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@@ -0,0 +1,114 @@
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+/*
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+ * Functions related to segment and merge handling
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+ */
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+#include <linux/kernel.h>
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+#include <linux/module.h>
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+#include <linux/bio.h>
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+#include <linux/blkdev.h>
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+#include <linux/scatterlist.h>
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+
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+#include "blk.h"
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+
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+static unsigned int __blk_recalc_rq_segments(struct request_queue *q,
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+ struct bio *bio)
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+{
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+ struct bio_vec *bv, *bvprv = NULL;
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+ int cluster, i, high, highprv = 1;
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+ unsigned int seg_size, nr_phys_segs;
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+ struct bio *fbio, *bbio;
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+
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+ if (!bio)
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+ return 0;
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+
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+ fbio = bio;
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+ cluster = blk_queue_cluster(q);
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+ seg_size = 0;
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+ nr_phys_segs = 0;
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+ for_each_bio(bio) {
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+ bio_for_each_segment(bv, bio, i) {
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+ /*
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+ * the trick here is making sure that a high page is
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+ * never considered part of another segment, since that
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+ * might change with the bounce page.
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+ */
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+ high = page_to_pfn(bv->bv_page) > queue_bounce_pfn(q);
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+ if (high || highprv)
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+ goto new_segment;
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+ if (cluster) {
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+ if (seg_size + bv->bv_len
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+ > queue_max_segment_size(q))
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+ goto new_segment;
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+ if (!BIOVEC_PHYS_MERGEABLE(bvprv, bv))
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+ goto new_segment;
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+ if (!BIOVEC_SEG_BOUNDARY(q, bvprv, bv))
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+ goto new_segment;
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+
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+ seg_size += bv->bv_len;
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+ bvprv = bv;
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+ continue;
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+ }
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+new_segment:
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+ if (nr_phys_segs == 1 && seg_size >
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+ fbio->bi_seg_front_size)
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+ fbio->bi_seg_front_size = seg_size;
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+
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+ nr_phys_segs++;
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+ bvprv = bv;
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+ seg_size = bv->bv_len;
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+ highprv = high;
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+ }
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+ bbio = bio;
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+ }
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+
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+ if (nr_phys_segs == 1 && seg_size > fbio->bi_seg_front_size)
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+ fbio->bi_seg_front_size = seg_size;
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+ if (seg_size > bbio->bi_seg_back_size)
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+ bbio->bi_seg_back_size = seg_size;
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+
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+ return nr_phys_segs;
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+}
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+
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+void blk_recalc_rq_segments(struct request *rq)
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+{
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+ rq->nr_phys_segments = __blk_recalc_rq_segments(rq->q, rq->bio);
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+}
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+
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+void blk_recount_segments(struct request_queue *q, struct bio *bio)
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+{
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+ struct bio *nxt = bio->bi_next;
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+
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+ bio->bi_next = NULL;
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+ bio->bi_phys_segments = __blk_recalc_rq_segments(q, bio);
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+ bio->bi_next = nxt;
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+ bio->bi_flags |= (1 << BIO_SEG_VALID);
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+}
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+EXPORT_SYMBOL(blk_recount_segments);
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+
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+static int blk_phys_contig_segment(struct request_queue *q, struct bio *bio,
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+ struct bio *nxt)
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+{
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+ if (!blk_queue_cluster(q))
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+ return 0;
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+
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+ if (bio->bi_seg_back_size + nxt->bi_seg_front_size >
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+ queue_max_segment_size(q))
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+ return 0;
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+
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+ if (!bio_has_data(bio))
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+ return 1;
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+
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+ if (!BIOVEC_PHYS_MERGEABLE(__BVEC_END(bio), __BVEC_START(nxt)))
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+ return 0;
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+
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+ /*
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+ * bio and nxt are contiguous in memory; check if the queue allows
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+ * these two to be merged into one
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+ */
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+ if (BIO_SEG_BOUNDARY(q, bio, nxt))
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+ return 1;
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+
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+ return 0;
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+}
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+
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+static void
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+__blk_segment_map_sg(struct request_queue *q, struct bio_vec *bvec,
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