Add the zoned queue limit to indicate the zoning model of a block
device. Defined values are 0 (BLK_ZONED_NONE) for regular block
devices, 1 (BLK_ZONED_HA) for host-aware zone block devices and 2
(BLK_ZONED_HM) for host-managed zone block devices. The drive managed
model is not defined here since these block devices do not provide any
command for accessing zone information. The helper functions
blk_queue_zoned and bdev_zoned return the zoned limit which can in turn
be used as a boolean to test if a block device is zoned.

The zoned attribute is also exported as a string to applications via
sysfs. BLK_ZONED_NONE shows as "none", BLK_ZONED_HA as "host-aware" and
BLK_ZONED_HM as "host-managed".

Signed-off-by: Damien Le Moal <damien.lem...@hgst.com>
---
 block/blk-settings.c   |  1 +
 block/blk-sysfs.c      | 18 ++++++++++++++++++
 include/linux/blkdev.h | 25 +++++++++++++++++++++++++
 3 files changed, 44 insertions(+)

diff --git a/block/blk-settings.c b/block/blk-settings.c
index f679ae1..b1d5b7f 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -107,6 +107,7 @@ void blk_set_default_limits(struct queue_limits *lim)
        lim->io_opt = 0;
        lim->misaligned = 0;
        lim->cluster = 1;
+       lim->zoned = BLK_ZONED_NONE;
 }
 EXPORT_SYMBOL(blk_set_default_limits);
 
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index f87a7e7..31ecff9 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -257,6 +257,18 @@ QUEUE_SYSFS_BIT_FNS(random, ADD_RANDOM, 0);
 QUEUE_SYSFS_BIT_FNS(iostats, IO_STAT, 0);
 #undef QUEUE_SYSFS_BIT_FNS
 
+static ssize_t queue_zoned_show(struct request_queue *q, char *page)
+{
+       switch (blk_queue_zoned(q)) {
+       case BLK_ZONED_HA:
+               return sprintf(page, "host-aware\n");
+       case BLK_ZONED_HM:
+               return sprintf(page, "host-managed\n");
+       default:
+               return sprintf(page, "none\n");
+       }
+}
+
 static ssize_t queue_nomerges_show(struct request_queue *q, char *page)
 {
        return queue_var_show((blk_queue_nomerges(q) << 1) |
@@ -485,6 +497,11 @@ static struct queue_sysfs_entry queue_nonrot_entry = {
        .store = queue_store_nonrot,
 };
 
+static struct queue_sysfs_entry queue_zoned_entry = {
+       .attr = {.name = "zoned", .mode = S_IRUGO },
+       .show = queue_zoned_show,
+};
+
 static struct queue_sysfs_entry queue_nomerges_entry = {
        .attr = {.name = "nomerges", .mode = S_IRUGO | S_IWUSR },
        .show = queue_nomerges_show,
@@ -546,6 +563,7 @@ static struct attribute *default_attrs[] = {
        &queue_discard_zeroes_data_entry.attr,
        &queue_write_same_max_entry.attr,
        &queue_nonrot_entry.attr,
+       &queue_zoned_entry.attr,
        &queue_nomerges_entry.attr,
        &queue_rq_affinity_entry.attr,
        &queue_iostats_entry.attr,
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index e79055c..1c74b19 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -261,6 +261,15 @@ struct blk_queue_tag {
 #define BLK_SCSI_MAX_CMDS      (256)
 #define BLK_SCSI_CMD_PER_LONG  (BLK_SCSI_MAX_CMDS / (sizeof(long) * 8))
 
+/*
+ * Zoned block device models (zoned limit).
+ */
+enum blk_zoned_model {
+       BLK_ZONED_NONE, /* Regular block device */
+       BLK_ZONED_HA,   /* Host-aware zoned block device */
+       BLK_ZONED_HM,   /* Host-managed zoned block device */
+};
+
 struct queue_limits {
        unsigned long           bounce_pfn;
        unsigned long           seg_boundary_mask;
@@ -290,6 +299,7 @@ struct queue_limits {
        unsigned char           cluster;
        unsigned char           discard_zeroes_data;
        unsigned char           raid_partial_stripes_expensive;
+       unsigned char           zoned;
 };
 
 struct request_queue {
@@ -627,6 +637,11 @@ static inline unsigned int blk_queue_cluster(struct 
request_queue *q)
        return q->limits.cluster;
 }
 
+static inline unsigned int blk_queue_zoned(struct request_queue *q)
+{
+       return q->limits.zoned;
+}
+
 /*
  * We regard a request as sync, if either a read or a sync write
  */
@@ -1354,6 +1369,16 @@ static inline unsigned int bdev_write_same(struct 
block_device *bdev)
        return 0;
 }
 
+static inline unsigned int bdev_zoned(struct block_device *bdev)
+{
+       struct request_queue *q = bdev_get_queue(bdev);
+
+       if (q)
+               return blk_queue_zoned(q);
+
+       return 0;
+}
+
 static inline int queue_dma_alignment(struct request_queue *q)
 {
        return q ? q->dma_alignment : 511;
-- 
2.7.4

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