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>

diff --git a/fs/block_dev.c b/fs/block_dev.c
index b07f1da1de4e34470fd64af913c9366e0d6c8513..3154fbe9ba44199c55c48d1188b4030768ed5d39 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1117,6 +1117,7 @@ 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;
@@ -1137,6 +1138,7 @@ 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);
@@ -1210,6 +1212,7 @@ 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);

diff --git a/include/linux/fs.h b/include/linux/fs.h
index ab5af170b956e17ac172341ba3a27a7e9ecee5ea..616b1c8e44314947f4b2d8d41d72f401613f4348 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -656,6 +656,7 @@ struct address_space {
         * must be enforced here for CRIS, to let the least significant bit
         * of struct page's "mapping" pointer be used for PAGE_MAPPING_ANON.
         */
+struct request_queue;
 
 struct block_device {
        dev_t                   bd_dev;  /* not a kdev_t - it's a search key */
@@ -678,6 +679,7 @@ struct block_device {
        unsigned                bd_part_count;
        int                     bd_invalidated;
        struct gendisk *        bd_disk;
+       struct request_queue *  bd_queue;
        struct list_head        bd_list;
        /*
         * Private data.  You must have bd_claim'ed the block_device