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xen/blkfront: Use QUEUE_ORDERED_DRAIN for old backends
If there's no feature-barrier key in xenstore, then it means its a fairly old backend which does uncached in-order writes, which means ORDERED_DRAIN is appropriate. Signed-off-by: Jeremy Fitzhardinge <jeremy.fitzhardinge@citrix.com>
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4dab46ff26
commit
7901d14144
@ -420,26 +420,22 @@ static int xlvbd_init_blk_queue(struct gendisk *gd, u16 sector_size)
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static int xlvbd_barrier(struct blkfront_info *info)
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{
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int err;
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unsigned ordered = QUEUE_ORDERED_NONE;
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const char *barrier;
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/*
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* If we don't have barrier support, then there's really no
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* way to guarantee write ordering, so we really just have to
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* send writes to the backend and hope for the best. If
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* barriers are supported then we can treat them as proper
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* ordering tags.
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*/
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if (info->feature_barrier)
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ordered = QUEUE_ORDERED_TAG;
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switch (info->feature_barrier) {
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case QUEUE_ORDERED_DRAIN: barrier = "enabled (drain)"; break;
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case QUEUE_ORDERED_TAG: barrier = "enabled (tag)"; break;
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case QUEUE_ORDERED_NONE: barrier = "disabled"; break;
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default: return -EINVAL;
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}
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err = blk_queue_ordered(info->rq, ordered);
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err = blk_queue_ordered(info->rq, info->feature_barrier);
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if (err)
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return err;
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printk(KERN_INFO "blkfront: %s: barriers %s\n",
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info->gd->disk_name,
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info->feature_barrier ? "enabled" : "disabled");
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info->gd->disk_name, barrier);
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return 0;
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}
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@ -665,7 +661,7 @@ static irqreturn_t blkif_interrupt(int irq, void *dev_id)
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printk(KERN_WARNING "blkfront: %s: write barrier op failed\n",
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info->gd->disk_name);
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error = -EOPNOTSUPP;
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info->feature_barrier = 0;
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info->feature_barrier = QUEUE_ORDERED_NONE;
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xlvbd_barrier(info);
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}
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/* fall through */
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@ -1003,6 +999,7 @@ static void blkfront_connect(struct blkfront_info *info)
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unsigned long sector_size;
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unsigned int binfo;
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int err;
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int barrier;
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switch (info->connected) {
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case BLKIF_STATE_CONNECTED:
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@ -1043,10 +1040,26 @@ static void blkfront_connect(struct blkfront_info *info)
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}
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err = xenbus_gather(XBT_NIL, info->xbdev->otherend,
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"feature-barrier", "%lu", &info->feature_barrier,
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"feature-barrier", "%lu", &barrier,
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NULL);
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/*
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* If there's no "feature-barrier" defined, then it means
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* we're dealing with a very old backend which writes
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* synchronously; draining will do what needs to get done.
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*
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* If there are barriers, then we can do full queued writes
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* with tagged barriers.
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*
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* If barriers are not supported, then there's no much we can
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* do, so just set ordering to NONE.
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*/
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if (err)
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info->feature_barrier = 0;
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info->feature_barrier = QUEUE_ORDERED_DRAIN;
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else if (barrier)
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info->feature_barrier = QUEUE_ORDERED_TAG;
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else
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info->feature_barrier = QUEUE_ORDERED_NONE;
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err = xlvbd_alloc_gendisk(sectors, info, binfo, sector_size);
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if (err) {
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