1 files changed, 303 insertions, 72 deletions

diff --git a/mm/z3fold.c b/mm/z3fold.c
index 6d3d3f698ebb..43754d8ebce8 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -41,6 +41,7 @@
 #include <linux/workqueue.h>
 #include <linux/slab.h>
 #include <linux/spinlock.h>
+#include <linux/rwlock.h>
 #include <linux/zpool.h>
 #include <linux/magic.h>
 
@@ -90,6 +91,7 @@ struct z3fold_buddy_slots {
 	 */
 	unsigned long slot[BUDDY_MASK + 1];
 	unsigned long pool; /* back link + flags */
+	rwlock_t lock;
 };
 #define HANDLE_FLAG_MASK	(0x03)
 
@@ -124,6 +126,7 @@ struct z3fold_header {
 	unsigned short start_middle;
 	unsigned short first_num:2;
 	unsigned short mapped_count:2;
+	unsigned short foreign_handles:2;
 };
 
 /**
@@ -178,6 +181,19 @@ enum z3fold_page_flags {
 	PAGE_CLAIMED, /* by either reclaim or free */
 };
 
+/*
+ * handle flags, go under HANDLE_FLAG_MASK
+ */
+enum z3fold_handle_flags {
+	HANDLES_ORPHANED = 0,
+};
+
+/*
+ * Forward declarations
+ */
+static struct z3fold_header *__z3fold_alloc(struct z3fold_pool *, size_t, bool);
+static void compact_page_work(struct work_struct *w);
+
 /*****************
  * Helpers
 *****************/
@@ -191,8 +207,6 @@ static int size_to_chunks(size_t size)
 #define for_each_unbuddied_list(_iter, _begin) \
 	for ((_iter) = (_begin); (_iter) < NCHUNKS; (_iter)++)
 
-static void compact_page_work(struct work_struct *w);
-
 static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
 							gfp_t gfp)
 {
@@ -204,6 +218,7 @@ static inline struct z3fold_buddy_slots *alloc_slots(struct z3fold_pool *pool,
 	if (slots) {
 		memset(slots->slot, 0, sizeof(slots->slot));
 		slots->pool = (unsigned long)pool;
+		rwlock_init(&slots->lock);
 	}
 
 	return slots;
@@ -219,25 +234,110 @@ static inline struct z3fold_buddy_slots *handle_to_slots(unsigned long handle)
 	return (struct z3fold_buddy_slots *)(handle & ~(SLOTS_ALIGN - 1));
 }
 
+/* Lock a z3fold page */
+static inline void z3fold_page_lock(struct z3fold_header *zhdr)
+{
+	spin_lock(&zhdr->page_lock);
+}
+
+/* Try to lock a z3fold page */
+static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
+{
+	return spin_trylock(&zhdr->page_lock);
+}
+
+/* Unlock a z3fold page */
+static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
+{
+	spin_unlock(&zhdr->page_lock);
+}
+
+
+static inline struct z3fold_header *__get_z3fold_header(unsigned long handle,
+							bool lock)
+{
+	struct z3fold_buddy_slots *slots;
+	struct z3fold_header *zhdr;
+	int locked = 0;
+
+	if (!(handle & (1 << PAGE_HEADLESS))) {
+		slots = handle_to_slots(handle);
+		do {
+			unsigned long addr;
+
+			read_lock(&slots->lock);
+			addr = *(unsigned long *)handle;
+			zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
+			if (lock)
+				locked = z3fold_page_trylock(zhdr);
+			read_unlock(&slots->lock);
+			if (locked)
+				break;
+			cpu_relax();
+		} while (lock);
+	} else {
+		zhdr = (struct z3fold_header *)(handle & PAGE_MASK);
+	}
+
+	return zhdr;
+}
+
+/* Returns the z3fold page where a given handle is stored */
+static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
+{
+	return __get_z3fold_header(h, false);
+}
+
+/* return locked z3fold page if it's not headless */
+static inline struct z3fold_header *get_z3fold_header(unsigned long h)
+{
+	return __get_z3fold_header(h, true);
+}
+
+static inline void put_z3fold_header(struct z3fold_header *zhdr)
+{
+	struct page *page = virt_to_page(zhdr);
+
+	if (!test_bit(PAGE_HEADLESS, &page->private))
+		z3fold_page_unlock(zhdr);
+}
+
 static inline void free_handle(unsigned long handle)
 {
 	struct z3fold_buddy_slots *slots;
+	struct z3fold_header *zhdr;
 	int i;
 	bool is_free;
 
 	if (handle & (1 << PAGE_HEADLESS))
 		return;
 
-	WARN_ON(*(unsigned long *)handle == 0);
-	*(unsigned long *)handle = 0;
+	if (WARN_ON(*(unsigned long *)handle == 0))
+		return;
+
+	zhdr = handle_to_z3fold_header(handle);
 	slots = handle_to_slots(handle);
+	write_lock(&slots->lock);
+	*(unsigned long *)handle = 0;
+	write_unlock(&slots->lock);
+	if (zhdr->slots == slots)
+		return; /* simple case, nothing else to do */
+
+	/* we are freeing a foreign handle if we are here */
+	zhdr->foreign_handles--;
 	is_free = true;
+	read_lock(&slots->lock);
+	if (!test_bit(HANDLES_ORPHANED, &slots->pool)) {
+		read_unlock(&slots->lock);
+		return;
+	}
 	for (i = 0; i <= BUDDY_MASK; i++) {
 		if (slots->slot[i]) {
 			is_free = false;
 			break;
 		}
 	}
+	read_unlock(&slots->lock);
 
 	if (is_free) {
 		struct z3fold_pool *pool = slots_to_pool(slots);
@@ -322,6 +422,7 @@ static struct z3fold_header *init_z3fold_page(struct page *page, bool headless,
 	zhdr->first_num = 0;
 	zhdr->start_middle = 0;
 	zhdr->cpu = -1;
+	zhdr->foreign_handles = 0;
 	zhdr->slots = slots;
 	zhdr->pool = pool;
 	INIT_LIST_HEAD(&zhdr->buddy);
@@ -341,24 +442,6 @@ static void free_z3fold_page(struct page *page, bool headless)
 	__free_page(page);
 }
 
-/* Lock a z3fold page */
-static inline void z3fold_page_lock(struct z3fold_header *zhdr)
-{
-	spin_lock(&zhdr->page_lock);
-}
-
-/* Try to lock a z3fold page */
-static inline int z3fold_page_trylock(struct z3fold_header *zhdr)
-{
-	return spin_trylock(&zhdr->page_lock);
-}
-
-/* Unlock a z3fold page */
-static inline void z3fold_page_unlock(struct z3fold_header *zhdr)
-{
-	spin_unlock(&zhdr->page_lock);
-}
-
 /* Helper function to build the index */
 static inline int __idx(struct z3fold_header *zhdr, enum buddy bud)
 {
@@ -389,7 +472,9 @@ static unsigned long __encode_handle(struct z3fold_header *zhdr,
 	if (bud == LAST)
 		h |= (zhdr->last_chunks << BUDDY_SHIFT);
 
+	write_lock(&slots->lock);
 	slots->slot[idx] = h;
+	write_unlock(&slots->lock);
 	return (unsigned long)&slots->slot[idx];
 }
 
@@ -398,22 +483,15 @@ static unsigned long encode_handle(struct z3fold_header *zhdr, enum buddy bud)
 	return __encode_handle(zhdr, zhdr->slots, bud);
 }
 
-/* Returns the z3fold page where a given handle is stored */
-static inline struct z3fold_header *handle_to_z3fold_header(unsigned long h)
-{
-	unsigned long addr = h;
-
-	if (!(addr & (1 << PAGE_HEADLESS)))
-		addr = *(unsigned long *)h;
-
-	return (struct z3fold_header *)(addr & PAGE_MASK);
-}
-
 /* only for LAST bud, returns zero otherwise */
 static unsigned short handle_to_chunks(unsigned long handle)
 {
-	unsigned long addr = *(unsigned long *)handle;
+	struct z3fold_buddy_slots *slots = handle_to_slots(handle);
+	unsigned long addr;
 
+	read_lock(&slots->lock);
+	addr = *(unsigned long *)handle;
+	read_unlock(&slots->lock);
 	return (addr & ~PAGE_MASK) >> BUDDY_SHIFT;
 }
 
@@ -425,10 +503,13 @@ static unsigned short handle_to_chunks(unsigned long handle)
 static enum buddy handle_to_buddy(unsigned long handle)
 {
 	struct z3fold_header *zhdr;
+	struct z3fold_buddy_slots *slots = handle_to_slots(handle);
 	unsigned long addr;
 
+	read_lock(&slots->lock);
 	WARN_ON(handle & (1 << PAGE_HEADLESS));
 	addr = *(unsigned long *)handle;
+	read_unlock(&slots->lock);
 	zhdr = (struct z3fold_header *)(addr & PAGE_MASK);
 	return (addr - zhdr->first_num) & BUDDY_MASK;
 }
@@ -442,6 +523,8 @@ static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
 {
 	struct page *page = virt_to_page(zhdr);
 	struct z3fold_pool *pool = zhdr_to_pool(zhdr);
+	bool is_free = true;
+	int i;
 
 	WARN_ON(!list_empty(&zhdr->buddy));
 	set_bit(PAGE_STALE, &page->private);
@@ -450,8 +533,25 @@ static void __release_z3fold_page(struct z3fold_header *zhdr, bool locked)
 	if (!list_empty(&page->lru))
 		list_del_init(&page->lru);
 	spin_unlock(&pool->lock);
+
+	/* If there are no foreign handles, free the handles array */
+	read_lock(&zhdr->slots->lock);
+	for (i = 0; i <= BUDDY_MASK; i++) {
+		if (zhdr->slots->slot[i]) {
+			is_free = false;
+			break;
+		}
+	}
+	if (!is_free)
+		set_bit(HANDLES_ORPHANED, &zhdr->slots->pool);
+	read_unlock(&zhdr->slots->lock);
+
+	if (is_free)
+		kmem_cache_free(pool->c_handle, zhdr->slots);
+
 	if (locked)
 		z3fold_page_unlock(zhdr);
+
 	spin_lock(&pool->stale_lock);
 	list_add(&zhdr->buddy, &pool->stale);
 	queue_work(pool->release_wq, &pool->work);
@@ -479,6 +579,7 @@ static void release_z3fold_page_locked_list(struct kref *ref)
 	struct z3fold_header *zhdr = container_of(ref, struct z3fold_header,
 					       refcount);
 	struct z3fold_pool *pool = zhdr_to_pool(zhdr);
+
 	spin_lock(&pool->lock);
 	list_del_init(&zhdr->buddy);
 	spin_unlock(&pool->lock);
@@ -559,6 +660,119 @@ static inline void *mchunk_memmove(struct z3fold_header *zhdr,
 		       zhdr->middle_chunks << CHUNK_SHIFT);
 }
 
+static inline bool buddy_single(struct z3fold_header *zhdr)
+{
+	return !((zhdr->first_chunks && zhdr->middle_chunks) ||
+			(zhdr->first_chunks && zhdr->last_chunks) ||
+			(zhdr->middle_chunks && zhdr->last_chunks));
+}
+
+static struct z3fold_header *compact_single_buddy(struct z3fold_header *zhdr)
+{
+	struct z3fold_pool *pool = zhdr_to_pool(zhdr);
+	void *p = zhdr;
+	unsigned long old_handle = 0;
+	size_t sz = 0;
+	struct z3fold_header *new_zhdr = NULL;
+	int first_idx = __idx(zhdr, FIRST);
+	int middle_idx = __idx(zhdr, MIDDLE);
+	int last_idx = __idx(zhdr, LAST);
+	unsigned short *moved_chunks = NULL;
+
+	/*
+	 * No need to protect slots here -- all the slots are "local" and
+	 * the page lock is already taken
+	 */
+	if (zhdr->first_chunks && zhdr->slots->slot[first_idx]) {
+		p += ZHDR_SIZE_ALIGNED;
+		sz = zhdr->first_chunks << CHUNK_SHIFT;
+		old_handle = (unsigned long)&zhdr->slots->slot[first_idx];
+		moved_chunks = &zhdr->first_chunks;
+	} else if (zhdr->middle_chunks && zhdr->slots->slot[middle_idx]) {
+		p += zhdr->start_middle << CHUNK_SHIFT;
+		sz = zhdr->middle_chunks << CHUNK_SHIFT;
+		old_handle = (unsigned long)&zhdr->slots->slot[middle_idx];
+		moved_chunks = &zhdr->middle_chunks;
+	} else if (zhdr->last_chunks && zhdr->slots->slot[last_idx]) {
+		p += PAGE_SIZE - (zhdr->last_chunks << CHUNK_SHIFT);
+		sz = zhdr->last_chunks << CHUNK_SHIFT;
+		old_handle = (unsigned long)&zhdr->slots->slot[last_idx];
+		moved_chunks = &zhdr->last_chunks;
+	}
+
+	if (sz > 0) {
+		enum buddy new_bud = HEADLESS;
+		short chunks = size_to_chunks(sz);
+		void *q;
+
+		new_zhdr = __z3fold_alloc(pool, sz, false);
+		if (!new_zhdr)
+			return NULL;
+
+		if (WARN_ON(new_zhdr == zhdr))
+			goto out_fail;
+
+		if (new_zhdr->first_chunks == 0) {
+			if (new_zhdr->middle_chunks != 0 &&
+					chunks >= new_zhdr->start_middle) {
+				new_bud = LAST;
+			} else {
+				new_bud = FIRST;
+			}
+		} else if (new_zhdr->last_chunks == 0) {
+			new_bud = LAST;
+		} else if (new_zhdr->middle_chunks == 0) {
+			new_bud = MIDDLE;
+		}
+		q = new_zhdr;
+		switch (new_bud) {
+		case FIRST:
+			new_zhdr->first_chunks = chunks;
+			q += ZHDR_SIZE_ALIGNED;
+			break;
+		case MIDDLE:
+			new_zhdr->middle_chunks = chunks;
+			new_zhdr->start_middle =
+				new_zhdr->first_chunks + ZHDR_CHUNKS;
+			q += new_zhdr->start_middle << CHUNK_SHIFT;
+			break;
+		case LAST:
+			new_zhdr->last_chunks = chunks;
+			q += PAGE_SIZE - (new_zhdr->last_chunks << CHUNK_SHIFT);
+			break;
+		default:
+			goto out_fail;
+		}
+		new_zhdr->foreign_handles++;
+		memcpy(q, p, sz);
+		write_lock(&zhdr->slots->lock);
+		*(unsigned long *)old_handle = (unsigned long)new_zhdr +
+			__idx(new_zhdr, new_bud);
+		if (new_bud == LAST)
+			*(unsigned long *)old_handle |=
+					(new_zhdr->last_chunks << BUDDY_SHIFT);
+		write_unlock(&zhdr->slots->lock);
+		add_to_unbuddied(pool, new_zhdr);
+		z3fold_page_unlock(new_zhdr);
+
+		*moved_chunks = 0;
+	}
+
+	return new_zhdr;
+
+out_fail:
+	if (new_zhdr) {
+		if (kref_put(&new_zhdr->refcount, release_z3fold_page_locked))
+			atomic64_dec(&pool->pages_nr);
+		else {
+			add_to_unbuddied(pool, new_zhdr);
+			z3fold_page_unlock(new_zhdr);
+		}
+	}
+	return NULL;
+
+}
+
 #define BIG_CHUNK_GAP	3
 /* Has to be called with lock held */
 static int z3fold_compact_page(struct z3fold_header *zhdr)
@@ -638,6 +852,15 @@ static void do_compact_page(struct z3fold_header *zhdr, bool locked)
 		return;
 	}
 
+	if (!zhdr->foreign_handles && buddy_single(zhdr) &&
+	    zhdr->mapped_count == 0 && compact_single_buddy(zhdr)) {
+		if (kref_put(&zhdr->refcount, release_z3fold_page_locked))
+			atomic64_dec(&pool->pages_nr);
+		else
+			z3fold_page_unlock(zhdr);
+		return;
+	}
+
 	z3fold_compact_page(zhdr);
 	add_to_unbuddied(pool, zhdr);
 	z3fold_page_unlock(zhdr);
@@ -690,7 +913,8 @@ lookup:
 		spin_unlock(&pool->lock);
 
 		page = virt_to_page(zhdr);
-		if (test_bit(NEEDS_COMPACTING, &page->private)) {
+		if (test_bit(NEEDS_COMPACTING, &page->private) ||
+		    test_bit(PAGE_CLAIMED, &page->private)) {
 			z3fold_page_unlock(zhdr);
 			zhdr = NULL;
 			put_cpu_ptr(pool->unbuddied);
@@ -734,7 +958,8 @@ lookup:
 			spin_unlock(&pool->lock);
 
 			page = virt_to_page(zhdr);
-			if (test_bit(NEEDS_COMPACTING, &page->private)) {
+			if (test_bit(NEEDS_COMPACTING, &page->private) ||
+			    test_bit(PAGE_CLAIMED, &page->private)) {
 				z3fold_page_unlock(zhdr);
 				zhdr = NULL;
 				if (can_sleep)
@@ -1000,7 +1225,7 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
 	enum buddy bud;
 	bool page_claimed;
 
-	zhdr = handle_to_z3fold_header(handle);
+	zhdr = get_z3fold_header(handle);
 	page = virt_to_page(zhdr);
 	page_claimed = test_and_set_bit(PAGE_CLAIMED, &page->private);
 
@@ -1014,6 +1239,7 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
 			spin_lock(&pool->lock);
 			list_del(&page->lru);
 			spin_unlock(&pool->lock);
+			put_z3fold_header(zhdr);
 			free_z3fold_page(page, true);
 			atomic64_dec(&pool->pages_nr);
 		}
@@ -1021,7 +1247,6 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
 	}
 
 	/* Non-headless case */
-	z3fold_page_lock(zhdr);
 	bud = handle_to_buddy(handle);
 
 	switch (bud) {
@@ -1037,11 +1262,13 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
 	default:
 		pr_err("%s: unknown bud %d\n", __func__, bud);
 		WARN_ON(1);
-		z3fold_page_unlock(zhdr);
+		put_z3fold_header(zhdr);
+		clear_bit(PAGE_CLAIMED, &page->private);
 		return;
 	}
 
-	free_handle(handle);
+	if (!page_claimed)
+		free_handle(handle);
 	if (kref_put(&zhdr->refcount, release_z3fold_page_locked_list)) {
 		atomic64_dec(&pool->pages_nr);
 		return;
@@ -1053,7 +1280,7 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
 	}
 	if (unlikely(PageIsolated(page)) ||
 	    test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
-		z3fold_page_unlock(zhdr);
+		put_z3fold_header(zhdr);
 		clear_bit(PAGE_CLAIMED, &page->private);
 		return;
 	}
@@ -1063,14 +1290,14 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
 		spin_unlock(&pool->lock);
 		zhdr->cpu = -1;
 		kref_get(&zhdr->refcount);
-		do_compact_page(zhdr, true);
 		clear_bit(PAGE_CLAIMED, &page->private);
+		do_compact_page(zhdr, true);
 		return;
 	}
 	kref_get(&zhdr->refcount);
-	queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
 	clear_bit(PAGE_CLAIMED, &page->private);
-	z3fold_page_unlock(zhdr);
+	queue_work_on(zhdr->cpu, pool->compact_wq, &zhdr->work);
+	put_z3fold_header(zhdr);
 }
 
 /**
@@ -1111,11 +1338,10 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
  */
 static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
 {
-	int i, ret = 0;
+	int i, ret = -1;
 	struct z3fold_header *zhdr = NULL;
 	struct page *page = NULL;
 	struct list_head *pos;
-	struct z3fold_buddy_slots slots;
 	unsigned long first_handle = 0, middle_handle = 0, last_handle = 0;
 
 	spin_lock(&pool->lock);
@@ -1153,6 +1379,12 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
 				zhdr = NULL;
 				continue; /* can't evict at this point */
 			}
+			if (zhdr->foreign_handles) {
+				clear_bit(PAGE_CLAIMED, &page->private);
+				z3fold_page_unlock(zhdr);
+				zhdr = NULL;
+				continue; /* can't evict such page */
+			}
 			kref_get(&zhdr->refcount);
 			list_del_init(&zhdr->buddy);
 			zhdr->cpu = -1;
@@ -1176,39 +1408,38 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
 			last_handle = 0;
 			middle_handle = 0;
 			if (zhdr->first_chunks)
-				first_handle = __encode_handle(zhdr, &slots,
-								FIRST);
+				first_handle = encode_handle(zhdr, FIRST);
 			if (zhdr->middle_chunks)
-				middle_handle = __encode_handle(zhdr, &slots,
-								MIDDLE);
+				middle_handle = encode_handle(zhdr, MIDDLE);
 			if (zhdr->last_chunks)
-				last_handle = __encode_handle(zhdr, &slots,
-								LAST);
+				last_handle = encode_handle(zhdr, LAST);
 			/*
 			 * it's safe to unlock here because we hold a
 			 * reference to this page
 			 */
 			z3fold_page_unlock(zhdr);
 		} else {
-			first_handle = __encode_handle(zhdr, &slots, HEADLESS);
+			first_handle = encode_handle(zhdr, HEADLESS);
 			last_handle = middle_handle = 0;
 		}
-
 		/* Issue the eviction callback(s) */
 		if (middle_handle) {
 			ret = pool->ops->evict(pool, middle_handle);
 			if (ret)
 				goto next;
+			free_handle(middle_handle);
 		}
 		if (first_handle) {
 			ret = pool->ops->evict(pool, first_handle);
 			if (ret)
 				goto next;
+			free_handle(first_handle);
 		}
 		if (last_handle) {
 			ret = pool->ops->evict(pool, last_handle);
 			if (ret)
 				goto next;
+			free_handle(last_handle);
 		}
 next:
 		if (test_bit(PAGE_HEADLESS, &page->private)) {
@@ -1264,14 +1495,13 @@ static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
 	void *addr;
 	enum buddy buddy;
 
-	zhdr = handle_to_z3fold_header(handle);
+	zhdr = get_z3fold_header(handle);
 	addr = zhdr;
 	page = virt_to_page(zhdr);
 
 	if (test_bit(PAGE_HEADLESS, &page->private))
 		goto out;
 
-	z3fold_page_lock(zhdr);
 	buddy = handle_to_buddy(handle);
 	switch (buddy) {
 	case FIRST:
@@ -1293,8 +1523,8 @@ static void *z3fold_map(struct z3fold_pool *pool, unsigned long handle)
 
 	if (addr)
 		zhdr->mapped_count++;
-	z3fold_page_unlock(zhdr);
 out:
+	put_z3fold_header(zhdr);
 	return addr;
 }
 
@@ -1309,18 +1539,17 @@ static void z3fold_unmap(struct z3fold_pool *pool, unsigned long handle)
 	struct page *page;
 	enum buddy buddy;
 
-	zhdr = handle_to_z3fold_header(handle);
+	zhdr = get_z3fold_header(handle);
 	page = virt_to_page(zhdr);
 
 	if (test_bit(PAGE_HEADLESS, &page->private))
 		return;
 
-	z3fold_page_lock(zhdr);
 	buddy = handle_to_buddy(handle);
 	if (buddy == MIDDLE)
 		clear_bit(MIDDLE_CHUNK_MAPPED, &page->private);
 	zhdr->mapped_count--;
-	z3fold_page_unlock(zhdr);
+	put_z3fold_header(zhdr);
 }
 
 /**
@@ -1352,19 +1581,21 @@ static bool z3fold_page_isolate(struct page *page, isolate_mode_t mode)
 	    test_bit(PAGE_STALE, &page->private))
 		goto out;
 
+	if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0)
+		goto out;
+
 	pool = zhdr_to_pool(zhdr);
+	spin_lock(&pool->lock);
+	if (!list_empty(&zhdr->buddy))
+		list_del_init(&zhdr->buddy);
+	if (!list_empty(&page->lru))
+		list_del_init(&page->lru);
+	spin_unlock(&pool->lock);
+
+	kref_get(&zhdr->refcount);
+	z3fold_page_unlock(zhdr);
+	return true;
 
-	if (zhdr->mapped_count == 0) {
-		kref_get(&zhdr->refcount);
-		if (!list_empty(&zhdr->buddy))
-			list_del_init(&zhdr->buddy);
-		spin_lock(&pool->lock);
-		if (!list_empty(&page->lru))
-			list_del(&page->lru);
-		spin_unlock(&pool->lock);
-		z3fold_page_unlock(zhdr);
-		return true;
-	}
 out:
 	z3fold_page_unlock(zhdr);
 	return false;
@@ -1387,7 +1618,7 @@ static int z3fold_page_migrate(struct address_space *mapping, struct page *newpa
 	if (!z3fold_page_trylock(zhdr)) {
 		return -EAGAIN;
 	}
-	if (zhdr->mapped_count != 0) {
+	if (zhdr->mapped_count != 0 || zhdr->foreign_handles != 0) {
 		z3fold_page_unlock(zhdr);
 		return -EBUSY;
 	}