From ee5a1dbfec57cc1ffdedf2bd767c84d5e0498ed8 Mon Sep 17 00:00:00 2001 From: Ming Lei Date: Thu, 6 Jun 2019 16:34:10 +0800 Subject: [PATCH] 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 Cc: Bart Van Assche Cc: Ewan D. Milne Cc: Hannes Reinecke Cc: Finn Thain Cc: Guenter Roeck Reported-by: Guenter Roeck Tested-by: Guenter Roeck Reviewed-by: Finn Thain Signed-off-by: Ming Lei Signed-off-by: Martin K. Petersen --- drivers/scsi/esp_scsi.c | 20 +++++++++++++------- drivers/scsi/esp_scsi.h | 2 ++ 2 files changed, 15 insertions(+), 7 deletions(-) diff --git a/drivers/scsi/esp_scsi.c b/drivers/scsi/esp_scsi.c index 76fd02ccbf49..1e3ea9dc74d2 100644 --- a/drivers/scsi/esp_scsi.c +++ b/drivers/scsi/esp_scsi.c @@ -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 scatterlist *sg = scsi_sglist(cmd); int total = 0, i; + struct scatterlist *s; if (cmd->sc_data_direction == DMA_NONE) 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. */ 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]); - total += sg_dma_len(&sg[i]); + + scsi_for_each_sg(cmd, s, spriv->num_sg, i) { + s->dma_address = (uintptr_t)sg_virt(s); + total += sg_dma_len(s); } } else { spriv->num_sg = scsi_dma_map(cmd); - for (i = 0; i < spriv->num_sg; i++) - total += sg_dma_len(&sg[i]); + scsi_for_each_sg(cmd, s, spriv->num_sg, i) + total += sg_dma_len(s); } spriv->cur_residue = sg_dma_len(sg); + spriv->prv_sg = NULL; spriv->cur_sg = sg; 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; } 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); } } @@ -464,6 +468,7 @@ static void esp_save_pointers(struct esp *esp, struct esp_cmd_entry *ent) return; } ent->saved_cur_residue = spriv->cur_residue; + ent->saved_prv_sg = spriv->prv_sg; ent->saved_cur_sg = spriv->cur_sg; 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; } spriv->cur_residue = ent->saved_cur_residue; + spriv->prv_sg = ent->saved_prv_sg; spriv->cur_sg = ent->saved_cur_sg; 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); if (spriv->cur_residue == sg_dma_len(spriv->cur_sg)) { - spriv->cur_sg--; + spriv->cur_sg = spriv->prv_sg; spriv->cur_residue = 1; } else spriv->cur_residue++; diff --git a/drivers/scsi/esp_scsi.h b/drivers/scsi/esp_scsi.h index aa87a6b72dcc..91b32f2a1a1b 100644 --- a/drivers/scsi/esp_scsi.h +++ b/drivers/scsi/esp_scsi.h @@ -251,6 +251,7 @@ struct esp_cmd_priv { int num_sg; int cur_residue; + struct scatterlist *prv_sg; struct scatterlist *cur_sg; int tot_residue; }; @@ -273,6 +274,7 @@ struct esp_cmd_entry { struct scsi_cmnd *cmd; unsigned int saved_cur_residue; + struct scatterlist *saved_prv_sg; struct scatterlist *saved_cur_sg; unsigned int saved_tot_residue;