• J
    bdi: Fix warnings in __mark_inode_dirty for /dev/zero and friends · 692ebd17
    Jan Kara 提交于
    Inodes of devices such as /dev/zero can get dirty for example via
    utime(2) syscall or due to atime update. Backing device of such inodes
    (zero_bdi, etc.) is however unable to handle dirty inodes and thus
    __mark_inode_dirty complains.  In fact, inode should be rather dirtied
    against backing device of the filesystem holding it. This is generally a
    good rule except for filesystems such as 'bdev' or 'mtd_inodefs'. Inodes
    in these pseudofilesystems are referenced from ordinary filesystem
    inodes and carry mapping with real data of the device. Thus for these
    inodes we have to use inode->i_mapping->backing_dev_info as we did so
    far. We distinguish these filesystems by checking whether sb->s_bdi
    points to a non-trivial backing device or not.
    
    Example: Assume we have an ext3 filesystem on /dev/sda1 mounted on /.
    There's a device inode A described by a path "/dev/sdb" on this
    filesystem. This inode will be dirtied against backing device "8:0"
    after this patch. bdev filesystem contains block device inode B coupled
    with our inode A. When someone modifies a page of /dev/sdb, it's B that
    gets dirtied and the dirtying happens against the backing device "8:16".
    Thus both inodes get filed to a correct bdi list.
    
    Cc: stable@kernel.org
    Signed-off-by: NJan Kara <jack@suse.cz>
    Signed-off-by: NJens Axboe <jaxboe@fusionio.com>
    692ebd17
fs-writeback.c 31.6 KB