From 85ad1d13ee9b3db00615ea24b031c15e5ba14fd1 Mon Sep 17 00:00:00 2001 From: Guoqing Jiang Date: Tue, 3 May 2016 22:22:13 -0400 Subject: md: set MD_CHANGE_PENDING in a atomic region Some code waits for a metadata update by: 1. flagging that it is needed (MD_CHANGE_DEVS or MD_CHANGE_CLEAN) 2. setting MD_CHANGE_PENDING and waking the management thread 3. waiting for MD_CHANGE_PENDING to be cleared If the first two are done without locking, the code in md_update_sb() which checks if it needs to repeat might test if an update is needed before step 1, then clear MD_CHANGE_PENDING after step 2, resulting in the wait returning early. So make sure all places that set MD_CHANGE_PENDING are atomicial, and bit_clear_unless (suggested by Neil) is introduced for the purpose. Cc: Martin Kepplinger Cc: Andrew Morton Cc: Denys Vlasenko Cc: Sasha Levin Cc: Reviewed-by: NeilBrown Signed-off-by: Guoqing Jiang Signed-off-by: Shaohua Li --- include/linux/bitops.h | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) (limited to 'include/linux/bitops.h') diff --git a/include/linux/bitops.h b/include/linux/bitops.h index defeaac0745f..299e76b59fe9 100644 --- a/include/linux/bitops.h +++ b/include/linux/bitops.h @@ -227,6 +227,22 @@ static inline unsigned long __ffs64(u64 word) }) #endif +#ifndef bit_clear_unless +#define bit_clear_unless(ptr, _clear, _test) \ +({ \ + const typeof(*ptr) clear = (_clear), test = (_test); \ + typeof(*ptr) old, new; \ + \ + do { \ + old = ACCESS_ONCE(*ptr); \ + new = old & ~clear; \ + } while (!(old & test) && \ + cmpxchg(ptr, old, new) != old); \ + \ + !(old & test); \ +}) +#endif + #ifndef find_last_bit /** * find_last_bit - find the last set bit in a memory region -- cgit v1.2.3-59-g8ed1b