From: tuxoko <tuxoko@gmail.com>
Date: Sat, 8 Oct 2016 03:53:58 +0000 (-0700)
Subject: Linux 4.8 compat: Fix RW_READ_HELD
X-Git-Tag: zfs-0.8.0-rc1~152^2~76
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=2529b3a80e1bf1713c0ecbedb246654a0968b4d2;p=zfs

Linux 4.8 compat: Fix RW_READ_HELD

Linux 4.8, starting from torvalds/linux@19c5d690e, will set owner to 1 when
read held instead of leave it NULL. So we change the condition to
`rw_owner(rwp) <= 1` in RW_READ_HELD.

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Signed-off-by: Chunwei Chen <david.chen@osnexus.com>
Closes zfsonlinux/zfs#5233
Closes #577
---

diff --git a/include/sys/rwlock.h b/include/sys/rwlock.h
index facebe3ba..4197785db 100644
--- a/include/sys/rwlock.h
+++ b/include/sys/rwlock.h
@@ -114,7 +114,12 @@ spl_rw_lockdep_on_maybe(krwlock_t *rwp)			\
 static inline int
 RW_READ_HELD(krwlock_t *rwp)
 {
-	return (spl_rwsem_is_locked(SEM(rwp)) && rw_owner(rwp) == NULL);
+	/*
+	 * Linux 4.8 will set owner to 1 when read held instead of leave it
+	 * NULL. So we check whether owner <= 1.
+	 */
+	return (spl_rwsem_is_locked(SEM(rwp)) &&
+	    (unsigned long)rw_owner(rwp) <= 1);
 }
 
 static inline int