[linux-lvm] Re: [OOPS] full snapshot (with test vfs locking patch for reiserfs snapshots in 11-pre)
Chris Mason
mason at suse.com
Mon Oct 8 17:40:54 UTC 2001
On Monday, October 08, 2001 01:05:48 PM -0400 Ed Tomlinson <tomlins at CAM.ORG> wrote:
> On October 8, 2001 12:54 pm, Chris Mason wrote:
>> On Monday, October 08, 2001 11:53:46 AM -0400 Ed Tomlinson
>>
>> <tomlins at CAM.ORG> wrote:
>> > Hi Chris,
>> >
>> > To summerize, with 2.4.11-pre5 and lvm-1.01-rc4 + your test vfslocking
>> > patch for 2.4.11-pre I, unlike you, was able to make snapshots and
>> > reiserfsck them without problems. Then I tried a debench 50 run and
>> > got an oops.
>>
>> Confirmed, similar oops here. Do you get this with rc4 in 2.4.10?
>
> Funny you should ask... Guess what was runing when this email arrived?
> The answer is that with 2.4.10 + lvm 1.01-rc4 the snapshot deactivates
> correctly - I do not see an oops.
>
Hmmm, looks like pure luck then. It does not look like all the callers of lvm_snapshot_remap_block are properly checking to make sure the snapshot is still valid (hasn't been run through lvm_snapshot_release).
Try this:
-chris
Index: 0.21/drivers/md/lvm-snap.c
--- 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 13:35:41 -0400
@@ -108,6 +108,9 @@
lv_block_exception_t * ret;
int i = 0;
+ if (!hash_table || !lv->lv_block_exception)
+ return NULL ;
+
hash_table = &hash_table[hashfn(org_dev, org_start, mask, chunk_size)];
ret = NULL;
for (next = hash_table->next; next != hash_table; next = next->next)
@@ -140,6 +143,8 @@
unsigned long mask = lv->lv_snapshot_hash_mask;
int chunk_size = lv->lv_chunk_size;
+ if (!hash_table)
+ BUG() ;
hash_table = &hash_table[hashfn(org_dev, org_start, mask, chunk_size)];
list_add(&exception->hash, hash_table);
}
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