Commit 23c47d2a authored by Minchan Kim's avatar Minchan Kim Committed by Linus Torvalds
Browse files

bdi: introduce BDI_CAP_SYNCHRONOUS_IO 

As discussed at

  https://lkml.kernel.org/r/<20170728165604.10455-1-ross.zwisler@linux.intel.com>

someday we will remove rw_page().  If so, we need something to detect
such super-fast storage on which synchronous IO operations like the
current rw_page are always a win.

Introduces BDI_CAP_SYNCHRONOUS_IO to indicate such devices.  With it, we
could use various optimization techniques.

Link: http://lkml.kernel.org/r/1505886205-9671-3-git-send-email-minchan@kernel.org


Signed-off-by: default avatarMinchan Kim <minchan@kernel.org>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Ross Zwisler <ross.zwisler@linux.intel.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Ilya Dryomov <idryomov@gmail.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Huang Ying <ying.huang@intel.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent e447a015

drivers/block/brd.c

+2 −0
Original line number Diff line number Diff line
@@ -20,6 +20,7 @@ 
#include <linux/radix-tree.h>

#include <linux/fs.h>

#include <linux/slab.h>

#include <linux/backing-dev.h>

#ifdef CONFIG_BLK_DEV_RAM_DAX

#include <linux/pfn_t.h>

#include <linux/dax.h>
@@ -448,6 +449,7 @@ static struct brd_device *brd_alloc(int i) 
	disk->flags		= GENHD_FL_EXT_DEVT;

	sprintf(disk->disk_name, "ram%d", i);

	set_capacity(disk, rd_size * 2);

	disk->queue->backing_dev_info->capabilities |= BDI_CAP_SYNCHRONOUS_IO;



#ifdef CONFIG_BLK_DEV_RAM_DAX

	queue_flag_set_unlocked(QUEUE_FLAG_DAX, brd->brd_queue);

drivers/block/zram/zram_drv.c

+1 −1
Original line number Diff line number Diff line
@@ -1558,7 +1558,7 @@ static int zram_add(void) 
		blk_queue_max_write_zeroes_sectors(zram->disk->queue, UINT_MAX);



	zram->disk->queue->backing_dev_info->capabilities |=

					BDI_CAP_STABLE_WRITES;

			(BDI_CAP_STABLE_WRITES | BDI_CAP_SYNCHRONOUS_IO);

	add_disk(zram->disk);



	ret = sysfs_create_group(&disk_to_dev(zram->disk)->kobj,

drivers/nvdimm/btt.c

+3 −0
Original line number Diff line number Diff line
@@ -23,6 +23,7 @@ 
#include <linux/ndctl.h>

#include <linux/fs.h>

#include <linux/nd.h>

#include <linux/backing-dev.h>

#include "btt.h"

#include "nd.h"
@@ -1402,6 +1403,8 @@ static int btt_blk_init(struct btt *btt) 
	btt->btt_disk->private_data = btt;

	btt->btt_disk->queue = btt->btt_queue;

	btt->btt_disk->flags = GENHD_FL_EXT_DEVT;

	btt->btt_disk->queue->backing_dev_info->capabilities |=

			BDI_CAP_SYNCHRONOUS_IO;



	blk_queue_make_request(btt->btt_queue, btt_make_request);

	blk_queue_logical_block_size(btt->btt_queue, btt->sector_size);

drivers/nvdimm/pmem.c

+2 −0
Original line number Diff line number Diff line
@@ -31,6 +31,7 @@ 
#include <linux/uio.h>

#include <linux/dax.h>

#include <linux/nd.h>

#include <linux/backing-dev.h>

#include "pmem.h"

#include "pfn.h"

#include "nd.h"
@@ -394,6 +395,7 @@ static int pmem_attach_disk(struct device *dev, 
	disk->fops		= &pmem_fops;

	disk->queue		= q;

	disk->flags		= GENHD_FL_EXT_DEVT;

	disk->queue->backing_dev_info->capabilities |= BDI_CAP_SYNCHRONOUS_IO;

	nvdimm_namespace_disk_name(ndns, disk->disk_name);

	set_capacity(disk, (pmem->size - pmem->pfn_pad - pmem->data_offset)

			/ 512);

include/linux/backing-dev.h

+8 −0
Original line number Diff line number Diff line
@@ -122,6 +122,8 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio); 
 * BDI_CAP_STRICTLIMIT:    Keep number of dirty pages below bdi threshold.

 *

 * BDI_CAP_CGROUP_WRITEBACK: Supports cgroup-aware writeback.

 * BDI_CAP_SYNCHRONOUS_IO: Device is so fast that asynchronous IO would be

 *			   inefficient.

 */

#define BDI_CAP_NO_ACCT_DIRTY	0x00000001

#define BDI_CAP_NO_WRITEBACK	0x00000002
@@ -129,6 +131,7 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio); 
#define BDI_CAP_STABLE_WRITES	0x00000008

#define BDI_CAP_STRICTLIMIT	0x00000010

#define BDI_CAP_CGROUP_WRITEBACK 0x00000020

#define BDI_CAP_SYNCHRONOUS_IO	0x00000040



#define BDI_CAP_NO_ACCT_AND_WRITEBACK \

	(BDI_CAP_NO_WRITEBACK | BDI_CAP_NO_ACCT_DIRTY | BDI_CAP_NO_ACCT_WB)
@@ -174,6 +177,11 @@ static inline int wb_congested(struct bdi_writeback *wb, int cong_bits) 
long congestion_wait(int sync, long timeout);

long wait_iff_congested(struct pglist_data *pgdat, int sync, long timeout);



static inline bool bdi_cap_synchronous_io(struct backing_dev_info *bdi)

{

	return bdi->capabilities & BDI_CAP_SYNCHRONOUS_IO;

}



static inline bool bdi_cap_stable_pages_required(struct backing_dev_info *bdi)

{

	return bdi->capabilities & BDI_CAP_STABLE_WRITES;

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