bdi: remove BDI_CAP_SYNCHRONOUS_IO

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>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/drivers/block/brd.c b/drivers/block/brd.c
index 2723a70..cc49a92 100644 (file)
--- 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 91ccfe4..e21ca84 100644 (file)
--- 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 0d71014..12ff6f8 100644 (file)
--- 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 140cf3b..1711fdf 100644 (file)
--- 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 52583b6..860ea33 100644 (file)
--- 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 b90f869..96a7c47 100644 (file)
--- 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))) {