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authorGuoqing Jiang <gqjiang@suse.com>2016-05-03 22:22:13 -0400
committerShaohua Li <shli@fb.com>2016-05-09 09:24:02 -0700
commit85ad1d13ee9b3db00615ea24b031c15e5ba14fd1 (patch)
treeff8cd0a32ae44fa7d306cee622c9eea96a9de076 /include/linux/bitops.h
parentfe67d19a2d7b31f1c29efbe1819c921d4a9bb012 (diff)
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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 <martink@posteo.de> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: Sasha Levin <sasha.levin@oracle.com> Cc: <linux-kernel@vger.kernel.org> Reviewed-by: NeilBrown <neilb@suse.com> Signed-off-by: Guoqing Jiang <gqjiang@suse.com> Signed-off-by: Shaohua Li <shli@fb.com>
Diffstat (limited to 'include/linux/bitops.h')
-rw-r--r--include/linux/bitops.h16
1 files changed, 16 insertions, 0 deletions
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