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authorJens Axboe <axboe@fb.com>2016-04-12 12:32:46 -0600
committerJens Axboe <axboe@fb.com>2016-04-12 15:46:27 -0600
commit93e9d8e836cb1a9a58b33eb6643bf061c6119ef2 (patch)
tree17a50abdadaa58686983510230932323bf5d123c /block/blk-sysfs.c
parente0489487ec9cd79ee1fa0dc5d3789c08b0e51a2c (diff)
downloadlinux-0-day-93e9d8e836cb1a9a58b33eb6643bf061c6119ef2.tar.gz
block: add ability to flag write back caching on a device
Add an internal helper and flag for setting whether a queue has write back caching, or write through (or none). Add a sysfs file to show this as well, and make it changeable from user space. This will replace the (awkward) blk_queue_flush() interface that drivers currently use to inform the block layer of write cache state and capabilities. Signed-off-by: Jens Axboe <axboe@fb.com> Reviewed-by: Christoph Hellwig <hch@lst.de>
Diffstat (limited to 'block/blk-sysfs.c')
-rw-r--r--block/blk-sysfs.c39
1 files changed, 39 insertions, 0 deletions
diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 995b58d..9920596 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -347,6 +347,38 @@ static ssize_t queue_poll_store(struct request_queue *q, const char *page,
return ret;
}
+static ssize_t queue_wc_show(struct request_queue *q, char *page)
+{
+ if (test_bit(QUEUE_FLAG_WC, &q->queue_flags))
+ return sprintf(page, "write back\n");
+
+ return sprintf(page, "write through\n");
+}
+
+static ssize_t queue_wc_store(struct request_queue *q, const char *page,
+ size_t count)
+{
+ int set = -1;
+
+ if (!strncmp(page, "write back", 10))
+ set = 1;
+ else if (!strncmp(page, "write through", 13) ||
+ !strncmp(page, "none", 4))
+ set = 0;
+
+ if (set == -1)
+ return -EINVAL;
+
+ spin_lock_irq(q->queue_lock);
+ if (set)
+ queue_flag_set(QUEUE_FLAG_WC, q);
+ else
+ queue_flag_clear(QUEUE_FLAG_WC, q);
+ spin_unlock_irq(q->queue_lock);
+
+ return count;
+}
+
static struct queue_sysfs_entry queue_requests_entry = {
.attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
.show = queue_requests_show,
@@ -478,6 +510,12 @@ static struct queue_sysfs_entry queue_poll_entry = {
.store = queue_poll_store,
};
+static struct queue_sysfs_entry queue_wc_entry = {
+ .attr = {.name = "write_cache", .mode = S_IRUGO | S_IWUSR },
+ .show = queue_wc_show,
+ .store = queue_wc_store,
+};
+
static struct attribute *default_attrs[] = {
&queue_requests_entry.attr,
&queue_ra_entry.attr,
@@ -503,6 +541,7 @@ static struct attribute *default_attrs[] = {
&queue_iostats_entry.attr,
&queue_random_entry.attr,
&queue_poll_entry.attr,
+ &queue_wc_entry.attr,
NULL,
};