}
}
-static int wait_for_discard(void *word)
-{
- schedule();
- return 0;
-}
-
#define SWAPFILE_CLUSTER 256
#define LATENCY_LIMIT 256
info->data = 0;
}
+/* Add a cluster to discard list and schedule it to do discard */
+static void swap_cluster_schedule_discard(struct swap_info_struct *si,
+ unsigned int idx)
+{
+ /*
+ * If scan_swap_map() can't find a free cluster, it will check
+ * si->swap_map directly. To make sure the discarding cluster isn't
+ * taken by scan_swap_map(), mark the swap entries bad (occupied). It
+ * will be cleared after discard
+ */
+ memset(si->swap_map + idx * SWAPFILE_CLUSTER,
+ SWAP_MAP_BAD, SWAPFILE_CLUSTER);
+
+ if (cluster_is_null(&si->discard_cluster_head)) {
+ cluster_set_next_flag(&si->discard_cluster_head,
+ idx, 0);
+ cluster_set_next_flag(&si->discard_cluster_tail,
+ idx, 0);
+ } else {
+ unsigned int tail = cluster_next(&si->discard_cluster_tail);
+ cluster_set_next(&si->cluster_info[tail], idx);
+ cluster_set_next_flag(&si->discard_cluster_tail,
+ idx, 0);
+ }
+
+ schedule_work(&si->discard_work);
+}
+
+/*
+ * Doing discard actually. After a cluster discard is finished, the cluster
+ * will be added to free cluster list. caller should hold si->lock.
+*/
+static void swap_do_scheduled_discard(struct swap_info_struct *si)
+{
+ struct swap_cluster_info *info;
+ unsigned int idx;
+
+ info = si->cluster_info;
+
+ while (!cluster_is_null(&si->discard_cluster_head)) {
+ idx = cluster_next(&si->discard_cluster_head);
+
+ cluster_set_next_flag(&si->discard_cluster_head,
+ cluster_next(&info[idx]), 0);
+ if (cluster_next(&si->discard_cluster_tail) == idx) {
+ cluster_set_null(&si->discard_cluster_head);
+ cluster_set_null(&si->discard_cluster_tail);
+ }
+ spin_unlock(&si->lock);
+
+ discard_swap_cluster(si, idx * SWAPFILE_CLUSTER,
+ SWAPFILE_CLUSTER);
+
+ spin_lock(&si->lock);
+ cluster_set_flag(&info[idx], CLUSTER_FLAG_FREE);
+ if (cluster_is_null(&si->free_cluster_head)) {
+ cluster_set_next_flag(&si->free_cluster_head,
+ idx, 0);
+ cluster_set_next_flag(&si->free_cluster_tail,
+ idx, 0);
+ } else {
+ unsigned int tail;
+
+ tail = cluster_next(&si->free_cluster_tail);
+ cluster_set_next(&info[tail], idx);
+ cluster_set_next_flag(&si->free_cluster_tail,
+ idx, 0);
+ }
+ memset(si->swap_map + idx * SWAPFILE_CLUSTER,
+ 0, SWAPFILE_CLUSTER);
+ }
+}
+
+static void swap_discard_work(struct work_struct *work)
+{
+ struct swap_info_struct *si;
+
+ si = container_of(work, struct swap_info_struct, discard_work);
+
+ spin_lock(&si->lock);
+ swap_do_scheduled_discard(si);
+ spin_unlock(&si->lock);
+}
+
/*
* The cluster corresponding to page_nr will be used. The cluster will be
* removed from free cluster list and its usage counter will be increased.
cluster_count(&cluster_info[idx]) - 1);
if (cluster_count(&cluster_info[idx]) == 0) {
+ /*
+ * If the swap is discardable, prepare discard the cluster
+ * instead of free it immediately. The cluster will be freed
+ * after discard.
+ */
+ if ((p->flags & (SWP_WRITEOK | SWP_PAGE_DISCARD)) ==
+ (SWP_WRITEOK | SWP_PAGE_DISCARD)) {
+ swap_cluster_schedule_discard(p, idx);
+ return;
+ }
+
cluster_set_flag(&cluster_info[idx], CLUSTER_FLAG_FREE);
if (cluster_is_null(&p->free_cluster_head)) {
cluster_set_next_flag(&p->free_cluster_head, idx, 0);
* It's possible scan_swap_map() uses a free cluster in the middle of free
* cluster list. Avoiding such abuse to avoid list corruption.
*/
-static inline bool scan_swap_map_recheck_cluster(struct swap_info_struct *si,
+static bool
+scan_swap_map_ssd_cluster_conflict(struct swap_info_struct *si,
unsigned long offset)
{
+ struct percpu_cluster *percpu_cluster;
+ bool conflict;
+
offset /= SWAPFILE_CLUSTER;
- return !cluster_is_null(&si->free_cluster_head) &&
+ conflict = !cluster_is_null(&si->free_cluster_head) &&
offset != cluster_next(&si->free_cluster_head) &&
cluster_is_free(&si->cluster_info[offset]);
+
+ if (!conflict)
+ return false;
+
+ percpu_cluster = this_cpu_ptr(si->percpu_cluster);
+ cluster_set_null(&percpu_cluster->index);
+ return true;
+}
+
+/*
+ * Try to get a swap entry from current cpu's swap entry pool (a cluster). This
+ * might involve allocating a new cluster for current CPU too.
+ */
+static void scan_swap_map_try_ssd_cluster(struct swap_info_struct *si,
+ unsigned long *offset, unsigned long *scan_base)
+{
+ struct percpu_cluster *cluster;
+ bool found_free;
+ unsigned long tmp;
+
+new_cluster:
+ cluster = this_cpu_ptr(si->percpu_cluster);
+ if (cluster_is_null(&cluster->index)) {
+ if (!cluster_is_null(&si->free_cluster_head)) {
+ cluster->index = si->free_cluster_head;
+ cluster->next = cluster_next(&cluster->index) *
+ SWAPFILE_CLUSTER;
+ } else if (!cluster_is_null(&si->discard_cluster_head)) {
+ /*
+ * we don't have free cluster but have some clusters in
+ * discarding, do discard now and reclaim them
+ */
+ swap_do_scheduled_discard(si);
+ *scan_base = *offset = si->cluster_next;
+ goto new_cluster;
+ } else
+ return;
+ }
+
+ found_free = false;
+
+ /*
+ * Other CPUs can use our cluster if they can't find a free cluster,
+ * check if there is still free entry in the cluster
+ */
+ tmp = cluster->next;
+ while (tmp < si->max && tmp < (cluster_next(&cluster->index) + 1) *
+ SWAPFILE_CLUSTER) {
+ if (!si->swap_map[tmp]) {
+ found_free = true;
+ break;
+ }
+ tmp++;
+ }
+ if (!found_free) {
+ cluster_set_null(&cluster->index);
+ goto new_cluster;
+ }
+ cluster->next = tmp + 1;
+ *offset = tmp;
+ *scan_base = tmp;
}
static unsigned long scan_swap_map(struct swap_info_struct *si,
unsigned long scan_base;
unsigned long last_in_cluster = 0;
int latency_ration = LATENCY_LIMIT;
- int found_free_cluster = 0;
/*
* We try to cluster swap pages by allocating them sequentially
si->flags += SWP_SCANNING;
scan_base = offset = si->cluster_next;
+ /* SSD algorithm */
+ if (si->cluster_info) {
+ scan_swap_map_try_ssd_cluster(si, &offset, &scan_base);
+ goto checks;
+ }
+
if (unlikely(!si->cluster_nr--)) {
if (si->pages - si->inuse_pages < SWAPFILE_CLUSTER) {
si->cluster_nr = SWAPFILE_CLUSTER - 1;
goto checks;
}
- if (si->flags & SWP_PAGE_DISCARD) {
- /*
- * Start range check on racing allocations, in case
- * they overlap the cluster we eventually decide on
- * (we scan without swap_lock to allow preemption).
- * It's hardly conceivable that cluster_nr could be
- * wrapped during our scan, but don't depend on it.
- */
- if (si->lowest_alloc)
- goto checks;
- si->lowest_alloc = si->max;
- si->highest_alloc = 0;
- }
-check_cluster:
- if (!cluster_is_null(&si->free_cluster_head)) {
- offset = cluster_next(&si->free_cluster_head) *
- SWAPFILE_CLUSTER;
- last_in_cluster = offset + SWAPFILE_CLUSTER - 1;
- si->cluster_next = offset;
- si->cluster_nr = SWAPFILE_CLUSTER - 1;
- found_free_cluster = 1;
- goto checks;
- } else if (si->cluster_info) {
- /*
- * Checking free cluster is fast enough, we can do the
- * check every time
- */
- si->cluster_nr = 0;
- si->lowest_alloc = 0;
- goto checks;
- }
spin_unlock(&si->lock);
offset -= SWAPFILE_CLUSTER - 1;
si->cluster_next = offset;
si->cluster_nr = SWAPFILE_CLUSTER - 1;
- found_free_cluster = 1;
goto checks;
}
if (unlikely(--latency_ration < 0)) {
offset -= SWAPFILE_CLUSTER - 1;
si->cluster_next = offset;
si->cluster_nr = SWAPFILE_CLUSTER - 1;
- found_free_cluster = 1;
goto checks;
}
if (unlikely(--latency_ration < 0)) {
offset = scan_base;
spin_lock(&si->lock);
si->cluster_nr = SWAPFILE_CLUSTER - 1;
- si->lowest_alloc = 0;
}
checks:
- if (scan_swap_map_recheck_cluster(si, offset))
- goto check_cluster;
+ if (si->cluster_info) {
+ while (scan_swap_map_ssd_cluster_conflict(si, offset))
+ scan_swap_map_try_ssd_cluster(si, &offset, &scan_base);
+ }
if (!(si->flags & SWP_WRITEOK))
goto no_page;
if (!si->highest_bit)
si->cluster_next = offset + 1;
si->flags -= SWP_SCANNING;
- if (si->lowest_alloc) {
- /*
- * Only set when SWP_PAGE_DISCARD, and there's a scan
- * for a free cluster in progress or just completed.
- */
- if (found_free_cluster) {
- /*
- * To optimize wear-levelling, discard the
- * old data of the cluster, taking care not to
- * discard any of its pages that have already
- * been allocated by racing tasks (offset has
- * already stepped over any at the beginning).
- */
- if (offset < si->highest_alloc &&
- si->lowest_alloc <= last_in_cluster)
- last_in_cluster = si->lowest_alloc - 1;
- si->flags |= SWP_DISCARDING;
- spin_unlock(&si->lock);
-
- if (offset < last_in_cluster)
- discard_swap_cluster(si, offset,
- last_in_cluster - offset + 1);
-
- spin_lock(&si->lock);
- si->lowest_alloc = 0;
- si->flags &= ~SWP_DISCARDING;
-
- smp_mb(); /* wake_up_bit advises this */
- wake_up_bit(&si->flags, ilog2(SWP_DISCARDING));
-
- } else if (si->flags & SWP_DISCARDING) {
- /*
- * Delay using pages allocated by racing tasks
- * until the whole discard has been issued. We
- * could defer that delay until swap_writepage,
- * but it's easier to keep this self-contained.
- */
- spin_unlock(&si->lock);
- wait_on_bit(&si->flags, ilog2(SWP_DISCARDING),
- wait_for_discard, TASK_UNINTERRUPTIBLE);
- spin_lock(&si->lock);
- } else {
- /*
- * Note pages allocated by racing tasks while
- * scan for a free cluster is in progress, so
- * that its final discard can exclude them.
- */
- if (offset < si->lowest_alloc)
- si->lowest_alloc = offset;
- if (offset > si->highest_alloc)
- si->highest_alloc = offset;
- }
- }
return offset;
scan:
else
continue;
}
- count = si->swap_map[i];
+ count = ACCESS_ONCE(si->swap_map[i]);
if (count && swap_count(count) != SWAP_MAP_BAD)
break;
}
{
struct swap_info_struct *si = swap_info[type];
struct mm_struct *start_mm;
- unsigned char *swap_map;
+ volatile unsigned char *swap_map; /* swap_map is accessed without
+ * locking. Mark it as volatile
+ * to prevent compiler doing
+ * something odd.
+ */
unsigned char swcount;
struct page *page;
swp_entry_t entry;
* reused since sys_swapoff() already disabled
* allocation from here, or alloc_page() failed.
*/
- if (!*swap_map)
+ swcount = *swap_map;
+ /*
+ * We don't hold lock here, so the swap entry could be
+ * SWAP_MAP_BAD (when the cluster is discarding).
+ * Instead of fail out, We can just skip the swap
+ * entry because swapoff will wait for discarding
+ * finish anyway.
+ */
+ if (!swcount || swcount == SWAP_MAP_BAD)
continue;
retval = -ENOMEM;
break;
goto out_dput;
}
+ flush_work(&p->discard_work);
+
destroy_swap_extents(p);
if (p->flags & SWP_CONTINUED)
free_swap_count_continuations(p);
spin_unlock(&swap_lock);
frontswap_invalidate_area(type);
mutex_unlock(&swapon_mutex);
+ free_percpu(p->percpu_cluster);
+ p->percpu_cluster = NULL;
vfree(swap_map);
vfree(cluster_info);
vfree(frontswap_map);
cluster_set_null(&p->free_cluster_head);
cluster_set_null(&p->free_cluster_tail);
+ cluster_set_null(&p->discard_cluster_head);
+ cluster_set_null(&p->discard_cluster_tail);
for (i = 0; i < swap_header->info.nr_badpages; i++) {
unsigned int page_nr = swap_header->info.badpages[i];
if (IS_ERR(p))
return PTR_ERR(p);
+ INIT_WORK(&p->discard_work, swap_discard_work);
+
name = getname(specialfile);
if (IS_ERR(name)) {
error = PTR_ERR(name);
error = -ENOMEM;
goto bad_swap;
}
+ p->percpu_cluster = alloc_percpu(struct percpu_cluster);
+ if (!p->percpu_cluster) {
+ error = -ENOMEM;
+ goto bad_swap;
+ }
+ for_each_possible_cpu(i) {
+ struct percpu_cluster *cluster;
+ cluster = per_cpu_ptr(p->percpu_cluster, i);
+ cluster_set_null(&cluster->index);
+ }
}
error = swap_cgroup_swapon(p->type, maxpages);
error = 0;
goto out;
bad_swap:
+ free_percpu(p->percpu_cluster);
+ p->percpu_cluster = NULL;
if (inode && S_ISBLK(inode->i_mode) && p->bdev) {
set_blocksize(p->bdev, p->old_block_size);
blkdev_put(p->bdev, FMODE_READ | FMODE_WRITE | FMODE_EXCL);
goto unlock_out;
count = p->swap_map[offset];
+
+ /*
+ * swapin_readahead() doesn't check if a swap entry is valid, so the
+ * swap entry could be SWAP_MAP_BAD. Check here with lock held.
+ */
+ if (unlikely(swap_count(count) == SWAP_MAP_BAD)) {
+ err = -ENOENT;
+ goto unlock_out;
+ }
+
has_cache = count & SWAP_HAS_CACHE;
count &= ~SWAP_HAS_CACHE;
err = 0;
projects / karo-tx-linux.git / blobdiff