little bit of love to scsi_io_completion

PATCH In review Boaz Harrosh 3 participants 16 messages Jan 4, 2010 – Jan 5, 2010 SCSI

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Boaz Harrosh

author

2010-01-04 12:11 UTC #0 lore raw

cover little bit of love to scsi_io_completion

Three small incremental patches to clean up scsi_io_completion and friends. There should be absolutely no functional change after this patchset, only readability improvements.

This patchset should open up the stage for the fixes Alan needs and farther enhancements.

(Mike, Hannes, I know you have pending work here, please point me to patches and
I'll rebase them for you)

List of patches
[PATCH 1/3] scsi_lib: request_queue is only needed inside scsi_requeue_command [PATCH 2/3] scsi_lib: Remove that __scsi_release_buffers contraption [PATCH 3/3] scsi_lib: Collapse scsi_end_request into only user

Are on top of scsi-misc Please consider for inclusion Boaz

Boaz Harrosh

author

2010-01-04 12:13 UTC #1 lore raw

PATCH 1/3 scsi_lib: request_queue is only needed inside scsi_requeue_command

This is a pure cleanup. Just starting the engines for things to come.

Signed-off-by Boaz Harrosh <[email protected]>

---
 drivers/scsi/scsi_lib.c |   11 +++++------
 1 files changed, 5 insertions(+), 6 deletions(-)

drivers/scsi/scsi_lib.c +5 -6

index c664242..05f988a 100644
@@ -475,9 +475,10 @@ static void scsi_run_queue(struct request_queue *q)
  *		sector.
  * Notes:	Upon return, cmd is a stale pointer.
  */
-static void scsi_requeue_command(struct request_queue *q, struct scsi_cmnd *cmd)
+static void scsi_requeue_command(struct scsi_cmnd *cmd)
 {
 	struct request *req = cmd->request;
+	struct request_queue *q = req->q;
 	unsigned long flags;
 
 	spin_lock_irqsave(q->queue_lock, flags);

@@ -538,7 +539,6 @@ static void __scsi_release_buffers(struct scsi_cmnd *, int);
 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;
 
 	/*

@@ -557,7 +557,7 @@ static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
 				 * queue, and goose the queue again.
 				 */
 				scsi_release_buffers(cmd);
-				scsi_requeue_command(q, cmd);
+				scsi_requeue_command(cmd);
 				cmd = NULL;
 			}
 			return cmd;

@@ -706,7 +706,6 @@ EXPORT_SYMBOL(scsi_release_buffers);
 void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 {
 	int result = cmd->result;
-	struct request_queue *q = cmd->device->request_queue;
 	struct request *req = cmd->request;
 	int error = 0;
 	struct scsi_sense_hdr sshdr;

@@ -900,7 +899,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 			scsi_print_command(cmd);
 		}
 		if (blk_end_request_err(req, error))
-			scsi_requeue_command(q, cmd);
+			scsi_requeue_command(cmd);
 		else
 			scsi_next_command(cmd);
 		break;

@@ -909,7 +908,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		 * A new command will be prepared and issued.
 		 */
 		scsi_release_buffers(cmd);
-		scsi_requeue_command(q, cmd);
+		scsi_requeue_command(cmd);
 		break;
 	case ACTION_RETRY:
 		/* Retry the same command immediately */

Signature · 1 line

1.6.6

Boaz Harrosh

author

2010-01-04 12:15 UTC #2 lore raw

PATCH 2/3 scsi_lib: Remove that __scsi_release_buffers contraption

In reply to Boaz Harrosh

Remove "do_bidi_check" by checking and nullifying cmd->request when blk_end_* indicates the request is no longer valid.

Signed-off-by Boaz Harrosh <[email protected]>

---
 drivers/scsi/scsi_lib.c |   41 +++++++++++++++++------------------------
 1 files changed, 17 insertions(+), 24 deletions(-)

drivers/scsi/scsi_lib.c +17 ~~-24~~

index 05f988a..8d8b4eb 100644
@@ -512,8 +512,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-static void __scsi_release_buffers(struct scsi_cmnd *, int);
-
 /*
  * Function:    scsi_end_request()
  *

@@ -564,11 +562,12 @@ static struct scsi_cmnd *scsi_end_request(struct scsi_cmnd *cmd, int error,
 		}
 	}
 
+	cmd->request = NULL;
 	/*
 	 * 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_release_buffers(cmd);
 	scsi_next_command(cmd);
 	return NULL;
 }

@@ -624,26 +623,6 @@ static void scsi_free_sgtable(struct scsi_data_buffer *sdb)
 	__sg_free_table(&sdb->table, SCSI_MAX_SG_SEGMENTS, scsi_sg_free);
 }
 
-static void __scsi_release_buffers(struct scsi_cmnd *cmd, int do_bidi_check)
-{
-
-	if (cmd->sdb.table.nents)
-		scsi_free_sgtable(&cmd->sdb);
-
-	memset(&cmd->sdb, 0, sizeof(cmd->sdb));
-
-	if (do_bidi_check && scsi_bidi_cmnd(cmd)) {
-		struct scsi_data_buffer *bidi_sdb =
-			cmd->request->next_rq->special;
-		scsi_free_sgtable(bidi_sdb);
-		kmem_cache_free(scsi_sdb_cache, bidi_sdb);
-		cmd->request->next_rq->special = NULL;
-	}
-
-	if (scsi_prot_sg_count(cmd))
-		scsi_free_sgtable(cmd->prot_sdb);
-}
-
 /*
  * Function:    scsi_release_buffers()
  *

@@ -663,7 +642,21 @@ static void __scsi_release_buffers(struct scsi_cmnd *cmd, int do_bidi_check)
  */
 void scsi_release_buffers(struct scsi_cmnd *cmd)
 {
-	__scsi_release_buffers(cmd, 1);
+	if (cmd->sdb.table.nents)
+		scsi_free_sgtable(&cmd->sdb);
+
+	memset(&cmd->sdb, 0, sizeof(cmd->sdb));
+
+	if (cmd->request && scsi_bidi_cmnd(cmd)) {
+		struct scsi_data_buffer *bidi_sdb =
+			cmd->request->next_rq->special;
+		scsi_free_sgtable(bidi_sdb);
+		kmem_cache_free(scsi_sdb_cache, bidi_sdb);
+		cmd->request->next_rq->special = NULL;
+	}
+
+	if (scsi_prot_sg_count(cmd))
+		scsi_free_sgtable(cmd->prot_sdb);
 }
 EXPORT_SYMBOL(scsi_release_buffers);

Signature · 1 line

1.6.6

Boaz Harrosh

author

2010-01-04 12:17 UTC #3 lore raw

PATCH 3/3 scsi_lib: Collapse scsi_end_request into only user

In reply to Boaz Harrosh

Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.

There is absolutely no functional and/or side effects changes after this patch.

Patch was inspired by Alan Stern.

CC Alan Stern <[email protected]>

Signed-off-by Boaz Harrosh <[email protected]>

---
 drivers/scsi/scsi_lib.c |   90 +++++++++++-----------------------------------
 1 files changed, 22 insertions(+), 68 deletions(-)

drivers/scsi/scsi_lib.c +22 ~~-68~~

index 8d8b4eb..326b228 100644
@@ -512,66 +512,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-/*
- * 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 *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(cmd);
-				cmd = NULL;
-			}
-			return cmd;
-		}
-	}
-
-	cmd->request = NULL;
-	/*
-	 * 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);
-	scsi_next_command(cmd);
-	return NULL;
-}
-
 static inline unsigned int scsi_sgtable_index(unsigned short nents)
 {
 	unsigned int index;

@@ -704,7 +644,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	struct scsi_sense_hdr sshdr;
 	int sense_valid = 0;
 	int sense_deferred = 0;
-	enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
+	enum {ACTION_FAIL, ACTION_REPREP, ACTION_NEXT_CMND, ACTION_RETRY,
 	      ACTION_DELAYED_RETRY} action;
 	char *description = NULL;

@@ -773,13 +713,22 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		error = 0;
 	}
 
-	/*
-	 * A number of bytes were successfully read.  If there
-	 * are leftovers and there is some kind of error
-	 * (result != 0), retry the rest.
-	 */
-	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
-		return;
+	if (!blk_end_request(req, error, good_bytes)) {
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+		goto do_action;
+	}
+
+	if (error && scsi_noretry_cmd(cmd)) {
+		/* kill remainder if no retrys */
+		blk_end_request_all(req, error);
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+		goto do_action;
+	} else if (result == 0) {
+		action = ACTION_REPREP;
+		goto do_action;
+	}
 
 	error = -EIO;

@@ -878,6 +827,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		action = ACTION_FAIL;
 	}
 
+do_action:
 	switch (action) {
 	case ACTION_FAIL:
 		/* Give up and fail the remainder of the request */

@@ -896,6 +846,10 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		else
 			scsi_next_command(cmd);
 		break;
+	case ACTION_NEXT_CMND:
+		scsi_release_buffers(cmd);
+		scsi_next_command(cmd);
+		break;
 	case ACTION_REPREP:
 		/* Unprep the request and put it back at the head of the queue.
 		 * A new command will be prepared and issued.

Signature · 1 line

1.6.6

Matthew Wilcox

2010-01-04 13:23 UTC #4 lore raw

Re: [PATCH 3/3] scsi_lib: Collapse scsi_end_request into only user

Quoted 2 lines · Boaz Harrosh

Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.

I'm not entirely convinced about that -- scsi_io_completion is currently over 200 lines long and needs to be made shorter, not longer. That said, I see no reason that the current factoring of scsi_io_completion() makes sense; pushing the decoding of the sense key into a separate function looks like a more profitable idea. It would also let you do without the nasty gotos you add in this patch.

Quoted 147 lines

There is absolutely no functional and/or side effects changes after this patch.

Patch was inspired by Alan Stern.

CC Alan Stern <[email protected]>

Signed-off-by Boaz Harrosh <[email protected]>

---
 drivers/scsi/scsi_lib.c |   90 +++++++++++-----------------------------------
 1 files changed, 22 insertions(+), 68 deletions(-)

drivers/scsi/scsi_lib.c +22 ~~-68~~

index 8d8b4eb..326b228 100644
@@ -512,66 +512,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-/*
- * 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 *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(cmd);
-				cmd = NULL;
-			}
-			return cmd;
-		}
-	}
-
-	cmd->request = NULL;
-	/*
-	 * 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);
-	scsi_next_command(cmd);
-	return NULL;
-}
-
 static inline unsigned int scsi_sgtable_index(unsigned short nents)
 {
 	unsigned int index;

@@ -704,7 +644,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	struct scsi_sense_hdr sshdr;
 	int sense_valid = 0;
 	int sense_deferred = 0;
-	enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
+	enum {ACTION_FAIL, ACTION_REPREP, ACTION_NEXT_CMND, ACTION_RETRY,
 	      ACTION_DELAYED_RETRY} action;
 	char *description = NULL;

@@ -773,13 +713,22 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		error = 0;
 	}
 
-	/*
-	 * A number of bytes were successfully read.  If there
-	 * are leftovers and there is some kind of error
-	 * (result != 0), retry the rest.
-	 */
-	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
-		return;
+	if (!blk_end_request(req, error, good_bytes)) {
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+		goto do_action;
+	}
+
+	if (error && scsi_noretry_cmd(cmd)) {
+		/* kill remainder if no retrys */
+		blk_end_request_all(req, error);
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+		goto do_action;
+	} else if (result == 0) {
+		action = ACTION_REPREP;
+		goto do_action;
+	}
 
 	error = -EIO;

@@ -878,6 +827,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		action = ACTION_FAIL;
 	}
 
+do_action:
 	switch (action) {
 	case ACTION_FAIL:
 		/* Give up and fail the remainder of the request */

@@ -896,6 +846,10 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		else
 			scsi_next_command(cmd);
 		break;
+	case ACTION_NEXT_CMND:
+		scsi_release_buffers(cmd);
+		scsi_next_command(cmd);
+		break;
 	case ACTION_REPREP:
 		/* Unprep the request and put it back at the head of the queue.
 		 * A new command will be prepared and issued.

Signature · 7 lines

1.6.6


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Signature · 4 lines

Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."

Boaz Harrosh

author

2010-01-04 13:56 UTC #5 lore raw

Re: [PATCH 3/3] scsi_lib: Collapse scsi_end_request into only user

Quoted 11 lines · Matthew Wilcox

Quoted 2 lines · Boaz Harrosh
Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.
I'm not entirely convinced about that -- scsi_io_completion is currently over 200 lines long and needs to be made shorter, not longer. That said, I see no reason that the current factoring of scsi_io_completion() makes sense; pushing the decoding of the sense key into a separate function looks like a more profitable idea. It would also let you do without the nasty gotos you add in this patch.

I agree, but I want that Alan's retries handling, Hannes's sense for FS_COMMANDS and mainly the question about good_bytes!=0 and retries are answered first. Then we can see what the code is really like and make a clean cut.

I'll attempt a second version without the goto.

Quoted 6 lines

Quoted 6 lines
There is absolutely no functional and/or side effects changes after this patch.
Patch was inspired by Alan Stern.
CC Alan Stern <[email protected]>
Signed-off-by Boaz Harrosh <[email protected]>

<snip>

Boaz

Boaz Harrosh

author

2010-01-04 14:07 UTC #6 lore raw

PATCH 3/3 scsi_lib: Collapse scsi_end_request into only user

In reply to Boaz Harrosh

Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.

There is absolutely no functional and/or side effects changes after this patch.

Patch was inspired by Alan Stern. (version 2 comments by Matthew Wilcox)

CC Alan Stern <[email protected]>

CC Matthew Wilcox <[email protected]>

Signed-off-by Boaz Harrosh <[email protected]>

---
 drivers/scsi/scsi_lib.c |   90 +++++++++--------------------------------------
 1 files changed, 17 insertions(+), 73 deletions(-)

drivers/scsi/scsi_lib.c +17 ~~-73~~

index 8d8b4eb..48ebc96 100644
@@ -512,66 +512,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-/*
- * 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 *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(cmd);
-				cmd = NULL;
-			}
-			return cmd;
-		}
-	}
-
-	cmd->request = NULL;
-	/*
-	 * 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);
-	scsi_next_command(cmd);
-	return NULL;
-}
-
 static inline unsigned int scsi_sgtable_index(unsigned short nents)
 {
 	unsigned int index;

@@ -704,7 +644,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	struct scsi_sense_hdr sshdr;
 	int sense_valid = 0;
 	int sense_deferred = 0;
-	enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
+	enum {ACTION_FAIL, ACTION_REPREP, ACTION_NEXT_CMND, ACTION_RETRY,
 	      ACTION_DELAYED_RETRY} action;
 	char *description = NULL;

@@ -773,17 +713,17 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		error = 0;
 	}
 
-	/*
-	 * A number of bytes were successfully read.  If there
-	 * are leftovers and there is some kind of error
-	 * (result != 0), retry the rest.
-	 */
-	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
-		return;
-
-	error = -EIO;
-
-	if (host_byte(result) == DID_RESET) {
+	if (likely(!blk_end_request(req, error, good_bytes))) {
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (error && scsi_noretry_cmd(cmd)) {
+		/* kill remainder if no retrys */
+		blk_end_request_all(req, error);
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (result == 0) {
+		action = ACTION_REPREP;
+	} else if (host_byte(result) == DID_RESET) {
 		/* Third party bus reset or reset for error recovery
 		 * reasons.  Just retry the command and see what
 		 * happens.

@@ -891,11 +831,15 @@ 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))
+		if (blk_end_request_err(req, error ? error : -EIO))
 			scsi_requeue_command(cmd);
 		else
 			scsi_next_command(cmd);
 		break;
+	case ACTION_NEXT_CMND:
+		scsi_release_buffers(cmd);
+		scsi_next_command(cmd);
+		break;
 	case ACTION_REPREP:
 		/* Unprep the request and put it back at the head of the queue.
 		 * A new command will be prepared and issued.

Signature · 1 line

1.6.6

Boaz Harrosh

author

2010-01-04 14:12 UTC #7 lore raw

Re: [PATCH 3/3 version 2] scsi_lib: Collapse scsi_end_request into only user

Quoted 8 lines · Boaz Harrosh

Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.
There is absolutely no functional and/or side effects changes after this patch.
Patch was inspired by Alan Stern. (version 2 comments by Matthew Wilcox)

Matthew please check me out here. I want absolutely equivalent code. I think Alan's mistake was to introduce enhancements together with cleanups. The issue is with "error = -EIO" but since error is only used at blk_end_request_err I think this approach is correct and is goto-less.

Thanks for reviewing

Boaz

Quoted 133 lines

CC Alan Stern <[email protected]>

CC Matthew Wilcox <[email protected]>

Signed-off-by Boaz Harrosh <[email protected]>

---
 drivers/scsi/scsi_lib.c |   90 +++++++++--------------------------------------
 1 files changed, 17 insertions(+), 73 deletions(-)

drivers/scsi/scsi_lib.c +17 ~~-73~~

index 8d8b4eb..48ebc96 100644
@@ -512,66 +512,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-/*
- * 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 *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(cmd);
-				cmd = NULL;
-			}
-			return cmd;
-		}
-	}
-
-	cmd->request = NULL;
-	/*
-	 * 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);
-	scsi_next_command(cmd);
-	return NULL;
-}
-
 static inline unsigned int scsi_sgtable_index(unsigned short nents)
 {
 	unsigned int index;

@@ -704,7 +644,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	struct scsi_sense_hdr sshdr;
 	int sense_valid = 0;
 	int sense_deferred = 0;
-	enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
+	enum {ACTION_FAIL, ACTION_REPREP, ACTION_NEXT_CMND, ACTION_RETRY,
 	      ACTION_DELAYED_RETRY} action;
 	char *description = NULL;

@@ -773,17 +713,17 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		error = 0;
 	}
 
-	/*
-	 * A number of bytes were successfully read.  If there
-	 * are leftovers and there is some kind of error
-	 * (result != 0), retry the rest.
-	 */
-	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
-		return;
-
-	error = -EIO;
-
-	if (host_byte(result) == DID_RESET) {
+	if (likely(!blk_end_request(req, error, good_bytes))) {
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (error && scsi_noretry_cmd(cmd)) {
+		/* kill remainder if no retrys */
+		blk_end_request_all(req, error);
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (result == 0) {
+		action = ACTION_REPREP;
+	} else if (host_byte(result) == DID_RESET) {
 		/* Third party bus reset or reset for error recovery
 		 * reasons.  Just retry the command and see what
 		 * happens.

@@ -891,11 +831,15 @@ 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))
+		if (blk_end_request_err(req, error ? error : -EIO))
 			scsi_requeue_command(cmd);
 		else
 			scsi_next_command(cmd);
 		break;
+	case ACTION_NEXT_CMND:
+		scsi_release_buffers(cmd);
+		scsi_next_command(cmd);
+		break;
 	case ACTION_REPREP:
 		/* Unprep the request and put it back at the head of the queue.
 		 * A new command will be prepared and issued.

Alan Stern

2010-01-04 18:23 UTC #8 lore raw

Re: [PATCH 3/3 version 2] scsi_lib: Collapse scsi_end_request into only user

In reply to Boaz Harrosh

Quoted 19 lines · Boaz Harrosh

Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.
There is absolutely no functional and/or side effects changes after this patch.
Patch was inspired by Alan Stern. (version 2 comments by Matthew Wilcox)
drivers/scsi/scsi_lib.c +1 ~~-11~~
-	/*
-	 * A number of bytes were successfully read.  If there
-	 * are leftovers and there is some kind of error
-	 * (result != 0), retry the rest.
-	 */
-	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
-		return;
-
-	error = -EIO;
-
-	if (host_byte(result) == DID_RESET) {
+	if (likely(!blk_end_request(req, error, good_bytes))) {

drivers/scsi/scsi_lib.c void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) · line 726

Quoted 10 lines

drivers/scsi/scsi_lib.c +10 -0

+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (error && scsi_noretry_cmd(cmd)) {
+		/* kill remainder if no retrys */
+		blk_end_request_all(req, error);
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (result == 0) {
+		action = ACTION_REPREP;
+	} else if (host_byte(result) == DID_RESET) {

A few comments in these new "if" cases would help readers to understand the logic here.

My personal preference is to reverse the order of the "if (error && scsi_noretry_cmd(cmd))" and the "if (result == 0)" sections. It would make more sense; that way we'd have:

	If the request is finished [blk_end_request() == 0]
		...
	else if the request was successful but has more work to do
			(result == 0)
		...
	else if there was an error and retries are disallowed
		...
	else ... [other error handling]

Interchanging the order wouldn't make any functional difference, because the code above this point guarantees that we can never have result == 0 and error != 0.

Apart from these small issues, it looks perfect.

Alan Stern

Boaz Harrosh

author

2010-01-05 07:27 UTC #9 lore raw

Re: [PATCH 3/3 version 2] scsi_lib: Collapse scsi_end_request into only user

Quoted 48 lines · Alan Stern

Quoted 19 lines · Boaz Harrosh
Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.
There is absolutely no functional and/or side effects changes after this patch.
Patch was inspired by Alan Stern. (version 2 comments by Matthew Wilcox)
drivers/scsi/scsi_lib.c +1 ~~-11~~
-	/*
-	 * A number of bytes were successfully read.  If there
-	 * are leftovers and there is some kind of error
-	 * (result != 0), retry the rest.
-	 */
-	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
-		return;
-
-	error = -EIO;
-
-	if (host_byte(result) == DID_RESET) {
+	if (likely(!blk_end_request(req, error, good_bytes))) {
drivers/scsi/scsi_lib.c void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) · line 726
Quoted 10 lines
drivers/scsi/scsi_lib.c +10 -0
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (error && scsi_noretry_cmd(cmd)) {
+		/* kill remainder if no retrys */
+		blk_end_request_all(req, error);
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (result == 0) {
+		action = ACTION_REPREP;
+	} else if (host_byte(result) == DID_RESET) {
A few comments in these new "if" cases would help readers to understand the logic here.
My personal preference is to reverse the order of the "if (error && scsi_noretry_cmd(cmd))" and the "if (result == 0)" sections. It would make more sense; that way we'd have:
	If the request is finished [blk_end_request() == 0]
		...
	else if the request was successful but has more work to do
			(result == 0)
		...
	else if there was an error and retries are disallowed
		...
	else ... [other error handling]

Quoted 8 lines

Interchanging the order wouldn't make any functional difference, because the code above this point guarantees that we can never have result == 0 and error != 0.
Apart from these small issues, it looks perfect.
Alan Stern

Thanks Alan.

I agree with your comments and will send a new version.

Boaz

Boaz Harrosh

author

2010-01-05 07:53 UTC #10 lore raw

PATCH 3/3 scsi_lib: Collapse scsi_end_request into only user

In reply to Boaz Harrosh

Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.

There is absolutely no functional and/or side effects changes after this patch.

Patch was inspired by Alan Stern.

CC Alan Stern <[email protected]>

CC Matthew Wilcox <[email protected]>

Signed-off-by Boaz Harrosh <[email protected]>

---
 drivers/scsi/scsi_lib.c |   92 ++++++++++-------------------------------------
 1 files changed, 19 insertions(+), 73 deletions(-)

drivers/scsi/scsi_lib.c +19 ~~-73~~

index 8d8b4eb..41df4e8 100644
@@ -512,66 +512,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-/*
- * 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 *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(cmd);
-				cmd = NULL;
-			}
-			return cmd;
-		}
-	}
-
-	cmd->request = NULL;
-	/*
-	 * 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);
-	scsi_next_command(cmd);
-	return NULL;
-}
-
 static inline unsigned int scsi_sgtable_index(unsigned short nents)
 {
 	unsigned int index;

@@ -704,7 +644,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	struct scsi_sense_hdr sshdr;
 	int sense_valid = 0;
 	int sense_deferred = 0;
-	enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
+	enum {ACTION_FAIL, ACTION_REPREP, ACTION_NEXT_CMND, ACTION_RETRY,
 	      ACTION_DELAYED_RETRY} action;
 	char *description = NULL;

@@ -773,17 +713,19 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		error = 0;
 	}
 
-	/*
-	 * A number of bytes were successfully read.  If there
-	 * are leftovers and there is some kind of error
-	 * (result != 0), retry the rest.
-	 */
-	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
-		return;
-
-	error = -EIO;
-
-	if (host_byte(result) == DID_RESET) {
+	if (likely(0 == blk_end_request(req, error, good_bytes))) {
+		/* All is done and good move to next command */
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (result == 0) {
+		/* Wrote some bytes but request was split */
+		action = ACTION_REPREP;
+	} else if (error && scsi_noretry_cmd(cmd)) {
+		/* kill remainder if no retries */
+		blk_end_request_all(req, error);
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (host_byte(result) == DID_RESET) {
 		/* Third party bus reset or reset for error recovery
 		 * reasons.  Just retry the command and see what
 		 * happens.

@@ -891,11 +833,15 @@ 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))
+		if (blk_end_request_err(req, error ? error : -EIO))
 			scsi_requeue_command(cmd);
 		else
 			scsi_next_command(cmd);
 		break;
+	case ACTION_NEXT_CMND:
+		scsi_release_buffers(cmd);
+		scsi_next_command(cmd);
+		break;
 	case ACTION_REPREP:
 		/* Unprep the request and put it back at the head of the queue.
 		 * A new command will be prepared and issued.

Signature · 1 line

1.6.6

Boaz Harrosh

author

2010-01-05 08:49 UTC #11 lore raw

Re: [PATCH 3/3 version 3] scsi_lib: Collapse scsi_end_request into only user

Quoted 131 lines · Boaz Harrosh

Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.

There is absolutely no functional and/or side effects changes after this patch.

Patch was inspired by Alan Stern.

CC Alan Stern <[email protected]>

CC Matthew Wilcox <[email protected]>

Signed-off-by Boaz Harrosh <[email protected]>

---
 drivers/scsi/scsi_lib.c |   92 ++++++++++-------------------------------------
 1 files changed, 19 insertions(+), 73 deletions(-)

drivers/scsi/scsi_lib.c +14 ~~-72~~

index 8d8b4eb..41df4e8 100644
@@ -512,66 +512,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-/*
- * 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 *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(cmd);
-				cmd = NULL;
-			}
-			return cmd;
-		}
-	}
-
-	cmd->request = NULL;
-	/*
-	 * 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);
-	scsi_next_command(cmd);
-	return NULL;
-}
-
 static inline unsigned int scsi_sgtable_index(unsigned short nents)
 {
 	unsigned int index;

@@ -704,7 +644,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	struct scsi_sense_hdr sshdr;
 	int sense_valid = 0;
 	int sense_deferred = 0;
-	enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
+	enum {ACTION_FAIL, ACTION_REPREP, ACTION_NEXT_CMND, ACTION_RETRY,
 	      ACTION_DELAYED_RETRY} action;
 	char *description = NULL;

@@ -773,17 +713,19 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		error = 0;
 	}
 
-	/*
-	 * A number of bytes were successfully read.  If there
-	 * are leftovers and there is some kind of error
-	 * (result != 0), retry the rest.
-	 */
-	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
-		return;
-
-	error = -EIO;
-
-	if (host_byte(result) == DID_RESET) {
+	if (likely(0 == blk_end_request(req, error, good_bytes))) {
+		/* All is done and good move to next command */
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (result == 0) {
+		/* Wrote some bytes but request was split */
+		action = ACTION_REPREP;
+	} else if (error && scsi_noretry_cmd(cmd)) {
+		/* kill remainder if no retries */
+		blk_end_request_all(req, error);
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (host_byte(result) == DID_RESET) {
 		/* Third party bus reset or reset for error recovery
 		 * reasons.  Just retry the command and see what
 		 * happens.

@@ -891,11 +833,15 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 				scsi_print_sense("", cmd);
 			scsi_print_command(cmd);
 		}

drivers/scsi/scsi_lib.c void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) · line 844

Quoted 10 lines

drivers/scsi/scsi_lib.c +5 -1

-		if (blk_end_request_err(req, error))
+		if (blk_end_request_err(req, error ? error : -EIO))
 			scsi_requeue_command(cmd);
 		else
 			scsi_next_command(cmd);
 		break;
+	case ACTION_NEXT_CMND:
+		scsi_release_buffers(cmd);
+		scsi_next_command(cmd);
+		break;

In a switch expression, Does the first case have an advantage?
I would think that even if the branch predictor does it's job the cache proximity to the head of the switch would matter. Is there a likely() for case statements?

In anyway I thinks I'll send a 4th version with this case at the top of the switch

Boaz

Quoted 3 lines

drivers/scsi/scsi_lib.c +0 -0

 	case ACTION_REPREP:
 		/* Unprep the request and put it back at the head of the queue.
 		 * A new command will be prepared and issued.

Boaz Harrosh

author

2010-01-05 09:07 UTC #12 lore raw

PATCH 3/3 scsi_lib: Collapse scsi_end_request into only user

In reply to Boaz Harrosh

Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.

There is absolutely no functional and/or side effects changes after this patch.

Patch was inspired by Alan Stern.

CC Alan Stern <[email protected]>

CC Matthew Wilcox <[email protected]>

Signed-off-by Boaz Harrosh <[email protected]>

---
 drivers/scsi/scsi_lib.c |   92 ++++++++++-------------------------------------
 1 files changed, 19 insertions(+), 73 deletions(-)

drivers/scsi/scsi_lib.c +19 ~~-73~~

index 8d8b4eb..523453f 100644
@@ -512,66 +512,6 @@ void scsi_run_host_queues(struct Scsi_Host *shost)
 		scsi_run_queue(sdev->request_queue);
 }
 
-/*
- * 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 *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(cmd);
-				cmd = NULL;
-			}
-			return cmd;
-		}
-	}
-
-	cmd->request = NULL;
-	/*
-	 * 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);
-	scsi_next_command(cmd);
-	return NULL;
-}
-
 static inline unsigned int scsi_sgtable_index(unsigned short nents)
 {
 	unsigned int index;

@@ -704,7 +644,7 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	struct scsi_sense_hdr sshdr;
 	int sense_valid = 0;
 	int sense_deferred = 0;
-	enum {ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
+	enum {ACTION_NEXT_CMND, ACTION_FAIL, ACTION_REPREP, ACTION_RETRY,
 	      ACTION_DELAYED_RETRY} action;
 	char *description = NULL;

@@ -773,17 +713,19 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 		error = 0;
 	}
 
-	/*
-	 * A number of bytes were successfully read.  If there
-	 * are leftovers and there is some kind of error
-	 * (result != 0), retry the rest.
-	 */
-	if (scsi_end_request(cmd, error, good_bytes, result == 0) == NULL)
-		return;
-
-	error = -EIO;
-
-	if (host_byte(result) == DID_RESET) {
+	if (likely(0 == blk_end_request(req, error, good_bytes))) {
+		/* All is done and good move to next command */
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (result == 0) {
+		/* Wrote some bytes but request was split */
+		action = ACTION_REPREP;
+	} else if (error && scsi_noretry_cmd(cmd)) {
+		/* kill remainder if no retries */
+		blk_end_request_all(req, error);
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (host_byte(result) == DID_RESET) {
 		/* Third party bus reset or reset for error recovery
 		 * reasons.  Just retry the command and see what
 		 * happens.

@@ -879,6 +821,10 @@ void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes)
 	}
 
 	switch (action) {
+	case ACTION_NEXT_CMND :
+		scsi_release_buffers(cmd);
+		scsi_next_command(cmd);
+		break;
 	case ACTION_FAIL:
 		/* Give up and fail the remainder of the request */
 		scsi_release_buffers(cmd);

@@ -891,7 +837,7 @@ 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))
+		if (blk_end_request_err(req, error ? error : -EIO))
 			scsi_requeue_command(cmd);
 		else
 			scsi_next_command(cmd);

Signature · 1 line

1.6.6

Alan Stern

2010-01-05 15:20 UTC #13 lore raw

Re: [PATCH 3/3 version 4] scsi_lib: Collapse scsi_end_request into only user

Quoted 5 lines · Boaz Harrosh

Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.
There is absolutely no functional and/or side effects changes after this patch.

Here are some suggestions for changes to the comments. These are quite minor and you might not want to bother updating the patch yet again...

drivers/scsi/scsi_lib.c void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) · line 717

Quoted 2 lines

drivers/scsi/scsi_lib.c +2 -0

+	if (likely(0 == blk_end_request(req, error, good_bytes))) {
+		/* All is done and good move to next command */

		/* The command completed successfully; move on to the next. */

drivers/scsi/scsi_lib.c void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) · line 721

Quoted 4 lines

drivers/scsi/scsi_lib.c +4 -0

+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (result == 0) {
+		/* Wrote some bytes but request was split */

		/* The command was successful but not all the data was
		 * transferred; re-prep the command to handle the rest.
		 */

drivers/scsi/scsi_lib.c void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) · line 724

Quoted 3 lines

drivers/scsi/scsi_lib.c +3 -0

+		action = ACTION_REPREP;
+	} else if (error && scsi_noretry_cmd(cmd)) {
+		/* kill remainder if no retries */

		/* Error.  Kill the request since retries are disallowed. */

drivers/scsi/scsi_lib.c void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) · line 728

Quoted 4 lines

drivers/scsi/scsi_lib.c +4 -0

+		blk_end_request_all(req, error);
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (host_byte(result) == DID_RESET) {

Alan Stern

Boaz Harrosh

author

2010-01-05 16:24 UTC #14 lore raw

Re: [PATCH 3/3 version 4] scsi_lib: Collapse scsi_end_request into only user

Quoted 11 lines · Alan Stern

Quoted 5 lines · Boaz Harrosh
Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.
There is absolutely no functional and/or side effects changes after this patch.
Here are some suggestions for changes to the comments. These are quite minor and you might not want to bother updating the patch yet again...

Sure, NP. thanks for checking me out, coming from Hebrew I do need support in these matters. Will update tomorrow.

Alan can I add your Review-by: this time around?

Quoted 20 lines

drivers/scsi/scsi_lib.c void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) · line 717
Quoted 2 lines
drivers/scsi/scsi_lib.c +2 -0
+	if (likely(0 == blk_end_request(req, error, good_bytes))) {
+		/* All is done and good move to next command */
		/* The command completed successfully; move on to the next. */
drivers/scsi/scsi_lib.c void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) · line 721
Quoted 4 lines
drivers/scsi/scsi_lib.c +4 -0
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (result == 0) {
+		/* Wrote some bytes but request was split */
		/* The command was successful but not all the data was
		 * transferred; re-prep the command to handle the rest.
		 */
drivers/scsi/scsi_lib.c void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) · line 724
Quoted 3 lines
drivers/scsi/scsi_lib.c +3 -0
+		action = ACTION_REPREP;
+	} else if (error && scsi_noretry_cmd(cmd)) {
+		/* kill remainder if no retries */
		/* Error.  Kill the request since retries are disallowed. */

Quoted 7 lines

drivers/scsi/scsi_lib.c void scsi_io_completion(struct scsi_cmnd *cmd, unsigned int good_bytes) · line 728
Quoted 4 lines
drivers/scsi/scsi_lib.c +4 -0
+		blk_end_request_all(req, error);
+		cmd->request = NULL;
+		action = ACTION_NEXT_CMND;
+	} else if (host_byte(result) == DID_RESET) {
Alan Stern

Thanks
Boaz

Alan Stern

2010-01-05 16:33 UTC #15 lore raw

Re: [PATCH 3/3 version 4] scsi_lib: Collapse scsi_end_request into only user

Quoted 9 lines · Boaz Harrosh

Quoted 8 lines · Alan Stern
Quoted 5 lines · Boaz Harrosh
Embedding scsi_end_request() into scsi_io_completion actually simplifies the code and makes it clearer what's going on.
There is absolutely no functional and/or side effects changes after this patch.

Quoted 8 lines

Quoted 3 lines
Here are some suggestions for changes to the comments. These are quite minor and you might not want to bother updating the patch yet again...
Sure, NP. thanks for checking me out, coming from Hebrew I do need support in these matters. Will update tomorrow.
Alan can I add your Review-by: this time around?

Yes. This is a good step. It will make adding functional changes a lot easier, and it will help if anyone wants to split up scsi_io_completion() into several smaller routines.

Alan Stern