds in one zbudpage, the field is a counter
* that must not exceed two.
*/
struct zbudpage {
union {
struct page page;
struct {
unsigned long space_for_flags;
struct {
unsigned zbud0_size:12;
unsigned zbud1_size:12;
unsigned unevictable:2;
};
struct list_head budlist;
struct list_head lru;
};
};
};
struct zbudref {
union {
struct zbudpage *zbudpage;
unsigned long zbudref;
};
};
#define CHUNK_SHIFT 6
#define CHUNK_SIZE (1 << CHUNK_SHIFT)
#define CHUNK_MASK (~(CHUNK_SIZE-1))
#define NCHUNKS (PAGE_SIZE >> CHUNK_SHIFT)
#define MAX_CHUNK (NCHUNKS-1)
/*
* The following functions deal with the difference between struct
* page and struct zbudpage. Note the hack of using the pageflags
* from struct page; this is to avoid duplicating all the complex
* pageflag macros.
*/
static inline void zbudpage_spin_lock(struct zbudpage *zbudpage)
{
struct page *page = (struct page *)zbudpage;
while (unlikely(test_and_set_bit_lock(PG_locked, &page->flags))) {
do {
cpu_relax();
} while (test_bit(PG_locked, &page->flags));
}
}
static inline void zbudpage_spin_unlock(struct zbudpage *zbudpage)
{
struct page *page = (struct page *)zbudpage;
clear_bit(PG_locked, &page->flags);
}
static inline int zbudpage_spin_trylock(struct zbudpage *zbudpage)
{
return trylock_page((struct page *)zbudpage);
}
static inline int zbudpage_is_locked(struct zbudpage *zbudpage)
{
return PageLocked((struct page *)zbudpage);
}
static inline void *kmap_zbudpage_atomic(struct zbudpage *zbudpage)
{
return kmap_atomic((struct page *)zbudpage);
}
/*
* A dying zbudpage is an ephemeral page in the process of being evicted.
* Any data contained in the zbudpage is invalid and we are just waiting for
* the tmem pampds to be invalidated before freeing the page
*/
static inline int zbudpage_is_dying(struct zbudpage *zbudpage)
{
struct page *page = (struct page *)zbudpage;
return test_bit(PG_reclaim, &page->flags);
}
static inline void zbudpage_set_dying(struct zbudpage *zbudpage)
{
struct page *page = (struct page *)zbudpage;
set_bit(PG_reclaim, &page->flags);
}
static inline void zbudpage_clear_dying(struct zbudpage *zbudpage)
{
struct page *page = (struct page *)zbudpage;
clear_bit(PG_reclaim, &page->flags);
}
/*
* A zombie zbudpage is a persistent page in the process of being evicted.
* The data contained in the zbudpage is valid and we are just waiting for
* the tmem pampds to be invalidated before freeing the page
*/
static inline int zbudpage_is_zombie(struct zbudpage *zbudpage)
{
struct page *page = (struct page *)zbudpage;
return test_bit(PG_dirty, &page->flags);
}
static inline void zbudpage_set_zombie(struct zbudpage *zbudpage)
{
struct page *page = (struct page *)zbudpage;
set_bit(PG_dirty, &page->flags);
}
static inline void zbudpage_clear_zombie(struct zbudpage *zbudpage)
{
struct page *page = (struct page *)zbudpage;
clear_bit(PG_dirty, &page->flags);
}
static inline void kunmap_zbudpage_atomic(void *zbpg)
{
kunmap_atomic(zbpg);
}
/*
* zbud "translation" and helper functions
*/
static inline struct zbudpage *zbudref_to_zbudpage(struct zbudref *zref)
{
unsigned long zbud = (unsigned long)zref;
zbud &= ~1UL;
return (struct zbudpage *)zbud;
}
static inline struct zbudref *zbudpage_to_zbudref(struct zbudpage *zbudpage,
unsigned budnum)
{
unsigned long zbud = (unsigned long)zbudpage;
BUG_ON(budnum > 1);
zbud |= budnum;
return (struct zbudref *)zbud;
}
static inline int zbudref_budnum(struct zbudref *zbudref)
{
unsigned long zbud = (unsigned long)zbudref;
return zbud & 1UL;
}
static inline unsigned zbud_max_size(void)
{
return MAX_CHUNK << CHUNK_SHIFT;
}
static inline unsigned zbud_size_to_chunks(unsigned size)
{
BUG_ON(size == 0 || size > zbud_max_size());
return (size + CHUNK_SIZE - 1) >> CHUNK_SHIFT;
}
/* can only be used between kmap_zbudpage_atomic/kunmap_zbudpage_atomic! */
static inline char *zbud_data(void *zbpg,
unsigned budnum, unsigned size)
{
char *p;
BUG_ON(size == 0 || size > zbud_max_size());
p = (char *)zbpg;
if (budnum == 1)
p += PAGE_SIZE - ((size + CHUNK_SIZE - 1) & CHUNK_MASK);
return p;
}
/*
* These are all informative and exposed through debugfs... except for
* the arrays... anyone know how to do that? To avoid confusion for
* debugfs viewers, some of these should also be atomic_long_t, but
* I don't know how to expose atomics via debugfs either...
*/
static unsigned long zbud_eph_pageframes;
static unsigned long zbud_pers_pageframes;
static unsigned long zbud_eph_zpages;
static unsigned long zbud_pers_zpages;
static u64 zbud_eph_zbytes;
static u64 zbud_pers_zbytes;
static unsigned long zbud_eph_evicted_pageframes;
static unsigned long zbud_pers_evicted_pageframes;
static unsigned long zbud_eph_cumul_zpages;
static unsigned long zbud_pers_cumul_zpages;
static u64 zbud_eph_cumul_zbytes;
static u64 zbud_pers_cumul_zbytes;
static unsigned long zbud_eph_cumul_chunk_counts[NCHUNKS];
static unsigned long zbud_pers_cumul_chunk_counts[NCHUNKS];
static unsigned long zbud_eph_buddied_count;
static unsigned long zbud_pers_buddied_count;
static unsigned long zbud_eph_unbuddied_count;
static unsigned long zbud_pers_unbuddied_count;
static unsigned long zbud_eph_zombie_count;
static unsigned long zbud_pers_zombie_count;
static atomic_t zbud_eph_zombie_atomic;
static atomic_t zbud_pers_zombie_atomic;
#ifdef CONFIG_DEBUG_FS
#include <linux/debugfs.h>
#define zdfs debugfs_create_size_t
#define zdfs64 debugfs_create_u64
static int zbud_debugfs_init(void)
{
struct dentry *root = debugfs_create_dir("zbud", NULL);
if (root == NULL)
return -ENXIO;
/*
* would be nice to dump the sizes of the unbuddied
* arrays, like was done with sysfs, but it doesn't
* look like debugfs is flexible enough to do that
*/
zdfs64("eph_zbytes", S_IRUGO, root, &zbud_eph_zbytes);
zdfs64("eph_cumul_zbytes", S_IRUGO, root, &zbud_eph_cumul_zbytes);
zdfs64("pers_zbytes", S_IRUGO, root, &zbud_pers_zbytes);
zdfs64("pers_cumul_zbytes", S_IRUGO, root, &zbud_pers_cumul_zbytes);
zdfs("eph_cumul_zpages", S_IRUGO, root, &zbud_eph_cumul_zpages);
zdfs("eph_evicted_pageframes", S_IRUGO, root,
&zbud_eph_evicted_pageframes);
zdfs("eph_zpages", S_IRUGO, root, &zbud_eph_zpages);
zdfs("eph_pageframes", S_IRUGO, root, &zbud_eph_pageframes);
zdfs("eph_buddied_count", S_IRUGO, root, &zbud_eph_buddied_count);
zdfs("eph_unbuddied_count", S_IRUGO, root, &zbud_eph_unbuddied_count);
zdfs("pers_cumul_zpages", S_IRUGO, root, &zbud_pers_cumul_zpages);
zdfs("pers_evicted_pageframes", S_IRUGO, root,
&zbud_pers_evicted_pageframes);
zdfs("pers_zpages", S_IRUGO, root, &zbud_pers_zpages);
zdfs("pers_pageframes", S_IRUGO, root, &zbud_pers_pageframes);
zdfs("pers_buddied_count", S_IRUGO, root, &zbud_pers_buddied_count);
zdfs("pers_unbuddied_count", S_IRUGO, root, &zbud_pers_unbuddied_count);
zdfs("pers_zombie_count", S_IRUGO, root, &zbud_pers_zombie_count);
return 0;
}
#undef zdfs
#undef zdfs64
#endif
/* protects the buddied list and all unbuddied lists */
static DEFINE_SPINLOCK(zbud_eph_lists_lock);
static DEFINE_SPINLOCK(zbud_pers_lists_lock);
struct zbud_unbuddied {
struct list_head list;
unsigned count;
};
/* list N contains pages with N chunks USED and NCHUNKS-N unused */
/* element 0 is never used but optimizing that isn't worth it */
static struct zbud_unbuddied zbud_eph_unbuddied[NCHUNKS];
static struct zbud_unbuddied zbud_pers_unbuddied[NCHUNKS];
static LIST_HEAD(zbud_eph_lru_list);
static LIST_HEAD(zbud_pers_lru_list);
static LIST_HEAD(zbud_eph_buddied_list);
static LIST_HEAD(zbud_pers_buddied_list);
static LIST_HEAD(zbud_eph_zombie_list);
static LIST_HEAD(zbud_pers_zombie_list);
/*
* Given a struct page, transform it to a zbudpage so that it can be
* used by zbud and initialize fields as necessary.
*/
static inline struct zbudpage *zbud_init_zbudpage(struct page *page, bool eph)
{
struct zbudpage *zbudpage = (struct zbudpage *)page;
BUG_ON(page == NULL);
INIT_LIST_HEAD(&zbudpage->budlist);
INIT_LIST_HEAD(&zbudpage->lru);
zbudpage->zbud0_size = 0;
zbudpage->zbud1_size = 0;
zbudpage->unevictable = 0;
if (eph)
zbud_eph_pageframes++;
else
zbud_pers_pageframes++;
return zbudpage;
}
/* "Transform" a zbudpage back to a struct page suitable to free. */
static inline struct page *zbud_unuse_zbudpage(struct zbudpage *zbudpage,
bool eph)
{
struct page *page = (struct page *)zbudpage;
BUG_ON(!list_empty(&zbudpage->budlist));
BUG_ON(!list_empty(&zbudpage->lru));
BUG_ON(zbudpage->zbud0_size != 0);
BUG_ON(zbudpage->zbud1_size != 0);
BUG_ON(!PageLocked(page));
BUG_ON(zbudpage->unevictable != 0);
BUG_ON(zbudpage_is_dying(zbudpage));
BUG_ON(zbudpage_is_zombie(zbudpage));
if (eph)
zbud_eph_pageframes--;
else
zbud_pers_pageframes--;
zbudpage_spin_unlock(zbudpage);
reset_page_mapcount(page);
init_page_count(page);
page->index = 0;
return page;
}
/* Mark a zbud as unused and do accounting */
static inline void zbud_unuse_zbud(struct zbudpage *zbudpage,
int budnum, bool eph)
{
unsigned size;
BUG_ON(!zbudpage_is_locked(zbudpage));
if (budnum == 0) {
size = zbudpage->zbud0_size;
zbudpage->zbud0_size = 0;
} else {
size = zbudpage->zbud1_size;
zbudpage->zbud1_size = 0;
}
if (eph) {
zbud_eph_zbytes -= size;
zbud_eph_zpages--;
} else {
zbud_pers_zbytes -= size;
zbud_pers_zpages--;
}
}
/*
* Given a zbudpage/budnum/size, a tmem handle, and a kmapped pointer
* to some data, set up the zbud appropriately including data copying
* and accounting. Note that if cdata is NULL, the data copying is
* skipped. (This is useful for lazy writes such as for RAMster.)
*/
static void zbud_init_zbud(struct zbudpage *zbudpage, struct tmem_handle *th,
bool eph, void *cdata,
unsigned budnum, unsigned size)
{
char *to;
void *zbpg;
struct tmem_handle *to_th;
unsigned nchunks = zbud_size_to_chunks(size);
BUG_ON(!zbudpage_is_locked(zbudpage));
zbpg = kmap_zbudpage_atomic(zbudpage);
to = zbud_data(zbpg, budnum, size);
to_th = (struct tmem_handle *)to;
to_th->index = th->index;
to_th->oid = th->oid;
to_th->pool_id = th->pool_id;
to_th->client_id = th->client_id;
to += sizeof(struct tmem_handle);
if (cdata != NULL)
memcpy(to, cdata, size - sizeof(struct tmem_handle));
kunmap_zbudpage_atomic(zbpg);
if (budnum == 0)
zbudpage->zbud0_size = size;
else
zbudpage->zbud1_size = size;
if (eph) {
zbud_eph_cumul_chunk_counts[nchunks]++;
zbud_eph_zpages++;
zbud_eph_cumul_zpages++;
zbud_eph_zbytes += size;
zbud_eph_cumul_zbytes += size;
} else {
zbud_pers_cumul_chunk_counts[nchunks]++;
zbud_pers_zpages++;
zbud_pers_cumul_zpages++;
zbud_pers_zbytes += size;
zbud_pers_cumul_zbytes += size;
}
}
/*
* Given a locked dying zbudpage, read out the tmem handles from the data,
* unlock the page, then use the handles to tell tmem to flush out its
* references
*/
static void zbud_evict_tmem(struct zbudpage *zbudpage)
{
int i, j;
uint32_t pool_id[2], client_id[2];
uint32_t index[2];
struct tmem_oid oid[2];
struct tmem_pool *pool;
void *zbpg;
struct tmem_handle *th;
unsigned size;
/* read out the tmem handles from the data and set aside */
zbpg = kmap_zbudpage_atomic(zbudpage);
for (i = 0, j = 0; i < 2; i++) {
size = (i == 0) ? zbudpage->zbud0_size : zbudpage->zbud1_size;
if (size) {
th = (struct tmem_handle *)zbud_data(zbpg, i, size);
client_id[j] = th->client_id;
pool_id[j] = th->pool_id;
oid[j] = th->oid;
index[j] = th->index;
j++;
zbud_unuse_zbud(zbudpage, i, true);
}
}
kunmap_zbudpage_atomic(zbpg);
zbudpage_spin_unlock(zbudpage);
/* zbudpage is now an unlocked dying... tell tmem to flush pointers */
for (i = 0; i < j; i++) {
pool = zcache_get_pool_by_id(client_id[i], pool_id[i]);
if (pool != NULL) {
tmem_flush_page(pool, &oid[i], index[i]);
zcache_put_pool(pool);
}
}
}
/*
* Externally callable zbud handling routines.
*/
/*
* Return the maximum size compressed page that can be stored (secretly
* setting aside space for the tmem handle.
*/
unsigned int zbud_max_buddy_size(void)
{
return zbud_max_size() - sizeof(struct tmem_handle);
}
/*
* Given a zbud reference, free the corresponding zbud from all lists,
* mark it as unused, do accounting, and if the freeing of the zbud
* frees up an entire pageframe, return it to the caller (else NULL).
*/
struct page *zbud_free_and_delist(struct zbudref *zref, bool eph,
unsigned int *zsize, unsigned int *zpages)
{
unsigned long budnum = zbudref_budnum(zref);
struct zbudpage *zbudpage = zbudref_to_zbudpage(zref);
struct page *page = NULL;
unsigned chunks, bud_size, other_bud_size;
spinlock_t *lists_lock =
eph ? &zbud_eph_lists_lock : &zbud_pers_lists_lock;
struct zbud_unbuddied *unbud =
eph ? zbud_eph_unbuddied : zbud_pers_unbuddied;
spin_lock(lists_lock);
zbudpage_spin_lock(zbudpage);
if (zbudpage_is_dying(zbudpage)) {
/* ignore dying zbudpage... see zbud_evict_pageframe_lru() */
zbudpage_spin_unlock(zbudpage);
spin_unlock(lists_lock);
*zpages = 0;
*zsize = 0;
goto out;
}
if (budnum == 0) {
bud_size = zbudpage->zbud0_size;
other_bud_size = zbudpage->zbud1_size;
} else {
bud_size = zbudpage->zbud1_size;
other_bud_size = zbudpage->zbud0_size;
}
*zsize = bud_size - sizeof(struct tmem_handle);
*zpages = 1;
zbud_unuse_zbud(zbudpage, budnum, eph);
if (other_bud_size == 0) { /* was unbuddied: unlist and free */
chunks = zbud_size_to_chunks(bud_size) ;
if (zbudpage_is_zombie(zbudpage)) {
if (eph)
zbud_pers_zombie_count =
atomic_dec_return(&zbud_eph_zombie_atomic);
else
zbud_pers_zombie_count =
atomic_dec_return(&zbud_pers_zombie_atomic);
zbudpage_clear_zombie(zbudpage);
} else {
BUG_ON(list_empty(&unbud[chunks].list));
list_del_init(&zbudpage->budlist);
unbud[chunks].count--;
}
list_del_init(&zbudpage->lru);
spin_unlock(lists_lock);
if (eph)
zbud_eph_unbuddied_count--;
else
zbud_pers_unbuddied_count--;
page = zbud_unuse_zbudpage(zbudpage, eph);
} else { /* was buddied: move remaining buddy to unbuddied list */
chunks = zbud_size_to_chunks(other_bud_size) ;
if (!zbudpage_is_zombie(zbudpage)) {
list_del_init(&zbudpage->budlist);
list_add_tail(&zbudpage->budlist, &unbud[chunks].list);
unbud[chunks].count++;
}
if (eph) {
zbud_eph_buddied_count--;
zbud_eph_unbuddied_count++;
} else {
zbud_pers_unbuddied_count++;
zbud_pers_buddied_count--;
}
/* don't mess with lru, no need to move it */
zbudpage_spin_unlock(zbudpage);
spin_unlock(lists_lock);
}
out:
return page;
}
/*
* Given a tmem handle, and a kmapped pointer to compressed data of
* the given size, try to find an unbuddied zbudpage in which to
* create a zbud. If found, put it there, mark the zbudpage unevictable,
* and return a zbudref to it. Else return NULL.
*/
struct zbudref *zbud_match_prep(struct tmem_handle *th, bool eph,
void *cdata, unsigned size)
{
struct zbudpage *zbudpage = NULL, *zbudpage2;
unsigned long budnum = 0UL;
unsigned nchunks;
int i, found_good_buddy = 0;
spinlock_t *lists_lock =
eph ? &zbud_eph_lists_lock : &zbud_pers_lists_lock;
struct zbud_unbuddied *unbud =
eph ? zbud_eph_unbuddied : zbud_pers_unbuddied;
size += sizeof(struct tmem_handle);
nchunks = zbud_size_to_chunks(size);
for (i = MAX_CHUNK - nchunks + 1; i > 0; i--) {
spin_lock(lists_lock);
if (!list_empty(&unbud[i].list)) {
list_for_each_entry_safe(zbudpage, zbudpage2,
&unbud[i].list, budlist) {
if (zbudpage_spin_trylock(zbudpage)) {
found_good_buddy = i;
goto found_unbuddied;
}
}
}
spin_unlock(lists_lock);
}
zbudpage = NULL;
goto out;
found_unbuddied:
BUG_ON(!zbudpage_is_locked(zbudpage));
BUG_ON(!((zbudpage->zbud0_size == 0) ^ (zbudpage->zbud1_size == 0)));
if (zbudpage->zbud0_size == 0)
budnum = 0UL;
else if (zbudpage->zbud1_size == 0)
budnum = 1UL;
list_del_init(&zbudpage->budlist);
if (eph) {
list_add_tail(&zbudpage->budlist, &zbud_eph_buddied_list);
unbud[found_good_buddy].count--;
zbud_eph_unbuddied_count--;
zbud_eph_buddied_count++;
/* "promote" raw zbudpage to most-recently-used */
list_del_init(&zbudpage->lru);
list_add_tail(&zbudpage->lru, &zbud_eph_lru_list);
} else {
list_add_tail(&zbudpage->budlist, &zbud_pers_buddied_list);
unbud[found_good_buddy].count--;
zbud_pers_unbuddied_count--;
zbud_pers_buddied_count++;
/* "promote" raw zbudpage to most-recently-used */
list_del_init(&zbudpage->lru);
list_add_tail(&zbudpage->lru, &zbud_pers_lru_list);
}
zbud_init_zbud(zbudpage, th, eph, cdata, budnum, size);
zbudpage->unevictable++;
BUG_ON(zbudpage->unevictable == 3);
zbudpage_spin_unlock(zbudpage);
spin_unlock(lists_lock);
out:
return zbudpage_to_zbudref(zbudpage, budnum);
}
/*
* Given a tmem handle, and a kmapped pointer to compressed data of
* the given size, and a newly allocated struct page, create an unevictable
* zbud in that new page and return a zbudref to it.
*/
struct zbudref *zbud_create_prep(struct tmem_handle *th, bool eph,
void *cdata, unsigned size,
struct page *newpage)
{
struct zbudpage *zbudpage;
unsigned long budnum = 0;
unsigned nchunks;
spinlock_t *lists_lock =
eph ? &zbud_eph_lists_lock : &zbud_pers_lists_lock;
struct zbud_unbuddied *unbud =
eph ? zbud_eph_unbuddied : zbud_pers_unbuddied;
#if 0
/* this may be worth it later to support decompress-in-place? */
static unsigned long counter;
budnum = counter++ & 1; /* alternate using zbud0 and zbud1 */
#endif
if (size > zbud_max_buddy_size())
return NULL;
if (newpage == NULL)
return NULL;
size += sizeof(struct tmem_handle);
nchunks = zbud_size_to_chunks(size) ;
spin_lock(lists_lock);
zbudpage = zbud_init_zbudpage(newpage, eph);
zbudpage_spin_lock(zbudpage);
list_add_tail(&zbudpage->budlist, &unbud[nchunks].list);
if (eph) {
list_add_tail(&zbudpage->lru, &zbud_eph_lru_list);
zbud_eph_unbuddied_count++;
} else {
list_add_tail(&zbudpage->lru, &zbud_pers_lru_list);
zbud_pers_unbuddied_count++;
}
unbud[nchunks].count++;
zbud_init_zbud(zbudpage, th, eph, cdata, budnum, size);
zbudpage->unevictable++;
BUG_ON(zbudpage->unevictable == 3);
zbudpage_spin_unlock(zbudpage);
spin_unlock(lists_lock);
return zbudpage_to_zbudref(zbudpage, budnum);
}
/*
* Finish creation of a zbud by, assuming another zbud isn't being created
* in parallel, marking it evictable.
*/
void zbud_create_finish(struct zbudref *zref, bool eph)
{
struct zbudpage *zbudpage = zbudref_to_zbudpage(zref);
spinlock_t *lists_lock =
eph ? &zbud_eph_lists_lock : &zbud_pers_lists_lock;
spin_lock(lists_lock);
zbudpage_spin_lock(zbudpage);
BUG_ON(zbudpage_is_dying(zbudpage));
zbudpage->unevictable--;
BUG_ON((int)zbudpage->unevictable < 0);
zbudpage_spin_unlock(zbudpage);
spin_unlock(lists_lock);
}
/*
* Given a zbudref and a struct page, decompress the data from
* the zbud into the physical page represented by the struct page
* by upcalling to zcache_decompress
*/
int zbud_decompress(struct page *data_page, struct zbudref *zref, bool eph,
void (*decompress)(char *, unsigned int, char *))
{
struct zbudpage *zbudpage = zbudref_to_zbudpage(zref);
unsigned long budnum = zbudref_budnum(zref);
void *zbpg;
char *to_va, *from_va;
unsigned size;
int ret = -1;
spinlock_t *lists_lock =
eph ? &zbud_eph_lists_lock : &zbud_pers_lists_lock;
spin_lock(lists_lock);
zbudpage_spin_lock(zbudpage);
if (zbudpage_is_dying(zbudpage)) {
/* ignore dying zbudpage... see zbud_evict_pageframe_lru() */
goto out;
}
zbpg = kmap_zbudpage_atomic(zbudpage);
to_va = kmap_atomic(data_page);
if (budnum == 0)
size = zbudpage->zbud0_size;
else
size = zbudpage->zbud1_size;
BUG_ON(size == 0 || size > zbud_max_size());
from_va = zbud_data(zbpg, budnum, size);
from_va += sizeof(struct tmem_handle);
size -= sizeof(struct tmem_handle);
decompress(from_va, size, to_va);
kunmap_atomic(to_va);
kunmap_zbudpage_atomic(zbpg);
ret = 0;
out:
zbudpage_spin_unlock(zbudpage);
spin_unlock(lists_lock);
return ret;
}
/*
* Given a zbudref and a kernel pointer, copy the data from
* the zbud to the kernel pointer.
*/
int zbud_copy_from_zbud(char *to_va, struct zbudref *zref,
size_t *sizep, bool eph)
{
struct zbudpage *zbudpage = zbudref_to_zbudpage(zref);
unsigned long budnum = zbudref_budnum(zref);
void *zbpg;
char *from_va;
unsigned size;
int ret = -1;
spinlock_t *lists_lock =
eph ? &zbud_eph_lists_lock : &zbud_pers_lists_lock;
spin_lock(lists_lock);
zbudpage_spin_lock(zbudpage);
if (zbudpage_is_dying(zbudpage)) {
/* ignore dying zbudpage... see zbud_evict_pageframe_lru() */
goto out;
}
zbpg = kmap_zbudpage_atomic(zbudpage);
if (budnum == 0)
size = zbudpage->zbud0_size;
else
size = zbudpage->zbud1_size;
BUG_ON(size == 0 || size > zbud_max_size());
from_va = zbud_data(zbpg, budnum, size);
from_va += sizeof(struct tmem_handle);
size -= sizeof(struct tmem_handle);
*sizep = size;
memcpy(to_va, from_va, size);
kunmap_zbudpage_atomic(zbpg);
ret = 0;
out:
zbudpage_spin_unlock(zbudpage);
spin_unlock(lists_lock);
return ret;
}
/*
* Given a zbudref and a kernel pointer, copy the data from
* the kernel pointer to the zbud.
*/
int zbud_copy_to_zbud(struct zbudref *zref, char *from_va, bool eph)
{
struct zbudpage *zbudpage = zbudref_to_zbudpage(zref);
unsigned long budnum = zbudref_budnum(zref);
void *zbpg;
char *to_va;
unsigned size;
int ret = -1;
spinlock_t *lists_lock =
eph ? &zbud_eph_lists_lock : &zbud_pers_lists_lock;
spin_lock(lists_lock);
zbudpage_spin_lock(zbudpage);
if (zbudpage_is_dying(zbudpage)) {
/* ignore dying zbudpage... see zbud_evict_pageframe_lru() */
goto out;
}
zbpg = kmap_zbudpage_atomic(zbudpage);
if (budnum == 0)
size = zbudpage->zbud0_size;
else
size = zbudpage->zbud1_size;
BUG_ON(size == 0 || size > zbud_max_size());
to_va = zbud_data(zbpg, budnum, size);
to_va += sizeof(struct tmem_handle);
size -= sizeof(struct tmem_handle);
memcpy(to_va, from_va, size);
kunmap_zbudpage_atomic(zbpg);
ret = 0;
out:
zbudpage_spin_unlock(zbudpage);
spin_unlock(lists_lock);
return ret;
}
/*
* Choose an ephemeral LRU zbudpage that is evictable (not locked), ensure
* there are no references to it remaining, and return the now unused
* (and re-init'ed) struct page and the total amount of compressed
* data that was evicted.
*/
struct page *zbud_evict_pageframe_lru(unsigned int *zsize, unsigned int *zpages)
{
struct zbudpage *zbudpage = NULL, *zbudpage2;
struct zbud_unbuddied *unbud = zbud_eph_unbuddied;
struct page *page = NULL;
bool irqs_disabled = irqs_disabled();
/*
* Since this can be called indirectly from cleancache_put, which
* has interrupts disabled, as well as frontswap_put, which does not,
* we need to be able to handle both cases, even though it is ugly.
*/
if (irqs_disabled)
spin_lock(&zbud_eph_lists_lock);
else
spin_lock_bh(&zbud_eph_lists_lock);
*zsize = 0;
if (list_empty(&zbud_eph_lru_list))
goto unlock_out;
list_for_each_entry_safe(zbudpage, zbudpage2, &zbud_eph_lru_list, lru) {
/* skip a locked zbudpage */
if (unlikely(!zbudpage_spin_trylock(zbudpage)))
continue;
/* skip an unevictable zbudpage */
if (unlikely(zbudpage->unevictable != 0)) {
zbudpage_spin_unlock(zbudpage);
continue;
}
/* got a locked evictable page */
goto evict_page;
}
unlock_out:
/* no unlocked evictable pages, give up */
if (irqs_disabled)
spin_unlock(&zbud_eph_lists_lock);
else
spin_unlock_bh(&zbud_eph_lists_lock);
goto out;
evict_page:
list_del_init(&zbudpage->budlist);
list_del_init(&zbudpage->lru);
zbudpage_set_dying(zbudpage);
/*
* the zbudpage is now "dying" and attempts to read, write,
* or delete data from it will be ignored
*/
if (zbudpage->zbud0_size != 0 && zbudpage->zbud1_size != 0) {
*zsize = zbudpage->zbud0_size + zbudpage->zbud1_size -
(2 * sizeof(struct tmem_handle));
*zpages = 2;
} else if (zbudpage->zbud0_size != 0) {
unbud[zbud_size_to_chunks(zbudpage->zbud0_size)].count--;
*zsize = zbudpage->zbud0_size - sizeof(struct tmem_handle);
*zpages = 1;
} else if (zbudpage->zbud1_size != 0) {
unbud[zbud_size_to_chunks(zbudpage->zbud1_size)].count--;
*zsize = zbudpage->zbud1_size - sizeof(struct tmem_handle);
*zpages = 1;
} else {
BUG();
}
spin_unlock(&zbud_eph_lists_lock);
zbud_eph_evicted_pageframes++;
if (*zpages == 1)
zbud_eph_unbuddied_count--;
else
zbud_eph_buddied_count--;
zbud_evict_tmem(zbudpage);
zbudpage_spin_lock(zbudpage);
zbudpage_clear_dying(zbudpage);
page = zbud_unuse_zbudpage(zbudpage, true);
if (!irqs_disabled)
local_bh_enable();
out:
return page;
}
/*
* Choose a persistent LRU zbudpage that is evictable (not locked), zombify it,
* read the tmem_handle(s) out of it into the passed array, and return the
* number of zbuds. Caller must perform necessary tmem functions and,
* indirectly, zbud functions to fetch any valid data and cause the
* now-zombified zbudpage to eventually be freed. We track the zombified
* zbudpage count so it is possible to observe if there is a leak.
FIXME: describe (ramster) case where data pointers are passed in for memcpy
*/
unsigned int zbud_make_zombie_lru(struct tmem_handle *th, unsigned char **data,
unsigned int *zsize, bool eph)
{
struct zbudpage *zbudpage = NULL, *zbudpag2;
struct tmem_handle *thfrom;
char *from_va;
void *zbpg;
unsigned size;
int ret = 0, i;
spinlock_t *lists_lock =
eph ? &zbud_eph_lists_lock : &zbud_pers_lists_lock;
struct list_head *lru_list =
eph ? &zbud_eph_lru_list : &zbud_pers_lru_list;
spin_lock_bh(lists_lock);
if (list_empty(lru_list))
goto out;
list_for_each_entry_safe(zbudpage, zbudpag2, lru_list, lru) {
/* skip a locked zbudpage */
if (unlikely(!zbudpage_spin_trylock(zbudpage)))
continue;
/* skip an unevictable zbudpage */
if (unlikely(zbudpage->unevictable != 0)) {
zbudpage_spin_unlock(zbudpage);
continue;
}
/* got a locked evictable page */
goto zombify_page;
}
/* no unlocked evictable pages, give up */
goto out;
zombify_page:
/* got an unlocked evictable page, zombify it */
list_del_init(&zbudpage->budlist);
zbudpage_set_zombie(zbudpage);
/* FIXME what accounting do I need to do here? */
list_del_init(&zbudpage->lru);
if (eph) {
list_add_tail(&zbudpage->lru, &zbud_eph_zombie_list);
zbud_eph_zombie_count =
atomic_inc_return(&zbud_eph_zombie_atomic);
} else {
list_add_tail(&zbudpage->lru, &zbud_pers_zombie_list);
zbud_pers_zombie_count =
atomic_inc_return(&zbud_pers_zombie_atomic);
}
/* FIXME what accounting do I need to do here? */
zbpg = kmap_zbudpage_atomic(zbudpage);
for (i = 0; i < 2; i++) {
size = (i == 0) ? zbudpage->zbud0_size : zbudpage->zbud1_size;
if (size) {
from_va = zbud_data(zbpg, i, size);
thfrom = (struct tmem_handle *)from_va;
from_va += sizeof(struct tmem_handle);
size -= sizeof(struct tmem_handle);
if (th != NULL)
th[ret] = *thfrom;
if (data != NULL)
memcpy(data[ret], from_va, size);
if (zsize != NULL)
*zsize++ = size;
ret++;
}
}
kunmap_zbudpage_atomic(zbpg);
zbudpage_spin_unlock(zbudpage);
out:
spin_unlock_bh(lists_lock);
return ret;
}
void __init zbud_init(void)
{
int i;
#ifdef CONFIG_DEBUG_FS
zbud_debugfs_init();
#endif
BUG_ON((sizeof(struct tmem_handle) * 2 > CHUNK_SIZE));
BUG_ON(sizeof(struct zbudpage) > sizeof(struct page));
for (i = 0; i < NCHUNKS; i++) {
INIT_LIST_HEAD(&zbud_eph_unbuddied[i].list);
INIT_LIST_HEAD(&zbud_pers_unbuddied[i].list);
}
}