block: Add the QUEUE_FLAG_PREEMPT_ONLY request queue flag

This flag will be used in the next patch to let the block layer
core know whether or not a SCSI request queue has been quiesced.
A quiesced SCSI queue namely only processes RQF_PREEMPT requests.

Signed-off-by: Bart Van Assche <bart.vanassche@wdc.com>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Tested-by: Martin Steigerwald <martin@lichtvoll.de>
Tested-by: Oleksandr Natalenko <oleksandr@natalenko.name>
Cc: Ming Lei <ming.lei@redhat.com>
Cc: Christoph Hellwig <hch@lst.de>
Cc: Johannes Thumshirn <jthumshirn@suse.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/block/blk-core.c b/block/blk-core.c
index 17eed16a6e0405857cf4b2431049384d523cc713..edc27689911656cea2a38ec7624575256e79c135 100644 (file)
--- a/block/blk-core.c
+++ b/block/blk-core.c
@@ -348,6 +348,36 @@ void blk_sync_queue(struct request_queue *q)
 }
 EXPORT_SYMBOL(blk_sync_queue);
 
+/**
+ * blk_set_preempt_only - set QUEUE_FLAG_PREEMPT_ONLY
+ * @q: request queue pointer
+ *
+ * Returns the previous value of the PREEMPT_ONLY flag - 0 if the flag was not
+ * set and 1 if the flag was already set.
+ */
+int blk_set_preempt_only(struct request_queue *q)
+{
+       unsigned long flags;
+       int res;
+
+       spin_lock_irqsave(q->queue_lock, flags);
+       res = queue_flag_test_and_set(QUEUE_FLAG_PREEMPT_ONLY, q);
+       spin_unlock_irqrestore(q->queue_lock, flags);
+
+       return res;
+}
+EXPORT_SYMBOL_GPL(blk_set_preempt_only);
+
+void blk_clear_preempt_only(struct request_queue *q)
+{
+       unsigned long flags;
+
+       spin_lock_irqsave(q->queue_lock, flags);
+       queue_flag_clear(QUEUE_FLAG_PREEMPT_ONLY, q);
+       spin_unlock_irqrestore(q->queue_lock, flags);
+}
+EXPORT_SYMBOL_GPL(blk_clear_preempt_only);
+
 /**
  * __blk_run_queue_uncond - run a queue whether or not it has been stopped
  * @q: The queue to run

diff --git a/block/blk-mq-debugfs.c b/block/blk-mq-debugfs.c
index bb7f084152033b371d08cbbed1964d544642e047..e4f2bb936e6630c6f529d9be97ccd27cc828b682 100644 (file)
--- a/block/blk-mq-debugfs.c
+++ b/block/blk-mq-debugfs.c
@@ -74,6 +74,7 @@ static const char *const blk_queue_flag_name[] = {
        QUEUE_FLAG_NAME(REGISTERED),
        QUEUE_FLAG_NAME(SCSI_PASSTHROUGH),
        QUEUE_FLAG_NAME(QUIESCED),
+       QUEUE_FLAG_NAME(PREEMPT_ONLY),
 };
 #undef QUEUE_FLAG_NAME
 

diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h
index 1af5ddd0f6318ac57bf7ca9db9e7f612a751ef87..2147e2381a22cc95ba90fa3bb1cc704331223e87 100644 (file)
--- a/include/linux/blkdev.h
+++ b/include/linux/blkdev.h
@@ -632,6 +632,7 @@ struct request_queue {
 #define QUEUE_FLAG_REGISTERED  26      /* queue has been registered to a disk */
 #define QUEUE_FLAG_SCSI_PASSTHROUGH 27 /* queue supports SCSI commands */
 #define QUEUE_FLAG_QUIESCED    28      /* queue has been quiesced */
+#define QUEUE_FLAG_PREEMPT_ONLY        29      /* only process REQ_PREEMPT requests */
 
 #define QUEUE_FLAG_DEFAULT     ((1 << QUEUE_FLAG_IO_STAT) |            \
                                 (1 << QUEUE_FLAG_SAME_COMP)    |       \
@@ -732,6 +733,11 @@ static inline void queue_flag_clear(unsigned int flag, struct request_queue *q)
        ((rq)->cmd_flags & (REQ_FAILFAST_DEV|REQ_FAILFAST_TRANSPORT| \
                             REQ_FAILFAST_DRIVER))
 #define blk_queue_quiesced(q)  test_bit(QUEUE_FLAG_QUIESCED, &(q)->queue_flags)
+#define blk_queue_preempt_only(q)                              \
+       test_bit(QUEUE_FLAG_PREEMPT_ONLY, &(q)->queue_flags)
+
+extern int blk_set_preempt_only(struct request_queue *q);
+extern void blk_clear_preempt_only(struct request_queue *q);
 
 static inline bool blk_account_rq(struct request *rq)
 {