Many of the uses of get_random_bytes() do not actually need
cryptographically secure random numbers.  Replace those uses with a
call to prandom_u32(), which is faster and which doesn't consume
entropy from the /dev/random driver.
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

As Dave Chinner pointed out at the 2013 LSF/MM workshop, it's
important that metadata I/O requests are marked as such to avoid
priority inversions caused by I/O bandwidth throttling.
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Signed-off-by: NDmitry Monakhov <dmonakhov@openvz.org>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org

Because the function 'sb_getblk' seldomly fails to return NULL
value,it will be better to use 'unlikely' to optimize it.
Signed-off-by: NWang Shilong <wangsl-fnst@cn.fujitsu.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

The only reason for sb_getblk() failing is if it can't allocate the
buffer_head.  So ENOMEM is more appropriate than EIO.  In addition,
make sure that the file system is marked as being inconsistent if
sb_getblk() fails.
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Cc: stable@vger.kernel.org

We remove most of frozen checks since upper layer takes care of blocking all
writes. We have to handle protection in ext4_page_mkwrite() in a special way
because we cannot use generic block_page_mkwrite(). Also we add a freeze
protection to ext4_evict_inode() so that iput() of unlinked inode cannot modify
a frozen filesystem (we cannot easily instrument ext4_journal_start() /
ext4_journal_stop() with freeze protection because we are missing the
superblock pointer in ext4_journal_stop() in nojournal mode).

CC: linux-ext4@vger.kernel.org
CC: "Theodore Ts'o" <tytso@mit.edu>
BugLink: https://bugs.launchpad.net/bugs/897421Tested-by: NKamal Mostafa <kamal@canonical.com>
Tested-by: NPeter M. Petrakis <peter.petrakis@canonical.com>
Tested-by: NDann Frazier <dann.frazier@canonical.com>
Tested-by: NMassimo Morana <massimo.morana@canonical.com>
Acked-by: N"Theodore Ts'o" <tytso@mit.edu>
Signed-off-by: NJan Kara <jack@suse.cz>
Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>

Compute and verify a checksum for the MMP block.
Signed-off-by: NDarrick J. Wong <djwong@us.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Sparse complained about this endian bug in fs/ext4/mmp.c.
Signed-off-by: NSantosh Nayak <santoshprasadnayak@gmail.com>
Reviewed-by: NJohann Lombardi <johann@whamcloud.com>
Reviewed-by: NAndreas Dilger <adilger@dilger.ca>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

As part of startup, the MMP initialization code does this:

mmp->mmp_seq = seq = cpu_to_le32(mmp_new_seq());

Next, mmp->mmp_seq is written out to disk, a delay happens, and then
the MMP block is read back in and the sequence value is tested:

if (seq != le32_to_cpu(mmp->mmp_seq)) {
	/* fail the mount */

On a LE system such as x86, the *le32* functions do nothing and this
works.  Unfortunately, on a BE system such as ppc64, this comparison
becomes:

if (cpu_to_le32(new_seq) != le32_to_cpu(cpu_to_le32(new_seq)) {
	/* fail the mount */

Except for a few palindromic sequence numbers, this test always causes
the mount to fail, which makes MMP filesystems generally unmountable
on ppc64.  The attached patch fixes this situation.
Signed-off-by: NDarrick J. Wong <djwong@us.ibm.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Current logic would print an error message only once, and then
'failed_writes' would stay at 1.  Rework the loop to increment
'failed_writes' and print the error message every
s_mmp_update_interval * 60 seconds, as intended according to the
comment.
Signed-off-by: NNikitas Angelinas <nikitas_angelinas@xyratex.com>
Signed-off-by: NAndrew Perepechko <andrew_perepechko@xyratex.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>
Acked-by: NAndreas Dilger <adilger@dilger.ca>

sysname holds "Linux" by default, i.e. what appears when doing a "uname
-s"; nodename should be used to print the machine's hostname, i.e. what
is returned when doing a "uname -n" or "hostname", and what
gethostname(2)/sethostname(2) manipulate, in order to notify the
administrator of the node which is contending to mount the filesystem.
Acked-by: NAndreas Dilger <adilger@dilger.ca>
Signed-off-by: NNikitas Angelinas <nikitas_angelinas@xyratex.com>
Signed-off-by: NAndrew Perepechko <andrew_perepechko@xyratex.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>

Prevent an ext4 filesystem from being mounted multiple times.
A sequence number is stored on disk and is periodically updated (every 5
seconds by default) by a mounted filesystem.
At mount time, we now wait for s_mmp_update_interval seconds to make sure
that the MMP sequence does not change.
In case of failure, the nodename, bdevname and the time at which the MMP
block was last updated is displayed.
Signed-off-by: NAndreas Dilger <adilger@whamcloud.com>
Signed-off-by: NJohann Lombardi <johann@whamcloud.com>
Signed-off-by: N"Theodore Ts'o" <tytso@mit.edu>