Ric Wheeler wrote:
Mark Lord wrote:
Eric D. Mudama wrote:
Actually, it's possibly worse, since each failure in libata will
generate 3-4 retries.
(note: libata does *not* generate retries for medium errors;
the looping is driven by the SCSI mid-layer code).
It really beats the alternative of a forced reboot
due to, say, superblock I/O failing because it happened
to get merged with an unrelated I/O which then failed..
Etc..
Definitely an improvement.
The number of retries is an entirely separate issue.
If we really care about it, then we should fix SD_MAX_RETRIES.
The current value of 5 is *way* too high. It should be zero or one.
..
I think that drives retry enough, we should leave retry at zero for
normal (non-removable) drives. Should this be a policy we can set like
we do with NCQ queue depth via /sys ?
Or perhaps we could have the mid-layer always "early-exit"
without retries for "MEDIUM_ERROR", and still do retries for the rest.
When libata reports a MEDIUM_ERROR to us, we *know* it's non-recoverable,
as the drive itself has already done internal retries (libata uses the
"with retry" ATA opcodes for this).
But meanwhile, we still have the original issue too, where a single stray
bad sector can blow a system out of the water, because the mid-layer
currently aborts everything after it from a large merged request.
Thus the original patch from this thread. :)
Cheers
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