The patch titled
Subject: bdi: introduce BDI_CAP_SYNCHRONOUS_IO
has been added to the -mm tree. Its filename is
bdi-introduce-bdi_cap_synchronous_io.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/bdi-introduce-bdi_cap_synchronous_io.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/bdi-introduce-bdi_cap_synchronous_io.patch
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------------------------------------------------------
From: Minchan Kim <minchan@xxxxxxxxxx>
Subject: bdi: introduce BDI_CAP_SYNCHRONOUS_IO
As discussed at
lkml.kernel.org/r/<20170728165604.10455-1-ross.zwisler@xxxxxxxxxxxxxxx>,
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@xxxxxxxxxx
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Christoph Hellwig <hch@xxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Ross Zwisler <ross.zwisler@xxxxxxxxxxxxxxx>
Cc: Hugh Dickins <hughd@xxxxxxxxxx>
Cc: Ilya Dryomov <idryomov@xxxxxxxxx>
Cc: Jens Axboe <axboe@xxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/block/brd.c | 2 ++
drivers/block/zram/zram_drv.c | 2 +-
drivers/nvdimm/btt.c | 3 +++
drivers/nvdimm/pmem.c | 2 ++
include/linux/backing-dev.h | 8 ++++++++
5 files changed, 16 insertions(+), 1 deletion(-)
diff -puN drivers/block/brd.c~bdi-introduce-bdi_cap_synchronous_io drivers/block/brd.c
--- a/drivers/block/brd.c~bdi-introduce-bdi_cap_synchronous_io
+++ a/drivers/block/brd.c
@@ -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>
@@ -449,6 +450,7 @@ static struct brd_device *brd_alloc(int
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);
diff -puN drivers/block/zram/zram_drv.c~bdi-introduce-bdi_cap_synchronous_io drivers/block/zram/zram_drv.c
--- a/drivers/block/zram/zram_drv.c~bdi-introduce-bdi_cap_synchronous_io
+++ a/drivers/block/zram/zram_drv.c
@@ -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,
diff -puN drivers/nvdimm/btt.c~bdi-introduce-bdi_cap_synchronous_io drivers/nvdimm/btt.c
--- a/drivers/nvdimm/btt.c~bdi-introduce-bdi_cap_synchronous_io
+++ a/drivers/nvdimm/btt.c
@@ -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);
diff -puN drivers/nvdimm/pmem.c~bdi-introduce-bdi_cap_synchronous_io drivers/nvdimm/pmem.c
--- a/drivers/nvdimm/pmem.c~bdi-introduce-bdi_cap_synchronous_io
+++ a/drivers/nvdimm/pmem.c
@@ -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 devic
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);
diff -puN include/linux/backing-dev.h~bdi-introduce-bdi_cap_synchronous_io include/linux/backing-dev.h
--- a/include/linux/backing-dev.h~bdi-introduce-bdi_cap_synchronous_io
+++ a/include/linux/backing-dev.h
@@ -123,6 +123,8 @@ int bdi_set_max_ratio(struct backing_dev
* 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
@@ -130,6 +132,7 @@ int bdi_set_max_ratio(struct backing_dev
#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)
@@ -177,6 +180,11 @@ long wait_iff_congested(struct pglist_da
int pdflush_proc_obsolete(struct ctl_table *table, int write,
void __user *buffer, size_t *lenp, loff_t *ppos);
+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;
_
Patches currently in -mm which might be from minchan@xxxxxxxxxx are
zram-fix-null-dereference-of-handle.patch
zram-fix-null-dereference-of-handle-v2.patch
zram-set-bdi_cap_stable_writes-once.patch
bdi-introduce-bdi_cap_synchronous_io.patch
mm-swap-introduce-swp_synchronous_io.patch
mm-swap-skip-swapcache-for-swapin-of-synchronous-device.patch
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