Eric Lee / smarc-ti-linux-kernel

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Commit e461338b6cd4074e39a0d5fdd1dc5582fbca1520

Authored by Martin K. Petersen
Committed by Christoph Hellwig
1 parent b7392d2247
Exists in ti-lsk-linux-4.1.y and in 10 other branches dlt-processor-sdk-linux-03.00.00.04, processor-sdk-linux-02.00.01, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04

sd: tweak discard heuristics to work around QEMU SCSI issue 

7985090aa020 changed the discard heuristics to give preference to the
WRITE SAME commands that (unlike UNMAP) guarantee deterministic results.

Ming Lei discovered that QEMU SCSI's WRITE SAME implementation
internally relied on limits that were only communicated for the UNMAP
case. And therefore discard commands backed by WRITE SAME would fail.

Tweak the heuristics so we still pick UNMAP in the LBPRZ=0 case and only
prefer the WRITE SAME variants if the device has the LBPRZ flag set.

Reported-by: Ming Lei <ming.lei@canonical.com>
Tested-by: Ming Lei <ming.lei@canonical.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Acked-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Christoph Hellwig <hch@lst.de>

Showing 1 changed file with 3 additions and 2 deletions Side-by-side Diff

... ... @@ -2623,8 +2623,9 @@
2623 2623 sd_config_discard(sdkp, SD_LBP_WS16);
2624 2624  
2625 2625 } else { /* LBP VPD page tells us what to use */
2626   -
2627   - if (sdkp->lbpws)
  2626 + if (sdkp->lbpu && sdkp->max_unmap_blocks && !sdkp->lbprz)
  2627 + sd_config_discard(sdkp, SD_LBP_UNMAP);
  2628 + else if (sdkp->lbpws)
2628 2629 sd_config_discard(sdkp, SD_LBP_WS16);
2629 2630 else if (sdkp->lbpws10)
2630 2631 sd_config_discard(sdkp, SD_LBP_WS10);