linux_dsm_epyc7002/fs/btrfs/async-thread.h
Zhao Lei 20b2e3029e btrfs: Fix lockdep warning of wr_ctx->wr_lock in scrub_free_wr_ctx()
lockdep report following warning in test:
 [25176.843958] =================================
 [25176.844519] [ INFO: inconsistent lock state ]
 [25176.845047] 4.1.0-rc3 #22 Tainted: G        W
 [25176.845591] ---------------------------------
 [25176.846153] inconsistent {SOFTIRQ-ON-W} -> {IN-SOFTIRQ-W} usage.
 [25176.846713] fsstress/26661 [HC0[0]:SC1[1]:HE1:SE0] takes:
 [25176.847246]  (&wr_ctx->wr_lock){+.?...}, at: [<ffffffffa04cdc6d>] scrub_free_ctx+0x2d/0xf0 [btrfs]
 [25176.847838] {SOFTIRQ-ON-W} state was registered at:
 [25176.848396]   [<ffffffff810bf460>] __lock_acquire+0x6a0/0xe10
 [25176.848955]   [<ffffffff810bfd1e>] lock_acquire+0xce/0x2c0
 [25176.849491]   [<ffffffff816489af>] mutex_lock_nested+0x7f/0x410
 [25176.850029]   [<ffffffffa04d04ff>] scrub_stripe+0x4df/0x1080 [btrfs]
 [25176.850575]   [<ffffffffa04d11b1>] scrub_chunk.isra.19+0x111/0x130 [btrfs]
 [25176.851110]   [<ffffffffa04d144c>] scrub_enumerate_chunks+0x27c/0x510 [btrfs]
 [25176.851660]   [<ffffffffa04d3b87>] btrfs_scrub_dev+0x1c7/0x6c0 [btrfs]
 [25176.852189]   [<ffffffffa04e918e>] btrfs_dev_replace_start+0x36e/0x450 [btrfs]
 [25176.852771]   [<ffffffffa04a98e0>] btrfs_ioctl+0x1e10/0x2d20 [btrfs]
 [25176.853315]   [<ffffffff8121c5b8>] do_vfs_ioctl+0x318/0x570
 [25176.853868]   [<ffffffff8121c851>] SyS_ioctl+0x41/0x80
 [25176.854406]   [<ffffffff8164da17>] system_call_fastpath+0x12/0x6f
 [25176.854935] irq event stamp: 51506
 [25176.855511] hardirqs last  enabled at (51506): [<ffffffff810d4ce5>] vprintk_emit+0x225/0x5e0
 [25176.856059] hardirqs last disabled at (51505): [<ffffffff810d4b77>] vprintk_emit+0xb7/0x5e0
 [25176.856642] softirqs last  enabled at (50886): [<ffffffff81067a23>] __do_softirq+0x363/0x640
 [25176.857184] softirqs last disabled at (50949): [<ffffffff8106804d>] irq_exit+0x10d/0x120
 [25176.857746]
 other info that might help us debug this:
 [25176.858845]  Possible unsafe locking scenario:
 [25176.859981]        CPU0
 [25176.860537]        ----
 [25176.861059]   lock(&wr_ctx->wr_lock);
 [25176.861705]   <Interrupt>
 [25176.862272]     lock(&wr_ctx->wr_lock);
 [25176.862881]
  *** DEADLOCK ***

Reason:
 Above warning is caused by:
 Interrupt
 -> bio_endio()
 -> ...
 -> scrub_put_ctx()
 -> scrub_free_ctx() *1
 -> ...
 -> mutex_lock(&wr_ctx->wr_lock);

 scrub_put_ctx() is allowed to be called in end_bio interrupt, but
 in code design, it will never call scrub_free_ctx(sctx) in interrupe
 context(above *1), because btrfs_scrub_dev() get one additional
 reference of sctx->refs, which makes scrub_free_ctx() only called
 withine btrfs_scrub_dev().

 Now the code runs out of our wish, because free sequence in
 scrub_pending_bio_dec() have a gap.

 Current code:
 -----------------------------------+-----------------------------------
 scrub_pending_bio_dec()            |  btrfs_scrub_dev
 -----------------------------------+-----------------------------------
 atomic_dec(&sctx->bios_in_flight); |
 wake_up(&sctx->list_wait);         |
                                    | scrub_put_ctx()
                                    | -> atomic_dec_and_test(&sctx->refs)
 scrub_put_ctx(sctx);               |
 -> atomic_dec_and_test(&sctx->refs)|
 -> scrub_free_ctx()                |
 -----------------------------------+-----------------------------------

 We expected:
 -----------------------------------+-----------------------------------
 scrub_pending_bio_dec()            |  btrfs_scrub_dev
 -----------------------------------+-----------------------------------
 atomic_dec(&sctx->bios_in_flight); |
 wake_up(&sctx->list_wait);         |
 scrub_put_ctx(sctx);               |
 -> atomic_dec_and_test(&sctx->refs)|
                                    | scrub_put_ctx()
                                    | -> atomic_dec_and_test(&sctx->refs)
                                    | -> scrub_free_ctx()
 -----------------------------------+-----------------------------------

Fix:
 Move scrub_pending_bio_dec() to a workqueue, to avoid this function run
 in interrupt context.
 Tested by check tracelog in debug.

Changelog v1->v2:
 Use workqueue instead of adjust function call sequence in v1,
 because v1 will introduce a bug pointed out by:
 Filipe David Manana <fdmanana@gmail.com>

Reported-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: Zhao Lei <zhaolei@cn.fujitsu.com>
Reviewed-by: Filipe Manana <fdmanana@suse.com>
Signed-off-by: Chris Mason <clm@fb.com>
2015-06-10 07:04:52 -07:00

84 lines
2.9 KiB
C

/*
* Copyright (C) 2007 Oracle. All rights reserved.
* Copyright (C) 2014 Fujitsu. All rights reserved.
*
* This program is free software; you can redistribute it and/or
* modify it under the terms of the GNU General Public
* License v2 as published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
* General Public License for more details.
*
* You should have received a copy of the GNU General Public
* License along with this program; if not, write to the
* Free Software Foundation, Inc., 59 Temple Place - Suite 330,
* Boston, MA 021110-1307, USA.
*/
#ifndef __BTRFS_ASYNC_THREAD_
#define __BTRFS_ASYNC_THREAD_
#include <linux/workqueue.h>
struct btrfs_workqueue;
/* Internal use only */
struct __btrfs_workqueue;
struct btrfs_work;
typedef void (*btrfs_func_t)(struct btrfs_work *arg);
typedef void (*btrfs_work_func_t)(struct work_struct *arg);
struct btrfs_work {
btrfs_func_t func;
btrfs_func_t ordered_func;
btrfs_func_t ordered_free;
/* Don't touch things below */
struct work_struct normal_work;
struct list_head ordered_list;
struct __btrfs_workqueue *wq;
unsigned long flags;
};
#define BTRFS_WORK_HELPER_PROTO(name) \
void btrfs_##name(struct work_struct *arg)
BTRFS_WORK_HELPER_PROTO(worker_helper);
BTRFS_WORK_HELPER_PROTO(delalloc_helper);
BTRFS_WORK_HELPER_PROTO(flush_delalloc_helper);
BTRFS_WORK_HELPER_PROTO(cache_helper);
BTRFS_WORK_HELPER_PROTO(submit_helper);
BTRFS_WORK_HELPER_PROTO(fixup_helper);
BTRFS_WORK_HELPER_PROTO(endio_helper);
BTRFS_WORK_HELPER_PROTO(endio_meta_helper);
BTRFS_WORK_HELPER_PROTO(endio_meta_write_helper);
BTRFS_WORK_HELPER_PROTO(endio_raid56_helper);
BTRFS_WORK_HELPER_PROTO(endio_repair_helper);
BTRFS_WORK_HELPER_PROTO(rmw_helper);
BTRFS_WORK_HELPER_PROTO(endio_write_helper);
BTRFS_WORK_HELPER_PROTO(freespace_write_helper);
BTRFS_WORK_HELPER_PROTO(delayed_meta_helper);
BTRFS_WORK_HELPER_PROTO(readahead_helper);
BTRFS_WORK_HELPER_PROTO(qgroup_rescan_helper);
BTRFS_WORK_HELPER_PROTO(extent_refs_helper);
BTRFS_WORK_HELPER_PROTO(scrub_helper);
BTRFS_WORK_HELPER_PROTO(scrubwrc_helper);
BTRFS_WORK_HELPER_PROTO(scrubnc_helper);
BTRFS_WORK_HELPER_PROTO(scrubparity_helper);
struct btrfs_workqueue *btrfs_alloc_workqueue(const char *name,
unsigned int flags,
int max_active,
int thresh);
void btrfs_init_work(struct btrfs_work *work, btrfs_work_func_t helper,
btrfs_func_t func,
btrfs_func_t ordered_func,
btrfs_func_t ordered_free);
void btrfs_queue_work(struct btrfs_workqueue *wq,
struct btrfs_work *work);
void btrfs_destroy_workqueue(struct btrfs_workqueue *wq);
void btrfs_workqueue_set_max(struct btrfs_workqueue *wq, int max);
void btrfs_set_work_high_priority(struct btrfs_work *work);
#endif