block: get rid of struct blk_issue_stat

struct blk_issue_stat squashes three things into one u64:

- The time the driver started working on a request
- The original size of the request (for the io.low controller)
- Flags for writeback throttling

It turns out that on x86_64, we have a 4 byte hole in struct request
which we can fill with the non-timestamp fields from blk_issue_stat,
simplifying things quite a bit.

Signed-off-by: Omar Sandoval <osandov@fb.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 18 insertions, 8 deletions

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 5c4eee043191..f2c2fc011e6b 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -206,8 +206,18 @@ struct request {
         struct gendisk *rq_disk;
         struct hd_struct *part;
         unsigned long start_time;
-        struct blk_issue_stat issue_stat;
-        /* Number of scatter-gather DMA addr+len pairs after
+        /* Time that I/O was submitted to the device. */
+        u64 io_start_time_ns;
+
+#ifdef CONFIG_BLK_WBT
+        unsigned short wbt_flags;
+#endif
+#ifdef CONFIG_BLK_DEV_THROTTLING_LOW
+        unsigned short throtl_size;
+#endif
+
+        /*
+         * Number of scatter-gather DMA addr+len pairs after
          * physical address coalescing is performed.
          */
         unsigned short nr_phys_segments;
@@ -267,8 +277,8 @@ struct request {
 
 #ifdef CONFIG_BLK_CGROUP
         struct request_list *rl;                /* rl this rq is alloced from */
-        unsigned long long start_time_ns;
-        unsigned long long io_start_time_ns;    /* when passed to hardware */
+        unsigned long long cgroup_start_time_ns;
+        unsigned long long cgroup_io_start_time_ns;    /* when passed to hardware */
 #endif
 };
 
@@ -1797,25 +1807,25 @@ int kblockd_mod_delayed_work_on(int cpu, struct delayed_work *dwork, unsigned lo
 static inline void set_start_time_ns(struct request *req)
 {
         preempt_disable();
-        req->start_time_ns = sched_clock();
+        req->cgroup_start_time_ns = sched_clock();
         preempt_enable();
 }
 
 static inline void set_io_start_time_ns(struct request *req)
 {
         preempt_disable();
-        req->io_start_time_ns = sched_clock();
+        req->cgroup_io_start_time_ns = sched_clock();
         preempt_enable();
 }
 
 static inline uint64_t rq_start_time_ns(struct request *req)
 {
-        return req->start_time_ns;
+        return req->cgroup_start_time_ns;
 }
 
 static inline uint64_t rq_io_start_time_ns(struct request *req)
 {
-        return req->io_start_time_ns;
+        return req->cgroup_io_start_time_ns;
 }
 #else
 static inline void set_start_time_ns(struct request *req) {}