block: add documentation for inflight

Complements v2.6.32 commit a9327cac440b ("Seperate read and write
statistics of in_flight requests") and commit 316d315bffa4 ("block:
Seperate read and write statistics of in_flight requests v2").

Signed-off-by: Steffen Maier <maier@linux.ibm.com>
Reviewed-by: Jens Axboe <axboe@kernel.dk>
Link: https://lore.kernel.org/r/20211019130230.77594-1-maier@linux.ibm.com
Signed-off-by: Jonathan Corbet <corbet@lwn.net>

diff --git a/Documentation/ABI/testing/sysfs-block b/Documentation/ABI/testing/sysfs-block
index a0ed87386639bb35ceb16b6f6511f198f95549ca..b16b0c45a272e39310f1bce8809947fe8d16982a 100644 (file)
--- a/Documentation/ABI/testing/sysfs-block
+++ b/Documentation/ABI/testing/sysfs-block
@@ -28,6 +28,22 @@ Description:
                For more details refer Documentation/admin-guide/iostats.rst
 
 
+What:          /sys/block/<disk>/inflight
+Date:          October 2009
+Contact:       Jens Axboe <axboe@kernel.dk>, Nikanth Karthikesan <knikanth@suse.de>
+Description:
+               Reports the number of I/O requests currently in progress
+               (pending / in flight) in a device driver. This can be less
+               than the number of requests queued in the block device queue.
+               The report contains 2 fields: one for read requests
+               and one for write requests.
+               The value type is unsigned int.
+               Cf. Documentation/block/stat.rst which contains a single value for
+               requests in flight.
+               This is related to nr_requests in Documentation/block/queue-sysfs.rst
+               and for SCSI device also its queue_depth.
+
+
 What:          /sys/block/<disk>/diskseq
 Date:          February 2021
 Contact:       Matteo Croce <mcroce@microsoft.com>