[PATCH] update max_sectors documentation

The max_sectors has been split into max_hw_sectors and max_sectors for some
time. A patch to have blk_queue_max_sectors enforce this was sent by
me and it broke IDE. This patch updates the documentation.

Signed-off-by: Jens Axboe <axboe@suse.de>

1 files changed, 12 insertions, 2 deletions

diff --git a/Documentation/block/biodoc.txt b/Documentation/block/biodoc.txt
index 8e63831971d5..f989a9e839b4 100644
--- a/Documentation/block/biodoc.txt
+++ b/Documentation/block/biodoc.txt
@@ -132,8 +132,18 @@ Some new queue property settings:
                 limit. No highmem default.
 
         blk_queue_max_sectors(q, max_sectors)
-                Maximum size request you can handle in units of 512 byte
-                sectors. 255 default.
+                Sets two variables that limit the size of the request.
+
+                - The request queue's max_sectors, which is a soft size in
+                in units of 512 byte sectors, and could be dynamically varied
+                by the core kernel.
+
+                - The request queue's max_hw_sectors, which is a hard limit
+                and reflects the maximum size request a driver can handle
+                in units of 512 byte sectors.
+
+                The default for both max_sectors and max_hw_sectors is
+                255. The upper limit of max_sectors is 1024.
 
         blk_queue_max_phys_segments(q, max_segments)
                 Maximum physical segments you can handle in a request. 128