When serializing extents, run-length encoding is supposed to
1) RLE all sequential LBAs
2) RLE zero LBAs (unallocated)
There is one special case, with sequential LBAs that start
with 0 LBA. This is RLE as 1) case, but results in descriptor
matching case 2). Which causes loss of allocated clusters.
This requires following conditions to be met:
- blobstore has just a single cluster reserved for MD
- blob is thin provisioned
- first allocation occurs on cluster_num=1
For last part to be true, very first write for blob has to be
issued to LBA between cluster_size and 2*cluster_size.
Causing allocation of second cluster in blobstore and assiging
it LBA equal to number of LBAs per cluster.
To fix this, case 1) disallows to RLE zeroes.
Signed-off-by: Tomasz Zawadzki <tomasz.zawadzki@intel.com>
Change-Id: I136282407966310c882ca97c960e9a71c442c469
Reviewed-on: https://review.gerrithub.io/c/spdk/spdk/+/475494
Reviewed-by: Ben Walker <benjamin.walker@intel.com>
Reviewed-by: Jim Harris <james.r.harris@intel.com>
Tested-by: SPDK CI Jenkins <sys_sgci@intel.com>
0d1aa0252d