ext4: Don't allow nonextenst mount option for large filesystem

The block mapped inode format can address only blocks within 2**32. This
causes a number of issues, the biggest of which is that the block
allocator needs to be taught that certain inodes can not utilize block
numbers > 2**32.  So until this is fixed, it is simplest to fail
mounting of file systems with more than 2**32 blocks if the -o noextents
option is given.

Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

1 files changed, 15 insertions, 0 deletions

diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 4e104dd0ec21..2bf9cdd7a036 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -1004,6 +1004,7 @@ static int parse_options (char *options, struct super_block *sb,
         int qtype, qfmt;
         char *qname;
 #endif
+        ext4_fsblk_t last_block;
 
         if (!options)
                 return 1;
@@ -1326,6 +1327,20 @@ set_qf_format:
                         set_opt (sbi->s_mount_opt, EXTENTS);
                         break;
                 case Opt_noextents:
+                        /*
+                         * When e2fsprogs support resizing an already existing
+                         * ext3 file system to greater than 2**32 we need to
+                         * add support to block allocator to handle growing
+                         * already existing block  mapped inode so that blocks
+                         * allocated for them fall within 2**32
+                         */
+                        last_block = ext4_blocks_count(sbi->s_es) - 1;
+                        if (last_block  > 0xffffffffULL) {
+                                printk(KERN_ERR "EXT4-fs: Filesystem too "
+                                                "large to mount with "
+                                                "-o noextents options\n");
+                                return 0;
+                        }
                         clear_opt (sbi->s_mount_opt, EXTENTS);
                         break;
                 case Opt_i_version: