mm: swap: relaim the cached parts that got scanned
This commit implements reclaim during scan for cluster allocator. Cluster scanning were unable to reuse SWAP_HAS_CACHE slots, which could result in low allocation success rate or early OOM. So to ensure maximum allocation success rate, integrate reclaiming with scanning. If found a range of suitable swap slots but fragmented due to HAS_CACHE, just try to reclaim the slots. Link: https://lkml.kernel.org/r/20240730-swap-allocator-v5-8-cb9c148b9297@kernel.org Signed-off-by: Kairui Song <kasong@tencent.com> Reported-by: Barry Song <21cnbao@gmail.com> Cc: Chris Li <chrisl@kernel.org> Cc: "Huang, Ying" <ying.huang@intel.com> Cc: Hugh Dickins <hughd@google.com> Cc: Kalesh Singh <kaleshsingh@google.com> Cc: Ryan Roberts <ryan.roberts@arm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
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477cb7ba28
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661383c611
@ -301,6 +301,7 @@ struct swap_info_struct {
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/* list of cluster that contains at least one free slot */
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struct list_head frag_clusters[SWAP_NR_ORDERS];
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/* list of cluster that are fragmented or contented */
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unsigned int frag_cluster_nr[SWAP_NR_ORDERS];
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unsigned int lowest_bit; /* index of first free in swap_map */
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unsigned int highest_bit; /* index of last free in swap_map */
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unsigned int pages; /* total of usable pages of swap */
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138
mm/swapfile.c
138
mm/swapfile.c
@ -513,6 +513,10 @@ static void free_cluster(struct swap_info_struct *si, struct swap_cluster_info *
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VM_BUG_ON(ci->count != 0);
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lockdep_assert_held(&si->lock);
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lockdep_assert_held(&ci->lock);
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if (ci->flags & CLUSTER_FLAG_FRAG)
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si->frag_cluster_nr[ci->order]--;
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/*
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* If the swap is discardable, prepare discard the cluster
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* instead of free it immediately. The cluster will be freed
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@ -572,29 +576,82 @@ static void dec_cluster_info_page(struct swap_info_struct *p,
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if (!(ci->flags & CLUSTER_FLAG_NONFULL)) {
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VM_BUG_ON(ci->flags & CLUSTER_FLAG_FREE);
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if (ci->flags & CLUSTER_FLAG_FRAG)
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if (ci->flags & CLUSTER_FLAG_FRAG) {
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p->frag_cluster_nr[ci->order]--;
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list_move_tail(&ci->list, &p->nonfull_clusters[ci->order]);
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else
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} else {
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list_add_tail(&ci->list, &p->nonfull_clusters[ci->order]);
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}
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ci->flags = CLUSTER_FLAG_NONFULL;
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}
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}
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static inline bool cluster_scan_range(struct swap_info_struct *si, unsigned int start,
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unsigned int nr_pages)
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static bool cluster_reclaim_range(struct swap_info_struct *si,
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struct swap_cluster_info *ci,
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unsigned long start, unsigned long end)
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{
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unsigned char *p = si->swap_map + start;
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unsigned char *end = p + nr_pages;
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unsigned char *map = si->swap_map;
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unsigned long offset;
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while (p < end)
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if (*p++)
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spin_unlock(&ci->lock);
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spin_unlock(&si->lock);
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for (offset = start; offset < end; offset++) {
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switch (READ_ONCE(map[offset])) {
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case 0:
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continue;
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case SWAP_HAS_CACHE:
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if (__try_to_reclaim_swap(si, offset, TTRS_ANYWAY | TTRS_DIRECT) > 0)
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continue;
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goto out;
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default:
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goto out;
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}
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}
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out:
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spin_lock(&si->lock);
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spin_lock(&ci->lock);
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/*
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* Recheck the range no matter reclaim succeeded or not, the slot
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* could have been be freed while we are not holding the lock.
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*/
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for (offset = start; offset < end; offset++)
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if (READ_ONCE(map[offset]))
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return false;
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return true;
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}
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static bool cluster_scan_range(struct swap_info_struct *si,
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struct swap_cluster_info *ci,
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unsigned long start, unsigned int nr_pages)
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{
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unsigned long offset, end = start + nr_pages;
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unsigned char *map = si->swap_map;
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bool need_reclaim = false;
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static inline void cluster_alloc_range(struct swap_info_struct *si, struct swap_cluster_info *ci,
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for (offset = start; offset < end; offset++) {
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switch (READ_ONCE(map[offset])) {
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case 0:
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continue;
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case SWAP_HAS_CACHE:
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if (!vm_swap_full())
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return false;
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need_reclaim = true;
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continue;
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default:
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return false;
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}
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}
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if (need_reclaim)
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return cluster_reclaim_range(si, ci, start, end);
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return true;
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}
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static void cluster_alloc_range(struct swap_info_struct *si, struct swap_cluster_info *ci,
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unsigned int start, unsigned char usage,
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unsigned int order)
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{
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@ -615,6 +672,8 @@ static inline void cluster_alloc_range(struct swap_info_struct *si, struct swap_
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if (ci->count == SWAPFILE_CLUSTER) {
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VM_BUG_ON(!(ci->flags &
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(CLUSTER_FLAG_FREE | CLUSTER_FLAG_NONFULL | CLUSTER_FLAG_FRAG)));
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if (ci->flags & CLUSTER_FLAG_FRAG)
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si->frag_cluster_nr[ci->order]--;
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list_del(&ci->list);
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ci->flags = 0;
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}
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@ -640,7 +699,7 @@ static unsigned int alloc_swap_scan_cluster(struct swap_info_struct *si, unsigne
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}
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while (offset <= end) {
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if (cluster_scan_range(si, offset, nr_pages)) {
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if (cluster_scan_range(si, ci, offset, nr_pages)) {
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cluster_alloc_range(si, ci, offset, usage, order);
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*foundp = offset;
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if (ci->count == SWAPFILE_CLUSTER) {
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@ -668,9 +727,8 @@ static unsigned long cluster_alloc_swap_entry(struct swap_info_struct *si, int o
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unsigned char usage)
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{
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struct percpu_cluster *cluster;
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struct swap_cluster_info *ci, *n;
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struct swap_cluster_info *ci;
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unsigned int offset, found = 0;
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LIST_HEAD(fraged);
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new_cluster:
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lockdep_assert_held(&si->lock);
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@ -690,25 +748,42 @@ new_cluster:
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}
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if (order < PMD_ORDER) {
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list_for_each_entry_safe(ci, n, &si->nonfull_clusters[order], list) {
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list_move_tail(&ci->list, &fraged);
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unsigned int frags = 0;
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while (!list_empty(&si->nonfull_clusters[order])) {
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ci = list_first_entry(&si->nonfull_clusters[order],
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struct swap_cluster_info, list);
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list_move_tail(&ci->list, &si->frag_clusters[order]);
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ci->flags = CLUSTER_FLAG_FRAG;
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si->frag_cluster_nr[order]++;
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offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci),
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&found, order, usage);
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frags++;
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if (found)
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break;
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}
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if (!found) {
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list_for_each_entry_safe(ci, n, &si->frag_clusters[order], list) {
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/*
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* Nonfull clusters are moved to frag tail if we reached
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* here, count them too, don't over scan the frag list.
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*/
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while (frags < si->frag_cluster_nr[order]) {
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ci = list_first_entry(&si->frag_clusters[order],
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struct swap_cluster_info, list);
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/*
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* Rotate the frag list to iterate, they were all failing
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* high order allocation or moved here due to per-CPU usage,
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* this help keeping usable cluster ahead.
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*/
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list_move_tail(&ci->list, &si->frag_clusters[order]);
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offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci),
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&found, order, usage);
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frags++;
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if (found)
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break;
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}
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}
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list_splice_tail(&fraged, &si->frag_clusters[order]);
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}
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if (found)
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@ -729,25 +804,28 @@ new_cluster:
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/* Order 0 stealing from higher order */
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for (int o = 1; o < SWAP_NR_ORDERS; o++) {
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if (!list_empty(&si->frag_clusters[o])) {
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/*
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* Clusters here have at least one usable slots and can't fail order 0
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* allocation, but reclaim may drop si->lock and race with another user.
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*/
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while (!list_empty(&si->frag_clusters[o])) {
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ci = list_first_entry(&si->frag_clusters[o],
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struct swap_cluster_info, list);
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offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci), &found,
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0, usage);
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VM_BUG_ON(!found);
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goto done;
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}
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if (!list_empty(&si->nonfull_clusters[o])) {
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ci = list_first_entry(&si->nonfull_clusters[o], struct swap_cluster_info,
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list);
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offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci),
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&found, 0, usage);
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VM_BUG_ON(!found);
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if (found)
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goto done;
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}
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while (!list_empty(&si->nonfull_clusters[o])) {
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ci = list_first_entry(&si->nonfull_clusters[o],
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struct swap_cluster_info, list);
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offset = alloc_swap_scan_cluster(si, cluster_offset(si, ci),
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&found, 0, usage);
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if (found)
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goto done;
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}
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}
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done:
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cluster->next[order] = offset;
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return found;
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@ -3042,6 +3120,7 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
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for (i = 0; i < SWAP_NR_ORDERS; i++) {
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INIT_LIST_HEAD(&p->nonfull_clusters[i]);
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INIT_LIST_HEAD(&p->frag_clusters[i]);
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p->frag_cluster_nr[i] = 0;
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}
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for (i = 0; i < swap_header->info.nr_badpages; i++) {
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@ -3085,7 +3164,6 @@ static int setup_swap_map_and_extents(struct swap_info_struct *p,
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if (!cluster_info)
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return nr_extents;
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/*
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* Reduce false cache line sharing between cluster_info and
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* sharing same address space.
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