1 files changed, 29 insertions, 0 deletions

diff --git a/fs/libfs.c b/fs/libfs.c
index 0a9da95317f7..62baa0387d6e 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -913,6 +913,35 @@ int generic_file_fsync(struct file *file, int datasync)
 }
 EXPORT_SYMBOL(generic_file_fsync);
 
+/**
+ * generic_check_addressable - Check addressability of file system
+ * @blocksize_bits:     log of file system block size
+ * @num_blocks:         number of blocks in file system
+ *
+ * Determine whether a file system with @num_blocks blocks (and a
+ * block size of 2**@blocksize_bits) is addressable by the sector_t
+ * and page cache of the system.  Return 0 if so and -EFBIG otherwise.
+ */
+int generic_check_addressable(unsigned blocksize_bits, u64 num_blocks)
+{
+        u64 last_fs_block = num_blocks - 1;
+        u64 last_fs_page =
+                last_fs_block >> (PAGE_CACHE_SHIFT - blocksize_bits);
+
+        if (unlikely(num_blocks == 0))
+                return 0;
+
+        if ((blocksize_bits < 9) || (blocksize_bits > PAGE_CACHE_SHIFT))
+                return -EINVAL;
+
+        if ((last_fs_block > (sector_t)(~0ULL) >> (blocksize_bits - 9)) ||
+            (last_fs_page > (pgoff_t)(~0ULL))) {
+                return -EFBIG;
+        }
+        return 0;
+}
+EXPORT_SYMBOL(generic_check_addressable);
+
 /*
  * No-op implementation of ->fsync for in-memory filesystems.
  */