summaryrefslogtreecommitdiffstats
path: root/kernel/Documentation/block/request.txt
diff options
context:
space:
mode:
authorYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 12:17:53 -0700
committerYunhong Jiang <yunhong.jiang@intel.com>2015-08-04 15:44:42 -0700
commit9ca8dbcc65cfc63d6f5ef3312a33184e1d726e00 (patch)
tree1c9cafbcd35f783a87880a10f85d1a060db1a563 /kernel/Documentation/block/request.txt
parent98260f3884f4a202f9ca5eabed40b1354c489b29 (diff)
Add the rt linux 4.1.3-rt3 as base
Import the rt linux 4.1.3-rt3 as OPNFV kvm base. It's from git://git.kernel.org/pub/scm/linux/kernel/git/rt/linux-rt-devel.git linux-4.1.y-rt and the base is: commit 0917f823c59692d751951bf5ea699a2d1e2f26a2 Author: Sebastian Andrzej Siewior <bigeasy@linutronix.de> Date: Sat Jul 25 12:13:34 2015 +0200 Prepare v4.1.3-rt3 Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de> We lose all the git history this way and it's not good. We should apply another opnfv project repo in future. Change-Id: I87543d81c9df70d99c5001fbdf646b202c19f423 Signed-off-by: Yunhong Jiang <yunhong.jiang@intel.com>
Diffstat (limited to 'kernel/Documentation/block/request.txt')
-rw-r--r--kernel/Documentation/block/request.txt88
1 files changed, 88 insertions, 0 deletions
diff --git a/kernel/Documentation/block/request.txt b/kernel/Documentation/block/request.txt
new file mode 100644
index 000000000..754e104ed
--- /dev/null
+++ b/kernel/Documentation/block/request.txt
@@ -0,0 +1,88 @@
+
+struct request documentation
+
+Jens Axboe <jens.axboe@oracle.com> 27/05/02
+
+1.0
+Index
+
+2.0 Struct request members classification
+
+ 2.1 struct request members explanation
+
+3.0
+
+
+2.0
+Short explanation of request members
+
+Classification flags:
+
+ D driver member
+ B block layer member
+ I I/O scheduler member
+
+Unless an entry contains a D classification, a device driver must not access
+this member. Some members may contain D classifications, but should only be
+access through certain macros or functions (eg ->flags).
+
+<linux/blkdev.h>
+
+2.1
+Member Flag Comment
+------ ---- -------
+
+struct list_head queuelist BI Organization on various internal
+ queues
+
+void *elevator_private I I/O scheduler private data
+
+unsigned char cmd[16] D Driver can use this for setting up
+ a cdb before execution, see
+ blk_queue_prep_rq
+
+unsigned long flags DBI Contains info about data direction,
+ request type, etc.
+
+int rq_status D Request status bits
+
+kdev_t rq_dev DBI Target device
+
+int errors DB Error counts
+
+sector_t sector DBI Target location
+
+unsigned long hard_nr_sectors B Used to keep sector sane
+
+unsigned long nr_sectors DBI Total number of sectors in request
+
+unsigned long hard_nr_sectors B Used to keep nr_sectors sane
+
+unsigned short nr_phys_segments DB Number of physical scatter gather
+ segments in a request
+
+unsigned short nr_hw_segments DB Number of hardware scatter gather
+ segments in a request
+
+unsigned int current_nr_sectors DB Number of sectors in first segment
+ of request
+
+unsigned int hard_cur_sectors B Used to keep current_nr_sectors sane
+
+int tag DB TCQ tag, if assigned
+
+void *special D Free to be used by driver
+
+char *buffer D Map of first segment, also see
+ section on bouncing SECTION
+
+struct completion *waiting D Can be used by driver to get signalled
+ on request completion
+
+struct bio *bio DBI First bio in request
+
+struct bio *biotail DBI Last bio in request
+
+struct request_queue *q DB Request queue this request belongs to
+
+struct request_list *rl B Request list this request came from