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 --- fs/fat/fat.h | 1 + fs/fat/inode.c | 12 ++++++++++++ 2 files changed, 13 insertions(+) (limited to 'fs') diff --git a/fs/fat/fat.h b/fs/fat/fat.h index 66994f316e1..951d12b61b5 100644 --- a/fs/fat/fat.h +++ b/fs/fat/fat.h @@ -82,6 +82,7 @@ struct msdos_sb_info { int fatent_shift; struct fatent_operations *fatent_ops; struct inode *fat_inode; + struct inode *fsinfo_inode; struct ratelimit_state ratelimit; diff --git a/fs/fat/inode.c b/fs/fat/inode.c index b3d290c1b51..84c602b4bb2 100644 --- a/fs/fat/inode.c +++ b/fs/fat/inode.c @@ -490,6 +490,7 @@ static void fat_put_super(struct super_block *sb) if (sb->s_dirt) fat_write_super(sb); + iput(sbi->fsinfo_inode); iput(sbi->fat_inode); unload_nls(sbi->nls_disk); @@ -1244,6 +1245,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat, void (*setup)(struct super_block *)) { struct inode *root_inode = NULL, *fat_inode = NULL; + struct inode *fsinfo_inode = NULL; struct buffer_head *bh; struct fat_boot_sector *b; struct msdos_sb_info *sbi; @@ -1490,6 +1492,14 @@ int fat_fill_super(struct super_block *sb, void *data, int silent, int isvfat, goto out_fail; MSDOS_I(fat_inode)->i_pos = 0; sbi->fat_inode = fat_inode; + + fsinfo_inode = new_inode(sb); + if (!fsinfo_inode) + goto out_fail; + fsinfo_inode->i_ino = MSDOS_FSINFO_INO; + sbi->fsinfo_inode = fsinfo_inode; + insert_inode_hash(fsinfo_inode); + root_inode = new_inode(sb); if (!root_inode) goto out_fail; @@ -1516,6 +1526,8 @@ out_invalid: fat_msg(sb, KERN_INFO, "Can't find a valid FAT filesystem"); out_fail: + if (fsinfo_inode) + iput(fsinfo_inode); if (fat_inode) iput(fat_inode); unload_nls(sbi->nls_io); -- cgit v1.2.3-70-g09d2