The patch titled
Subject: include/linux/bitops.h: set_mask_bits() to return old value
has been added to the -mm tree. Its filename is
bitopsh-set_mask_bits-to-return-old-value.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/bitopsh-set_mask_bits-to-return-old-value.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/bitopsh-set_mask_bits-to-return-old-value.patch
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------------------------------------------------------
From: Vineet Gupta <vineet.gupta1@xxxxxxxxxxxx>
Subject: include/linux/bitops.h: set_mask_bits() to return old value
| > Also, set_mask_bits is used in fs quite a bit and we can possibly come up
| > with a generic llsc based implementation (w/o the cmpxchg loop)
|
| May I also suggest changing the return value of set_mask_bits() to old.
|
| You can compute the new value given old, but you cannot compute the old
| value given new, therefore old is the better return value. Also, no
| current user seems to use the return value, so changing it is without
| risk.
Link: http://lkml.kernel.org/g/20150807110955.GH16853@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Link: http://lkml.kernel.org/r/1548275584-18096-4-git-send-email-vgupta@xxxxxxxxxxxx
Signed-off-by: Vineet Gupta <vgupta@xxxxxxxxxxxx>
Suggested-by: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Reviewed-by: Anthony Yznaga <anthony.yznaga@xxxxxxxxxx>
Acked-by: Will Deacon <will.deacon@xxxxxxx>
Cc: Miklos Szeredi <mszeredi@xxxxxxxxxx>
Cc: Ingo Molnar <mingo@xxxxxxxxxx>
Cc: Jani Nikula <jani.nikula@xxxxxxxxx>
Cc: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Alexander Viro <viro@xxxxxxxxxxxxxxxxxx>
Cc: Oleg Nesterov <oleg@xxxxxxxxxx>
Cc: Theodore Ts'o <tytso@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/bitops.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/include/linux/bitops.h~bitopsh-set_mask_bits-to-return-old-value
+++ a/include/linux/bitops.h
@@ -246,7 +246,7 @@ static __always_inline void __assign_bit
new__ = (old__ & ~mask__) | bits__; \
} while (cmpxchg(ptr, old__, new__) != old__); \
\
- new__; \
+ old__; \
})
#endif
_
Patches currently in -mm which might be from vineet.gupta1@xxxxxxxxxxxx are
coredump-replace-opencoded-set_mask_bits.patch
fs-inode_set_flags-replace-opencoded-set_mask_bits.patch
bitopsh-set_mask_bits-to-return-old-value.patch
