block, drivers, fs: rename REQ_FLUSH to REQ_PREFLUSH

To avoid confusion between REQ_OP_FLUSH, which is handled by
request_fn drivers, and upper layers requesting the block layer
perform a flush sequence along with possibly a WRITE, this patch
renames REQ_FLUSH to REQ_PREFLUSH.

Signed-off-by: Mike Christie <mchristi@redhat.com>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Hannes Reinecke <hare@suse.com>
Signed-off-by: Jens Axboe <axboe@fb.com>

1 files changed, 11 insertions, 11 deletions

diff --git a/Documentation/block/writeback_cache_control.txt b/Documentation/block/writeback_cache_control.txt
index da70bdacd503..8a6bdada5f6b 100644
--- a/Documentation/block/writeback_cache_control.txt
+++ b/Documentation/block/writeback_cache_control.txt
@@ -20,11 +20,11 @@ a forced cache flush, and the Force Unit Access (FUA) flag for requests.
 Explicit cache flushes
 ----------------------
 
-The REQ_FLUSH flag can be OR ed into the r/w flags of a bio submitted from
+The REQ_PREFLUSH flag can be OR ed into the r/w flags of a bio submitted from
 the filesystem and will make sure the volatile cache of the storage device
 has been flushed before the actual I/O operation is started.  This explicitly
 guarantees that previously completed write requests are on non-volatile
-storage before the flagged bio starts. In addition the REQ_FLUSH flag can be
+storage before the flagged bio starts. In addition the REQ_PREFLUSH flag can be
 set on an otherwise empty bio structure, which causes only an explicit cache
 flush without any dependent I/O.  It is recommend to use
 the blkdev_issue_flush() helper for a pure cache flush.
@@ -41,21 +41,21 @@ signaled after the data has been committed to non-volatile storage.
 Implementation details for filesystems
 --------------------------------------
 
-Filesystems can simply set the REQ_FLUSH and REQ_FUA bits and do not have to
+Filesystems can simply set the REQ_PREFLUSH and REQ_FUA bits and do not have to
 worry if the underlying devices need any explicit cache flushing and how
-the Forced Unit Access is implemented.  The REQ_FLUSH and REQ_FUA flags
+the Forced Unit Access is implemented.  The REQ_PREFLUSH and REQ_FUA flags
 may both be set on a single bio.
 
 
 Implementation details for make_request_fn based block drivers
 --------------------------------------------------------------
 
-These drivers will always see the REQ_FLUSH and REQ_FUA bits as they sit
+These drivers will always see the REQ_PREFLUSH and REQ_FUA bits as they sit
 directly below the submit_bio interface.  For remapping drivers the REQ_FUA
 bits need to be propagated to underlying devices, and a global flush needs
-to be implemented for bios with the REQ_FLUSH bit set.  For real device
-drivers that do not have a volatile cache the REQ_FLUSH and REQ_FUA bits
-on non-empty bios can simply be ignored, and REQ_FLUSH requests without
+to be implemented for bios with the REQ_PREFLUSH bit set.  For real device
+drivers that do not have a volatile cache the REQ_PREFLUSH and REQ_FUA bits
+on non-empty bios can simply be ignored, and REQ_PREFLUSH requests without
 data can be completed successfully without doing any work.  Drivers for
 devices with volatile caches need to implement the support for these
 flags themselves without any help from the block layer.
@@ -65,8 +65,8 @@ Implementation details for request_fn based block drivers
 --------------------------------------------------------------
 
 For devices that do not support volatile write caches there is no driver
-support required, the block layer completes empty REQ_FLUSH requests before
-entering the driver and strips off the REQ_FLUSH and REQ_FUA bits from
+support required, the block layer completes empty REQ_PREFLUSH requests before
+entering the driver and strips off the REQ_PREFLUSH and REQ_FUA bits from
 requests that have a payload.  For devices with volatile write caches the
 driver needs to tell the block layer that it supports flushing caches by
 doing:
@@ -74,7 +74,7 @@ doing:
 	blk_queue_write_cache(sdkp->disk->queue, true, false);
 
 and handle empty REQ_OP_FLUSH requests in its prep_fn/request_fn.  Note that
-REQ_FLUSH requests with a payload are automatically turned into a sequence
+REQ_PREFLUSH requests with a payload are automatically turned into a sequence
 of an empty REQ_OP_FLUSH request followed by the actual write by the block
 layer.  For devices that also support the FUA bit the block layer needs
 to be told to pass through the REQ_FUA bit using: