block: separate priority boosting from REQ_META

Add a new REQ_PRIO to let requests preempt others in the cfq I/O schedule,
and lave REQ_META purely for marking requests as metadata in blktrace.

All existing callers of REQ_META except for XFS are updated to also
set REQ_PRIO for now.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Reviewed-by: Namhyung Kim <namhyung@gmail.com>
Signed-off-by: Jens Axboe <jaxboe@fusionio.com>

2 files changed, 4 insertions, 3 deletions

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index 1dfa18feeb3e..c7cbb3d85d9e 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -650,7 +650,7 @@ struct buffer_head *ext4_bread(handle_t *handle, struct inode *inode,
                 return bh;
         if (buffer_uptodate(bh))
                 return bh;
-        ll_rw_block(READ | REQ_META, 1, &bh);
+        ll_rw_block(READ | REQ_META | REQ_PRIO, 1, &bh);
         wait_on_buffer(bh);
         if (buffer_uptodate(bh))
                 return bh;
@@ -3301,7 +3301,7 @@ make_io:
                 trace_ext4_load_inode(inode);
                 get_bh(bh);
                 bh->b_end_io = end_buffer_read_sync;
-                submit_bh(READ | REQ_META, bh);
+                submit_bh(READ | REQ_META | REQ_PRIO, bh);
                 wait_on_buffer(bh);
                 if (!buffer_uptodate(bh)) {
                         EXT4_ERROR_INODE_BLOCK(inode, block,
diff --git a/fs/ext4/namei.c b/fs/ext4/namei.c
index d36315ae629e..1c924faeb6c8 100644
--- a/fs/ext4/namei.c
+++ b/fs/ext4/namei.c
@@ -922,7 +922,8 @@ restart:
                                 bh = ext4_getblk(NULL, dir, b++, 0, &err);
                                 bh_use[ra_max] = bh;
                                 if (bh)
-                                        ll_rw_block(READ | REQ_META, 1, &bh);
+                                        ll_rw_block(READ | REQ_META | REQ_PRIO,
+                                                    1, &bh);
                         }
                 }
                 if ((bh = bh_use[ra_ptr++]) == NULL)