scsi: core: Make SCSI Status CONDITION MET equivalent to GOOD (1875ede0) · Commits · 戴 / test

The SCSI PRE-FETCH (10 or 16) command is present both on hard disks and some SSDs. It is useful when the address of the next block(s) to be read is known but it is not following the LBA of the current READ (so read-ahead won't help). It returns two "good" SCSI Status values. If the requested blocks have fitted (or will most likely fit (when the IMMED bit is set)) into the disk's cache, it returns CONDITION MET. If it didn't (or will not) fit then it returns GOOD status. The goal of this patch is to stop the SCSI subsystem treating the CONDITION MET SCSI status as an error. The current state makes the PRE-FETCH command effectively unusable via pass-throughs. Signed-off-by:

Douglas Gilbert <dgilbert@interlog.com> Reviewed-by:

Bart Van Assche <bart.vanassche@wdc.com> Signed-off-by:

Martin K. Petersen <martin.petersen@oracle.com>

drivers/scsi/scsi_lib.c

+11 −0

Original line number	Diff line number	Diff line
		@@ -867,6 +867,17 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
		/* for passthrough error may be set */
		error = BLK_STS_OK;
		}
		/*
		* Another corner case: the SCSI status byte is non-zero but 'good'.
		* Example: PRE-FETCH command returns SAM_STAT_CONDITION_MET when
		* it is able to fit nominated LBs in its cache (and SAM_STAT_GOOD
		* if it can't fit). Treat SAM_STAT_CONDITION_MET and the related
		* intermediate statuses (both obsolete in SAM-4) as good.
		*/
		if (status_byte(result) && scsi_status_is_good(result)) {
		result = 0;
		error = BLK_STS_OK;
		}

		/*
		* special case: failed zero length commands always need to

include/scsi/scsi.h

+2 −0

Original line number	Diff line number	Diff line
		@@ -47,6 +47,8 @@ static inline int scsi_status_is_good(int status)
		*/
		status &= 0xfe;
		return ((status == SAM_STAT_GOOD) \|\|
		(status == SAM_STAT_CONDITION_MET) \|\|
		/* Next two "intermediate" statuses are obsolete in SAM-4 */
		(status == SAM_STAT_INTERMEDIATE) \|\|
		(status == SAM_STAT_INTERMEDIATE_CONDITION_MET) \|\|
		/* FIXME: this is obsolete in SAM-3 */

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