block: add zone specific block statuses

A zoned device with limited resources to open or activate zones may
return an error when the host exceeds those limits. The same command may
be successful if retried later, but the host needs to wait for specific
zone states before it should expect a retry to succeed. Have the block
layer provide an appropriate status for these conditions so applications
can distinuguish this error for special handling.

Cc: linux-api@vger.kernel.org
Cc: Niklas Cassel <niklas.cassel@wdc.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Damien Le Moal <damien.lemoal@wdc.com>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: Martin K. Petersen <martin.petersen@oracle.com>
Signed-off-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

Documentation/block/queue-sysfs.rst

@@ -124,6 +124,10 @@ For zoned block devices (zoned attribute indicating "host-managed" or
 EXPLICIT OPEN, IMPLICIT OPEN or CLOSED, is limited by this value.
 If this value is 0, there is no limit.
 
+If the host attempts to exceed this limit, the driver should report this error
+with BLK_STS_ZONE_ACTIVE_RESOURCE, which user space may see as the EOVERFLOW
+errno.
+
 max_open_zones (RO)
 -------------------
 For zoned block devices (zoned attribute indicating "host-managed" or
@@ -131,6 +135,10 @@ For zoned block devices (zoned attribute indicating "host-managed" or
 EXPLICIT OPEN or IMPLICIT OPEN, is limited by this value.
 If this value is 0, there is no limit.
 
+If the host attempts to exceed this limit, the driver should report this error
+with BLK_STS_ZONE_OPEN_RESOURCE, which user space may see as the ETOOMANYREFS
+errno.
+
 max_sectors_kb (RW)
 -------------------
 This is the maximum number of kilobytes that the block layer will allow

block/blk-core.c

@@ -186,6 +186,10 @@ static const struct {
 	/* device mapper special case, should not leak out: */
 	[BLK_STS_DM_REQUEUE]	= { -EREMCHG, "dm internal retry" },
 
+	/* zone device specific errors */
+	[BLK_STS_ZONE_OPEN_RESOURCE]	= { -ETOOMANYREFS, "open zones exceeded" },
+	[BLK_STS_ZONE_ACTIVE_RESOURCE]	= { -EOVERFLOW, "active zones exceeded" },
+
 	/* everything else not covered above: */
 	[BLK_STS_IOERR]		= { -EIO,	"I/O" },
 };

include/linux/blk_types.h

@@ -104,6 +104,24 @@ typedef u8 __bitwise blk_status_t;
  */
 #define BLK_STS_ZONE_RESOURCE	((__force blk_status_t)14)
 
+/*
+ * BLK_STS_ZONE_OPEN_RESOURCE is returned from the driver in the completion
+ * path if the device returns a status indicating that too many zone resources
+ * are currently open. The same command should be successful if resubmitted
+ * after the number of open zones decreases below the device's limits, which is
+ * reported in the request_queue's max_open_zones.
+ */
+#define BLK_STS_ZONE_OPEN_RESOURCE	((__force blk_status_t)15)
+
+/*
+ * BLK_STS_ZONE_ACTIVE_RESOURCE is returned from the driver in the completion
+ * path if the device returns a status indicating that too many zone resources
+ * are currently active. The same command should be successful if resubmitted
+ * after the number of active zones decreases below the device's limits, which
+ * is reported in the request_queue's max_active_zones.
+ */
+#define BLK_STS_ZONE_ACTIVE_RESOURCE	((__force blk_status_t)16)
+
 /**
  * blk_path_error - returns true if error may be path related
  * @error: status the request was completed with