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authorArtem Bityutskiy <artem.bityutskiy@linux.intel.com>2012-05-31 16:26:13 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2012-05-31 17:49:28 -0700
commit78491189ddb6d84d4a4abae992ed891a236d0263 (patch)
treef451b46a2c0a505b6812b696e03604b8613b3df0 /fs/fat/fatent.c
parent330fe3c4c6509e0418c434b5bcf80e65cffab477 (diff)
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>
Diffstat (limited to 'fs/fat/fatent.c')
-rw-r--r--fs/fat/fatent.c7
1 files changed, 6 insertions, 1 deletions
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,