block: add REQ_BACKGROUND

This adds a new request flag, REQ_BACKGROUND, that callers can use to
tell the block layer that this is background (non-urgent) IO.

Signed-off-by: Jens Axboe <axboe@fb.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index bb92102..562ac46 100644 (file)
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -177,6 +177,7 @@ enum req_flag_bits {
        __REQ_FUA,              /* forced unit access */
        __REQ_PREFLUSH,         /* request for cache flush */
        __REQ_RAHEAD,           /* read ahead, can fail anytime */
+       __REQ_BACKGROUND,       /* background IO */
        __REQ_NR_BITS,          /* stops here */
 };
 
@@ -192,6 +193,7 @@ enum req_flag_bits {
 #define REQ_FUA                        (1ULL << __REQ_FUA)
 #define REQ_PREFLUSH           (1ULL << __REQ_PREFLUSH)
 #define REQ_RAHEAD             (1ULL << __REQ_RAHEAD)
+#define REQ_BACKGROUND         (1ULL << __REQ_BACKGROUND)
 
 #define REQ_FAILFAST_MASK \
        (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER)