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scsi: pmcraid: 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>
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@ -3270,7 +3270,7 @@ static int pmcraid_copy_sglist(
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int direction
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)
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{
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struct scatterlist *scatterlist;
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struct scatterlist *sg;
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void *kaddr;
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int bsize_elem;
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int i;
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@ -3279,10 +3279,10 @@ static int pmcraid_copy_sglist(
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/* Determine the actual number of bytes per element */
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bsize_elem = PAGE_SIZE * (1 << sglist->order);
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scatterlist = sglist->scatterlist;
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sg = sglist->scatterlist;
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for (i = 0; i < (len / bsize_elem); i++, buffer += bsize_elem) {
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struct page *page = sg_page(&scatterlist[i]);
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for (i = 0; i < (len / bsize_elem); i++, sg = sg_next(sg), buffer += bsize_elem) {
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struct page *page = sg_page(sg);
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kaddr = kmap(page);
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if (direction == DMA_TO_DEVICE)
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@ -3297,11 +3297,11 @@ static int pmcraid_copy_sglist(
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return -EFAULT;
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}
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scatterlist[i].length = bsize_elem;
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sg->length = bsize_elem;
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}
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if (len % bsize_elem) {
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struct page *page = sg_page(&scatterlist[i]);
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struct page *page = sg_page(sg);
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kaddr = kmap(page);
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@ -3312,7 +3312,7 @@ static int pmcraid_copy_sglist(
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kunmap(page);
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scatterlist[i].length = len % bsize_elem;
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sg->length = len % bsize_elem;
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}
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if (rc) {
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