[PATCH 09/13] bdi: remove BDI_CAP_SYNCHRONOUS_IO

Christoph Hellwig
2020-09-24T06:52:25Z

BDI_CAP_SYNCHRONOUS_IO is only checked in the swap code, and used to
decided if ->rw_page can be used on a block device. Just check up for
the method instead. The only complication is that zram needs a second
set of block_device_operations as it can switch between modes that
actually support ->rw_page and those who don't.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Jan Kara <jack@suse.cz>
Reviewed-by: Johannes Thumshirn <johannes.thumshirn@wdc.com>
---
drivers/block/brd.c | 1 -
drivers/block/zram/zram_drv.c | 19 +++++++++++++------
drivers/nvdimm/btt.c | 2 --
drivers/nvdimm/pmem.c | 1 -
include/linux/backing-dev.h | 9 ---------
mm/swapfile.c | 2 +-
6 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 2723a70eb85593..cc49a921339f77 100644
--- a/drivers/block/brd.c
+++ b/drivers/block/brd.c
@@ -403,7 +403,6 @@ 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);
- brd->brd_queue->backing_dev_info->capabilities |= BDI_CAP_SYNCHRONOUS_IO;

/* Tell the block layer that this is not a rotational device */
blk_queue_flag_set(QUEUE_FLAG_NONROT, brd->brd_queue);
diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
index 91ccfe444525b4..e21ca844d7c291 100644
--- a/drivers/block/zram/zram_drv.c
+++ b/drivers/block/zram/zram_drv.c
@@ -52,6 +52,9 @@ static unsigned int num_devices = 1;
*/
static size_t huge_class_size;

+static const struct block_device_operations zram_devops;
+static const struct block_device_operations zram_wb_devops;
+
static void zram_free_page(struct zram *zram, size_t index);
static int zram_bvec_read(struct zram *zram, struct bio_vec *bvec,
u32 index, int offset, struct bio *bio);
@@ -408,8 +411,7 @@ static void reset_bdev(struct zram *zram)
zram->backing_dev = NULL;
zram->old_block_size = 0;
zram->bdev = NULL;
- zram->disk->queue->backing_dev_info->capabilities |=
- BDI_CAP_SYNCHRONOUS_IO;
+ zram->disk->fops = &zram_devops;
kvfree(zram->bitmap);
zram->bitmap = NULL;
}
@@ -529,8 +531,7 @@ static ssize_t backing_dev_store(struct device *dev,
* freely but in fact, IO is going on so finally could cause
* use-after-free when the IO is really done.
*/
- zram->disk->queue->backing_dev_info->capabilities &=
- ~BDI_CAP_SYNCHRONOUS_IO;
+ zram->disk->fops = &zram_wb_devops;
up_write(&zram->init_lock);

pr_info("setup backing device %s\n", file_name);
@@ -1820,6 +1821,13 @@ static const struct block_device_operations zram_devops = {
.owner = THIS_MODULE
};

+static const struct block_device_operations zram_wb_devops = {
+ .open = zram_open,
+ .submit_bio = zram_submit_bio,
+ .swap_slot_free_notify = zram_slot_free_notify,
+ .owner = THIS_MODULE
+};
+
static DEVICE_ATTR_WO(compact);
static DEVICE_ATTR_RW(disksize);
static DEVICE_ATTR_RO(initstate);
@@ -1947,8 +1955,7 @@ static int zram_add(void)
if (ZRAM_LOGICAL_BLOCK_SIZE == PAGE_SIZE)
blk_queue_max_write_zeroes_sectors(zram->disk->queue, UINT_MAX);

- zram->disk->queue->backing_dev_info->capabilities |=
- (BDI_CAP_STABLE_WRITES | BDI_CAP_SYNCHRONOUS_IO);
+ zram->disk->queue->backing_dev_info->capabilities |= BDI_CAP_STABLE_WRITES;
device_add_disk(NULL, zram->disk, zram_disk_attr_groups);

strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
diff --git a/drivers/nvdimm/btt.c b/drivers/nvdimm/btt.c
index 0d710140bf93be..12ff6f8784ac11 100644
--- a/drivers/nvdimm/btt.c
+++ b/drivers/nvdimm/btt.c
@@ -1537,8 +1537,6 @@ 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_logical_block_size(btt->btt_queue, btt->sector_size);
blk_queue_max_hw_sectors(btt->btt_queue, UINT_MAX);
diff --git a/drivers/nvdimm/pmem.c b/drivers/nvdimm/pmem.c
index 140cf3b9000c60..1711fdfd8d2816 100644
--- a/drivers/nvdimm/pmem.c
+++ b/drivers/nvdimm/pmem.c
@@ -475,7 +475,6 @@ static int pmem_attach_disk(struct device *dev,
disk->queue = q;
disk->flags = GENHD_FL_EXT_DEVT;
disk->private_data = pmem;
- 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 --git a/include/linux/backing-dev.h b/include/linux/backing-dev.h
index 52583b6f2ea05d..860ea33571bce5 100644
--- a/include/linux/backing-dev.h
+++ b/include/linux/backing-dev.h
@@ -122,9 +122,6 @@ int bdi_set_max_ratio(struct backing_dev_info *bdi, unsigned int max_ratio);
* BDI_CAP_NO_WRITEBACK: Don't write pages back
* BDI_CAP_NO_ACCT_WB: Don't automatically account writeback pages
* BDI_CAP_STRICTLIMIT: Keep number of dirty pages below bdi threshold.
- *
- * 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
@@ -132,7 +129,6 @@ 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)
@@ -174,11 +170,6 @@ static inline int wb_congested(struct bdi_writeback *wb, int cong_bits)
long congestion_wait(int sync, long timeout);
long wait_iff_congested(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;
diff --git a/mm/swapfile.c b/mm/swapfile.c
index b90f8692074397..96a7c47dd533e4 100644
--- a/mm/swapfile.c
+++ b/mm/swapfile.c
@@ -3240,7 +3240,7 @@ SYSCALL_DEFINE2(swapon, const char __user *, specialfile, int, swap_flags)
if (bdi_cap_stable_pages_required(inode_to_bdi(inode)))
p->flags |= SWP_STABLE_WRITES;

- if (bdi_cap_synchronous_io(inode_to_bdi(inode)))
+ if (p->bdev && p->bdev->bd_disk->fops->rw_page)
p->flags |= SWP_SYNCHRONOUS_IO;

if (p->bdev && blk_queue_nonrot(bdev_get_queue(p->bdev))) {
--
2.28.0