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Subject[PATCH 3.12 66/88] scsi: remove scsi_end_request
Date
From: Christoph Hellwig <hch@lst.de>

3.12-stable review patch. If anyone has any objections, please let me know.

===============

commit bc85dc500f9df9b2eec15077e5046672c46adeaa upstream.

By folding scsi_end_request into its only caller we can significantly clean
up the completion logic. We can use simple goto labels now to only have
a single place to finish or requeue command there instead of the previous
convoluted logic.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Nicholas Bellinger <nab@linux-iscsi.org>
Reviewed-by: Mike Christie <michaelc@cs.wisc.edu>
Reviewed-by: Hannes Reinecke <hare@suse.de>
[jwang: backport to 3.12]
Signed-off-by: Jack Wang <jinpu.wang@profitbricks.com>
Signed-off-by: Jiri Slaby <jslaby@suse.cz>
---
drivers/scsi/scsi_lib.c | 113 +++++++++++++-----------------------------------
1 file changed, 31 insertions(+), 82 deletions(-)

diff --git a/drivers/scsi/scsi_lib.c b/drivers/scsi/scsi_lib.c
index 2b01c88ad416..4b7893364c7a 100644
--- a/drivers/scsi/scsi_lib.c
+++ b/drivers/scsi/scsi_lib.c
@@ -540,66 +540,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)

static void __scsi_release_buffers(struct scsi_cmnd *, int);

-/*
- * Function: scsi_end_request()
- *
- * Purpose: Post-processing of completed commands (usually invoked at end
- * of upper level post-processing and scsi_io_completion).
- *
- * Arguments: cmd - command that is complete.
- * error - 0 if I/O indicates success, < 0 for I/O error.
- * bytes - number of bytes of completed I/O
- * requeue - indicates whether we should requeue leftovers.
- *
- * Lock status: Assumed that lock is not held upon entry.
- *
- * Returns: cmd if requeue required, NULL otherwise.
- *
- * Notes: This is called for block device requests in order to
- * mark some number of sectors as complete.
- *
- * We are guaranteeing that the request queue will be goosed
- * at some point during this call.
- * Notes: If cmd was requeued, upon return it will be a stale pointer.
- */
-static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
- int bytes, int requeue)
-{
- struct request_queue *q = cmd->device->request_queue;
- struct request *req = cmd->request;
-
- /*
- * If there are blocks left over at the end, set up the command
- * to queue the remainder of them.
- */
- if (blk_end_request(req, error, bytes)) {
- /* kill remainder if no retrys */
- if (error && scsi_noretry_cmd(cmd))
- blk_end_request_all(req, error);
- else {
- if (requeue) {
- /*
- * Bleah. Leftovers again. Stick the
- * leftovers in the front of the
- * queue, and goose the queue again.
- */
- scsi_release_buffers(cmd);
- scsi_requeue_command(q, cmd);
- cmd = NULL;
- }
- return cmd;
- }
- }
-
- /*
- * This will goose the queue request function at the end, so we don't
- * need to worry about launching another command.
- */
- __scsi_release_buffers(cmd, 0);
- scsi_next_command(cmd);
- return NULL;
-}
-
static inline unsigned int scsi_sgtable_index(unsigned short nents)
{
unsigned int index;
@@ -751,16 +691,9 @@ static int __scsi_error_from_host_byte(struct scsi_cmnd *cmd, int result)
*
* Returns: Nothing
*
- * Notes: This function is matched in terms of capabilities to
- * the function that created the scatter-gather list.
- * In other words, if there are no bounce buffers
- * (the normal case for most drivers), we don't need
- * the logic to deal with cleaning up afterwards.
- *
- * We must call scsi_end_request(). This will finish off
- * the specified number of sectors. If we are done, the
- * command block will be released and the queue function
- * will be goosed. If we are not done then we have to
+ * Notes: We will finish off the specified number of sectors. If we
+ * are done, the command block will be released and the queue
+ * function will be goosed. If we are not done then we have to
* figure out what to do next:
*
* a) We can call scsi_requeue_command(). The request
@@ -769,7 +702,7 @@ static int __scsi_error_from_host_byte(struct scsi_cmnd *cmd, int result)
* be used if we made forward progress, or if we want
* to switch from READ(10) to READ(6) for example.
*
- * b) We can call scsi_queue_insert(). The request will
+ * b) We can call __scsi_queue_insert(). The request will
* be put back on the queue and retried using the same
* command as before, possibly after a delay.
*
@@ -873,12 +806,25 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
}

/*
- * A number of bytes were successfully read. If there
- * are leftovers and there is some kind of error
- * (result != 0), retry the rest.
+ * If we finished all bytes in the request we are done now.
*/
- if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
- return;
+ if (!blk_end_request(req, error, good_bytes))
+ goto next_command;
+
+ /*
+ * Kill remainder if no retrys.
+ */
+ if (error && scsi_noretry_cmd(cmd)) {
+ blk_end_request_all(req, error);
+ goto next_command;
+ }
+
+ /*
+ * If there had been no error, but we have leftover bytes in the
+ * requeues just queue the command up again.
+ */
+ if (result == 0)
+ goto requeue;

error = __scsi_error_from_host_byte(cmd, result);

@@ -1000,7 +946,6 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
switch (action) {
case ACTION_FAIL:
/* Give up and fail the remainder of the request */
- scsi_release_buffers(cmd);
if (!(req->cmd_flags & REQ_QUIET)) {
if (description)
scmd_printk(KERN_INFO, cmd, "%s\n",
@@ -1010,12 +955,11 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
scsi_print_sense("", cmd);
scsi_print_command(cmd);
}
- if (blk_end_request_err(req, error))
- scsi_requeue_command(q, cmd);
- else
- scsi_next_command(cmd);
- break;
+ if (!blk_end_request_err(req, error))
+ goto next_command;
+ /*FALLTHRU*/
case ACTION_REPREP:
+ requeue:
/* Unprep the request and put it back at the head of the queue.
* A new command will be prepared and issued.
*/
@@ -1031,6 +975,11 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
__scsi_queue_insert(cmd, SCSI_MLQUEUE_DEVICE_BUSY, 0);
break;
}
+ return;
+
+next_command:
+ __scsi_release_buffers(cmd, 0);
+ scsi_next_command(cmd);
}

static int scsi_init_sgtable(struct request *req, struct scsi_data_buffer *sdb,
--
2.9.1
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