Hello, James. This patchset is split up of REQ_SPECIAL update patches (#01-02) of previous patchset posted on March 31. Explicit setting of REQ_SOFTBARRIER in scsi_init_io() is added. This patchset makes REQ_SPECIAL mean that the request is a special request and REQ_SOFTBARRIER setting explicit. Previously, REQ_SPECIAL duplicately meant the request has been prepp'ed by SCSI midlayer and/or the request is a special request. This left special requests handling in the midlayer subtley inconsistent. Also, the setting of REQ_SPECIAL was done by the block layer using blk_insert_request() mostly but sometimes by the SCSI midlayer (when returning BLK_PREP_DEFER from scsi_prep_fn()). blk_insert_request() was used for two different purposes. * enqueue special requests * turn on REQ_SPECIAL|REQ_SOFTBARRIER and call blk_requeue_request(). The second somewhat unobvious feature of blk_insert_request() is used only by SCSI midlayer and SCSI midlayer depended on it to set REQ_SOFTBARRIER. Unfortunately, when the SCSI midlayer sets REQ_SPECIAL explicitly (sg allocation failure path) it didn't set REQ_SOFTBARRIER, creating a *highly* unlikely but still existing dead lock condition caused by allowing reorder of a request which has its cmd allocated. IMHO, this proves the subtlety of current situation. This patch makes SCSI midlayer use blk_requeue_request() for reqeueuing and setting of REQ_SOFTBARRIER explicit. To prevent more misuses, the last patch in this patchset remove requeue feature from blk_insert_request(). Requeueing should be done with blk_requeue_request() not blk_insert_request(). [ Start of patch descriptions ] 01_scsi_REQ_SPECIAL_semantic_scsi_init_io.patch : replace REQ_SPECIAL with REQ_SOFTBARRIER in scsi_init_io() scsi_init_io() used to set REQ_SPECIAL when it fails sg allocation before requeueing the request by returning BLKPREP_DEFER. REQ_SPECIAL is being updated to mean special requests and we need to set REQ_SOFTBARRIER for half-prepp'ed requests. So, replace REQ_SPECIAL with REQ_SOFTBARRIER. 02_scsi_REQ_SPECIAL_semantic_scsi_queue_insert.patch : make scsi_queue_insert() use blk_requeue_request() scsi_queue_insert() used to use blk_insert_request() for requeueing requests. This behavior depends on the unobvious behavior of blk_insert_request() setting REQ_SPECIAL and REQ_SOFTBARRIER when requeueing. This patch makes scsi_queue_insert() use blk_requeue_request() and explicitly set REQ_SOFTBARRIER. As REQ_SPECIAL now means special requests, the flag is not set on requeue. Note that scsi_queue_insert() now calls scsi_run_queue() itself, and the prototype of the function is added right above scsi_queue_insert(). This is temporary, as later requeue path consolidation patchset removes scsi_queue_insert(). By adding temporary prototype, we can do away with unnecessary changes. 03_scsi_REQ_SPECIAL_semantic_scsi_requeue_command.patch : make scsi_requeue_request() use blk_requeue_request() scsi_requeue_request() used to use blk_insert_request() for requeueing requests. This behavior depends on the unobvious behavior of blk_insert_request() setting REQ_SPECIAL and REQ_SOFTBARRIER when requeueing. This patch makes scsi_requeue_request() use blk_requeue_request() and explicitly set REQ_SOFTBARRIER. As REQ_SPECIAL now means special requests, the flag is not set on requeue. 04_scsi_blk_insert_request_no_requeue.patch : remove requeue feature from blk_insert_request() blk_insert_request() has a unobivous feature of requeuing a request setting REQ_SPECIAL|REQ_SOFTBARRIER. SCSI midlayer was the only user and as previous patches removed the usage, remove the feature from blk_insert_request(). Only special requests should be queued with blk_insert_request(). All requeueing should go through blk_requeue_request(). [ End of patch descriptions ] This patchset completes preparation for scsi_request_fn() reimplementation patchset. As it seemed better to clear up requeue paths inside scsi_request_fn() first, requeue path consolidation patchset follows scsi_request_fn() reimplementation patchset. Thanks a lot. - : send the line "unsubscribe linux-scsi" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
