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authorFinn Thain <fthain@telegraphics.com.au>2019-06-18 04:37:57 +0300
committerMartin K. Petersen <martin.petersen@oracle.com>2019-06-20 22:21:33 +0300
commit0e9fdd2b315c0fde535336ea09499a927e415566 (patch)
treea3dd0529f49e6e396e8f699819c55faf2de68342 /drivers/scsi/NCR5380.c
parentc3c0fd9b108f6360ceaade790571be097df1f3ef (diff)
downloadlinux-0e9fdd2b315c0fde535336ea09499a927e415566.tar.xz
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 <schmitzmic@gmail.com> Reviewed-by: Michael Schmitz <schmitzmic@gmail.com> Reviewed-by: Christoph Hellwig <hch@lst.de> Reviewed-by: Bart Van Assche <bvanassche@acm.org> Signed-off-by: Finn Thain <fthain@telegraphics.com.au> Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
Diffstat (limited to 'drivers/scsi/NCR5380.c')
-rw-r--r--drivers/scsi/NCR5380.c41
1 files changed, 18 insertions, 23 deletions
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);