NTFS: The big ntfs write(2) rewrite has arrived. We now implement our own

Features

========

- This is a complete rewrite of the NTFS driver that used to be in the kernel.

  This new driver implements NTFS read support and is functionally equivalent

  to the old ntfs driver.

- This is a complete rewrite of the NTFS driver that used to be in the 2.4 and

  earlier kernels.  This new driver implements NTFS read support and is

  functionally equivalent to the old ntfs driver and it also implements limited

  write support.  The biggest limitation at present is that files/directories

  cannot be created or deleted.  See below for the list of write features that

  are so far supported.  Another limitation is that writing to compressed files

  is not implemented at all.  Also, neither read nor write access to encrypted

  files is so far implemented.

- The new driver has full support for sparse files on NTFS 3.x volumes which

  the old driver isn't happy with.

- The new driver supports execution of binaries due to mmap() now being

- The new driver supports fsync(2), fdatasync(2), and msync(2).

- The new driver supports readv(2) and writev(2).

- The new driver supports access time updates (including mtime and ctime).

- The new driver supports truncate(2) and open(2) with O_TRUNC.  But at present

  only very limited support for highly fragmented files, i.e. ones which have

  their data attribute split across multiple extents, is included.  Another

  limitation is that at present truncate(2) will never create sparse files,

  since to mark a file sparse we need to modify the directory entry for the

  file and we do not implement directory modifications yet.

- The new driver supports write(2) which can both overwrite existing data and

  extend the file size so that you can write beyond the existing data.  Also,

  writing into sparse regions is supported and the holes are filled in with

  clusters.  But at present only limited support for highly fragmented files,

  i.e. ones which have their data attribute split across multiple extents, is

  included.  Another limitation is that write(2) will never create sparse

  files, since to mark a file sparse we need to modify the directory entry for

  the file and we do not implement directory modifications yet.

Supported mount options

=======================

Note, a technical ChangeLog aimed at kernel hackers is in fs/ntfs/ChangeLog.

2.1.25:

	- Write support is now extended with write(2) being able to both

	  overwrite existing file data and to extend files.  Also, if a write

	  to a sparse region occurs, write(2) will fill in the hole.  Note,

	  mmap(2) based writes still do not support writing into holes or

	  writing beyond the initialized size.

	- Write support has a new feature and that is that truncate(2) and

	  open(2) with O_TRUNC are now implemented thus files can be both made

	  smaller and larger.

	- Note: Both write(2) and truncate(2)/open(2) with O_TRUNC still have

	  limitations in that they

	  - only provide limited support for highly fragmented files.

	  - only work on regular, i.e. uncompressed and unencrypted files.

	  - never create sparse files although this will change once directory

	    operations are implemented.

	- Lots of bug fixes and enhancements across the board.

2.1.24:

	- Support journals ($LogFile) which have been modified by chkdsk.  This

	  means users can boot into Windows after we marked the volume dirty.

ToDo/Notes:

	- Find and fix bugs.

	- In between ntfs_prepare/commit_write, need exclusion between

	  simultaneous file extensions.  This is given to us by holding i_sem

	  on the inode.  The only places in the kernel when a file is resized

	  are prepare/commit write and ntfs_truncate() for both of which i_sem

	  is held.  Just have to be careful in read-/writepage and other helpers

	- The only places in the kernel where a file is resized are

	  ntfs_file_write*() and ntfs_truncate() for both of which i_sem is

	  held.  Just have to be careful in read-/writepage and other helpers

	  not running under i_sem that we play nice...  Also need to be careful

	  with initialized_size extention in ntfs_prepare_write and writepage.

	  UPDATE: The only things that need to be checked are

	  prepare/commit_write as well as the compressed write and the other

	  attribute resize/write cases like index attributes, etc.  For now

	  none of these are implemented so are safe.

	  with initialized_size extension in ntfs_file_write*() and writepage.

	  UPDATE: The only things that need to be checked are the compressed

	  write and the other attribute resize/write cases like index

	  attributes, etc.  For now none of these are implemented so are safe.

	- Implement filling in of holes in aops.c::ntfs_writepage() and its

	  helpers.

	- Implement mft.c::sync_mft_mirror_umount().  We currently will just

	  leave the volume dirty on umount if the final iput(vol->mft_ino)

	  causes a write of any mirrored mft records due to the mft mirror

	- Enable the code for setting the NT4 compatibility flag when we start

	  making NTFS 1.2 specific modifications.

2.1.25-WIP

2.1.25 - (Almost) fully implement write(2) and truncate(2).

	- Change ntfs_map_runlist_nolock(), ntfs_attr_find_vcn_nolock() and

	  {__,}ntfs_cluster_free() to also take an optional attribute search

	  extend the allocation of an attributes.  Optionally, the data size,

	  but not the initialized size can be extended, too.

	- Implement fs/ntfs/inode.[hc]::ntfs_truncate().  It only supports

	  uncompressed and unencrypted files.

	  uncompressed and unencrypted files and it never creates sparse files

	  at least for the moment (making a file sparse requires us to modify

	  its directory entries and we do not support directory operations at

	  the moment).  Also, support for highly fragmented files, i.e. ones

	  whose data attribute is split across multiple extents, is severly

	  limited.  When such a case is encountered, EOPNOTSUPP is returned.

	- Enable ATTR_SIZE attribute changes in ntfs_setattr().  This completes

	  the initial implementation of file truncation.  Now both open(2)ing

	  a file with the O_TRUNC flag and the {,f}truncate(2) system calls

	  and cond_resched() in the main loop as we could be dirtying a lot of

	  pages and this ensures we play nice with the VM and the system as a

	  whole.

	- Implement file operations ->write, ->aio_write, ->writev for regular

	  files.  This replaces the old use of generic_file_write(), et al and

	  the address space operations ->prepare_write and ->commit_write.

	  This means that both sparse and non-sparse (unencrypted and

	  uncompressed) files can now be extended using the normal write(2)

	  code path.  There are two limitations at present and these are that

	  we never create sparse files and that we only have limited support

	  for highly fragmented files, i.e. ones whose data attribute is split

	  across multiple extents.   When such a case is encountered,

	  EOPNOTSUPP is returned.

2.1.24 - Lots of bug fixes and support more clean journal states.

	     index.o inode.o mft.o mst.o namei.o runlist.o super.o sysctl.o \

	     unistr.o upcase.o

EXTRA_CFLAGS = -DNTFS_VERSION=\"2.1.25-WIP\"

EXTRA_CFLAGS = -DNTFS_VERSION=\"2.1.25\"

ifeq ($(CONFIG_NTFS_DEBUG),y)

EXTRA_CFLAGS += -DDEBUG