Signed-off-by: Luben Tuikov <ltuikov@xxxxxxxxx> --- * This is a preliminary patch. Feel free to apply it for inclusion and/or work/modify it to submit a more atomically-correct version. * Vendors: apply this to see an increasing sequence of tags on the wire and at your device, so that error recovery doesn't abort a task which isn't intended to be aborted especially in full duplex protocols when the command status and TMF can cross on the wire. See this thread: http://marc.info/?l=linux-scsi&m=128902337522893&w=2 block/blk-tag.c | 15 +++++++++++++-- include/linux/blkdev.h | 1 + 2 files changed, 14 insertions(+), 2 deletions(-) diff --git a/block/blk-tag.c b/block/blk-tag.c index ece65fc..f792e98 100644 --- a/block/blk-tag.c +++ b/block/blk-tag.c @@ -130,6 +130,7 @@ init_tag_map(struct request_queue *q, struct blk_queue_tag *tags, int depth) tags->max_depth = depth; tags->tag_index = tag_index; tags->tag_map = tag_map; + tags->last_tag = 0; return 0; fail: @@ -222,7 +223,7 @@ int blk_queue_resize_tags(struct request_queue *q, int new_depth) struct blk_queue_tag *bqt = q->queue_tags; struct request **tag_index; unsigned long *tag_map; - int max_depth, nr_ulongs; + int max_depth, nr_ulongs, last_tag; if (!bqt) return -ENXIO; @@ -251,6 +252,7 @@ int blk_queue_resize_tags(struct request_queue *q, int new_depth) tag_index = bqt->tag_index; tag_map = bqt->tag_map; max_depth = bqt->real_max_depth; + last_tag = bqt->last_tag; if (init_tag_map(q, bqt, new_depth)) return -ENOMEM; @@ -258,6 +260,7 @@ int blk_queue_resize_tags(struct request_queue *q, int new_depth) memcpy(bqt->tag_index, tag_index, max_depth * sizeof(struct request *)); nr_ulongs = ALIGN(max_depth, BITS_PER_LONG) / BITS_PER_LONG; memcpy(bqt->tag_map, tag_map, nr_ulongs * sizeof(unsigned long)); + bqt->last_tag = last_tag; kfree(tag_index); kfree(tag_map); @@ -364,12 +367,20 @@ int blk_queue_start_tag(struct request_queue *q, struct request *rq) return 1; } + if (bqt->last_tag == bqt->max_depth-1) + bqt->last_tag = 0; + do { - tag = find_first_zero_bit(bqt->tag_map, max_depth); + tag = find_next_zero_bit(bqt->tag_map, + max_depth, + bqt->last_tag+1); if (tag >= max_depth) return 1; } while (test_and_set_bit_lock(tag, bqt->tag_map)); + + bqt->last_tag = tag; + /* * We need lock ordering semantics given by test_and_set_bit_lock. * See blk_queue_end_tag for details. diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 5027a59..955222e 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -224,6 +224,7 @@ struct blk_queue_tag { int max_depth; /* what we will send to device */ int real_max_depth; /* what the array can hold */ atomic_t refcnt; /* map can be shared */ + int last_tag; }; #define BLK_SCSI_MAX_CMDS (256) -- 1.7.2.2.165.gbc382 -- To unsubscribe from this list: send the line "unsubscribe linux-usb" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
