summaryrefslogtreecommitdiffstats
path: root/Documentation
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2016-05-17 15:29:49 -0700
committerLinus Torvalds <torvalds@linux-foundation.org>2016-05-17 15:29:49 -0700
commita4d1dbed0e27030b3c3ca2d1d5c33a1b45bc53d2 (patch)
tree6f92002ba36efbee3adc1e7b2a0d4b0621c1f1a6 /Documentation
parentc2e7b207058d4ff6a9010430763fb561f307eb67 (diff)
parentb3a834b1596ac668df206aa2bb1f191c31f5f5e4 (diff)
downloadlinux-a4d1dbed0e27030b3c3ca2d1d5c33a1b45bc53d2.tar.bz2
Merge branch 'for-4.7/core' of git://git.kernel.dk/linux-block
Pull core block layer updates from Jens Axboe: "This is the core block IO changes for this merge window. Nothing earth shattering in here, it's mostly just fixes. In detail: - Fix for a long standing issue where wrong ordering in blk-mq caused order_to_size() to spew a warning. From Bart. - Async discard support from Christoph. Basically just splitting our sync interface into a submit + wait part. - Add a cleaner interface for flagging whether a device has a write back cache or not. We've previously overloaded blk_queue_flush() with this, but let's make it more explicit. Drivers cleaned up and updated in the drivers pull request. From me. - Fix for a double check for whether IO accounting is enabled or not. From Michael Callahan. - Fix for the async discard from Mike Snitzer, reinstating the early EOPNOTSUPP return if the device doesn't support discards. - Also from Mike, export bio_inc_remaining() so dm can drop it's private copy of it. - From Ming Lin, add support for passing in an offset for request payloads. - Tag function export from Sagi, which will be used in NVMe in the drivers pull. - Two blktrace related fixes from Shaohua. - Propagate NOMERGE flag when making a request from a bio, also from Shaohua. - An optimization to not parse cgroup paths in blk-throttle, if we don't need to. From Shaohua" * 'for-4.7/core' of git://git.kernel.dk/linux-block: blk-mq: fix undefined behaviour in order_to_size() blk-throttle: don't parse cgroup path if trace isn't enabled blktrace: add missed mask name blktrace: delete garbage for message trace block: make bio_inc_remaining() interface accessible again block: reinstate early return of -EOPNOTSUPP from blkdev_issue_discard block: Minor blk_account_io_start usage cleanup block: add __blkdev_issue_discard block: remove struct bio_batch block: copy NOMERGE flag from bio to request block: add ability to flag write back caching on a device blk-mq: Export tagset iter function block: add offset in blk_add_request_payload() writeback: Fix performance regression in wb_over_bg_thresh()
Diffstat (limited to 'Documentation')
-rw-r--r--Documentation/block/queue-sysfs.txt9
1 files changed, 9 insertions, 0 deletions
diff --git a/Documentation/block/queue-sysfs.txt b/Documentation/block/queue-sysfs.txt
index e5d914845be6..dce25d848d92 100644
--- a/Documentation/block/queue-sysfs.txt
+++ b/Documentation/block/queue-sysfs.txt
@@ -141,6 +141,15 @@ 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.
Jens Axboe <jens.axboe@oracle.com>, February 2009