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-rw-r--r--include/linux/swap.h7
-rw-r--r--include/linux/swapfile.h2
-rw-r--r--mm/frontswap.c13
-rw-r--r--mm/swapfile.c171
4 files changed, 78 insertions, 115 deletions
diff --git a/include/linux/swap.h b/include/linux/swap.h
index 5a14b928164e..8bb85d6d65f0 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -214,8 +214,8 @@ struct percpu_cluster {
struct swap_info_struct {
unsigned long flags; /* SWP_USED etc: see above */
signed short prio; /* swap priority of this type */
+ struct list_head list; /* entry in swap list */
signed char type; /* strange name for an index */
- signed char next; /* next type on the swap list */
unsigned int max; /* extent of the swap_map */
unsigned char *swap_map; /* vmalloc'ed array of usage counts */
struct swap_cluster_info *cluster_info; /* cluster info. Only for SSD */
@@ -255,11 +255,6 @@ struct swap_info_struct {
struct swap_cluster_info discard_cluster_tail; /* list tail of discard clusters */
};
-struct swap_list_t {
- int head; /* head of priority-ordered swapfile list */
- int next; /* swapfile to be used next */
-};
-
/* linux/mm/workingset.c */
void *workingset_eviction(struct address_space *mapping, struct page *page);
bool workingset_refault(void *shadow);
diff --git a/include/linux/swapfile.h b/include/linux/swapfile.h
index e282624e8c10..2eab382d593d 100644
--- a/include/linux/swapfile.h
+++ b/include/linux/swapfile.h
@@ -6,7 +6,7 @@
* want to expose them to the dozens of source files that include swap.h
*/
extern spinlock_t swap_lock;
-extern struct swap_list_t swap_list;
+extern struct list_head swap_list_head;
extern struct swap_info_struct *swap_info[];
extern int try_to_unuse(unsigned int, bool, unsigned long);
diff --git a/mm/frontswap.c b/mm/frontswap.c
index 1b24bdcb3197..fae11602e8a9 100644
--- a/mm/frontswap.c
+++ b/mm/frontswap.c
@@ -327,15 +327,12 @@ EXPORT_SYMBOL(__frontswap_invalidate_area);
static unsigned long __frontswap_curr_pages(void)
{
- int type;
unsigned long totalpages = 0;
struct swap_info_struct *si = NULL;
assert_spin_locked(&swap_lock);
- for (type = swap_list.head; type >= 0; type = si->next) {
- si = swap_info[type];
+ list_for_each_entry(si, &swap_list_head, list)
totalpages += atomic_read(&si->frontswap_pages);
- }
return totalpages;
}
@@ -347,11 +344,9 @@ static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
int si_frontswap_pages;
unsigned long total_pages_to_unuse = total;
unsigned long pages = 0, pages_to_unuse = 0;
- int type;
assert_spin_locked(&swap_lock);
- for (type = swap_list.head; type >= 0; type = si->next) {
- si = swap_info[type];
+ list_for_each_entry(si, &swap_list_head, list) {
si_frontswap_pages = atomic_read(&si->frontswap_pages);
if (total_pages_to_unuse < si_frontswap_pages) {
pages = pages_to_unuse = total_pages_to_unuse;
@@ -366,7 +361,7 @@ static int __frontswap_unuse_pages(unsigned long total, unsigned long *unused,
}
vm_unacct_memory(pages);
*unused = pages_to_unuse;
- *swapid = type;
+ *swapid = si->type;
ret = 0;
break;
}
@@ -413,7 +408,7 @@ void frontswap_shrink(unsigned long target_pages)
/*
* we don't want to hold swap_lock while doing a very
* lengthy try_to_unuse, but swap_list may change
- * so restart scan from swap_list.head each time
+ * so restart scan from swap_list_head each time
*/
spin_lock(&swap_lock);
ret = __frontswap_shrink(target_pages, &pages_to_unuse, &type);
diff --git a/mm/swapfile.c b/mm/swapfile.c
index 4a7f7e6992b6..6c95a8c63b1a 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -51,14 +51,17 @@ atomic_long_t nr_swap_pages;
/* protected with swap_lock. reading in vm_swap_full() doesn't need lock */
long total_swap_pages;
static int least_priority;
-static atomic_t highest_priority_index = ATOMIC_INIT(-1);
static const char Bad_file[] = "Bad swap file entry ";
static const char Unused_file[] = "Unused swap file entry ";
static const char Bad_offset[] = "Bad swap offset entry ";
static const char Unused_offset[] = "Unused swap offset entry ";
-struct swap_list_t swap_list = {-1, -1};
+/*
+ * all active swap_info_structs
+ * protected with swap_lock, and ordered by priority.
+ */
+LIST_HEAD(swap_list_head);
struct swap_info_struct *swap_info[MAX_SWAPFILES];
@@ -640,66 +643,54 @@ no_page:
swp_entry_t get_swap_page(void)
{
- struct swap_info_struct *si;
+ struct swap_info_struct *si, *next;
pgoff_t offset;
- int type, next;
- int wrapped = 0;
- int hp_index;
+ struct list_head *tmp;
spin_lock(&swap_lock);
if (atomic_long_read(&nr_swap_pages) <= 0)
goto noswap;
atomic_long_dec(&nr_swap_pages);
- for (type = swap_list.next; type >= 0 && wrapped < 2; type = next) {
- hp_index = atomic_xchg(&highest_priority_index, -1);
- /*
- * highest_priority_index records current highest priority swap
- * type which just frees swap entries. If its priority is
- * higher than that of swap_list.next swap type, we use it. It
- * isn't protected by swap_lock, so it can be an invalid value
- * if the corresponding swap type is swapoff. We double check
- * the flags here. It's even possible the swap type is swapoff
- * and swapon again and its priority is changed. In such rare
- * case, low prority swap type might be used, but eventually
- * high priority swap will be used after several rounds of
- * swap.
- */
- if (hp_index != -1 && hp_index != type &&
- swap_info[type]->prio < swap_info[hp_index]->prio &&
- (swap_info[hp_index]->flags & SWP_WRITEOK)) {
- type = hp_index;
- swap_list.next = type;
- }
-
- si = swap_info[type];
- next = si->next;
- if (next < 0 ||
- (!wrapped && si->prio != swap_info[next]->prio)) {
- next = swap_list.head;
- wrapped++;
- }
-
+ list_for_each(tmp, &swap_list_head) {
+ si = list_entry(tmp, typeof(*si), list);
spin_lock(&si->lock);
- if (!si->highest_bit) {
- spin_unlock(&si->lock);
- continue;
- }
- if (!(si->flags & SWP_WRITEOK)) {
+ if (!si->highest_bit || !(si->flags & SWP_WRITEOK)) {
spin_unlock(&si->lock);
continue;
}
- swap_list.next = next;
+ /*
+ * rotate the current swap_info that we're going to use
+ * to after any other swap_info that have the same prio,
+ * so that all equal-priority swap_info get used equally
+ */
+ next = si;
+ list_for_each_entry_continue(next, &swap_list_head, list) {
+ if (si->prio != next->prio)
+ break;
+ list_rotate_left(&si->list);
+ next = si;
+ }
spin_unlock(&swap_lock);
/* This is called for allocating swap entry for cache */
offset = scan_swap_map(si, SWAP_HAS_CACHE);
spin_unlock(&si->lock);
if (offset)
- return swp_entry(type, offset);
+ return swp_entry(si->type, offset);
spin_lock(&swap_lock);
- next = swap_list.next;
+ /*
+ * if we got here, it's likely that si was almost full before,
+ * and since scan_swap_map() can drop the si->lock, multiple
+ * callers probably all tried to get a page from the same si
+ * and it filled up before we could get one. So we need to
+ * try again. Since we dropped the swap_lock, there may now
+ * be non-full higher priority swap_infos, and this si may have
+ * even been removed from the list (although very unlikely).
+ * Let's start over.
+ */
+ tmp = &swap_list_head;
}
atomic_long_inc(&nr_swap_pages);
@@ -766,27 +757,6 @@ out:
return NULL;
}
-/*
- * This swap type frees swap entry, check if it is the highest priority swap
- * type which just frees swap entry. get_swap_page() uses
- * highest_priority_index to search highest priority swap type. The
- * swap_info_struct.lock can't protect us if there are multiple swap types
- * active, so we use atomic_cmpxchg.
- */
-static void set_highest_priority_index(int type)
-{
- int old_hp_index, new_hp_index;
-
- do {
- old_hp_index = atomic_read(&highest_priority_index);
- if (old_hp_index != -1 &&
- swap_info[old_hp_index]->prio >= swap_info[type]->prio)
- break;
- new_hp_index = type;
- } while (atomic_cmpxchg(&highest_priority_index,
- old_hp_index, new_hp_index) != old_hp_index);
-}
-
static unsigned char swap_entry_free(struct swap_info_struct *p,
swp_entry_t entry, unsigned char usage)
{
@@ -830,7 +800,6 @@ static unsigned char swap_entry_free(struct swap_info_struct *p,
p->lowest_bit = offset;
if (offset > p->highest_bit)
p->highest_bit = offset;
- set_highest_priority_index(p->type);
atomic_long_inc(&nr_swap_pages);
p->inuse_pages--;
frontswap_invalidate_page(p->type, offset);
@@ -1765,7 +1734,7 @@ static void _enable_swap_info(struct swap_info_struct *p, int prio,
unsigned char *swap_map,
struct swap_cluster_info *cluster_info)
{
- int i, prev;
+ struct swap_info_struct *si;
if (prio >= 0)
p->prio = prio;
@@ -1777,18 +1746,28 @@ static void _enable_swap_info(struct swap_info_struct *p, int prio,
atomic_long_add(p->pages, &nr_swap_pages);
total_swap_pages += p->pages;
- /* insert swap space into swap_list: */
- prev = -1;
- for (i = swap_list.head; i >= 0; i = swap_info[i]->next) {
- if (p->prio >= swap_info[i]->prio)
- break;
- prev = i;
+ assert_spin_locked(&swap_lock);
+ BUG_ON(!list_empty(&p->list));
+ /*
+ * insert into swap list; the list is in priority order,
+ * so that get_swap_page() can get a page from the highest
+ * priority swap_info_struct with available page(s), and
+ * swapoff can adjust the auto-assigned (i.e. negative) prio
+ * values for any lower-priority swap_info_structs when
+ * removing a negative-prio swap_info_struct
+ */
+ list_for_each_entry(si, &swap_list_head, list) {
+ if (p->prio >= si->prio) {
+ list_add_tail(&p->list, &si->list);
+ return;
+ }
}
- p->next = i;
- if (prev < 0)
- swap_list.head = swap_list.next = p->type;
- else
- swap_info[prev]->next = p->type;
+ /*
+ * this covers two cases:
+ * 1) p->prio is less than all existing prio
+ * 2) the swap list is empty
+ */
+ list_add_tail(&p->list, &swap_list_head);
}
static void enable_swap_info(struct swap_info_struct *p, int prio,
@@ -1823,8 +1802,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
struct address_space *mapping;
struct inode *inode;
struct filename *pathname;
- int i, type, prev;
- int err;
+ int err, found = 0;
unsigned int old_block_size;
if (!capable(CAP_SYS_ADMIN))
@@ -1842,17 +1820,16 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
goto out;
mapping = victim->f_mapping;
- prev = -1;
spin_lock(&swap_lock);
- for (type = swap_list.head; type >= 0; type = swap_info[type]->next) {
- p = swap_info[type];
+ list_for_each_entry(p, &swap_list_head, list) {
if (p->flags & SWP_WRITEOK) {
- if (p->swap_file->f_mapping == mapping)
+ if (p->swap_file->f_mapping == mapping) {
+ found = 1;
break;
+ }
}
- prev = type;
}
- if (type < 0) {
+ if (!found) {
err = -EINVAL;
spin_unlock(&swap_lock);
goto out_dput;
@@ -1864,20 +1841,16 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
spin_unlock(&swap_lock);
goto out_dput;
}
- if (prev < 0)
- swap_list.head = p->next;
- else
- swap_info[prev]->next = p->next;
- if (type == swap_list.next) {
- /* just pick something that's safe... */
- swap_list.next = swap_list.head;
- }
spin_lock(&p->lock);
if (p->prio < 0) {
- for (i = p->next; i >= 0; i = swap_info[i]->next)
- swap_info[i]->prio = p->prio--;
+ struct swap_info_struct *si = p;
+
+ list_for_each_entry_continue(si, &swap_list_head, list) {
+ si->prio++;
+ }
least_priority++;
}
+ list_del_init(&p->list);
atomic_long_sub(p->pages, &nr_swap_pages);
total_swap_pages -= p->pages;
p->flags &= ~SWP_WRITEOK;
@@ -1885,7 +1858,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
spin_unlock(&swap_lock);
set_current_oom_origin();
- err = try_to_unuse(type, false, 0); /* force all pages to be unused */
+ err = try_to_unuse(p->type, false, 0); /* force unuse all pages */
clear_current_oom_origin();
if (err) {
@@ -1926,7 +1899,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
frontswap_map = frontswap_map_get(p);
spin_unlock(&p->lock);
spin_unlock(&swap_lock);
- frontswap_invalidate_area(type);
+ frontswap_invalidate_area(p->type);
frontswap_map_set(p, NULL);
mutex_unlock(&swapon_mutex);
free_percpu(p->percpu_cluster);
@@ -1935,7 +1908,7 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
vfree(cluster_info);
vfree(frontswap_map);
/* Destroy swap account information */
- swap_cgroup_swapoff(type);
+ swap_cgroup_swapoff(p->type);
inode = mapping->host;
if (S_ISBLK(inode->i_mode)) {
@@ -2142,8 +2115,8 @@ static struct swap_info_struct *alloc_swap_info(void)
*/
}
INIT_LIST_HEAD(&p->first_swap_extent.list);
+ INIT_LIST_HEAD(&p->list);
p->flags = SWP_USED;
- p->next = -1;
spin_unlock(&swap_lock);
spin_lock_init(&p->lock);
Copyright © 1996 – 2023 Jason A. Donenfeld. All Rights Reverse Engineered.