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 11c2b4297d5a5da1eb3473927d030b3f90754a01..10c83e056dc926feda7e2f2be1d0291a1e63a2f5 100644 (file)
--- a/fs/block_dev.c
+++ b/fs/block_dev.c
@@ -1115,6 +1115,7 @@ 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;
@@ -1135,6 +1136,7 @@ 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);
                                        module_put(disk->fops->owner);
@@ -1208,6 +1210,7 @@ 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 88b241b8f7ecb8b718f46592e915b8299a4860eb..e7b118ce9d4ca58c10500027724984796116a14d 100644 (file)
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -655,6 +655,7 @@ 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 */
@@ -677,6 +678,7 @@ 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