• Josef Bacik's avatar
    Introduce freeze_super and thaw_super for the fsfreeze ioctl · 18e9e510
    Josef Bacik authored
    Currently the way we do freezing is by passing sb>s_bdev to freeze_bdev and then
    letting it do all the work.  But freezing is more of an fs thing, and doesn't
    really have much to do with the bdev at all, all the work gets done with the
    super.  In btrfs we do not populate s_bdev, since we can have multiple bdev's
    for one fs and setting s_bdev makes removing devices from a pool kind of tricky.
    This means that freezing a btrfs filesystem fails, which causes us to corrupt
    with things like tux-on-ice which use the fsfreeze mechanism.  So instead of
    populating sb->s_bdev with a random bdev in our pool, I've broken the actual fs
    freezing stuff into freeze_super and thaw_super.  These just take the
    super_block that we're freezing and does the appropriate work.  It's basically
    just copy and pasted from freeze_bdev.  I've then converted freeze_bdev over to
    use the new super helpers.  I've tested this with ext4 and btrfs and verified
    everything continues to work the same as before.
    The only new gotcha is multiple calls to the fsfreeze ioctl will return EBUSY if
    the fs is already frozen.  I thought this was a better solution than adding a
    freeze counter to the super_block, but if everybody hates this idea I'm open to
    suggestions.  Thanks,
    Signed-off-by: default avatarJosef Bacik <josef@redhat.com>
    Signed-off-by: default avatarAl Viro <viro@zeniv.linux.org.uk>
ioctl.c 15.9 KB