diff options
Diffstat (limited to 'Documentation/block')
| -rw-r--r-- | Documentation/block/00-INDEX | 4 | ||||
| -rw-r--r-- | Documentation/block/queue-sysfs.txt | 22 | ||||
| -rw-r--r-- | Documentation/block/writeback_cache_control.txt | 4 |
3 files changed, 28 insertions, 2 deletions
diff --git a/Documentation/block/00-INDEX b/Documentation/block/00-INDEX index e840b4761..e55103ace 100644 --- a/Documentation/block/00-INDEX +++ b/Documentation/block/00-INDEX @@ -2,6 +2,8 @@ - This file biodoc.txt - Notes on the Generic Block Layer Rewrite in Linux 2.5 +biovecs.txt + - Immutable biovecs and biovec iterators capability.txt - Generic Block Device Capability (/sys/block/<device>/capability) cfq-iosched.txt @@ -14,6 +16,8 @@ deadline-iosched.txt - Deadline IO scheduler tunables ioprio.txt - Block io priorities (in CFQ scheduler) +pr.txt + - Block layer support for Persistent Reservations null_blk.txt - Null block for block-layer benchmarking. queue-sysfs.txt diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt index e5d914845..9bc990abe 100644 --- a/Documentation/block/queue-sysfs.txt +++ b/Documentation/block/queue-sysfs.txt @@ -141,6 +141,28 @@ control of this block device to that new IO scheduler. Note that writing an IO scheduler name to this file will attempt to load that IO scheduler module, if it isn't already present in the system. +write_cache (RW) +---------------- +When read, this file will display whether the device has write back +caching enabled or not. It will return "write back" for the former +case, and "write through" for the latter. Writing to this file can +change the kernels view of the device, but it doesn't alter the +device state. This means that it might not be safe to toggle the +setting from "write back" to "write through", since that will also +eliminate cache flushes issued by the kernel. + +wb_lat_usec (RW) +---------------- +If the device is registered for writeback throttling, then this file shows +the target minimum read latency. If this latency is exceeded in a given +window of time (see wb_window_usec), then the writeback throttling will start +scaling back writes. + +wb_window_usec (RW) +------------------- +If the device is registered for writeback throttling, then this file shows +the value of the monitoring window in which we'll look at the target +latency. See wb_lat_usec. Jens Axboe <jens.axboe@oracle.com>, February 2009 diff --git a/Documentation/block/writeback_cache_control.txt b/Documentation/block/writeback_cache_control.txt index 83407d366..59e0516cb 100644 --- a/Documentation/block/writeback_cache_control.txt +++ b/Documentation/block/writeback_cache_control.txt @@ -71,7 +71,7 @@ requests that have a payload. For devices with volatile write caches the driver needs to tell the block layer that it supports flushing caches by doing: - blk_queue_flush(sdkp->disk->queue, REQ_FLUSH); + blk_queue_write_cache(sdkp->disk->queue, true, false); and handle empty REQ_FLUSH requests in its prep_fn/request_fn. Note that REQ_FLUSH requests with a payload are automatically turned into a sequence @@ -79,7 +79,7 @@ of an empty REQ_FLUSH request followed by the actual write by the block layer. For devices that also support the FUA bit the block layer needs to be told to pass through the REQ_FUA bit using: - blk_queue_flush(sdkp->disk->queue, REQ_FLUSH | REQ_FUA); + blk_queue_write_cache(sdkp->disk->queue, true, true); and the driver must handle write requests that have the REQ_FUA bit set in prep_fn/request_fn. If the FUA bit is not natively supported the block |