block, bdi: an active gendisk always has a request_queue associated with it

bdev_get_queue() returns the request_queue associated with the
specified block_device.  blk_get_backing_dev_info() makes use of
bdev_get_queue() to determine the associated bdi given a block_device.

All the callers of bdev_get_queue() including
blk_get_backing_dev_info() assume that bdev_get_queue() may return
NULL and implement NULL handling; however, bdev_get_queue() requires
the passed in block_device is opened and attached to its gendisk.
Because an active gendisk always has a valid request_queue associated
with it, bdev_get_queue() can never return NULL and neither can
blk_get_backing_dev_info().

Make it clear that neither of the two functions can return NULL and
remove NULL handling from all the callers.

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Chris Mason <clm@fb.com>
Cc: Dave Chinner <david@fromorbit.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

diff --git a/block/blk-core.c b/block/blk-core.c
index 93603e6ff479df3ea38a8e8925e429c2a096e504..81744617548955b84b6c912b3ab270c65674d274 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -83,18 +83,14 @@ void blk_queue_congestion_threshold(struct request_queue *q)
  * @bdev:      device
  *
  * Locates the passed device's request queue and returns the address of its
- * backing_dev_info
- *
- * Will return NULL if the request queue cannot be located.
+ * backing_dev_info.  This function can only be called if @bdev is opened
+ * and the return value is never NULL.
  */
 struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev)
 {
-       struct backing_dev_info *ret = NULL;
        struct request_queue *q = bdev_get_queue(bdev);
 
-       if (q)
-               ret = &q->backing_dev_info;
-       return ret;
+       return &q->backing_dev_info;
 }
 EXPORT_SYMBOL(blk_get_backing_dev_info);
 

diff --git a/block/compat_ioctl.c b/block/compat_ioctl.c
index 18b282ce361e12b20ac8952b1bfb1e7c178d1649..f678c733df404189bdff2a87a01225c6aa124816 100644 (file)
--- a/block/compat_ioctl.c
+++ b/block/compat_ioctl.c
@@ -709,8 +709,6 @@ long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)
                if (!arg)
                        return -EINVAL;
                bdi = blk_get_backing_dev_info(bdev);
-               if (bdi == NULL)
-                       return -ENOTTY;
                return compat_put_long(arg,
                                       (bdi->ra_pages * PAGE_CACHE_SIZE) / 512);
        case BLKROGET: /* compatible */
@@ -731,8 +729,6 @@ long compat_blkdev_ioctl(struct file *file, unsigned cmd, unsigned long arg)
                if (!capable(CAP_SYS_ADMIN))
                        return -EACCES;
                bdi = blk_get_backing_dev_info(bdev);
-               if (bdi == NULL)
-                       return -ENOTTY;
                bdi->ra_pages = (arg * 512) / PAGE_CACHE_SIZE;
                return 0;
        case BLKGETSIZE:

diff --git a/block/ioctl.c b/block/ioctl.c
index d6cda8147c91ea828ea0dcd45f21d4ec6773abd6..6c7bf903742f923c2f720869364da218ea1bbe95 100644 (file)
--- a/block/ioctl.c
+++ b/block/ioctl.c
@@ -356,8 +356,6 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
                if (!arg)
                        return -EINVAL;
                bdi = blk_get_backing_dev_info(bdev);
-               if (bdi == NULL)
-                       return -ENOTTY;
                return put_long(arg, (bdi->ra_pages * PAGE_CACHE_SIZE) / 512);
        case BLKROGET:
                return put_int(arg, bdev_read_only(bdev) != 0);
@@ -386,8 +384,6 @@ int blkdev_ioctl(struct block_device *bdev, fmode_t mode, unsigned cmd,
                if(!capable(CAP_SYS_ADMIN))
                        return -EACCES;
                bdi = blk_get_backing_dev_info(bdev);
-               if (bdi == NULL)
-                       return -ENOTTY;
                bdi->ra_pages = (arg * 512) / PAGE_CACHE_SIZE;
                return 0;
        case BLKBSZSET:

diff --git a/fs/block_dev.c b/fs/block_dev.c
index 6d7274619bf916c2dcf0d7744ba8d888d948d711..d3251eca64292e3e1f441c55d1bde4dbe45e03ac 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1173,8 +1173,6 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                        if (!ret) {
                                bd_set_size(bdev,(loff_t)get_capacity(disk)<<9);
                                bdi = blk_get_backing_dev_info(bdev);
-                               if (bdi == NULL)
-                                       bdi = &default_backing_dev_info;
                                bdev_inode_switch_bdi(bdev->bd_inode, bdi);
                        }
 

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index d0ed9e664f7d4d26c69a12498f80b3ad59809a43..39ff591ae1b4a8b0feeaebe3f39098ce47c4c525 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -1694,7 +1694,7 @@ static int btrfs_congested_fn(void *congested_data, int bdi_bits)
                if (!device->bdev)
                        continue;
                bdi = blk_get_backing_dev_info(device->bdev);
-               if (bdi && bdi_congested(bdi, bdi_bits)) {
+               if (bdi_congested(bdi, bdi_bits)) {
                        ret = 1;
                        break;
                }

diff --git a/fs/xfs/xfs_buf.c b/fs/xfs/xfs_buf.c
index cd7b8ca9b06410c5d34e92161906532a6221ef66..497fcde381d77e55a2e63eab89b4d88a3a1798f7 100644 (file)
--- a/fs/xfs/xfs_buf.c
+++ b/fs/xfs/xfs_buf.c
@@ -1678,8 +1678,6 @@ xfs_alloc_buftarg(
        btp->bt_dev =  bdev->bd_dev;
        btp->bt_bdev = bdev;
        btp->bt_bdi = blk_get_backing_dev_info(bdev);
-       if (!btp->bt_bdi)
-               goto error;
 
        if (xfs_setsize_buftarg_early(btp, bdev))
                goto error;

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 518b46555b80968c3d29df956f677763fe292c51..e267bf0db5590f295d359a906fdbd6099dc20db4 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -865,7 +865,7 @@ extern void blk_execute_rq_nowait(struct request_queue *, struct gendisk *,
 
 static inline struct request_queue *bdev_get_queue(struct block_device *bdev)
 {
-       return bdev->bd_disk->queue;
+       return bdev->bd_disk->queue;    /* this is never NULL */
 }
 
 /*