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-rw-r--r--include/linux/swap.h20
-rw-r--r--mm/swapfile.c192
2 files changed, 125 insertions, 87 deletions
diff --git a/include/linux/swap.h b/include/linux/swap.h
index cb5baebf31d6..8a3c4a1caa14 100644
--- a/include/linux/swap.h
+++ b/include/linux/swap.h
@@ -217,8 +217,6 @@ struct swap_info_struct {
unsigned int inuse_pages; /* number of those currently in use */
unsigned int cluster_next; /* likely index for next allocation */
unsigned int cluster_nr; /* countdown to next cluster search */
- unsigned int lowest_alloc; /* while preparing discard cluster */
- unsigned int highest_alloc; /* while preparing discard cluster */
struct swap_extent *curr_swap_extent;
struct swap_extent first_swap_extent;
struct block_device *bdev; /* swap device or bdev of swap file */
@@ -232,14 +230,18 @@ struct swap_info_struct {
* protect map scan related fields like
* swap_map, lowest_bit, highest_bit,
* inuse_pages, cluster_next,
- * cluster_nr, lowest_alloc and
- * highest_alloc. other fields are only
- * changed at swapon/swapoff, so are
- * protected by swap_lock. changing
- * flags need hold this lock and
- * swap_lock. If both locks need hold,
- * hold swap_lock first.
+ * cluster_nr, lowest_alloc,
+ * highest_alloc, free/discard cluster
+ * list. other fields are only changed
+ * at swapon/swapoff, so are protected
+ * by swap_lock. changing flags need
+ * hold this lock and swap_lock. If
+ * both locks need hold, hold swap_lock
+ * first.
*/
+ struct work_struct discard_work; /* discard worker */
+ struct swap_cluster_info discard_cluster_head; /* list head of discard clusters */
+ struct swap_cluster_info discard_cluster_tail; /* list tail of discard clusters */
};
struct swap_list_t {
diff --git a/mm/swapfile.c b/mm/swapfile.c
index d1fbeb486de5..dac47c66055c 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -175,12 +175,6 @@ static void discard_swap_cluster(struct swap_info_struct *si,
}
}
-static int wait_for_discard(void *word)
-{
- schedule();
- return 0;
-}
-
#define SWAPFILE_CLUSTER 256
#define LATENCY_LIMIT 256
@@ -242,6 +236,90 @@ static inline void cluster_set_null(struct swap_cluster_info *info)
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.
@@ -287,6 +365,16 @@ static void dec_cluster_info_page(struct swap_info_struct *p,
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_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);
@@ -319,7 +407,6 @@ 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
@@ -340,19 +427,6 @@ static unsigned long scan_swap_map(struct swap_info_struct *si,
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) *
@@ -360,15 +434,27 @@ check_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) {
/*
+ * we don't have free cluster but have some clusters in
+ * discarding, do discard now and reclaim them
+ */
+ if (!cluster_is_null(&si->discard_cluster_head)) {
+ si->cluster_nr = 0;
+ swap_do_scheduled_discard(si);
+ scan_base = offset = si->cluster_next;
+ if (!si->cluster_nr)
+ goto check_cluster;
+ si->cluster_nr--;
+ goto checks;
+ }
+
+ /*
* Checking free cluster is fast enough, we can do the
* check every time
*/
si->cluster_nr = 0;
- si->lowest_alloc = 0;
goto checks;
}
@@ -395,7 +481,6 @@ check_cluster:
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)) {
@@ -416,7 +501,6 @@ check_cluster:
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)) {
@@ -428,7 +512,6 @@ check_cluster:
offset = scan_base;
spin_lock(&si->lock);
si->cluster_nr = SWAPFILE_CLUSTER - 1;
- si->lowest_alloc = 0;
}
checks:
@@ -470,59 +553,6 @@ checks:
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:
@@ -1806,6 +1836,8 @@ SYSCALL_DEFINE1(swapoff, const char __user *, specialfile)
goto out_dput;
}
+ flush_work(&p->discard_work);
+
destroy_swap_extents(p);
if (p->flags & SWP_CONTINUED)
free_swap_count_continuations(p);
@@ -2172,6 +2204,8 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
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];
@@ -2281,6 +2315,8 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
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);
generated by cgit v1.2.3 (git 2.39.0) at 2024-11-01 03:53:46 +0300