diff options
| -rw-r--r-- | include/linux/bio.h | 12 |
1 files changed, 11 insertions, 1 deletions
diff --git a/include/linux/bio.h b/include/linux/bio.h index fb97221d7c3..ff5b4cf9e2d 100644 --- a/include/linux/bio.h +++ b/include/linux/bio.h @@ -123,13 +123,23 @@ struct bio { /* * bio bi_rw flags * - * bit 0 -- read (not set) or write (set) + * bit 0 -- data direction + * If not set, bio is a read from device. If set, it's a write to device. * bit 1 -- rw-ahead when set * bit 2 -- barrier + * Insert a serialization point in the IO queue, forcing previously + * submitted IO to be completed before this oen is issued. * bit 3 -- fail fast, don't want low level driver retries * bit 4 -- synchronous I/O hint: the block layer will unplug immediately + * Note that this does NOT indicate that the IO itself is sync, just + * that the block layer will not postpone issue of this IO by plugging. * bit 5 -- metadata request + * Used for tracing to differentiate metadata and data IO. May also + * get some preferential treatment in the IO scheduler * bit 6 -- discard sectors + * Informs the lower level device that this range of sectors is no longer + * used by the file system and may thus be freed by the device. Used + * for flash based storage. */ #define BIO_RW 0 /* Must match RW in req flags (blkdev.h) */ #define BIO_RW_AHEAD 1 /* Must match FAILFAST in req flags */ |