Hi,
lvextend doesn't allocate extents appropriately if the LV is mirrored.
Attached patch fixes the problem.
If this looks reasonable, please consider to include in LVM2.
Details of the problem:
Suppose I have 4 PVs with sufficient free space and a 2-sided
mirrored LV with size=4MB, I would expect the following LV
as a result of "lvextend -L+4MB":
# lvs -a -olv_name,seg_size,devices vg4
LV SSize Devices
lv0 8.00M lv0_mimage_0(0),lv0_mimage_1(0)
[lv0_mimage_0] 8.00M /dev/sda(0)
[lv0_mimage_1] 8.00M /dev/sdb(0)
[lv0_mlog] 4.00M /dev/sdc(0)
However, actual result was following:
# lvs -a -olv_name,seg_size,devices vg4
LV SSize Devices
lv0 8.00M lv0_mimage_0(0),lv0_mimage_1(0)
[lv0_mimage_0] 4.00M /dev/sda(0)
[lv0_mimage_0] 4.00M /dev/sdd(0)
[lv0_mimage_1] 4.00M /dev/sdb(0)
[lv0_mimage_1] 4.00M /dev/sda(1)
[lv0_mlog] 4.00M /dev/sdc(0)
In this case, failure of a PV (/dev/sda) would break whole LV (lv0),
which is not what we expect from mirrored LV.
The cause of the problem is that _check_contiguous() doesn't care
layered LV and cannot find out contiguousness between PV areas.
Thanks,
--
Jun'ichi Nomura, NEC Corporation of America
Finding contiguous PV segment for mirrored LV.
Check areas[] boundary in _check_contiguous().
Applicable to LVM2 2.02.09.
Steps to reproduce the problem:
# pvcreate /dev/sd[abcd]
# vgcreate vg4 /dev/sd[abcd]
# lvcreate -l1 -m1 -nlv0 vg4
# lvchange -an vg4/lv0
# lvextend -l+1 vg4/lv0
# lvs -a -olv_name,seg_size,devices vg4
--- LVM2/lib/metadata/lv_manip.c 2006-08-23 04:26:43.000000000 -0400
+++ LVM2.fix/lib/metadata/lv_manip.c 2006-08-23 04:29:37.000000000 -0400
@@ -642,12 +642,24 @@ static int _comp_area(const void *l, con
*/
static int _check_contiguous(struct lv_segment *prev_lvseg,
struct physical_volume *pv, struct pv_area *pva,
- struct pv_area **areas)
+ struct pv_area **areas, uint32_t areas_size)
{
struct pv_segment *prev_pvseg;
uint32_t s;
- for (s = 0; s < prev_lvseg->area_count; s++) {
+ for (s = 0; s < prev_lvseg->area_count && s < areas_size; s++) {
+ if (seg_type(prev_lvseg, s) == AREA_LV) {
+ struct logical_volume *lv;
+ struct lv_segment *lastseg;
+ lv = seg_lv(prev_lvseg, s);
+ lastseg = list_item(list_last(&lv->segments),
+ struct lv_segment);
+ if (_check_contiguous(lastseg, pv, pva, &areas[s],
+ areas_size - s))
+ return 1;
+ continue;
+ }
+
if (seg_type(prev_lvseg, s) != AREA_PV)
continue; /* FIXME Broken */
@@ -752,7 +764,8 @@ static int _find_parallel_space(struct a
if (prev_lvseg &&
_check_contiguous(prev_lvseg,
pvm->pv,
- pva, areas)) {
+ pva, areas,
+ areas_size)) {
contiguous_count++;
goto next_pv;
}
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