Messages in this thread | | | Subject | Re: [PATCH RFC 1/3] block: Add support for REQ_OP_ASSIGN_RANGE operation | From | "Martin K. Petersen" <> | Date | Sat, 21 Dec 2019 13:54:50 -0500 |
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Kirill,
> One more thing to discuss. The new REQ_NOZERO flag won't be supported > by many block devices (their number will be even less, than number of > REQ_OP_WRITE_ZEROES supporters). Will this be a good thing, in case of > we will be completing BLKDEV_ZERO_ALLOCATE bios in > __blkdev_issue_write_zeroes() before splitting? I mean introduction of > some flag in struct request_queue::limits. Completion of them with > -EOPNOTSUPP in block devices drivers looks suboptimal for me.
We already have the NOFALLBACK flag to let the user make that decision.
If that flag is not specified, and I receive an allocate request for a SCSI device that does not support ANCHOR, my expectation would be that I would do a regular write same.
If it's a filesystem that is the recipient of the operation and not a SCSI device, how to react would depend on how the filesystem handles unwritten extents, etc.
-- Martin K. Petersen Oracle Linux Engineering
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