Merge tag 'drm-misc-fixes-2018-11-21' of git://anongit.freedesktop.org/drm/drm-misc...

[sfrench/cifs-2.6.git] / mm / z3fold.c

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 4b366d181f35d12f9a1e600bb7083bbf4dfe7fff..aee9b0b8d9078a0bbf59a06509c6f7f7aa1360f3 100644 (file)
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -99,6 +99,7 @@ struct z3fold_header {
 #define NCHUNKS                ((PAGE_SIZE - ZHDR_SIZE_ALIGNED) >> CHUNK_SHIFT)
 
 #define BUDDY_MASK     (0x3)
+#define BUDDY_SHIFT    2
 
 /**
  * struct z3fold_pool - stores metadata for each z3fold pool
@@ -145,7 +146,7 @@ enum z3fold_page_flags {
        MIDDLE_CHUNK_MAPPED,
        NEEDS_COMPACTING,
        PAGE_STALE,
-       UNDER_RECLAIM
+       PAGE_CLAIMED, /* by either reclaim or free */
 };
 
 /*****************
@@ -174,7 +175,7 @@ static struct z3fold_header *init_z3fold_page(struct page *page,
        clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
        clear_bit(NEEDS_COMPACTING, &page->private);
        clear_bit(PAGE_STALE, &page->private);
-       clear_bit(UNDER_RECLAIM, &page->private);
+       clear_bit(PAGE_CLAIMED, &page->private);
 
        spin_lock_init(&zhdr->page_lock);
        kref_init(&zhdr->refcount);
@@ -223,8 +224,11 @@ static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
        unsigned long handle;
 
        handle = (unsigned long)zhdr;
-       if (bud != HEADLESS)
-               handle += (bud + zhdr->first_num) & BUDDY_MASK;
+       if (bud != HEADLESS) {
+               handle |= (bud + zhdr->first_num) & BUDDY_MASK;
+               if (bud == LAST)
+                       handle |= (zhdr->last_chunks << BUDDY_SHIFT);
+       }
        return handle;
 }
 
@@ -234,6 +238,12 @@ static struct z3fold_header *handle_to_z3fold_header(unsigned long handle)
        return (struct z3fold_header *)(handle & PAGE_MASK);
 }
 
+/* only for LAST bud, returns zero otherwise */
+static unsigned short handle_to_chunks(unsigned long handle)
+{
+       return (handle & ~PAGE_MASK) >> BUDDY_SHIFT;
+}
+
 /*
  * (handle & BUDDY_MASK) < zhdr->first_num is possible in encode_handle
  *  but that doesn't matter. because the masking will result in the
@@ -720,37 +730,39 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
        page = virt_to_page(zhdr);
 
        if (test_bit(PAGE_HEADLESS, &page->private)) {
-               /* HEADLESS page stored */
-               bud = HEADLESS;
-       } else {
-               z3fold_page_lock(zhdr);
-               bud = handle_to_buddy(handle);
-
-               switch (bud) {
-               case FIRST:
-                       zhdr->first_chunks = 0;
-                       break;
-               case MIDDLE:
-                       zhdr->middle_chunks = 0;
-                       zhdr->start_middle = 0;
-                       break;
-               case LAST:
-                       zhdr->last_chunks = 0;
-                       break;
-               default:
-                       pr_err("%s: unknown bud %d\n", __func__, bud);
-                       WARN_ON(1);
-                       z3fold_page_unlock(zhdr);
-                       return;
+               /* if a headless page is under reclaim, just leave.
+                * NB: we use test_and_set_bit for a reason: if the bit
+                * has not been set before, we release this page
+                * immediately so we don't care about its value any more.
+                */
+               if (!test_and_set_bit(PAGE_CLAIMED, &page->private)) {
+                       spin_lock(&pool->lock);
+                       list_del(&page->lru);
+                       spin_unlock(&pool->lock);
+                       free_z3fold_page(page);
+                       atomic64_dec(&pool->pages_nr);
                }
+               return;
        }
 
-       if (bud == HEADLESS) {
-               spin_lock(&pool->lock);
-               list_del(&page->lru);
-               spin_unlock(&pool->lock);
-               free_z3fold_page(page);
-               atomic64_dec(&pool->pages_nr);
+       /* Non-headless case */
+       z3fold_page_lock(zhdr);
+       bud = handle_to_buddy(handle);
+
+       switch (bud) {
+       case FIRST:
+               zhdr->first_chunks = 0;
+               break;
+       case MIDDLE:
+               zhdr->middle_chunks = 0;
+               break;
+       case LAST:
+               zhdr->last_chunks = 0;
+               break;
+       default:
+               pr_err("%s: unknown bud %d\n", __func__, bud);
+               WARN_ON(1);
+               z3fold_page_unlock(zhdr);
                return;
        }
 
@@ -758,7 +770,7 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
                atomic64_dec(&pool->pages_nr);
                return;
        }
-       if (test_bit(UNDER_RECLAIM, &page->private)) {
+       if (test_bit(PAGE_CLAIMED, &page->private)) {
                z3fold_page_unlock(zhdr);
                return;
        }
@@ -836,20 +848,30 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
                }
                list_for_each_prev(pos, &pool->lru) {
                        page = list_entry(pos, struct page, lru);
+
+                       /* this bit could have been set by free, in which case
+                        * we pass over to the next page in the pool.
+                        */
+                       if (test_and_set_bit(PAGE_CLAIMED, &page->private))
+                               continue;
+
+                       zhdr = page_address(page);
                        if (test_bit(PAGE_HEADLESS, &page->private))
-                               /* candidate found */
                                break;
 
-                       zhdr = page_address(page);
-                       if (!z3fold_page_trylock(zhdr))
+                       if (!z3fold_page_trylock(zhdr)) {
+                               zhdr = NULL;
                                continue; /* can't evict at this point */
+                       }
                        kref_get(&zhdr->refcount);
                        list_del_init(&zhdr->buddy);
                        zhdr->cpu = -1;
-                       set_bit(UNDER_RECLAIM, &page->private);
                        break;
                }
 
+               if (!zhdr)
+                       break;
+
                list_del_init(&page->lru);
                spin_unlock(&pool->lock);
 
@@ -898,6 +920,7 @@ next:
                if (test_bit(PAGE_HEADLESS, &page->private)) {
                        if (ret == 0) {
                                free_z3fold_page(page);
+                               atomic64_dec(&pool->pages_nr);
                                return 0;
                        }
                        spin_lock(&pool->lock);
@@ -905,7 +928,7 @@ next:
                        spin_unlock(&pool->lock);
                } else {
                        z3fold_page_lock(zhdr);
-                       clear_bit(UNDER_RECLAIM, &page->private);
+                       clear_bit(PAGE_CLAIMED, &page->private);
                        if (kref_put(&zhdr->refcount,
                                        release_z3fold_page_locked)) {
                                atomic64_dec(&pool->pages_nr);
@@ -964,7 +987,7 @@ static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
                set_bit(MIDDLE_CHUNK_MAPPED, &page->private);
                break;
        case LAST:
-               addr += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
+               addr += PAGE_SIZE - (handle_to_chunks(handle) << CHUNK_SHIFT);
                break;
        default:
                pr_err("unknown buddy id %d\n", buddy);