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DescriptionBruno Goncalves
2017-04-20 08:11:10 UTC
Description of problem:
It is possible to use lvconvert to set --cachepolicy cleaner and --cachemode writeback together, although this does not make sense.
Version-Release number of selected component (if applicable):
lvm2-2.02.169-1.el7.x86_64
device-mapper-1.02.138-1.el7.x86_64
How reproducible:
100%
Steps to Reproduce:
1.Create LV devices
fallocate -l 500M cache_policy.img
losetup /dev/loop0 cache_policy.img
fallocate -l 200M pool_policy.img
losetup /dev/loop1 pool_policy.img
vgcreate cache_sanity /dev/loop0 /dev/loop1
lvcreate -L 100M -n display_cache cache_sanity /dev/loop0
lvcreate -L 100M -n pool cache_sanity /dev/loop1
lvcreate -L 12M -n pool_meta cache_sanity /dev/loop1
2. Convert the pool
lvconvert --yes --type cache-pool --cachepolicy cleaner --cachemode writeback -c 32 --poolmetadata cache_sanity/pool_meta cache_sanity/pool
Actual results:
lvconvert --yes --type cache-pool --cachepolicy cleaner --cachemode writeback -c 32 --poolmetadata cache_sanity/pool_meta cache_sanity/pool
WARNING: Converting logical volume cache_sanity/pool and cache_sanity/pool_meta to cache pool's data and metadata volumes with metadata wiping.
THIS WILL DESTROY CONTENT OF LOGICAL VOLUME (filesystem etc.)
Converted cache_sanity/pool to cache pool.
Expected results:
The command should fail or give some warning message
Additional info:
This might cause problems when using the device
lvconvert --yes --type cache --cachepool cache_sanity/pool cache_sanity/display_cache
device-mapper: reload ioctl on (253:3) failed: Invalid argument
Failed to lock logical volume cache_sanity/display_cache.
lvremove -f cache_sanity/display_cache
WARNING: Reading VG cache_sanity from disk because lvmetad metadata is invalid.
Logical volume "display_cache" successfully removed
Yep - original version of lvm2 supported this combination by chance - however cleaner policy with writeback is not supported anymore - libdm is automatically always using 'writethrough' cache mode with cleaner policy.
We have couple choices here:
1.
Reject command because converting or creating any cached LV with cleaner policy is not really usable.
2.
Reject command because cleaner + writeback is not supported.
3.
Automagically switch to 'writethrough' with some printed WARNING.
Tested with lvm2-2.02.171-2.el7, the commands reject the options as expected:
# lvconvert --yes --type cache-pool --cachepolicy cleaner --cachemode writeback -c 32 --poolmetadata cache_sanity/pool_meta cache_sanity/pool
Cache mode "writeback" is not compatible with cache policy "cleaner".
Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.
For information on the advisory, and where to find the updated
files, follow the link below.
If the solution does not work for you, open a new bug report.
https://access.redhat.com/errata/RHBA-2017:2222