From 0d1e0c7cd5909d6c6aa0957179318e13fcca971a Mon Sep 17 00:00:00 2001
From: Josef Bacik <jbacik@fb.com>
Date: Tue, 3 Jul 2018 11:14:53 -0400
Subject: [PATCH] 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>
---
include/linux/blk-cgroup.h | 2 +-
include/linux/blk_types.h | 3 ++-
mm/page_io.c | 2 +-
3 files changed, 4 insertions(+), 3 deletions(-)
diff --git a/include/linux/blk-cgroup.h b/include/linux/blk-cgroup.h
index b41292726c0f3..a8f9ba8f33a48 100644
--- 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 3364d42ebe080..0ffc34c5cc83a 100644
--- 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 b41cf96445856..a552cb37e220d 100644
--- 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);
--
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