z3fold: fix reclaim lock-ups

Do not try to optimize in-page object layout while the page is under
reclaim.  This fixes lock-ups on reclaim and improves reclaim
performance at the same time.

[akpm@linux-foundation.org: coding-style fixes]
Link: http://lkml.kernel.org/r/20180430125800.444cae9706489f412ad12621@gmail.com
Signed-off-by: Vitaly Wool <vitaly.vul@sony.com>
Reported-by: Guenter Roeck <linux@roeck-us.net>
Tested-by: Guenter Roeck <linux@roeck-us.net>
Cc: <Oleksiy.Avramchenko@sony.com>
Cc: Matthew Wilcox <mawilcox@microsoft.com>
Cc: <stable@vger.kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 30 insertions, 12 deletions

diff --git a/mm/z3fold.c b/mm/z3fold.c
index c0bca6153b95..4b366d181f35 100644
--- a/mm/z3fold.c
+++ b/mm/z3fold.c
@@ -144,7 +144,8 @@ enum z3fold_page_flags {
         PAGE_HEADLESS = 0,
         MIDDLE_CHUNK_MAPPED,
         NEEDS_COMPACTING,
-        PAGE_STALE
+        PAGE_STALE,
+        UNDER_RECLAIM
 };
 
 /*****************
@@ -173,6 +174,7 @@ 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);
 
         spin_lock_init(&zhdr->page_lock);
         kref_init(&zhdr->refcount);
@@ -756,6 +758,10 @@ static void z3fold_free(struct z3fold_pool *pool, unsigned long handle)
                 atomic64_dec(&pool->pages_nr);
                 return;
         }
+        if (test_bit(UNDER_RECLAIM, &page->private)) {
+                z3fold_page_unlock(zhdr);
+                return;
+        }
         if (test_and_set_bit(NEEDS_COMPACTING, &page->private)) {
                 z3fold_page_unlock(zhdr);
                 return;
@@ -840,6 +846,8 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
                         kref_get(&zhdr->refcount);
                         list_del_init(&zhdr->buddy);
                         zhdr->cpu = -1;
+                        set_bit(UNDER_RECLAIM, &page->private);
+                        break;
                 }
 
                 list_del_init(&page->lru);
@@ -887,25 +895,35 @@ static int z3fold_reclaim_page(struct z3fold_pool *pool, unsigned int retries)
                                 goto next;
                 }
 next:
-                spin_lock(&pool->lock);
                 if (test_bit(PAGE_HEADLESS, &page->private)) {
                         if (ret == 0) {
-                                spin_unlock(&pool->lock);
                                 free_z3fold_page(page);
                                 return 0;
                         }
-                } else if (kref_put(&zhdr->refcount, release_z3fold_page)) {
-                        atomic64_dec(&pool->pages_nr);
+                        spin_lock(&pool->lock);
+                        list_add(&page->lru, &pool->lru);
+                        spin_unlock(&pool->lock);
+                } else {
+                        z3fold_page_lock(zhdr);
+                        clear_bit(UNDER_RECLAIM, &page->private);
+                        if (kref_put(&zhdr->refcount,
+                                        release_z3fold_page_locked)) {
+                                atomic64_dec(&pool->pages_nr);
+                                return 0;
+                        }
+                        /*
+                         * if we are here, the page is still not completely
+                         * free. Take the global pool lock then to be able
+                         * to add it back to the lru list
+                         */
+                        spin_lock(&pool->lock);
+                        list_add(&page->lru, &pool->lru);
                         spin_unlock(&pool->lock);
-                        return 0;
+                        z3fold_page_unlock(zhdr);
                 }
 
-                /*
-                 * Add to the beginning of LRU.
-                 * Pool lock has to be kept here to ensure the page has
-                 * not already been released
-                 */
-                list_add(&page->lru, &pool->lru);
+                /* We started off locked to we need to lock the pool back */
+                spin_lock(&pool->lock);
         }
         spin_unlock(&pool->lock);
         return -EAGAIN;