On Monday, October 08, 2001 09:57:59 PM -0400 Ed Tomlinson <tomlins@CAM.ORG> wrote:
> Hi Chris
>
>> Ok, that first patch won't quite fix it, as we can still oops
>> in lvm_snapshot_COW. This one works better for me:
>
> Looks like this one has problems too. Here is the oops I get with it:
>>> EIP; d680b178 <[lvm-mod]_disable_snapshot+10/44> <=====
> Trace; d680a50a <[lvm-mod]lvm_drop_snapshot+22/94>
> Trace; d680aafc <[lvm-mod]lvm_snapshot_COW+3b4/3f4>
> Trace; d680d3ca <[lvm-mod]lvm_name+8c2/e76>
Hmmm, this should be the same as the bug fixed by the second patch. We know the snapshot hasn't been released yet when lvm_snapshot_COW is called, so _disable_snapshot should not oops.
We've got a write lock on the lv semaphore, so nobody else should be calling lvm_drop_snapshot on us. I hate to ask, but are you sure you did an rmmod before the modules_install?
Regardless, we can fix the oops in _disable_snapshot, I just don't see how the locking allows it to happen. This incremental fix should do it:
--- 0.21/drivers/md/lvm-snap.c Sat, 06 Oct 2001 00:07:22 -0400
+++ 0.21(w)/drivers/md/lvm-snap.c Mon, 08 Oct 2001 22:39:54 -0400
@@ -687,6 +694,10 @@
static void _disable_snapshot(vg_t *vg, lv_t *lv) {
const char *err;
+ if (!lv->lv_block_exception) {
+ printk(KERN_ERR "%s -- snapshot already disabled\n", lvm_name);
+ return ;
+ }
lv->lv_block_exception[0].rsector_org = LVM_SNAPSHOT_DROPPED_SECTOR;
if(_write_COW_table_block(vg, lv, 0, &err) < 0) {
printk(KERN_ERR "%s -- couldn't disable snapshot: %s\n",
