blk: introduce REQ_SWAP

Just like REQ_META, it's important to know the IO coming down is swap
in order to guard against potential IO priority inversion issues with
cgroups.  Add REQ_SWAP and use it for all swap IO, and add it to our
bio_issue_as_root_blkg helper.

Signed-off-by: Josef Bacik <jbacik@fb.com>
Acked-by: Tejun Heo <tj@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index b41292726c0f32a9c8c8879a947eaa6374f6da3b..a8f9ba8f33a48ca5c74fa6d9c4998c8f3f5d0432 100644 (file)
--- a/include/linux/blk-cgroup.h
+++ b/include/linux/blk-cgroup.h
@@ -254,7 +254,7 @@ static inline struct blkcg *bio_blkcg(struct bio *bio)
  */
 static inline bool bio_issue_as_root_blkg(struct bio *bio)
 {
-       return (bio->bi_opf & REQ_META);
+       return (bio->bi_opf & (REQ_META | REQ_SWAP)) != 0;
 }
 
 /**

diff --git a/include/linux/blk_types.h b/include/linux/blk_types.h
index 3364d42ebe0807708f41fcf9b23e7086e8562292..0ffc34c5cc83a900594c1706047f941a4b8ac979 100644 (file)
--- a/include/linux/blk_types.h
+++ b/include/linux/blk_types.h
@@ -329,7 +329,7 @@ enum req_flag_bits {
 
        /* for driver use */
        __REQ_DRV,
-
+       __REQ_SWAP,             /* swapping request. */
        __REQ_NR_BITS,          /* stops here */
 };
 
@@ -351,6 +351,7 @@ enum req_flag_bits {
 #define REQ_NOUNMAP            (1ULL << __REQ_NOUNMAP)
 
 #define REQ_DRV                        (1ULL << __REQ_DRV)
+#define REQ_SWAP               (1ULL << __REQ_SWAP)
 
 #define REQ_FAILFAST_MASK \
        (REQ_FAILFAST_DEV | REQ_FAILFAST_TRANSPORT | REQ_FAILFAST_DRIVER)

diff --git a/mm/page_io.c b/mm/page_io.c
index b41cf96445856e480f872b33b81855b86551488c..a552cb37e220d78bdd4764d49f0fb7f6a65f54e7 100644 (file)
--- a/mm/page_io.c
+++ b/mm/page_io.c
@@ -338,7 +338,7 @@ int __swap_writepage(struct page *page, struct writeback_control *wbc,
                ret = -ENOMEM;
                goto out;
        }
-       bio->bi_opf = REQ_OP_WRITE | wbc_to_write_flags(wbc);
+       bio->bi_opf = REQ_OP_WRITE | REQ_SWAP | wbc_to_write_flags(wbc);
        count_swpout_vm_event(page);
        set_page_writeback(page);
        unlock_page(page);