ext3/ext4: Factor out disk addressability check
As part of adding support for OCFS2 to mount huge volumes, we need to
check that the sector_t and page cache of the system are capable of
addressing the entire volume.
An identical check already appears in ext3 and ext4. This patch moves
the addressability check into its own function in fs/libfs.c and
modifies ext3 and ext4 to invoke it.
[Edited to -EINVAL instead of BUG_ON() for bad blocksize_bits -- Joel]
Signed-off-by: Patrick LoPresti <lopresti@gmail.com>
Cc: linux-ext4@vger.kernel.org
Acked-by: Andreas Dilger <adilger@dilger.ca>
Signed-off-by: Joel Becker <joel.becker@oracle.com>
diff --git a/fs/libfs.c b/fs/libfs.c
index 0a9da95..8debe7b 100644
--- a/fs/libfs.c
+++ b/fs/libfs.c
@@ -913,6 +913,35 @@
}
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;
+
+ 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_block >
+ (pgoff_t)(~0ULL) >> (PAGE_CACHE_SHIFT - blocksize_bits))) {
+ return -EFBIG;
+ }
+ return 0;
+}
+EXPORT_SYMBOL(generic_check_addressable);
+
/*
* No-op implementation of ->fsync for in-memory filesystems.
*/