Red Hat Bugzilla – Bug 1477232
Unable to restore metadata from metadata snapshot (thin_dump -m -> thin_restore)
Last modified: 2017-08-01 10:13:46 EDT
Description of problem: Not able to restore swapped metadata dumped by thin_dump from metadata snapshot created by dmsetup message. [root@storageqe-21 thin]# thin_check /dev/mapper/vgtest-swapvol examining superblock examining devices tree examining mapping tree checking space map counts [root@storageqe-21 thin]# thin_dump /dev/mapper/vgtest-swapvol -o metadata [root@storageqe-21 thin]# thin_dump /dev/mapper/vgtest-swapvol -o metadata_snap -m [root@storageqe-21 thin]# thin_restore -i metadata -o /dev/mapper/vgtest-swapvol Restoring: [==================================================] 100% [root@storageqe-21 thin]# thin_restore -i metadata_snap -o /dev/mapper/vgtest-swapvol Restoring: [> ] | 0% mapping beyond end of data device (0 >= 0) [root@storageqe-21 thin]# diff metadata metadata_snap 1c1 < <superblock uuid="" time="0" transaction="10" flags="0" version="2" data_block_size="128" nr_data_blocks="1600"> --- > <superblock uuid="" time="0" transaction="10" flags="0" version="2" data_block_size="128" nr_data_blocks="0"> The only difference between the metadata is in "nr_data_blocks", where in regular it is 1600 and in snapshot 0. Version-Release number of selected component (if applicable): device-mapper-persistent-data-0.7.0-0.1.rc6.el7 How reproducible: 100% Steps to Reproduce: 1. get swapped metadata with metadata snapshot vgcreate vgtest /dev/loop1 lvcreate -T -L 100 vgtest -n thinpool lvcreate -T -V 10 vgtest/thinpool -n thinvol mkfs.ext4 /dev/vgtest/thinvol lvchange -an vgtest/thinvol lvcreate -T -V 10 vgtest/thinpool -n thinvol1 mkfs.ext4 /dev/vgtest/thinvol1 lvchange -an vgtest/thinvol1 dmsetup suspend /dev/mapper/vgtest-swapvol-tpool dmsetup message /dev/mapper/vgtest-swapvol-tpool 0 reserve_metadata_snap dmsetup resume /dev/mapper/vgtest-swapvol-tpool lvchange -an vgtest/thinpool lvcreate -L 100 vgtest -n swapvol lvchange -an vgtest/swapvol lvconvert -y --thinpool vgtest/thinpool --poolmetadata vgtest/swapvol lvchange -ay vgtest/swapvol 2.dump metadata snapshot thin_dump /dev/mapper/vgtest-swapvol -o metadata_snap 3.try to restore metadata thin_restore -i metadata_snap -o /dev/mapper/vgtest-swapvol Actual results: Restoring: [> ] | 0% mapping beyond end of data device (0 >= 0) Expected results: Restoring: [==================================================] 100% Additional info: Even though thin_dump manpage says it is not processable by thin_restore, this is quite important feature as the metadata might be corrupted but the metadata snapshot could be OK. For this reason both metadata dump and metadata snapshot dump should be restorable even though restoring either leads to loosing the metadata snapshot.