From 0e9fdd2b315c0fde535336ea09499a927e415566 Mon Sep 17 00:00:00 2001 From: Finn Thain Date: Tue, 18 Jun 2019 09:37:57 +0800 Subject: scsi: NCR5380: 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: Michael Schmitz Reviewed-by: Michael Schmitz Reviewed-by: Christoph Hellwig Reviewed-by: Bart Van Assche Signed-off-by: Finn Thain Signed-off-by: Martin K. Petersen --- drivers/scsi/NCR5380.c | 41 ++++++++++++++++++----------------------- 1 file changed, 18 insertions(+), 23 deletions(-) (limited to 'drivers/scsi/NCR5380.c') diff --git a/drivers/scsi/NCR5380.c b/drivers/scsi/NCR5380.c index fe0535affc14..4ef44fafe6ca 100644 --- a/drivers/scsi/NCR5380.c +++ b/drivers/scsi/NCR5380.c @@ -149,12 +149,10 @@ static inline void initialize_SCp(struct scsi_cmnd *cmd) if (scsi_bufflen(cmd)) { cmd->SCp.buffer = scsi_sglist(cmd); - cmd->SCp.buffers_residual = scsi_sg_count(cmd) - 1; cmd->SCp.ptr = sg_virt(cmd->SCp.buffer); cmd->SCp.this_residual = cmd->SCp.buffer->length; } else { cmd->SCp.buffer = NULL; - cmd->SCp.buffers_residual = 0; cmd->SCp.ptr = NULL; cmd->SCp.this_residual = 0; } @@ -163,6 +161,17 @@ static inline void initialize_SCp(struct scsi_cmnd *cmd) cmd->SCp.Message = 0; } +static inline void advance_sg_buffer(struct scsi_cmnd *cmd) +{ + struct scatterlist *s = cmd->SCp.buffer; + + if (!cmd->SCp.this_residual && s && !sg_is_last(s)) { + cmd->SCp.buffer = sg_next(s); + cmd->SCp.ptr = sg_virt(cmd->SCp.buffer); + cmd->SCp.this_residual = cmd->SCp.buffer->length; + } +} + /** * NCR5380_poll_politely2 - wait for two chip register values * @hostdata: host private data @@ -1672,12 +1681,7 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance) sun3_dma_setup_done != cmd) { int count; - if (!cmd->SCp.this_residual && cmd->SCp.buffers_residual) { - ++cmd->SCp.buffer; - --cmd->SCp.buffers_residual; - cmd->SCp.this_residual = cmd->SCp.buffer->length; - cmd->SCp.ptr = sg_virt(cmd->SCp.buffer); - } + advance_sg_buffer(cmd); count = sun3scsi_dma_xfer_len(hostdata, cmd); @@ -1727,15 +1731,11 @@ static void NCR5380_information_transfer(struct Scsi_Host *instance) * scatter-gather list, move onto the next one. */ - if (!cmd->SCp.this_residual && cmd->SCp.buffers_residual) { - ++cmd->SCp.buffer; - --cmd->SCp.buffers_residual; - cmd->SCp.this_residual = cmd->SCp.buffer->length; - cmd->SCp.ptr = sg_virt(cmd->SCp.buffer); - dsprintk(NDEBUG_INFORMATION, instance, "%d bytes and %d buffers left\n", - cmd->SCp.this_residual, - cmd->SCp.buffers_residual); - } + advance_sg_buffer(cmd); + dsprintk(NDEBUG_INFORMATION, instance, + "this residual %d, sg ents %d\n", + cmd->SCp.this_residual, + sg_nents(cmd->SCp.buffer)); /* * The preferred transfer method is going to be @@ -2136,12 +2136,7 @@ static void NCR5380_reselect(struct Scsi_Host *instance) if (sun3_dma_setup_done != tmp) { int count; - if (!tmp->SCp.this_residual && tmp->SCp.buffers_residual) { - ++tmp->SCp.buffer; - --tmp->SCp.buffers_residual; - tmp->SCp.this_residual = tmp->SCp.buffer->length; - tmp->SCp.ptr = sg_virt(tmp->SCp.buffer); - } + advance_sg_buffer(tmp); count = sun3scsi_dma_xfer_len(hostdata, tmp); -- cgit v1.2.3