From 020ac5b6bef15785f9dde9de89d2734ff97da733 Mon Sep 17 00:00:00 2001 From: Artem Bityutskiy Date: Thu, 31 May 2012 16:26:12 -0700 Subject: fat: introduce special inode for managing the FSINFO block This is patchset makes fatfs stop using the VFS '->write_super()' method for writing out the FSINFO block. The final goal is to get rid of the 'sync_supers()' kernel thread. This kernel thread wakes up every 5 seconds (by default) and calls '->write_super()' for all mounted file-systems. And the bad thing is that this is done even if all the superblocks are clean. Moreover, some file-systems do not even need this end they do not register the '->write_super()' method at all (e.g., btrfs). So 'sync_supers()' most often just generates useless wake-ups and wastes power. I am trying to make all file-systems independent of '->write_super()' and plan to remove 'sync_supers()' and '->write_super' completely once there are no more users. The '->write_supers()' method is mostly used by baroque file-systems like hfs, udf, etc. Modern file-systems like btrfs and xfs do not use it. This justifies removing this stuff from VFS completely and make every FS self-manage own superblock. Tested with xfstests. This patch: Preparation for further changes. It introduces a special inode ('fsinfo_inode') in FAT file-system which we'll later use for managing the FSINFO block. Note, this there is already one special inode ('fat_inode') which is used for managing the FAT tables. Introduce new 'MSDOS_FSINFO_INO' constant for this special inode. It is safe to do because FAT file-system does not store inode numbers on the media but generates them run-time. I've also cleaned up the comment to existing 'MSDOS_ROOT_INO' constant, while on it. Signed-off-by: Artem Bityutskiy Cc: OGAWA Hirofumi Cc: Al Viro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- include/linux/msdos_fs.h | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) (limited to 'include') diff --git a/include/linux/msdos_fs.h b/include/linux/msdos_fs.h index 34066e65fdeb..11cc2ac67e75 100644 --- a/include/linux/msdos_fs.h +++ b/include/linux/msdos_fs.h @@ -21,8 +21,9 @@ #define CT_LE_W(v) cpu_to_le16(v) #define CT_LE_L(v) cpu_to_le32(v) +#define MSDOS_ROOT_INO 1 /* The root inode number */ +#define MSDOS_FSINFO_INO 2 /* Used for managing the FSINFO block */ -#define MSDOS_ROOT_INO 1 /* == MINIX_ROOT_INO */ #define MSDOS_DIR_BITS 5 /* log2(sizeof(struct msdos_dir_entry)) */ /* directory limit */ -- cgit v1.2.2