// SPDX-License-Identifier: GPL-2.0-only
/*
* Copyright (C) 2018 HUAWEI, Inc.
* https://www.huawei.com/
*/
#include "internal.h"
struct z_erofs_gbuf {
spinlock_t lock;
void *ptr;
struct page **pages;
unsigned int nrpages;
};
static struct z_erofs_gbuf *z_erofs_gbufpool, *z_erofs_rsvbuf;
static unsigned int z_erofs_gbuf_count, z_erofs_gbuf_nrpages,
z_erofs_rsv_nrpages;
module_param_named(global_buffers, z_erofs_gbuf_count, uint, 0444);
module_param_named(reserved_pages, z_erofs_rsv_nrpages, uint, 0444);
static atomic_long_t erofs_global_shrink_cnt; /* for all mounted instances */
/* protected by 'erofs_sb_list_lock' */
static unsigned int shrinker_run_no;
/* protects the mounted 'erofs_sb_list' */
static DEFINE_SPINLOCK(erofs_sb_list_lock);
static LIST_HEAD(erofs_sb_list);
static struct shrinker *erofs_shrinker_info;
static unsigned int z_erofs_gbuf_id(void)
{
return raw_smp_processor_id() % z_erofs_gbuf_count;
}
void *z_erofs_get_gbuf(unsigned int requiredpages)
__acquires(gbuf->lock)
{
struct z_erofs_gbuf *gbuf;
migrate_disable();
gbuf = &z_erofs_gbufpool[z_erofs_gbuf_id()];
spin_lock(&gbuf->lock);
/* check if the buffer is too small */
if (requiredpages > gbuf->nrpages) {
spin_unlock(&gbuf->lock);
migrate_enable();
/* (for sparse checker) pretend gbuf->lock is still taken */
__acquire(gbuf->lock);
return NULL;
}
return gbuf->ptr;
}
void z_erofs_put_gbuf(void *ptr) __releases(gbuf->lock)
{
struct z_erofs_gbuf *gbuf;
gbuf = &z_erofs_gbufpool[z_erofs_gbuf_id()];
DBG_BUGON(gbuf->ptr != ptr);
spin_unlock(&gbuf->lock);
migrate_enable();
}
int z_erofs_gbuf_growsize(unsigned int nrpages)
{
static DEFINE_MUTEX(gbuf_resize_mutex);
struct page **tmp_pages = NULL;
struct z_erofs_gbuf *gbuf;
void *ptr, *old_ptr;
int last, i, j;
mutex_lock(&gbuf_resize_mutex);
/* avoid shrinking gbufs, since no idea how many fses rely on */
if (nrpages <= z_erofs_gbuf_nrpages) {
mutex_unlock(&gbuf_resize_mutex);
return 0;
}
for (i = 0; i < z_erofs_gbuf_count; ++i) {
gbuf = &z_erofs_gbufpool[i];
tmp_pages = kcalloc(nrpages, sizeof(*tmp_pages), GFP_KERNEL);
if (!tmp_pages)
goto out;
for (j = 0; j < gbuf->nrpages; ++j)
tmp_pages[j] = gbuf->pages[j];
do {
last = j;
j = alloc_pages_bulk_array(GFP_KERNEL, nrpages,
tmp_pages);
if (last == j)
goto out;
} while (j != nrpages);
ptr = vmap(tmp_pages, nrpages, VM_MAP, PAGE_KERNEL);
if (!ptr)
goto out;
spin_lock(&gbuf->lock);
kfree(gbuf->pages);
gbuf->pages = tmp_pages;
old_ptr = gbuf->ptr;
gbuf->ptr = ptr;
gbuf->nrpages = nrpages;
spin_unlock(&gbuf->lock);
if (old_ptr)
vunmap(old_ptr);
}
z_erofs_gbuf_nrpages = nrpages;
out:
if (i < z_erofs_gbuf_count && tmp_pages) {
for (j = 0; j < nrpages; ++j)
if (tmp_pages[j] && (j >= gbuf->nrpages ||
tmp_pages[j] != gbuf->pages[j]))
__free_page(tmp_pages[j]);
kfree(tmp_pages);
}
mutex_unlock(&gbuf_resize_mutex);
return i < z_erofs_gbuf_count ? -ENOMEM : 0;
}
int __init z_erofs_gbuf_init(void)
{
unsigned int i, total = num_possible_cpus();
if (z_erofs_gbuf_count)
total = min(z_erofs_gbuf_count, total);
z_erofs_gbuf_count = total;
/* The last (special) global buffer is the reserved buffer */
total += !!z_erofs_rsv_nrpages;
z_erofs_gbufpool = kcalloc(total, sizeof(*z_erofs_gbufpool),
GFP_KERNEL);
if (!z_erofs_gbufpool)
return -ENOMEM;
if (z_erofs_rsv_nrpages) {
z_erofs_rsvbuf = &z_erofs_gbufpool[total - 1];
z_erofs_rsvbuf->pages = kcalloc(z_erofs_rsv_nrpages,
sizeof(*z_erofs_rsvbuf->pages), GFP_KERNEL);
if (!z_erofs_rsvbuf->pages) {
z_erofs_rsvbuf = NULL;
z_erofs_rsv_nrpages = 0;
}
}
for (i = 0; i < total; ++i)
spin_lock_init(&z_erofs_gbufpool[i].lock);
return 0;
}
void z_erofs_gbuf_exit(void)
{
int i, j;
for (i = 0; i < z_erofs_gbuf_count + (!!z_erofs_rsvbuf); ++i) {
struct z_erofs_gbuf *gbuf = &z_erofs_gbufpool[i];
if (gbuf->ptr) {
vunmap(gbuf->ptr);
gbuf->ptr = NULL;
}
if (!gbuf->pages)
continue;
for (j = 0; j < gbuf->nrpages; ++j)
if (gbuf->pages[j])
put_page(gbuf->pages[j]);
kfree(gbuf->pages);
gbuf->pages = NULL;
}
kfree(z_erofs_gbufpool);
}
struct page *__erofs_allocpage(struct page **pagepool, gfp_t gfp, bool tryrsv)
{
struct page *page = *pagepool;
if (page) {
*pagepool = (struct page *)page_private(page);
} else if (tryrsv && z_erofs_rsvbuf && z_erofs_rsvbuf->nrpages) {
spin_lock(&z_erofs_rsvbuf->lock);
if (z_erofs_rsvbuf->nrpages)
page = z_erofs_rsvbuf->pages[--z_erofs_rsvbuf->nrpages];
spin_unlock(&z_erofs_rsvbuf->lock);
}
if (!page)
page = alloc_page(gfp);
DBG_BUGON(page && page_ref_count(page) != 1);
return page;
}
void erofs_release_pages(struct page **pagepool)
{
while (*pagepool) {
struct page *page = *pagepool;
*pagepool = (struct page *)page_private(page);
/* try to fill reserved global pool first */
if (z_erofs_rsvbuf && z_erofs_rsvbuf->nrpages <
z_erofs_rsv_nrpages) {
spin_lock(&z_erofs_rsvbuf->lock);
if (z_erofs_rsvbuf->nrpages < z_erofs_rsv_nrpages) {
z_erofs_rsvbuf->pages[z_erofs_rsvbuf->nrpages++]
= page;
spin_unlock(&z_erofs_rsvbuf->lock);
continue;
}
spin_unlock(&z_erofs_rsvbuf->lock);
}
put_page(page);
}
}
static bool erofs_workgroup_get(struct erofs_workgroup *grp)
{
if (lockref_get_not_zero(&grp->lockref))
return true;
spin_lock(&grp->lockref.lock);
if (__lockref_is_dead(&grp->lockref)) {
spin_unlock(&grp->lockref.lock);
return false;
}
if (!grp->lockref.count++)
atomic_long_dec(&erofs_global_shrink_cnt);
spin_unlock(&grp->lockref.lock);
return true;
}
struct erofs_workgroup *erofs_find_workgroup(struct super_block *sb,
pgoff_t index)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);
struct erofs_workgroup *grp;
repeat:
rcu_read_lock();
grp = xa_load(&sbi->managed_pslots, index);
if (grp) {
if (!erofs_workgroup_get(grp)) {
/* prefer to relax rcu read side */
rcu_read_unlock();
goto repeat;
}
DBG_BUGON(index != grp->index);
}
rcu_read_unlock();
return grp;
}
struct erofs_workgroup *erofs_insert_workgroup(struct super_block *sb,
struct erofs_workgroup *grp)
{
struct erofs_sb_info *const sbi = EROFS_SB(sb);
struct erofs_workgroup *pre;
DBG_BUGON(grp->lockref.count < 1);
repeat:
xa_lock(&sbi->managed_pslots);
pre = __xa_cmpxchg(&sbi->managed_pslots, grp->index,
NULL, grp, GFP_KERNEL);
if (pre) {
if (xa_is_err(pre)) {
pre = ERR_PTR(xa_err(pre));
} else if (!erofs_workgroup_get(pre)) {
/* try to legitimize the current in-tree one */
xa_unlock(&sbi->managed_pslots);
cond_resched();
goto repeat;
}
grp = pre;
}
xa_unlock(&sbi->managed_pslots);
return grp;
}
static void __erofs_workgroup_free(struct erofs_workgroup *grp)
{
atomic_long_dec(&erofs_global_shrink_cnt);
erofs_workgroup_free_rcu(grp);
}
void erofs_workgroup_put(struct erofs_workgroup *grp)
{
if (lockref_put_or_lock(&grp->lockref))
return;
DBG_BUGON(__lockref_is_dead(&grp->lockref));
if (grp->lockref.count == 1)
atomic_long_inc(&erofs_global_shrink_cnt);
--grp->lockref.count;
spin_unlock(&grp->lockref.lock);
}
static bool erofs_try_to_release_workgroup(struct erofs_sb_info *sbi,
struct erofs_workgroup *grp)
{
int free = false;
spin_lock(&grp->lockref.lock);
if (grp->lockref.count)
goto out;
/*
* Note that all cached pages should be detached before deleted from
* the XArray. Otherwise some cached pages could be still attached to
* the orphan old workgroup when the new one is available in the tree.
*/
if (erofs_try_to_free_all_cached_folios(sbi, grp))
goto out;
/*
* It's impossible to fail after the workgroup is freezed,
* however in order to avoid some race conditions, add a
* DBG_BUGON to observe this in advance.
*/
DBG_BUGON(__xa_erase(&sbi->managed_pslots, grp->index) != grp);
lockref_mark_dead(&grp->lockref);
free = true;
out:
spin_unlock(&grp->lockref.lock);
if (free)
__erofs_workgroup_free(grp);
return free;
}
static unsigned long erofs_shrink_workstation(struct erofs_sb_info *sbi,
unsigned long nr_shrink)
{
struct erofs_workgroup *grp;
unsigned int freed = 0;
unsigned long index;
xa_lock(&sbi->managed_pslots);
xa_for_each(&sbi->managed_pslots, index, grp) {
/* try to shrink each valid workgroup */
if (!erofs_try_to_release_workgroup(sbi, grp))
continue;
xa_unlock(&sbi->managed_pslots);
++freed;
if (!--nr_shrink)
return freed;
xa_lock(&sbi->managed_pslots);
}
xa_unlock(&sbi->managed_pslots);
return freed;
}
void erofs_shrinker_register(struct super_block *sb)
{
struct erofs_sb_info *sbi = EROFS_SB(sb);
mutex_init(&sbi->umount_mutex);
spin_lock(&erofs_sb_list_lock);
list_add(&sbi->list, &erofs_sb_list);
spin_unlock(&erofs_sb_list_lock);
}
void erofs_shrinker_unregister(struct super_block *sb)
{
struct erofs_sb_info *const sbi = EROFS_SB(sb);
mutex_lock(&sbi->umount_mutex);
/* clean up all remaining workgroups in memory */
erofs_shrink_workstation(sbi, ~0UL);
spin_lock(&erofs_sb_list_lock);
list_del(&sbi->list);
spin_unlock(&erofs_sb_list_lock);
mutex_unlock(&sbi->umount_mutex);
}
static unsigned long erofs_shrink_count(struct shrinker *shrink,
struct shrink_control *sc)
{
return atomic_long_read(&erofs_global_shrink_cnt);
}
static unsigned long erofs_shrink_scan(struct shrinker *shrink,
struct shrink_control *sc)
{
struct erofs_sb_info *sbi;
struct list_head *p;
unsigned long nr = sc->nr_to_scan;
unsigned int run_no;
unsigned long freed = 0;
spin_lock(&erofs_sb_list_lock);
do {
run_no = ++shrinker_run_no;
} while (run_no == 0);
/* Iterate over all mounted superblocks and try to shrink them */
p = erofs_sb_list.next;
while (p != &erofs_sb_list) {
sbi = list_entry(p, struct erofs_sb_info, list);
/*
* We move the ones we do to the end of the list, so we stop
* when we see one we have already done.
*/
if (sbi->shrinker_run_no == run_no)
break;
if (!mutex_trylock(&sbi->umount_mutex)) {
p = p->next;
continue;
}
spin_unlock(&erofs_sb_list_lock);
sbi->shrinker_run_no = run_no;
freed += erofs_shrink_workstation(sbi, nr - freed);
spin_lock(&erofs_sb_list_lock);
/* Get the next list element before we move this one */
p = p->next;
/*
* Move this one to the end of the list to provide some
* fairness.
*/
list_move_tail(&sbi->list, &erofs_sb_list);
mutex_unlock(&sbi->umount_mutex);
if (freed >= nr)
break;
}
spin_unlock(&erofs_sb_list_lock);
return freed;
}
int __init erofs_init_shrinker(void)
{
erofs_shrinker_info = shrinker_alloc(0, "erofs-shrinker");
if (!erofs_shrinker_info)
return -ENOMEM;
erofs_shrinker_info->count_objects = erofs_shrink_count;
erofs_shrinker_info->scan_objects = erofs_shrink_scan;
shrinker_register(erofs_shrinker_info);
return 0;
}
void erofs_exit_shrinker(void)
{
shrinker_free(erofs_shrinker_info);
}
Codebase Browser
linux