From 78491189ddb6d84d4a4abae992ed891a236d0263 Mon Sep 17 00:00:00 2001 From: Artem Bityutskiy Date: Thu, 31 May 2012 16:26:13 -0700 Subject: 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 Cc: OGAWA Hirofumi Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- fs/fat/fatent.c | 7 ++++++- 1 file changed, 6 insertions(+), 1 deletion(-) (limited to 'fs/fat/fatent.c') diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c index 81815487e04d..31f08ab62c56 100644 --- a/fs/fat/fatent.c +++ b/fs/fat/fatent.c @@ -310,7 +310,12 @@ void fat_ent_access_init(struct super_block *sb) static void mark_fsinfo_dirty(struct super_block *sb) { - sb->s_dirt = 1; + struct msdos_sb_info *sbi = MSDOS_SB(sb); + + if (sb->s_flags & MS_RDONLY || sbi->fat_bits != 32) + return; + + __mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC); } static inline int fat_ent_update_ptr(struct super_block *sb, -- cgit v1.2.3-59-g8ed1b