Now, btrfs-progs has a kernel scrub equivalent.
A new option, --offline is added to "btrfs scrub start".
If --offline is given, btrfs scrub will just act like kernel scrub, to
check every copy of extent and do a report on corrupted data and if it's
recoverable.
The advantage compare to kernel scrub is:
1) No race
Unlike kernel scrub, which is done in parallel, offline scrub is done
by a single thread.
Although it may be slower than kernel one, it's safer and no false
alert.
2) Correctness
Kernel has a known bug (fix submitted) which will recovery RAID5/6
data but screw up P/Q, due to the hardness coding in kernel.
While in btrfs-progs, no page, (almost) no memory size limit, we're
can focus on the scrub, and make things easier.
New offline scrub can detect and report P/Q corruption with
recoverability report, while kernel will only report data stripe error.
Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Su <suy.fnst@cn.fujitsu.com>
Signed-off-by: Gu Jinxiang <gujx@cn.fujitsu.com>
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