fs/ntfs3: Add ioctl operation for directories (FITRIM)

While ntfs3 supports discards, FITRIM ioctl() command has defined
only for regular files. This may confuse users trying to invoke
`fstrim` utility with the directory argument (for example, call
`fstrim <mountpoint>` which is the common practice). In this case,
ioctl() returns -ENOTTY without any error messages in kernel ring
buffer, this may be easily interpreted as no support for discards
in ntfs3 driver.

Currently only FITRIM command implemented in ntfs_ioctl() and
passed inode used only for dereferencing NTFS superblock, so
no need for separate ioctl() handler for directories, just add
existing ntfs_ioctl() handler to ntfs_dir_operations.

Signed-off-by: Nekun <nekokun@firemail.cc>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3: Use i_size_read and i_size_write

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3: Add and fix comments

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3: Improve ntfs_dir_count

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3: Modified fix directory element type detection

Unfortunately reparse attribute is used for many purposes (several dozens).
It is not possible here to know is this name symlink or not.
To get exactly the type of name we should to open inode (read mft).
getattr for opened file (fstat) correctly returns symlink.

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3: Fix directory element type detection

Calling stat() from userspace correctly identified junctions in an NTFS
partition as symlinks, but using readdir() and iterating through the
directory containing the same junction did not identify the junction
as a symlink.

When emitting directory contents, check FILE_ATTRIBUTE_REPARSE_POINT
attribute to detect junctions and report them as links.

Signed-off-by: Gabriel Marcano <gabemarcano@yahoo.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3: Fix sparse problems

Fixing various problems, detected by sparse.

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3: Rework ntfs_utf16_to_nls

Now ntfs_utf16_to_nls takes length as one of arguments.
If length of symlink > 255, then we tried to convert
length of symlink +- some random number.
Now 255 symbols limit was removed.

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3: Remove unneeded header files from c files

We have lot of unnecessary headers in these files. Remove them so that
we help compiler a little bit.

Signed-off-by: Kari Argillander <kari.argillander@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3: Convert mount options to pointer in sbi

Use pointer to mount options. We want to do this because we will use new
mount api which will benefit that we have spi and mount options in
different allocations. When we remount we do not have to make whole new
spi it is enough that we will allocate just mount options.

Please note that we can do example remount lot cleaner but things will
change in next patch so this should be just functional.

Signed-off-by: Kari Argillander <kari.argillander@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3: Restyle comments to better align with kernel-doc

Capitalize comments and end with period for better reading.

Also function comments are now little more kernel-doc style. This way we
can easily convert them to kernel-doc style if we want. Note that these
are not yet complete with this style. Example function comments start
with /* and in kernel-doc style they start /**.

Use imperative mood in function descriptions.

Change words like ntfs -> NTFS, linux -> Linux.

Use "we" not "I" when commenting code.

Signed-off-by: Kari Argillander <kari.argillander@gmail.com>
Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>

fs/ntfs3: Add file operations and implementation

This adds file operations and implementation

Signed-off-by: Konstantin Komarov <almaz.alexandrovich@paragon-software.com>