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authorBart Van Assche <bvanassche@acm.org>2021-08-09 16:03:04 -0700
committerMartin K. Petersen <martin.petersen@oracle.com>2021-08-11 22:25:36 -0400
commit51f3a478892873337c54068d1185bcd797000a52 (patch)
tree2dfb7deb4b8dc178f4a799bdc4151bfe71254108
parent10163cee1f06fc2e17bcf7bbc2982337202d1d5c (diff)
downloadlinux-51f3a478892873337c54068d1185bcd797000a52.tar.bz2
scsi: core: Introduce the scsi_cmd_to_rq() function
The 'request' member of struct scsi_cmnd is superfluous. The struct request and struct scsi_cmnd data structures are adjacent and hence the request pointer can be derived easily from a scsi_cmnd pointer. Introduce a helper function that performs that conversion in a type-safe way. This patch is the first step towards removing the request member from struct scsi_cmnd. Making that change has the following advantages: - This is a performance optimization since adding an offset to a pointer takes less time than dereferencing a pointer. - struct scsi_cmnd becomes smaller. Link: https://lore.kernel.org/r/20210809230355.8186-2-bvanassche@acm.org Cc: Christoph Hellwig <hch@lst.de> Cc: Hannes Reinecke <hare@suse.de> Cc: Ming Lei <ming.lei@redhat.com> Reviewed-by: Hannes Reinecke <hare@suse.de> Signed-off-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
-rw-r--r--include/scsi/scsi_cmnd.h6
1 files changed, 6 insertions, 0 deletions
diff --git a/include/scsi/scsi_cmnd.h b/include/scsi/scsi_cmnd.h
index 90da9617d28a..e76278ea1fee 100644
--- a/include/scsi/scsi_cmnd.h
+++ b/include/scsi/scsi_cmnd.h
@@ -146,6 +146,12 @@ struct scsi_cmnd {
unsigned int extra_len; /* length of alignment and padding */
};
+/* Variant of blk_mq_rq_from_pdu() that verifies the type of its argument. */
+static inline struct request *scsi_cmd_to_rq(struct scsi_cmnd *scmd)
+{
+ return blk_mq_rq_from_pdu(scmd);
+}
+
/*
* Return the driver private allocation behind the command.
* Only works if cmd_size is set in the host template.