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Re: [dm-devel] [PATCHSET block#for-2.6.36-post] block: replace barrier with sequenced flush



Tejun Heo, on 08/23/2010 04:14 PM wrote:
I think that's correct and changing the priority of DM_ENDIO_REQUEUE
for REQ_FLUSH down to the lowest should be fine.
(I didn't know that FLUSH failure implies data loss possibility.)

At least on ATA, FLUSH failure implies that data is already lost, so
the error can't be ignored or retried.

In SCSI there are conditions when a command, including FLUSH (SYNC_CACHE), failed which don't imply lost data. For them the caller expected to retry the failed command. Most common cases are Unit Attentions and TASK QUEUE FULL status.

Vlad


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