1 files changed, 31 insertions, 13 deletions

diff --git a/mm/shmem.c b/mm/shmem.c
index 67afba5117f2..50c5b8f3a359 100644
--- a/mm/shmem.c
+++ b/mm/shmem.c
@@ -643,7 +643,7 @@ static void shmem_evict_inode(struct inode *inode)
                 kfree(info->symlink);
 
         simple_xattrs_free(&info->xattrs);
-        BUG_ON(inode->i_blocks);
+        WARN_ON(inode->i_blocks);
         shmem_free_inode(inode->i_sb);
         clear_inode(inode);
 }
@@ -910,25 +910,29 @@ static struct mempolicy *shmem_get_sbmpol(struct shmem_sb_info *sbinfo)
 static struct page *shmem_swapin(swp_entry_t swap, gfp_t gfp,
                         struct shmem_inode_info *info, pgoff_t index)
 {
-        struct mempolicy mpol, *spol;
         struct vm_area_struct pvma;
-
-        spol = mpol_cond_copy(&mpol,
-                        mpol_shared_policy_lookup(&info->policy, index));
+        struct page *page;
 
         /* Create a pseudo vma that just contains the policy */
         pvma.vm_start = 0;
         /* Bias interleave by inode number to distribute better across nodes */
         pvma.vm_pgoff = index + info->vfs_inode.i_ino;
         pvma.vm_ops = NULL;
-        pvma.vm_policy = spol;
-        return swapin_readahead(swap, gfp, &pvma, 0);
+        pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
+
+        page = swapin_readahead(swap, gfp, &pvma, 0);
+
+        /* Drop reference taken by mpol_shared_policy_lookup() */
+        mpol_cond_put(pvma.vm_policy);
+
+        return page;
 }
 
 static struct page *shmem_alloc_page(gfp_t gfp,
                         struct shmem_inode_info *info, pgoff_t index)
 {
         struct vm_area_struct pvma;
+        struct page *page;
 
         /* Create a pseudo vma that just contains the policy */
         pvma.vm_start = 0;
@@ -937,10 +941,12 @@ static struct page *shmem_alloc_page(gfp_t gfp,
         pvma.vm_ops = NULL;
         pvma.vm_policy = mpol_shared_policy_lookup(&info->policy, index);
 
-        /*
-         * alloc_page_vma() will drop the shared policy reference
-         */
-        return alloc_page_vma(gfp, &pvma, 0);
+        page = alloc_page_vma(gfp, &pvma, 0);
+
+        /* Drop reference taken by mpol_shared_policy_lookup() */
+        mpol_cond_put(pvma.vm_policy);
+
+        return page;
 }
 #else /* !CONFIG_NUMA */
 #ifdef CONFIG_TMPFS
@@ -1145,8 +1151,20 @@ repeat:
                 if (!error) {
                         error = shmem_add_to_page_cache(page, mapping, index,
                                                 gfp, swp_to_radix_entry(swap));
-                        /* We already confirmed swap, and make no allocation */
-                        VM_BUG_ON(error);
+                        /*
+                         * We already confirmed swap under page lock, and make
+                         * no memory allocation here, so usually no possibility
+                         * of error; but free_swap_and_cache() only trylocks a
+                         * page, so it is just possible that the entry has been
+                         * truncated or holepunched since swap was confirmed.
+                         * shmem_undo_range() will have done some of the
+                         * unaccounting, now delete_from_swap_cache() will do
+                         * the rest (including mem_cgroup_uncharge_swapcache).
+                         * Reset swap.val? No, leave it so "failed" goes back to
+                         * "repeat": reading a hole and writing should succeed.
+                         */
+                        if (error)
+                                delete_from_swap_cache(page);
                 }
                 if (error)
                         goto failed;