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scsi: s390: zfcp_fc: 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: Steffen Maier <maier@linux.ibm.com>
Cc: Benjamin Block <bblock@linux.ibm.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: linux-s390@vger.kernel.org
Acked-by: Benjamin Block <bblock@linux.ibm.com>
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 09:37:51 +08:00 committed by Martin K. Petersen
parent da5567369f
commit 013be03840
1 changed files with 2 additions and 2 deletions
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4
drivers/s390/scsi/zfcp_fc.c
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@ -620,7 +620,7 @@ static void zfcp_fc_sg_free_table(struct scatterlist *sg, int count)
{
int i;
for (i = 0; i < count; i++, sg++)
for (i = 0; i < count; i++, sg = sg_next(sg))
if (sg)
free_page((unsigned long) sg_virt(sg));
else
@ -641,7 +641,7 @@ static int zfcp_fc_sg_setup_table(struct scatterlist *sg, int count)
int i;
sg_init_table(sg, count);
for (i = 0; i < count; i++, sg++) {
for (i = 0; i < count; i++, sg = sg_next(sg)) {
addr = (void *) get_zeroed_page(GFP_KERNEL);
if (!addr) {
zfcp_fc_sg_free_table(sg, i);