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Condition was swapped - however since it's been based on 'random'
memory content it's been missed as attribute has not been set.
So now we have quite a few possible results when testing.
We have old status without separate metadata and
we have kernels with fixed snapshot leak bug.
(in-release update)
Code uses target driver version for better estimation of
max size of COW device for snapshot.
The bug can be tested with this script:
VG=vg1
lvremove -f $VG/origin
set -e
lvcreate -L 2143289344b -n origin $VG
lvcreate -n snap -c 8k -L 2304M -s $VG/origin
dd if=/dev/zero of=/dev/$VG/snap bs=1M count=2044 oflag=direct
The bug happens when these two conditions are met
* origin size is divisible by (chunk_size/16) - so that the last
metadata area is filled completely
* the miscalculated snapshot metadata size is divisible by extent size -
so that there is no padding to extent boundary which would otherwise
save us
Signed-off-by:Mikulas Patocka <mpatocka@redhat.com>
Switch to use ext2 to make it usable on older systems.
Previous test has not been able to catching problem.
Multiple tests are now put in.
FIXME: validate what is doing kernel target when
the header is undeleted and same chunk size is used.
It seems snapshot target successfully resumes and
just complains COW is not big enough:
kernel: dm-8: rw=0, want=40, limit=24
kernel: attempt to access beyond end of device
When chunk size is different it fails instantly.
For checking this with lvm2 and this test case use this patch:
--- a/tools/lvcreate.c
+++ b/tools/lvcreate.c
@@ -769,7 +769,7 @@ static int _read_activation_params(struct
lvcreate_params *lp,
lp->permission = arg_uint_value(cmd, permission_ARG,
LVM_READ | LVM_WRITE);
- if (lp->snapshot) {
+ if (0 && lp->snapshot) {
/* Snapshot has to zero COW header */
lp->zero = 1;
lp->wipe_signatures = 0;
---
and switch to use -c 4 for both snapshots
When read-only snapshot was created, tool was skipping header
initialization of cow device. If it happened device has been
already containing header from some previous snapshot, it's
been 'reused' for a newly created snapshot instead of being cleared.
Add 'can_use_16T' to detect systems where we could
safely use 16T devices without causing system deadlocks.
16T size leads on those to endless loops in udevd
- it calls blkid which tries cached read from such device
- this ends in endless loop.
Related problems:
https://bugzilla.redhat.com/show_bug.cgi?id=1015028
