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Date: Tue, 11 Jun 2019 09:10:58 -0400 (EDT)
From: Pankaj Gupta <pagupta@...hat.com>
To: Mike Snitzer <snitzer@...hat.com>
Cc: cohuck@...hat.com, jack@...e.cz, kvm@...r.kernel.org,
mst@...hat.com, jasowang@...hat.com, david@...morbit.com,
qemu-devel@...gnu.org, virtualization@...ts.linux-foundation.org,
dm-devel@...hat.com, adilger kernel <adilger.kernel@...ger.ca>,
zwisler@...nel.org, aarcange@...hat.com,
dave jiang <dave.jiang@...el.com>, jstaron@...gle.com,
linux-nvdimm@...ts.01.org,
vishal l verma <vishal.l.verma@...el.com>, david@...hat.com,
willy@...radead.org, hch@...radead.org, linux-acpi@...r.kernel.org,
jmoyer@...hat.com, linux-ext4@...r.kernel.org, lenb@...nel.org,
kilobyte@...band.pl, rdunlap@...radead.org, riel@...riel.com,
yuval shaia <yuval.shaia@...cle.com>, stefanha@...hat.com,
pbonzini@...hat.com, dan j williams <dan.j.williams@...el.com>,
lcapitulino@...hat.com, kwolf@...hat.com, nilal@...hat.com,
tytso@....edu, xiaoguangrong eric <xiaoguangrong.eric@...il.com>,
darrick wong <darrick.wong@...cle.com>, rjw@...ysocki.net,
linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
linux-fsdevel@...r.kernel.org, imammedo@...hat.com
Subject: Re: [Qemu-devel] [PATCH v11 4/7] dm: enable synchronous dax
Hi Mike,
Thanks for the review Please find my reply inline.
>
> dm_table_supports_dax() is called multiple times (from
> dm_table_set_restrictions and dm_table_determine_type). It is strange
> to have a getter have a side-effect of being a setter too. Overloading
> like this could get you in trouble in the future.
>
> Are you certain this is what you want?
I agree with you.
>
> Or would it be better to refactor dm_table_supports_dax() to take an
> iterate_devices_fn arg and have callers pass the appropriate function?
> Then have dm_table_set_restrictions() caller do:
>
> if (dm_table_supports_dax(t, device_synchronous, NULL))
> set_dax_synchronous(t->md->dax_dev);
>
> (NULL arg implies dm_table_supports_dax() refactoring would take a int
> *data pointer rather than int type).
>
> Mike
>
I am sending below patch as per your suggestion. Does it look
near to what you have in mind?
Thank you,
Pankaj
===============
diff --git a/drivers/md/dm-table.c b/drivers/md/dm-table.c
index 350cf0451456..8d89acc8b8c2 100644
--- a/drivers/md/dm-table.c
+++ b/drivers/md/dm-table.c
@@ -881,7 +881,7 @@ void dm_table_set_type(struct dm_table *t, enum dm_queue_mode type)
EXPORT_SYMBOL_GPL(dm_table_set_type);
/* validate the dax capability of the target device span */
-static int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
+int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
sector_t start, sector_t len, void *data)
{
int blocksize = *(int *) data;
@@ -890,7 +890,15 @@ static int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
start, len);
}
-bool dm_table_supports_dax(struct dm_table *t, int blocksize)
+/* Check devices support synchronous DAX */
+static int device_synchronous(struct dm_target *ti, struct dm_dev *dev,
+ sector_t start, sector_t len, void *data)
+{
+ return dax_synchronous(dev->dax_dev);
+}
+
+bool dm_table_supports_dax(struct dm_table *t,
+ iterate_devices_callout_fn iterate_fn, int *blocksize)
{
struct dm_target *ti;
unsigned i;
@@ -903,8 +911,7 @@ bool dm_table_supports_dax(struct dm_table *t, int blocksize)
return false;
if (!ti->type->iterate_devices ||
- !ti->type->iterate_devices(ti, device_supports_dax,
- &blocksize))
+ !ti->type->iterate_devices(ti, iterate_fn, blocksize))
return false;
}
@@ -940,6 +947,7 @@ static int dm_table_determine_type(struct dm_table *t)
struct dm_target *tgt;
struct list_head *devices = dm_table_get_devices(t);
enum dm_queue_mode live_md_type = dm_get_md_type(t->md);
+ int page_size = PAGE_SIZE;
if (t->type != DM_TYPE_NONE) {
/* target already set the table's type */
@@ -984,7 +992,7 @@ static int dm_table_determine_type(struct dm_table *t)
verify_bio_based:
/* We must use this table as bio-based */
t->type = DM_TYPE_BIO_BASED;
- if (dm_table_supports_dax(t, PAGE_SIZE) ||
+ if (dm_table_supports_dax(t, device_supports_dax, &page_size) ||
(list_empty(devices) && live_md_type == DM_TYPE_DAX_BIO_BASED)) {
t->type = DM_TYPE_DAX_BIO_BASED;
} else {
@@ -1883,6 +1891,7 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
struct queue_limits *limits)
{
bool wc = false, fua = false;
+ int page_size = PAGE_SIZE;
/*
* Copy table's limits to the DM device's request_queue
@@ -1910,8 +1919,13 @@ void dm_table_set_restrictions(struct dm_table *t, struct request_queue *q,
}
blk_queue_write_cache(q, wc, fua);
- if (dm_table_supports_dax(t, PAGE_SIZE))
+ if (dm_table_supports_dax(t, device_supports_dax, &page_size)) {
+
blk_queue_flag_set(QUEUE_FLAG_DAX, q);
+ if (dm_table_supports_dax(t, device_synchronous, NULL))
+ set_dax_synchronous(t->md->dax_dev);
+ }
else
blk_queue_flag_clear(QUEUE_FLAG_DAX, q);
diff --git a/drivers/md/dm.c b/drivers/md/dm.c
index b1caa7188209..b92c42a72ad4 100644
--- a/drivers/md/dm.c
+++ b/drivers/md/dm.c
@@ -1119,7 +1119,7 @@ static bool dm_dax_supported(struct dax_device *dax_dev, struct block_device *bd
if (!map)
return false;
- ret = dm_table_supports_dax(map, blocksize);
+ ret = dm_table_supports_dax(map, device_supports_dax, &blocksize);
dm_put_live_table(md, srcu_idx);
diff --git a/drivers/md/dm.h b/drivers/md/dm.h
index 17e3db54404c..0475673337f3 100644
--- a/drivers/md/dm.h
+++ b/drivers/md/dm.h
@@ -72,7 +72,10 @@ bool dm_table_bio_based(struct dm_table *t);
bool dm_table_request_based(struct dm_table *t);
void dm_table_free_md_mempools(struct dm_table *t);
struct dm_md_mempools *dm_table_get_md_mempools(struct dm_table *t);
-bool dm_table_supports_dax(struct dm_table *t, int blocksize);
+bool dm_table_supports_dax(struct dm_table *t, iterate_devices_callout_fn fn,
+ int *blocksize);
+int device_supports_dax(struct dm_target *ti, struct dm_dev *dev,
+ sector_t start, sector_t len, void *data);
void dm_lock_md_type(struct mapped_device *md);
void dm_unlock_md_type(struct mapped_device *md);
--
2.20.1
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