Commit 013be038 authored Jun 18, 2019 by Ming Lei Committed by Martin K. Petersen Jun 20, 2019

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>

parent da556736

drivers/s390/scsi/zfcp_fc.c

+2 −2

Original line number	Diff line number	Diff line
		@@ -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);

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