1 files changed, 16 insertions, 7 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index c919ed578f0a..2e03d6031c24 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -193,7 +193,7 @@ static struct backing_dev_info shmem_backing_dev_info  __read_mostly = {
 };
 
 static LIST_HEAD(shmem_swaplist);
-static DEFINE_SPINLOCK(shmem_swaplist_lock);
+static DEFINE_MUTEX(shmem_swaplist_mutex);
 
 static void shmem_free_blocks(struct inode *inode, long pages)
 {
@@ -796,9 +796,9 @@ static void shmem_delete_inode(struct inode *inode)
                 inode->i_size = 0;
                 shmem_truncate(inode);
                 if (!list_empty(&info->swaplist)) {
-                        spin_lock(&shmem_swaplist_lock);
+                        mutex_lock(&shmem_swaplist_mutex);
                         list_del_init(&info->swaplist);
-                        spin_unlock(&shmem_swaplist_lock);
+                        mutex_unlock(&shmem_swaplist_mutex);
                 }
         }
         BUG_ON(inode->i_blocks);
@@ -851,6 +851,14 @@ static int shmem_unuse_inode(struct shmem_inode_info *info, swp_entry_t entry, s
         for (idx = SHMEM_NR_DIRECT; idx < limit; idx += ENTRIES_PER_PAGE, dir++) {
                 if (unlikely(idx == stage)) {
                         shmem_dir_unmap(dir-1);
+                        if (cond_resched_lock(&info->lock)) {
+                                /* check it has not been truncated */
+                                if (limit > info->next_index) {
+                                        limit = info->next_index;
+                                        if (idx >= limit)
+                                                goto lost2;
+                                }
+                        }
                         dir = shmem_dir_map(info->i_indirect) +
                             ENTRIES_PER_PAGE/2 + idx/ENTRIES_PER_PAGEPAGE;
                         while (!*dir) {
@@ -924,7 +932,7 @@ int shmem_unuse(swp_entry_t entry, struct page *page)
         struct shmem_inode_info *info;
         int found = 0;
 
-        spin_lock(&shmem_swaplist_lock);
+        mutex_lock(&shmem_swaplist_mutex);
         list_for_each_safe(p, next, &shmem_swaplist) {
                 info = list_entry(p, struct shmem_inode_info, swaplist);
                 if (!info->swapped)
@@ -935,8 +943,9 @@ int shmem_unuse(swp_entry_t entry, struct page *page)
                         found = 1;
                         break;
                 }
+                cond_resched();
         }
-        spin_unlock(&shmem_swaplist_lock);
+        mutex_unlock(&shmem_swaplist_mutex);
         return found;
 }
 
@@ -996,10 +1005,10 @@ static int shmem_writepage(struct page *page, struct writeback_control *wbc)
                 shmem_swp_unmap(entry);
                 spin_unlock(&info->lock);
                 if (list_empty(&info->swaplist)) {
-                        spin_lock(&shmem_swaplist_lock);
+                        mutex_lock(&shmem_swaplist_mutex);
                         /* move instead of add in case we're racing */
                         list_move_tail(&info->swaplist, &shmem_swaplist);
-                        spin_unlock(&shmem_swaplist_lock);
+                        mutex_unlock(&shmem_swaplist_mutex);
                 }
                 swap_duplicate(swap);
                 BUG_ON(page_mapped(page));