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scsi: wd33c93: 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]

Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Bart Van Assche <bvanassche@acm.org>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
Signed-off-by: Martin K. Petersen <martin.petersen@oracle.com>
This commit is contained in:
Ming Lei 2019-06-18 09:37:56 +08:00 committed by Martin K. Petersen
parent 57ef4e5109
commit c3c0fd9b10
1 changed files with 1 additions and 1 deletions
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2
drivers/scsi/wd33c93.c
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@ -744,7 +744,7 @@ transfer_bytes(const wd33c93_regs regs, struct scsi_cmnd *cmd,
* source or destination for THIS transfer.
*/
if (!cmd->SCp.this_residual && cmd->SCp.buffers_residual) {
++cmd->SCp.buffer;
cmd->SCp.buffer = sg_next(cmd->SCp.buffer);
--cmd->SCp.buffers_residual;
cmd->SCp.this_residual = cmd->SCp.buffer->length;
cmd->SCp.ptr = sg_virt(cmd->SCp.buffer);