linux/fs/fat
Artem Bityutskiy 78491189dd fat: switch to fsinfo_inode
Currently FAT file-system maps the VFS "superblock" abstraction to the
FSINFO block.  The FSINFO block contains non-essential data about the
amount of free clusters and the next free cluster.  FAT file-system can
always find out this information by scanning the FAT table, but having it
in the FSINFO block may speed things up sometimes.  So FAT file-system
relies on the VFS superblock write-out services to make sure the FSINFO
block is written out to the media from time to time.

The whole "superblock write-out" VFS infrastructure is served by the
'sync_supers()' kernel thread, which wakes up every 5 (by default) seconds
and writes out all dirty superblock using the '->write_super()' call-back.
 But the problem with this thread is that it wastes power by waking up the
system every 5 seconds no matter what.  So we want to kill it completely
and thus, we need to make file-systems to stop using the '->write_super'
VFS service, and then remove it together with the kernel thread.

This patch switches the FAT FSINFO block management from
'->write_super()'/'->s_dirt' to 'fsinfo_inode'/'->write_inode'.  Now,
instead of setting the 's_dirt' flag, we just mark the special
'fsinfo_inode' inode as dirty and let VFS invoke the '->write_inode'
call-back when needed, where we write-out the FSINFO block.

This patch also makes sure we do not mark the 'fsinfo_inode' inode as
dirty if we are not FAT32 (FAT16 and FAT12 do not have the FSINFO block)
or if we are in R/O mode.

As a bonus, we can also remove the '->sync_fs()' and '->write_super()' FAT
call-back function because they become unneeded.

Signed-off-by: Artem Bityutskiy <artem.bityutskiy@linux.intel.com>
Cc: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-05-31 17:49:28 -07:00
..
cache.c fat: Fix possible null deref in fat_cache_add() 2011-04-12 21:12:16 +09:00
dir.c fat: follow rename pack_hex_byte() to hex_byte_pack() 2011-10-31 17:30:57 -07:00
fat.h fat: introduce special inode for managing the FSINFO block 2012-05-31 17:49:27 -07:00
fatent.c fat: switch to fsinfo_inode 2012-05-31 17:49:28 -07:00
file.c fat: propagate umode_t 2012-01-03 22:55:09 -05:00
inode.c fat: switch to fsinfo_inode 2012-05-31 17:49:28 -07:00
Kconfig vfat: Note the NLS requirement 2009-04-17 09:32:11 -07:00
Makefile fat: move fs/vfat/* and fs/msdos/* to fs/fat 2008-11-06 15:41:20 -08:00
misc.c fat: Replace all printk with fat_msg() 2011-04-12 21:12:42 +09:00
namei_msdos.c switch ->create() to umode_t 2012-01-03 22:54:53 -05:00
namei_vfat.c fat: fix bug in enforcing Long File Name length 2012-03-23 16:58:40 -07:00