If we receive a file handle, either from NFS or open_by_handle_at(2),
and it points at an inode which has not been initialized, and the file
system has metadata checksums enabled, we shouldn't try to get the
inode, discover the checksum is invalid, and then declare the file
system as being inconsistent.

This can be reproduced by creating a test file system via "mke2fs -t
ext4 -O metadata_csum /tmp/foo.img 8M", mounting it, cd'ing into that
directory, and then running the following program.

#define _GNU_SOURCE
#include <fcntl.h>

struct handle {
	struct file_handle fh;
	unsigned char fid[MAX_HANDLE_SZ];
};

int main(int argc, char **argv)
{
	struct handle h = {{8, 1 }, { 12, }};

	open_by_handle_at(AT_FDCWD, &h.fh, O_RDONLY);
	return 0;
}

Google-Bug-Id: 120690101
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org

Commit e2b911c53584 ("ext4: clean up feature test macros with
predicate functions") broke the EXT4_IOC_GROUP_ADD ioctl.  This was
not noticed since only very old versions of resize2fs (before
e2fsprogs 1.42) use this ioctl.  However, using a new kernel with an
enterprise Linux userspace will cause attempts to use online resize to
fail with "No reserved GDT blocks".

Fixes: e2b911c53584 ("ext4: clean up feature test macros with predicate...")
Cc: stable@kernel.org # v4.4
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Signed-off-by: ruippan (潘睿) <ruippan@tencent.com>

Today, when sb_bread() returns NULL, this can either be because of an
I/O error or because the system failed to allocate the buffer.  Since
it's an old interface, changing would require changing many call
sites.

So instead we create our own ext4_sb_bread(), which also allows us to
set the REQ_META flag.

Also fixed a problem in the xattr code where a NULL return in a
function could also mean that the xattr was not found, which could
lead to the wrong error getting returned to userspace.

Fixes: ac27a0ec112a ("ext4: initial copy of files from ext3")
Cc: stable@kernel.org # 2.6.19
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Fixes: b40971426a83 ("ext4: add error checking to calls to ...")
Reported-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 2.6.38

Fixes: 1c6bd7173d66 ("ext4: convert file system to meta_bg if needed ...")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 3.7

Fixes: 117fff10d7f1 ("ext4: grow the s_flex_groups array as needed ...")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 3.7

Fixes: ac27a0ec112a ("ext4: initial copy of files from ext3")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 2.6.19

Fixes: 01f795f9e0d6 ("ext4: add online resizing support for meta_bg ...")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 3.7

Fixes: 33afdcc5402d ("ext4: add a function which sets up group blocks ...")
Cc: stable@kernel.org # 3.3
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

Currently bh is set to NULL only during first iteration of for cycle,
then this pointer is not cleared after end of using.
Therefore rollback after errors can lead to extra brelse(bh) call,
decrements bh counter and later trigger an unexpected warning in __brelse()

Patch moves brelse() calls in body of cycle to exclude requirement of
brelse() call in rollback.

Fixes: 33afdcc5402d ("ext4: add a function which sets up group blocks ...")
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>
Cc: stable@kernel.org # 3.3+