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authorLinus Torvalds <torvalds@linux-foundation.org>2018-02-04 22:16:35 +0300
committerLinus Torvalds <torvalds@linux-foundation.org>2018-02-04 22:16:35 +0300
commit64b28683deba132f301d1cecfc25c32e295f53a1 (patch)
treebe38a4e77c530fb129339f983a9d307c60312df8 /include/linux/buffer_head.h
parentd3658c2266012f270da52e3e0365536e394bd3bd (diff)
parent1d51877578799bfe0fcfe189d8233c9fccf05931 (diff)
downloadlinux-64b28683deba132f301d1cecfc25c32e295f53a1.tar.xz
Merge tag 'for-linus-20180204' of git://git.kernel.dk/linux-block
Pull more block updates from Jens Axboe: "Most of this is fixes and not new code/features: - skd fix from Arnd, fixing a build error dependent on sla allocator type. - blk-mq scheduler discard merging fixes, one from me and one from Keith. This fixes a segment miscalculation for blk-mq-sched, where we mistakenly think two segments are physically contigious even though the request isn't carrying real data. Also fixes a bio-to-rq merge case. - Don't re-set a bit on the buffer_head flags, if it's already set. This can cause scalability concerns on bigger machines and workloads. From Kemi Wang. - Add BLK_STS_DEV_RESOURCE return value to blk-mq, allowing us to distuingish between a local (device related) resource starvation and a global one. The latter might happen without IO being in flight, so it has to be handled a bit differently. From Ming" * tag 'for-linus-20180204' of git://git.kernel.dk/linux-block: block: skd: fix incorrect linux/slab_def.h inclusion buffer: Avoid setting buffer bits that are already set blk-mq-sched: Enable merging discard bio into request blk-mq: fix discard merge with scheduler attached blk-mq: introduce BLK_STS_DEV_RESOURCE
Diffstat (limited to 'include/linux/buffer_head.h')
-rw-r--r--include/linux/buffer_head.h5
1 files changed, 4 insertions, 1 deletions
diff --git a/include/linux/buffer_head.h b/include/linux/buffer_head.h
index 58a82f58e44e..894e5d125de6 100644
--- a/include/linux/buffer_head.h
+++ b/include/linux/buffer_head.h
@@ -81,11 +81,14 @@ struct buffer_head {
/*
* macro tricks to expand the set_buffer_foo(), clear_buffer_foo()
* and buffer_foo() functions.
+ * To avoid reset buffer flags that are already set, because that causes
+ * a costly cache line transition, check the flag first.
*/
#define BUFFER_FNS(bit, name) \
static __always_inline void set_buffer_##name(struct buffer_head *bh) \
{ \
- set_bit(BH_##bit, &(bh)->b_state); \
+ if (!test_bit(BH_##bit, &(bh)->b_state)) \
+ set_bit(BH_##bit, &(bh)->b_state); \
} \
static __always_inline void clear_buffer_##name(struct buffer_head *bh) \
{ \