[linux-lvm] lvcreate - race condition creating snapshots
Robert Valentan
rov_200603 at solid-soft.at
Sat Jun 10 17:31:37 UTC 2006
I think, there is a race condition in lvcreate while
makeing a new snapshot.
System: Tyan with 2 Opteron 246
xen 3.0.2-3
linux 2.6.16.13
lvm 2.02.07
3ware-Raid 9550 Raid5
Under xen i was unable to create a snapshot, I got
always "LV system/snap in use: not deactivating".
Without xen, i got occasionally a snapshot.
After i make a "dirty hack":
------ begin ----------
*** old/lvcreate.c 2006-06-10 19:22:37.000000000 +0200
--- lvcreate.c 2006-06-10 19:23:04.000000000 +0200
***************
*** 776,781 ****
--- 776,787 ----
/* Reset permission after zeroing */
if (!(lp->permission & LVM_WRITE))
lv->status &= ~LVM_WRITE;
+
+ { struct timeval tv ;
+ tv.tv_sec=10;
+ tv.tv_usec=0;
+ select(2, 0, 0, 0, &tv);
+ }
if (!deactivate_lv(cmd, lv)) {
log_err("Couldn't deactivate new snapshot.");
return 0;
------ end ---------
i got always a snapshot (on all 3 systems!). I think, there is an
other thread which is creating the new lv, and it will take longer as
the lvcreate will "think". I have to less knowledge to make a patch,
which is waiting for the correct event (creating lv complete).
--
regards
Robert Valentan
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