On Fri, 2010-09-10 at 12:44 -0700, Joel Becker wrote: > On Fri, Sep 10, 2010 at 12:06:46PM -0700, Nicholas A. Bellinger wrote: > > On Fri, 2010-09-10 at 08:28 -0700, Joel Becker wrote: > > > The trivial solution is to refcount your ACLs. You get both > > > allow_link() calls, so you should be able to increment a counter there, > > > and then drop them when the last drop_link() call is made. That will > > > keep your consumer structures around until all links are exhausted. > > > > > > > So I am a bit confused wrt to this last response.. The ->check_link() > > patch and it's use in the fabric independent code within > > target_core_fabric_configfs.c does exactly this for the 'MappedLUN' > > symlink case, eg: requires the consumer to do the allow_link() + > > drop_link() refcounting, and add the > > API check into fs/configfs/symlink.c:configfs_unlink() > > You can refcount without check_link(). So what do you recommend here..? > > > Is there another form of configfs consumer refcounting that you had in > > mind beyond using an atomic_t for this with ->check_link() here..? > > I'm saying that you won't crash if you don't free the ACLs on > the first drop_link(). That is, the drop_link() goes through as > configfs wants it to, but you don't crash. The problem is that the 'unlink sub_child/group1/src_0/src_link' can't signal to the other struct config_group to also call an internal 'unlink sub_child/group2/dst_0/dst_link' to drop the child link outside of it's struct config_group. > > > So beyond a configfs consumer solution, what do you think about checking > > for the sub_child/group2/dst_0/dst_link style of symlink > > in fs/configfs/symlink.c:configfs_symlink() in order to add some form of > > internal refcount when the symlink source is within the same consumer > > LKM, but outside of the parent struct config_group..? > > > > This would involve the conversion of fs/configfs/symlink.c: > > configfs_unlink() path to check for the existence of this internal > > refcount and returning -EPERM when any sub_child/group2/dst_0/dst_link > > exist when 'unlink sub_child/group1/src_0/src_link' is attempted. > > You're still fighting allowing the links to go away. You > haven't explained why that is necessary. You had a problem with a crash > because you expected one reference to your ACLs and actually have two, > but you can fix that without modifying configfs. If this is the case then I must be mis-understanding what you mean by configfs consumer refcounting from allow_link() and drop_link(). Can you give me a bit more detail where I should be looking..? Thanks! --nab -- To unsubscribe from this list: send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
