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Subject[PATCH v2 1/3] block: add QUEUE_FLAG_DAX for devices to advertise their DAX support
Date
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.

Signed-off-by: Toshi Kani <toshi.kani@hpe.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Martin Schwidefsky <schwidefsky@de.ibm.com>
Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
Cc: <linux-s390@vger.kernel.org>
---
drivers/block/brd.c | 4 +++-
drivers/nvdimm/pmem.c | 1 +
drivers/s390/block/dcssblk.c | 1 +
fs/block_dev.c | 5 +++--
include/linux/blkdev.h | 2 ++
5 files changed, 10 insertions(+), 3 deletions(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index f5b0d6f..dd96a93 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -509,7 +509,9 @@ static struct brd_device *brd_alloc(int i)
blk_queue_max_discard_sectors(brd->brd_queue, UINT_MAX);
brd->brd_queue->limits.discard_zeroes_data = 1;
queue_flag_set_unlocked(QUEUE_FLAG_DISCARD, brd->brd_queue);
-
+#ifdef CONFIG_BLK_DEV_RAM_DAX
+ queue_flag_set_unlocked(QUEUE_FLAG_DAX, brd->brd_queue);
+#endif
disk = brd->brd_disk = alloc_disk(max_part);
if (!disk)
goto out_free_queue;
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 608fc44..53b701b 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -283,6 +283,7 @@ static int pmem_attach_disk(struct device *dev,
blk_queue_max_hw_sectors(q, UINT_MAX);
blk_queue_bounce_limit(q, BLK_BOUNCE_ANY);
queue_flag_set_unlocked(QUEUE_FLAG_NONROT, q);
+ queue_flag_set_unlocked(QUEUE_FLAG_DAX, q);
q->queuedata = pmem;

disk = alloc_disk_node(0, nid);
diff --git a/drivers/s390/block/dcssblk.c b/drivers/s390/block/dcssblk.c
index bed53c4..093e9e1 100644
--- a/drivers/s390/block/dcssblk.c
+++ b/drivers/s390/block/dcssblk.c
@@ -618,6 +618,7 @@ dcssblk_add_store(struct device *dev, struct device_attribute *attr, const char
dev_info->gd->driverfs_dev = &dev_info->dev;
blk_queue_make_request(dev_info->dcssblk_queue, dcssblk_make_request);
blk_queue_logical_block_size(dev_info->dcssblk_queue, 4096);
+ queue_flag_set_unlocked(QUEUE_FLAG_DAX, dev_info->dcssblk_queue);

seg_byte_size = (dev_info->end - dev_info->start + 1);
set_capacity(dev_info->gd, seg_byte_size >> 9); // size in sectors
diff --git a/fs/block_dev.c b/fs/block_dev.c
index 71ccab1..d012be4 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -493,7 +493,7 @@ long bdev_direct_access(struct block_device *bdev, struct blk_dax_ctl *dax)

if (size < 0)
return size;
- if (!ops->direct_access)
+ if (!blk_queue_dax(bdev_get_queue(bdev)) || !ops->direct_access)
return -EOPNOTSUPP;
if ((sector + DIV_ROUND_UP(size, 512)) >
part_nr_sects_read(bdev->bd_part))
@@ -1287,7 +1287,8 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
bdev->bd_disk = disk;
bdev->bd_queue = disk->queue;
bdev->bd_contains = bdev;
- if (IS_ENABLED(CONFIG_BLK_DEV_DAX) && disk->fops->direct_access)
+ if (IS_ENABLED(CONFIG_BLK_DEV_DAX) &&
+ blk_queue_dax(disk->queue))
bdev->bd_inode->i_flags = S_DAX;
else
bdev->bd_inode->i_flags = 0;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 9746d22..1493ab3 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -505,6 +505,7 @@ struct request_queue {
#define QUEUE_FLAG_WC 23 /* Write back caching */
#define QUEUE_FLAG_FUA 24 /* device supports FUA writes */
#define QUEUE_FLAG_FLUSH_NQ 25 /* flush not queueuable */
+#define QUEUE_FLAG_DAX 26 /* device supports DAX */

#define QUEUE_FLAG_DEFAULT ((1 << QUEUE_FLAG_IO_STAT) | \
(1 << QUEUE_FLAG_STACKABLE) | \
@@ -594,6 +595,7 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
#define blk_queue_discard(q) test_bit(QUEUE_FLAG_DISCARD, &(q)->queue_flags)
#define blk_queue_secdiscard(q) (blk_queue_discard(q) && \
test_bit(QUEUE_FLAG_SECDISCARD, &(q)->queue_flags))
+#define blk_queue_dax(q) test_bit(QUEUE_FLAG_DAX, &(q)->queue_flags)

#define blk_noretry_request(rq) \
((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \
\
 
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