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From: paulmck@kernel.org
To: rcu@vger.kernel.org
Cc: linux-kernel@vger.kernel.org, kernel-team@fb.com,
	mingo@kernel.org, jiangshanlai@gmail.com, dipankar@in.ibm.com,
	akpm@linux-foundation.org, mathieu.desnoyers@efficios.com,
	josh@joshtriplett.org, tglx@linutronix.de, peterz@infradead.org,
	rostedt@goodmis.org, dhowells@redhat.com, edumazet@google.com,
	fweisbec@gmail.com, oleg@redhat.com, joel@joelfernandes.org,
	"Paul E. McKenney" <paulmck@kernel.org>
Subject: [PATCH tip/core/rcu 11/26] fs/btrfs: Add cond_resched() for try_release_extent_mapping() stalls
Date: Mon, 22 Jun 2020 17:21:32 -0700	[thread overview]
Message-ID: <20200623002147.25750-11-paulmck@kernel.org> (raw)
In-Reply-To: <20200623002128.GA25456@paulmck-ThinkPad-P72>

From: "Paul E. McKenney" <paulmck@kernel.org>

Very large I/Os can cause the following RCU CPU stall warning:

RIP: 0010:rb_prev+0x8/0x50
Code: 49 89 c0 49 89 d1 48 89 c2 48 89 f8 e9 e5 fd ff ff 4c 89 48 10 c3 4c =
89 06 c3 4c 89 40 10 c3 0f 1f 00 48 8b 0f 48 39 cf 74 38 <48> 8b 47 10 48 85 c0 74 22 48 8b 50 08 48 85 d2 74 0c 48 89 d0 48
RSP: 0018:ffffc9002212bab0 EFLAGS: 00000287 ORIG_RAX: ffffffffffffff13
RAX: ffff888821f93630 RBX: ffff888821f93630 RCX: ffff888821f937e0
RDX: 0000000000000000 RSI: 0000000000102000 RDI: ffff888821f93630
RBP: 0000000000103000 R08: 000000000006c000 R09: 0000000000000238
R10: 0000000000102fff R11: ffffc9002212bac8 R12: 0000000000000001
R13: ffffffffffffffff R14: 0000000000102000 R15: ffff888821f937e0
 __lookup_extent_mapping+0xa0/0x110
 try_release_extent_mapping+0xdc/0x220
 btrfs_releasepage+0x45/0x70
 shrink_page_list+0xa39/0xb30
 shrink_inactive_list+0x18f/0x3b0
 shrink_lruvec+0x38e/0x6b0
 shrink_node+0x14d/0x690
 do_try_to_free_pages+0xc6/0x3e0
 try_to_free_mem_cgroup_pages+0xe6/0x1e0
 reclaim_high.constprop.73+0x87/0xc0
 mem_cgroup_handle_over_high+0x66/0x150
 exit_to_usermode_loop+0x82/0xd0
 do_syscall_64+0xd4/0x100
 entry_SYSCALL_64_after_hwframe+0x44/0xa9

On a PREEMPT=n kernel, the try_release_extent_mapping() function's
"while" loop might run for a very long time on a large I/O.  This commit
therefore adds a cond_resched() to this loop, providing RCU any needed
quiescent states.

Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
---
 fs/btrfs/extent_io.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 68c9605..7042395 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4515,6 +4515,8 @@ int try_release_extent_mapping(struct page *page, gfp_t mask)
 
 			/* once for us */
 			free_extent_map(em);
+
+			cond_resched(); /* Allow large-extent preemption. */
 		}
 	}
 	return try_release_extent_state(tree, page, mask);
-- 
2.9.5


  parent reply	other threads:[~2020-06-23  0:23 UTC|newest]

Thread overview: 35+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-23  0:21 [PATCH tip/core/rcu 0/26] Miscellaneous fixes for v5.9 Paul E. McKenney
2020-06-23  0:21 ` [PATCH tip/core/rcu 01/26] rcu: Initialize and destroy rcu_synchronize only when necessary paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 02/26] mm/mmap.c: Add cond_resched() for exit_mmap() CPU stalls paulmck
2020-06-23  0:47   ` Shakeel Butt
2020-06-23  0:47     ` Shakeel Butt
2020-06-23  0:57     ` Paul E. McKenney
2020-06-23 19:34   ` Joel Fernandes
2020-06-23 20:55     ` Paul E. McKenney
2020-06-23 21:01       ` Joel Fernandes
2020-06-23  0:21 ` [PATCH tip/core/rcu 03/26] rcu: Simplify the calculation of rcu_state.ncpus paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 04/26] rcu: Add callbacks-invoked counters paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 05/26] rcu: Add comment documenting rcu_callback_map's purpose paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 06/26] trace: events: rcu: Change description of rcu_dyntick trace event paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 07/26] rcu: Grace-period-kthread related sleeps to idle priority paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 08/26] rcu: Priority-boost-related " paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 09/26] rcu: No-CBs-related " paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 10/26] rcu: Expedited grace-period " paulmck
2020-06-23  0:21 ` paulmck [this message]
2020-06-23  0:21 ` [PATCH tip/core/rcu 12/26] rcu: Update comment from rsp->rcu_gp_seq to rsp->gp_seq paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 13/26] tick/nohz: Narrow down noise while setting current task's tick dependency paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 14/26] rcu: fix some kernel-doc warnings paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 15/26] rcu: Remove initialized but unused rnp from check_slow_task() paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 16/26] rcu: Mark rcu_nmi_enter() call to rcu_cleanup_after_idle() noinstr paulmck
2020-06-23 17:04   ` Peter Zijlstra
2020-06-23 17:50     ` Paul E. McKenney
2020-06-23  0:21 ` [PATCH tip/core/rcu 17/26] lockdep: Complain only once about RCU in extended quiescent state paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 18/26] rcu: Replace 1 with true paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 19/26] rcu: Stop shrinker loop paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 20/26] rcu: gp_max is protected by root rcu_node's lock paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 21/26] rcu: grplo/grphi just records CPU number paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 22/26] rcu: grpnum just records group number paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 23/26] kernel/rcu/tree.c: Fix kernel-doc warnings paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 24/26] rcu: fix some " paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 25/26] rcu: Remove KCSAN stubs paulmck
2020-06-23  0:21 ` [PATCH tip/core/rcu 26/26] rcu: Remove KCSAN stubs from update.c paulmck

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