[PATCH 7/7] md: fix a suspicious RCU usage warning

[Mikulas Patocka <mpatocka@redhat.com>]

RCU protection was removed in the commit 2d32777d60de ("raid1: remove rcu
protection to access rdev from conf").

However, the code in fix_read_error does rcu_dereference outside
rcu_read_lock - this triggers the following warning. The warning is
triggered by a LVM2 test shell/integrity-caching.sh.

This commit removes rcu_dereference.

=============================
WARNING: suspicious RCU usage
6.7.0 #2 Not tainted
-----------------------------
drivers/md/raid1.c:2265 suspicious rcu_dereference_check() usage!

other info that might help us debug this:

rcu_scheduler_active = 2, debug_locks = 1
no locks held by mdX_raid1/1859.

stack backtrace:
CPU: 2 PID: 1859 Comm: mdX_raid1 Not tainted 6.7.0 #2
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014
Call Trace:
 <TASK>
 dump_stack_lvl+0x60/0x70
 lockdep_rcu_suspicious+0x153/0x1b0
 raid1d+0x1732/0x1750 [raid1]
 ? lock_acquire+0x9f/0x270
 ? finish_wait+0x3d/0x80
 ? md_thread+0xf7/0x130 [md_mod]
 ? lock_release+0xaa/0x230
 ? md_register_thread+0xd0/0xd0 [md_mod]
 md_thread+0xa0/0x130 [md_mod]
 ? housekeeping_test_cpu+0x30/0x30
 kthread+0xdc/0x110
 ? kthread_complete_and_exit+0x20/0x20
 ret_from_fork+0x28/0x40
 ? kthread_complete_and_exit+0x20/0x20
 ret_from_fork_asm+0x11/0x20
 </TASK>

Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Fixes: ca294b34aaf3 ("md/raid1: support read error check")

---
 drivers/md/raid1.c |    2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Index: linux-2.6/drivers/md/raid1.c
===================================================================
--- linux-2.6.orig/drivers/md/raid1.c
+++ linux-2.6/drivers/md/raid1.c
@@ -2262,7 +2262,7 @@ static void fix_read_error(struct r1conf
 	int sectors = r1_bio->sectors;
 	int read_disk = r1_bio->read_disk;
 	struct mddev *mddev = conf->mddev;
-	struct md_rdev *rdev = rcu_dereference(conf->mirrors[read_disk].rdev);
+	struct md_rdev *rdev = conf->mirrors[read_disk].rdev;
 
 	if (exceed_read_errors(mddev, rdev)) {
 		r1_bio->bios[r1_bio->read_disk] = IO_BLOCKED;