block: add a non-queueable flush flag

flush request isn't queueable in some drives. Add a flag to let driver
notify block layer about this. We can optimize flush performance with the
knowledge.

Stable: 2.6.39 only

Cc: stable@kernel.org
Signed-off-by: Shaohua Li <shaohua.li@intel.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

2 files changed, 13 insertions, 0 deletions

diff --git a/block/blk-settings.c b/block/blk-settings.c
index 1fa769293597..cd3c428e194f 100644
--- a/block/blk-settings.c
+++ b/block/blk-settings.c
@@ -790,6 +790,12 @@ void blk_queue_flush(struct request_queue *q, unsigned int flush)
 }
 EXPORT_SYMBOL_GPL(blk_queue_flush);
 
+void blk_queue_flush_queueable(struct request_queue *q, bool queueable)
+{
+        q->flush_not_queueable = !queueable;
+}
+EXPORT_SYMBOL_GPL(blk_queue_flush_queueable);
+
 static int __init blk_settings_init(void)
 {
         blk_max_low_pfn = max_low_pfn - 1;
diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index cbbfd98ad4a3..8bd2a271b2d8 100644
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -364,6 +364,7 @@ struct request_queue
          * for flush operations
          */
         unsigned int            flush_flags;
+        unsigned int            flush_not_queueable:1;
         unsigned int            flush_pending_idx:1;
         unsigned int            flush_running_idx:1;
         unsigned long           flush_pending_since;
@@ -843,6 +844,7 @@ extern void blk_queue_softirq_done(struct request_queue *, softirq_done_fn *);
 extern void blk_queue_rq_timed_out(struct request_queue *, rq_timed_out_fn *);
 extern void blk_queue_rq_timeout(struct request_queue *, unsigned int);
 extern void blk_queue_flush(struct request_queue *q, unsigned int flush);
+extern void blk_queue_flush_queueable(struct request_queue *q, bool queueable);
 extern struct backing_dev_info *blk_get_backing_dev_info(struct block_device *bdev);
 
 extern int blk_rq_map_sg(struct request_queue *, struct request *, struct scatterlist *);
@@ -1111,6 +1113,11 @@ static inline unsigned int block_size(struct block_device *bdev)
         return bdev->bd_block_size;
 }
 
+static inline bool queue_flush_queueable(struct request_queue *q)
+{
+        return !q->flush_not_queueable;
+}
+
 typedef struct {struct page *v;} Sector;
 
 unsigned char *read_dev_sector(struct block_device *, sector_t, Sector *);