vfs: cache request_queue in struct block_device

This makes it possible to get from the inode to the request_queue with one
less cache miss.  Used in followon optimization.

The livetime of the pointer is the same as the gendisk.

This assumes that the queue will always stay the same in the gendisk while
it's visible to block_devices.  I think that's safe correct?

Signed-off-by: Andi Kleen <ak@linux.intel.com>
Acked-by: Jeff Moyer <jmoyer@redhat.com>
Cc: Jens Axboe <axboe@kernel.dk>
Cc: Christoph Hellwig <hch@lst.de>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 3 insertions, 0 deletions

diff --git a/fs/block_dev.c b/fs/block_dev.c
index afe74dda632b..0e575d1304b4 100644
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1139,6 +1139,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
         mutex_lock_nested(&bdev->bd_mutex, for_part);
         if (!bdev->bd_openers) {
                 bdev->bd_disk = disk;
+                bdev->bd_queue = disk->queue;
                 bdev->bd_contains = bdev;
                 if (!partno) {
                         struct backing_dev_info *bdi;
@@ -1159,6 +1160,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
                                         disk_put_part(bdev->bd_part);
                                         bdev->bd_part = NULL;
                                         bdev->bd_disk = NULL;
+                                        bdev->bd_queue = NULL;
                                         mutex_unlock(&bdev->bd_mutex);
                                         disk_unblock_events(disk);
                                         put_disk(disk);
@@ -1232,6 +1234,7 @@ static int __blkdev_get(struct block_device *bdev, fmode_t mode, int for_part)
         disk_put_part(bdev->bd_part);
         bdev->bd_disk = NULL;
         bdev->bd_part = NULL;
+        bdev->bd_queue = NULL;
         bdev_inode_switch_bdi(bdev->bd_inode, &default_backing_dev_info);
         if (bdev != bdev->bd_contains)
                 __blkdev_put(bdev->bd_contains, mode, 1);