Hi I tried to tackle a particular bug that shows up in Debian for some time now. Some blamed the udev rules and I still can't completely rule them out. But this triggers a much worse bug in the error cleanup of the snapshot remove. I reproduced this with Debian/Linux 3.2.46/LVM 2.02.99 without udevd running and Fedora 19/LVM 2.02.98-10.fc19. On snapshot removal, LVM first converts the device into a regular LV (lv_remove_snapshot) and in a second step removes this LV (lv_remove_single). Is there a reason for this two step removal? An error during removal leaves a non-snapshot LV behind. I hold the cow device open so it will run into the error condition: | $ sleep 100 < /dev/mapper/vg-test_snap-cow& Then try to remove the LV: | $ lvremove vg/test_snap lv_remove_snapshot first suspends all devices: | #metadata/lv_manip.c:4429 Removing snapshot test_snap | #libdm-deptree.c:1314 Suspending vg-test_base (253:8) with device flush | #ioctl/libdm-iface.c:1724 dm suspend (253:8) NFS [16384] (*1) | #libdm-common.c:210 Suspended device counter increased to 1 | #ioctl/libdm-iface.c:1724 dm info (253:9) NF [16384] (*1) | #libdm-deptree.c:1314 Suspending vg-test_snap (253:9) with device flush | #ioctl/libdm-iface.c:1724 dm suspend (253:9) NFS [16384] (*1) | #libdm-common.c:210 Suspended device counter increased to 2 | #ioctl/libdm-iface.c:1724 dm info (253:10) NF [16384] (*1) | #libdm-deptree.c:1314 Suspending vg-test_base-real (253:10) with device flush | #ioctl/libdm-iface.c:1724 dm suspend (253:10) NFS [16384] (*1) | #libdm-common.c:210 Suspended device counter increased to 3 | #ioctl/libdm-iface.c:1724 dm info (253:11) NF [16384] (*1) | #libdm-deptree.c:1314 Suspending vg-test_snap-cow (253:11) with device flush | #ioctl/libdm-iface.c:1724 dm suspend (253:11) NFS [16384] (*1) | #libdm-common.c:210 Suspended device counter increased to 4 Commits the VG: | #format_text/format-text.c:735 Committing vg metadata (1276) to /dev/xvdb header at 4096 Resumes three of the devices, but not vg-test_base: | #libdm-deptree.c:1263 Resuming vg-test_snap-cow (253:11) | #ioctl/libdm-iface.c:1724 dm resume (253:11) NF [16384] (*1) | #libdm-common.c:1338 vg-test_snap-cow: Stacking NODE_ADD (253,11) 0:6 0660 [trust_udev] | #libdm-common.c:1348 vg-test_snap-cow: Stacking NODE_READ_AHEAD 0 (flags=0) | #libdm-common.c:221 Suspended device counter reduced to 3 | #libdm-deptree.c:1263 Resuming vg-test_base-real (253:10) | #ioctl/libdm-iface.c:1724 dm resume (253:10) NF [16384] (*1) | #libdm-common.c:1338 vg-test_base-real: Stacking NODE_ADD (253,10) 0:6 0660 [trust_udev] | #libdm-common.c:1348 vg-test_base-real: Stacking NODE_READ_AHEAD 0 (flags=0) | #libdm-common.c:221 Suspended device counter reduced to 2 | #libdm-deptree.c:1263 Resuming vg-test_snap (253:9) | #ioctl/libdm-iface.c:1724 dm resume (253:9) NF [16384] (*1) | #libdm-common.c:1338 vg-test_snap: Stacking NODE_ADD (253,9) 0:6 0660 [trust_udev] | #libdm-common.c:1348 vg-test_snap: Stacking NODE_READ_AHEAD 256 (flags=1) | #libdm-common.c:221 Suspended device counter reduced to 1 Now it fails to do lv_activate on the cow device, because it is still open: | #libdm-deptree.c:1562 Unable to deactivate open vg-test_snap-cow (253:11) | #metadata/snapshot_manip.c:291 Failed to activate test_snap. And exits without further error handling and with one suspended device: | libdevmapper exiting with 1 device(s) still suspended. Bastian -- Beam me up, Scotty, there's no intelligent life down here!
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