[PATCH] Bind Mount Extensions 0.04

[Herbert Poetzl <herbert@13thfloor.at>]

Greetings!

The following patch extends the 'noatime', 'nodiratime' and 
last but not least the 'ro' (read only) mount option to the 
vfs --bind mounts, allowing them to behave like any other 
mount, by honoring those mount flags (which are silently 
ignored by the current implementation)

an older version of this patch was included in 2.6.0-test6-mm2, 
and it is currently used by several people, without any issues, 
so I'd kindly request to consider it for inclusion into mainline.

if the size of the patch is an issue, I can break it down into
three parts, one preparing the existing structures, one adding
noatime/nodiratime and one doing the read only stuff.


the patch makes the following syscalls behave like expected

 - open (read/write/trunc), create
 - link, symlink, unlink
 - mknod (reg/block/char/fifo), mkfifo
 - mkdir, rmdir
 - (f)chown, (f)chmod, utime
 - access, truncate, mmap
 - ioctl (gen/ext2/ext3/reiser)


the following cases where verified for --bind ro (test tool) 
and showed no difference to a 'real' ro mounted filesystem:

 - open()
 - O_RDONLY: 	file, dir, symlink, broken, cdev, bdev, fifo, new
 - O_WRONLY: 	file, dir, symlink, broken, cdev, bdev, fifo, new
 - O_RDWR: 	file, dir, symlink, broken, cdev, bdev, fifo, new
 - O_CREAT: 	file
 
 - mkdir()  	dir, new, invalid
 - mkfifo() 	fifo, new, invalid

 - mknod()  	
 - S_IFREG: 	file, new, invalid
 - S_IFCHR: 	cdev, new, invalid
 - S_IFBLK: 	bdev, new, invalid
 - S_IFIFO: 	fifo, new, invalid
 
 - chown()  	file, invalid		 - fchown()	file
 - chmod()	file, invalid		 - fchmod()	file

 - link()   	file/file, file/invalid, invalid/file
 - symlink()	file/file, file/invalid, invalid/file
 
 - rename() 	file/file, file/invalid, invalid/file
 - rmdir()  	dir, new, invalid
 - truncate()	file, new invalid   	 - ftruncate()	file
 
 - unlink() 	file, bdev, cdev, fifo, new, invalid


you can download them here, if you prefer that over 
extracting them from emails ...

  http://www.13thfloor.at/patches/

TIA,
Herbert