ext4: fix byte order problems introduced by the COLLAPSE_RANGE patches

This commit tries to fix some byte order issues that is found by sparse
check.

$ make M=fs/ext4 C=2 CF=-D__CHECK_ENDIAN__
...
  CHECK   fs/ext4/extents.c
fs/ext4/extents.c:5232:41: warning: restricted __le32 degrades to integer
fs/ext4/extents.c:5236:52: warning: bad assignment (-=) to restricted __le32
fs/ext4/extents.c:5258:45: warning: bad assignment (-=) to restricted __le32
fs/ext4/extents.c:5303:28: warning: restricted __le32 degrades to integer
fs/ext4/extents.c:5318:18: warning: incorrect type in assignment (different base types)
fs/ext4/extents.c:5318:18:    expected unsigned int [unsigned] [usertype] ex_start
fs/ext4/extents.c:5318:18:    got restricted __le32 [usertype] ee_block
fs/ext4/extents.c:5319:24: warning: restricted __le32 degrades to integer
fs/ext4/extents.c:5334:31: warning: incorrect type in assignment (different base types)
...

Cc: Andreas Dilger <adilger.kernel@dilger.ca>
Cc: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Zheng Liu <wenqing.lz@taobao.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
ext4: get rid of EXT4_MAP_UNINIT flag

Currently EXT4_MAP_UNINIT is used in dioread_nolock case to mark the
cases where we're using dioread_nolock and we're writing into either
unallocated, or unwritten extent, because we need to make sure that
any DIO write into that inode will wait for the extent conversion.

However EXT4_MAP_UNINIT is not only entirely misleading name but also
unnecessary because we can check for EXT4_MAP_UNWRITTEN in the
dioread_nolock case instead.

This commit removes EXT4_MAP_UNINIT flag.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
ext4: rename uninitialized extents to unwritten

Currently in ext4 there is quite a mess when it comes to naming
unwritten extents. Sometimes we call it uninitialized and sometimes we
refer to it as unwritten.

The right name for the extent which has been allocated but does not
contain any written data is _unwritten_. Other file systems are
using this name consistently, even the buffer head state refers to it as
unwritten. We need to fix this confusion in ext4.

This commit changes every reference to an uninitialized extent (meaning
allocated but unwritten) to unwritten extent. This includes comments,
function names and variable names. It even covers abbreviation of the
word uninitialized (such as uninit) and some misspellings.

This commit does not change any of the code paths at all. This has been
confirmed by comparing md5sums of the assembly code of each object file
after all the function names were stripped from it.

Signed-off-by: Lukas Czerner <lczerner@redhat.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
ext4: inline generic_file_aio_write() into ext4_file_write()

Copy generic_file_aio_write() into ext4_file_write().  This is part of
a patch series which allows us to simplify ext4_file_write() and
ext4_file_dio_write(), by calling __generic_file_aio_write() directly.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
ext4: move ext4_file_dio_write() into ext4_file_write()

This commit doesn't actually change anything; it just moves code
around in preparation for some code simplification work.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
ext4: drop aio_mutex after grabbing i_mutex in ext4_file_write()

Once we have grabbed i_mutex, this will prevent any other writes from
proceeding, so we don't need to worry about any writes to unwritten
regions from taking place.  So drop the aio_mutex so that if there are
any other parallel writes happen to some other inode that happens to
hash to the same hash table entry, we won't end up blocking that work.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
ext4: factor out common code in ext4_file_write()

This shouldn't change any logic flow; just delete duplicated code.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
ext4: add locking for O_APPEND writes

Al Viro pointed out that we need to make sure we only allow one
O_APPEND write to proceed at a time so that the the s_bitmap_maxbytes
check can be properly checked.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
ext4: add a new spinlock i_raw_lock to protect the ext4's raw inode

To avoid potential data races, use a spinlock which protects the raw
(on-disk) inode.

Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>