ext4: don't try to modify s_flags if the the file system is read-only

commit 23301410972330c0ae9a8afc379ba2005e249cc6 upstream.

If an ext4 file system is created by some tool other than mke2fs
(perhaps by someone who has a pathalogical fear of the GPL) that
doesn't set one or the other of the EXT2_FLAGS_{UN}SIGNED_HASH flags,
and that file system is then mounted read-only, don't try to modify
the s_flags field.  Otherwise, if dm_verity is in use, the superblock
will change, causing an dm_verity failure.

Change-Id: I5eac6cfe3d70acb8459eb5203e1d94e488eb106b
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ext4: fix online resize with a non-standard blocks per group setting

commit 3d2660d0c9c2f296837078c189b68a47f6b2e3b5 upstream.

The set_flexbg_block_bitmap() function assumed that the number of
blocks in a blockgroup was sb->blocksize * 8, which is normally true,
but not always!  Use EXT4_BLOCKS_PER_GROUP(sb) instead, to fix block
bitmap corruption after:

mke2fs -t ext4 -g 3072 -i 4096 /dev/vdd 1G
mount -t ext4 /dev/vdd /vdd
resize2fs /dev/vdd 8G

Change-Id: Ie544796d19429f654a6163aaee21b9be87c88774
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Reported-by: Jon Bernard <jbernard@tuxion.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
ext4: don't leave i_crtime.tv_sec uninitialized

commit 19ea80603715d473600cd993b9987bc97d042e02 upstream.

If the i_crtime field is not present in the inode, don't leave the
field uninitialized.

Change-Id: I198680be69c16c1103f5c473bc9a828e53227ce0
Fixes: ef7f38359 ("ext4: Add nanosecond timestamps")
Reported-by: Vegard Nossum <vegard.nossum@oracle.com>
Tested-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>