Hello, James. This is repost of reqfn-reimplmentation patchset posted about a month ago. As REQ_SPECIAL semantics patchset, which this patchset depends on, has been accepted with slight modification (REQ_SOFTBARRIER handled by blk layer), this patchset is adjusted accordingly. Also, it's updated to use original scsi_add_timer function as timer API change patch isn't accepted yet. scsi_reqfn_reimplementation patch depends on the timer update patchset I've posted yesterday. The only dependency is the removal of scsi_dispatch_cmd() because the timer patchset modifies scsi_queue_insert() call in that function. If you decide to not accept the timer updates, just removing scsi_cmd_get_serial() and scsi_dispatch_cmd() by hand should suffice. Original description follows. This patchset reimplements scsi_request_fn(). All prep's are moved into prep_fn and all state checking/issueing are moved into scsi_reqfn. prep_fn() only terminates/defers unpreparable requests and all requests are terminated through scsi midlayer. [ Start of patch descriptions ] 01_scsi_reqfn_consolidate_error_handling.patch : consolidate error handling out of scsi_init_io() into scsi_prep_fn() This patch fixes a queue stall bug which occurred when sgtable allocation failed and device_busy == 0. When scsi_init_io() returns BLKPREP_DEFER or BLKPREP_KILL, it's supposed to free resources itself. This patch consolidates defer and kill handling into scsi_prep_fn(). Note that this patch doesn't consolidate state defer/kill handlings in scsi_prep_fn() as all state checks will be moved into scsi_reques_fn() by the following reqfn_reimpl patch. ret value checking was changed to switch() as in James's patch. Also, kill: comment is copied from James's patch. 02_scsi_reqfn_move_preps_to_prep_fn.patch : move request preps in other places into prep_fn() Move request preparations scattered in scsi_request_fn() and scsi_dispatch_cmd() into scsi_prep_fn() * CDB_SIZE check in scsi_dispatch_cmd() * SCSI-2 LUN preparation in scsi_dispatch_cmd() No invalid request reaches scsi_request_fn() anymore. Note that scsi_init_cmd_errh() is still left in scsi_request_fn(). As all requeued requests need its sense buffer and result value cleared, we can't move this to prep_fn() yet. This is moved into prep_fn in the following requeue path consoildation patchset. 03_scsi_reqfn_reimplementation.patch : reimplement scsi_request_fn() New scsi_request_fn() is formatted mostly as Chistoph Hellwig suggested. This patch rewrites scsi_request_fn(). scsi_dispatch_cmd() is merged into scsi_request_fn(). Goals are * Remove unnecessary operations (host_lock unlocking/locking, recursing into scsi_run_queue(), ...) * Consolidate defer/kill paths. * Be concise. The following bugs are fixed. * All killed requests now get fully prep'ed and pass through __scsi_done(). This is the only kill path. - scsi_cmnd leak in offline-kill path removed - unfinished request bug in scsi_dispatch_cmd():SDEV_DEL-kill path removed. - commands are never terminated directly from blk layer unless they are invalid, so no need to supply req->end_io callback for special requests. * Timer is added while holding host_lock, after all conditions are checked and serial number is assigned. This guarantees that until host_lock is released, the scsi_cmnd pointed to by cmd isn't released. That didn't hold in the original code and, theoretically, the original code could access already released cmd. * For the same reason, if shost->hostt->queuecommand() fails, we try to delete the timer before releasing host_lock. Other changes/notes * host_lock is acquired and released only once. enter (qlocked) -> enter loop -> dev-prep -> switch to hlock -\ ^---- switch to qlock <- issue <- host-prep <-/ * unnecessary if () on get_device() removed. * loop on elv_next_request() instead of blk_queue_plugged(). We now explicitly break out of loop when we plug and check if the queue has been plugged underneath us at the end of loop. * All device/host state checks are done in this function and done only once while holding qlock/host_lock respectively. * Requests which get deferred during dev-prep are never removed from request queue, so deferring is achieved by simply breaking out of the loop and returning. * Failure of blk_queue_start_tag() on tagged queue is a BUG now. This condition should have been catched by scsi_dev_queue_ready(). * req->special == NULL test removed. This just can't happen, and even if it ever happens, scsi_request_fn() will deterministically oops. * Requests which gets deferred during host-prep are requeued using blk_requeue_request(). This is the only requeue path. 04_scsi_reqfn_remove_wait_req_end_io.patch : remove unnecessary scsi_wait_req_end_io() As all requests are now terminated via scsi midlayer, we don't need to set end_io for special reqs, remove it. [ End of patch descriptions ] 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
