shmem: fix double uncharge in __shmem_file_setup()

If __shmem_file_setup() fails on struct file allocation it uncharges
memory commitment twice: first by shmem_unacct_size() and second time
implicitly in shmem_evict_inode() when it kills the newly created inode.

This patch removes shmem_unacct_size() from error path if the inode was
already there.

Signed-off-by: Konstantin Khlebnikov <[email protected]>
Acked-by: Hugh Dickins <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/shmem.c

@@ -2932,36 +2932,36 @@ static struct file *__shmem_file_setup(const char *name, loff_t size,
 	this.len = strlen(name);
 	this.hash = 0; /* will go */
 	sb = shm_mnt->mnt_sb;
+	path.mnt = mntget(shm_mnt);
 	path.dentry = d_alloc_pseudo(sb, &this);
 	if (!path.dentry)
 		goto put_memory;
 	d_set_d_op(path.dentry, &anon_ops);
-	path.mnt = mntget(shm_mnt);
 
 	res = ERR_PTR(-ENOSPC);
 	inode = shmem_get_inode(sb, NULL, S_IFREG | S_IRWXUGO, 0, flags);
 	if (!inode)
-		goto put_dentry;
+		goto put_memory;
 
 	inode->i_flags |= i_flags;
 	d_instantiate(path.dentry, inode);
 	inode->i_size = size;
 	clear_nlink(inode);	/* It is unlinked */
 	res = ERR_PTR(ramfs_nommu_expand_for_mapping(inode, size));
 	if (IS_ERR(res))
-		goto put_dentry;
+		goto put_path;
 
 	res = alloc_file(&path, FMODE_WRITE | FMODE_READ,
 		  &shmem_file_operations);
 	if (IS_ERR(res))
-		goto put_dentry;
+		goto put_path;
 
 	return res;
 
-put_dentry:
-	path_put(&path);
 put_memory:
 	shmem_unacct_size(flags, size);
+put_path:
+	path_put(&path);
 	return res;
 }