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SubjectRe: [PATCH v2 1/3] block: add QUEUE_FLAG_DAX for devices to advertise their DAX support
On Thu, Jun 23, 2016 at 8:36 PM, Kani, Toshimitsu <toshi.kani@hpe.com> wrote:
> On Thu, 2016-06-23 at 19:31 +0300, Yigal Korman wrote:
>> On Thu, Jun 23, 2016 at 2:54 AM, Toshi Kani <toshi.kani@hpe.com> wrote:
>> >
>> >
>> > Currently, presence of direct_access() in block_device_operations
>> > indicates support of DAX on its block device. Because
>> > block_device_operations is instantiated with 'const', this DAX
>> > capablity may not be enabled conditinally.
>> >
>> > In preparation for supporting DAX to device-mapper devices, add
>> > QUEUE_FLAG_DAX to request_queue flags to advertise their DAX
>> > support. This will allow to set the DAX capability based on how
>> > mapped device is composed.
>>
>> Hi Toshi,
>> This patch is very helpful!
>> I think QUEUE_FLAG_DAX can also help with identifying dax devices in
>> userspace.
>> Perhaps you'd be willing to squash the patch below with this one or
>> add it to your submission?
>
> Hi Yigal,
>
> Good idea. Mike can probably take it into his tree, but I will include it
> into the series if I needed to submit v3.
>
> Acked-by: Toshi Kani <toshi.kani@hpe.com>

Great, Thanks!
I'll follow the thread to see if it goes through or needs to be resubmitted.

>
> I have one minor comment below.

My reply below as well.

>
>> [PATCH] block: expose QUEUE_FLAG_DAX in sysfs
>>
>> There's currently no way to identify DAX enabled devices in userspace.
>>
>> Signed-off-by: Yigal Korman <yigal@plexistor.com>
>> ---
>> block/blk-sysfs.c | 15 +++++++++++++++
>> 1 file changed, 15 insertions(+)
>>
>> diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
>> index 9920596..d55126d 100644
>> --- a/block/blk-sysfs.c
>> +++ b/block/blk-sysfs.c
>> @@ -379,6 +379,15 @@ static ssize_t queue_wc_store(struct
>> request_queue *q, const char *page,
>> return count;
>> }
>>
>> +static ssize_t queue_dax_show(struct request_queue *q, char *page)
>> +{
>> + int bit;
>> +
>> + bit = test_bit(QUEUE_FLAG_DAX, &q->queue_flags);
>> +
>> + return queue_var_show(bit, page);
>
> This can be:
> return queue_var_show(blk_queue_dax(q), page);

Oh, sure, of course you're right. thanks.

Subject: [PATCH] block: expose QUEUE_FLAG_DAX in sysfs

There's currently no way to identify DAX enabled devices in userspace.

Signed-off-by: Yigal Korman <yigal@plexistor.com>
Acked-by: Toshi Kani <toshi.kani@hpe.com>
---
block/blk-sysfs.c | 11 +++++++++++
1 file changed, 11 insertions(+)

diff --git a/block/blk-sysfs.c b/block/blk-sysfs.c
index 9920596..f87a7e7 100644
--- a/block/blk-sysfs.c
+++ b/block/blk-sysfs.c
@@ -379,6 +379,11 @@ static ssize_t queue_wc_store(struct
request_queue *q, const char *page,
return count;
}

+static ssize_t queue_dax_show(struct request_queue *q, char *page)
+{
+ return queue_var_show(blk_queue_dax(q), page);
+}
+
static struct queue_sysfs_entry queue_requests_entry = {
.attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
.show = queue_requests_show,
@@ -516,6 +521,11 @@ static struct queue_sysfs_entry queue_wc_entry = {
.store = queue_wc_store,
};

+static struct queue_sysfs_entry queue_dax_entry = {
+ .attr = {.name = "dax", .mode = S_IRUGO },
+ .show = queue_dax_show,
+};
+
static struct attribute *default_attrs[] = {
&queue_requests_entry.attr,
&queue_ra_entry.attr,
@@ -542,6 +552,7 @@ static struct attribute *default_attrs[] = {
&queue_random_entry.attr,
&queue_poll_entry.attr,
&queue_wc_entry.attr,
+ &queue_dax_entry.attr,
NULL,
};

--
1.9.3
Thanks,
Yigal

>
> Thanks,
> -Toshi
>
>> +}
>> +
>> static struct queue_sysfs_entry queue_requests_entry = {
>> .attr = {.name = "nr_requests", .mode = S_IRUGO | S_IWUSR },
>> .show = queue_requests_show,
>> @@ -516,6 +525,11 @@ static struct queue_sysfs_entry queue_wc_entry = {
>> .store = queue_wc_store,
>> };
>>
>> +static struct queue_sysfs_entry queue_dax_entry = {
>> + .attr = {.name = "dax", .mode = S_IRUGO },
>> + .show = queue_dax_show,
>> +};
>> +
>> static struct attribute *default_attrs[] = {
>> &queue_requests_entry.attr,
>> &queue_ra_entry.attr,
>> @@ -542,6 +556,7 @@ static struct attribute *default_attrs[] = {
>> &queue_random_entry.attr,
>> &queue_poll_entry.attr,
>> &queue_wc_entry.attr,
>> + &queue_dax_entry.attr,
>> NULL,
>> };
>>

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