(resending) On Mon, 2015-05-18 at 10:01 +0200, Christoph Hellwig wrote: > On Mon, May 18, 2015 at 09:41:02AM +0200, Christoph Hellwig wrote: > > > Here's a first pass at this along with kref + completion conversion for > > > the special case PR ALL_TGT_PT=1 pointer dereference. > > > > Btw, I started hacking up a patch to merge se_port and t10_alua_tg_pt_gp_member > > in se_lun, which seems even better as it closes all kinds of other > > races. Can you keep this one back for now, I'll send out that patch > > ASAP after finishing some testing. > > Ok, testing showed that the baseline (your for-next tree from yesterday) > already doesn't work for tcm_loop and probably any generated nodeacl case, > and gets a: > > [ 12.830576] kernel BUG at ../drivers/target/target_core_device.c:337! > How did you hit this..? I'm not triggering this with normal tcm_loop LUN creation, nor generated node_acls for iscsi-target. This particular BUG_ON() should only be triggered when the generated -> explicit conversion happens, when the generated LUN does not match the explicit one created in configfs. In practice, this should fail with -EINVAL instead and not trigger a BUG_ON(). > I've also looked over your patch and found at least two issues with it: > > - given that core_dev_unexport clears ->lun_se_dev all the callers > in the stats code still need to check for it being zero > - the 64-bit stats still need a lock protecting them, or made atomics. > The same issue already applies with the base RCU patches for the counters > in the se_dev_entry, btw. > Fixing this up. > Anyway, below is my patch, which I think will be very useful as it > closes all kinds of races by merging the structures. Applying rcu > lookups for ->lun_se_dev and removign the busy loop for the refcount > would be a good next step on top of that. > This is obviously another huge change, and as a single patch is going to take a while to understand and review. That said, I'll take it for now and put the ALL_TGT_PT=1 changes on top. --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
