• J
    vfs: Fix sys_sync() and fsync_super() reliability (version 4) · 5a3e5cb8
    Jan Kara 提交于
    So far, do_sync() called:
      sync_inodes(0);
      sync_supers();
      sync_filesystems(0);
      sync_filesystems(1);
      sync_inodes(1);
    
    This ordering makes it kind of hard for filesystems as sync_inodes(0) need not
    submit all the IO (for example it skips inodes with I_SYNC set) so e.g. forcing
    transaction to disk in ->sync_fs() is not really enough. Therefore sys_sync has
    not been completely reliable on some filesystems (ext3, ext4, reiserfs, ocfs2
    and others are hit by this) when racing e.g. with background writeback. A
    similar problem hits also other filesystems (e.g. ext2) because of
    write_supers() being called before the sync_inodes(1).
    
    Change the ordering of calls in do_sync() - this requires a new function
    sync_blockdevs() to preserve the property that block devices are always synced
    after write_super() / sync_fs() call.
    
    The same issue is fixed in __fsync_super() function used on umount /
    remount read-only.
    
    [AV: build fixes]
    Signed-off-by: NJan Kara <jack@suse.cz>
    Signed-off-by: NAl Viro <viro@zeniv.linux.org.uk>
    5a3e5cb8
super.c 24.8 KB