Commit ee5a1dbf authored by Ming Lei's avatar Ming Lei Committed by Martin K. Petersen
Browse files

scsi: esp: use sg helper to iterate over scatterlist 



Unlike the legacy I/O path, scsi-mq preallocates a large array to hold
the scatterlist for each request. This static allocation can consume
substantial amounts of memory on modern controllers which support a
large number of concurrently outstanding requests.

To facilitate a switch to a smaller static allocation combined with a
dynamic allocation for requests that need it, we need to make sure all
SCSI drivers handle chained scatterlists correctly.

Convert remaining drivers that directly dereference the scatterlist
array to using the iterator functions.

[mkp: clarified commit message]

Cc: Christoph Hellwig <hch@lst.de>
Cc: Bart Van Assche <bvanassche@acm.org>
Cc: Ewan D. Milne <emilne@redhat.com>
Cc: Hannes Reinecke <hare@suse.com>
Cc: Finn Thain <fthain@telegraphics.com.au>
Cc: Guenter Roeck <linux@roeck-us.net>
Reported-by: default avatarGuenter Roeck <linux@roeck-us.net>
Tested-by: default avatarGuenter Roeck <linux@roeck-us.net>
Reviewed-by: default avatarFinn Thain <fthain@telegraphics.com.au>
Signed-off-by: default avatarMing Lei <ming.lei@redhat.com>
Signed-off-by: default avatarMartin K. Petersen <martin.petersen@oracle.com>
parent 0e9fdd2b

drivers/scsi/esp_scsi.c

+13 −7
Original line number Original line Diff line number Diff line
@@ -370,6 +370,7 @@ static void esp_map_dma(struct esp *esp, struct scsi_cmnd *cmd) 
	struct esp_cmd_priv *spriv = ESP_CMD_PRIV(cmd);

	struct esp_cmd_priv *spriv = ESP_CMD_PRIV(cmd);

	struct scatterlist *sg = scsi_sglist(cmd);

	struct scatterlist *sg = scsi_sglist(cmd);

	int total = 0, i;

	int total = 0, i;

	struct scatterlist *s;





	if (cmd->sc_data_direction == DMA_NONE)

	if (cmd->sc_data_direction == DMA_NONE)

		return;

		return;
@@ -380,16 +381,18 @@ static void esp_map_dma(struct esp *esp, struct scsi_cmnd *cmd) 
		 * a dma address, so perform an identity mapping.

		 * a dma address, so perform an identity mapping.

		 */

		 */

		spriv->num_sg = scsi_sg_count(cmd);

		spriv->num_sg = scsi_sg_count(cmd);

		for (i = 0; i < spriv->num_sg; i++) {



			sg[i].dma_address = (uintptr_t)sg_virt(&sg[i]);

		scsi_for_each_sg(cmd, s, spriv->num_sg, i) {

			total += sg_dma_len(&sg[i]);

			s->dma_address = (uintptr_t)sg_virt(s);

			total += sg_dma_len(s);

		}

		}

	} else {

	} else {

		spriv->num_sg = scsi_dma_map(cmd);

		spriv->num_sg = scsi_dma_map(cmd);

		for (i = 0; i < spriv->num_sg; i++)

		scsi_for_each_sg(cmd, s, spriv->num_sg, i)

			total += sg_dma_len(&sg[i]);

			total += sg_dma_len(s);

	}

	}

	spriv->cur_residue = sg_dma_len(sg);

	spriv->cur_residue = sg_dma_len(sg);

	spriv->prv_sg = NULL;

	spriv->cur_sg = sg;

	spriv->cur_sg = sg;

	spriv->tot_residue = total;

	spriv->tot_residue = total;

}

}
@@ -443,7 +446,8 @@ static void esp_advance_dma(struct esp *esp, struct esp_cmd_entry *ent, 
		p->tot_residue = 0;

		p->tot_residue = 0;

	}

	}

	if (!p->cur_residue && p->tot_residue) {

	if (!p->cur_residue && p->tot_residue) {

		p->cur_sg++;

		p->prv_sg = p->cur_sg;

		p->cur_sg = sg_next(p->cur_sg);

		p->cur_residue = sg_dma_len(p->cur_sg);

		p->cur_residue = sg_dma_len(p->cur_sg);

	}

	}

}

}
@@ -464,6 +468,7 @@ static void esp_save_pointers(struct esp *esp, struct esp_cmd_entry *ent) 
		return;

		return;

	}

	}

	ent->saved_cur_residue = spriv->cur_residue;

	ent->saved_cur_residue = spriv->cur_residue;

	ent->saved_prv_sg = spriv->prv_sg;

	ent->saved_cur_sg = spriv->cur_sg;

	ent->saved_cur_sg = spriv->cur_sg;

	ent->saved_tot_residue = spriv->tot_residue;

	ent->saved_tot_residue = spriv->tot_residue;

}

}
@@ -478,6 +483,7 @@ static void esp_restore_pointers(struct esp *esp, struct esp_cmd_entry *ent) 
		return;

		return;

	}

	}

	spriv->cur_residue = ent->saved_cur_residue;

	spriv->cur_residue = ent->saved_cur_residue;

	spriv->prv_sg = ent->saved_prv_sg;

	spriv->cur_sg = ent->saved_cur_sg;

	spriv->cur_sg = ent->saved_cur_sg;

	spriv->tot_residue = ent->saved_tot_residue;

	spriv->tot_residue = ent->saved_tot_residue;

}

}
@@ -1646,7 +1652,7 @@ static int esp_msgin_process(struct esp *esp) 
		spriv = ESP_CMD_PRIV(ent->cmd);

		spriv = ESP_CMD_PRIV(ent->cmd);





		if (spriv->cur_residue == sg_dma_len(spriv->cur_sg)) {

		if (spriv->cur_residue == sg_dma_len(spriv->cur_sg)) {

			spriv->cur_sg--;

			spriv->cur_sg = spriv->prv_sg;

			spriv->cur_residue = 1;

			spriv->cur_residue = 1;

		} else

		} else

			spriv->cur_residue++;

			spriv->cur_residue++;

drivers/scsi/esp_scsi.h

+2 −0
Original line number Original line Diff line number Diff line
@@ -251,6 +251,7 @@ 
struct esp_cmd_priv {

struct esp_cmd_priv {

	int			num_sg;

	int			num_sg;

	int			cur_residue;

	int			cur_residue;

	struct scatterlist	*prv_sg;

	struct scatterlist	*cur_sg;

	struct scatterlist	*cur_sg;

	int			tot_residue;

	int			tot_residue;

};

};
@@ -273,6 +274,7 @@ struct esp_cmd_entry { 
	struct scsi_cmnd	*cmd;

	struct scsi_cmnd	*cmd;





	unsigned int		saved_cur_residue;

	unsigned int		saved_cur_residue;

	struct scatterlist	*saved_prv_sg;

	struct scatterlist	*saved_cur_sg;

	struct scatterlist	*saved_cur_sg;

	unsigned int		saved_tot_residue;

	unsigned int		saved_tot_residue;

CRA Git | Maintained and supported by SUSTech CRA and CCSE