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Subject[PATCH] writeback: check wb shutdown for bw_dwork
Date
This fixes a KASAN splat in timer interrupt after removing a device

Move wb->work_lock to be irq-safe, as complete may be called from irq

Fixes: 45a2966fd641 ("writeback: fix bandwidth estimate for spiky workload")
Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
---
fs/fs-writeback.c | 12 ++++++------
mm/backing-dev.c | 10 +++++-----
mm/page-writeback.c | 6 +++++-
3 files changed, 16 insertions(+), 12 deletions(-)

diff --git a/fs/fs-writeback.c b/fs/fs-writeback.c
index 05221366a16d..08a1993ab7fd 100644
--- a/fs/fs-writeback.c
+++ b/fs/fs-writeback.c
@@ -134,10 +134,10 @@ static bool inode_io_list_move_locked(struct inode *inode,

static void wb_wakeup(struct bdi_writeback *wb)
{
- spin_lock_bh(&wb->work_lock);
+ spin_lock_irq(&wb->work_lock);
if (test_bit(WB_registered, &wb->state))
mod_delayed_work(bdi_wq, &wb->dwork, 0);
- spin_unlock_bh(&wb->work_lock);
+ spin_unlock_irq(&wb->work_lock);
}

static void finish_writeback_work(struct bdi_writeback *wb,
@@ -164,7 +164,7 @@ static void wb_queue_work(struct bdi_writeback *wb,
if (work->done)
atomic_inc(&work->done->cnt);

- spin_lock_bh(&wb->work_lock);
+ spin_lock_irq(&wb->work_lock);

if (test_bit(WB_registered, &wb->state)) {
list_add_tail(&work->list, &wb->work_list);
@@ -172,7 +172,7 @@ static void wb_queue_work(struct bdi_writeback *wb,
} else
finish_writeback_work(wb, work);

- spin_unlock_bh(&wb->work_lock);
+ spin_unlock_irq(&wb->work_lock);
}

/**
@@ -2082,13 +2082,13 @@ static struct wb_writeback_work *get_next_work_item(struct bdi_writeback *wb)
{
struct wb_writeback_work *work = NULL;

- spin_lock_bh(&wb->work_lock);
+ spin_lock_irq(&wb->work_lock);
if (!list_empty(&wb->work_list)) {
work = list_entry(wb->work_list.next,
struct wb_writeback_work, list);
list_del_init(&work->list);
}
- spin_unlock_bh(&wb->work_lock);
+ spin_unlock_irq(&wb->work_lock);
return work;
}

diff --git a/mm/backing-dev.c b/mm/backing-dev.c
index 95550b8fa7fe..de65cb1e5f76 100644
--- a/mm/backing-dev.c
+++ b/mm/backing-dev.c
@@ -260,10 +260,10 @@ void wb_wakeup_delayed(struct bdi_writeback *wb)
unsigned long timeout;

timeout = msecs_to_jiffies(dirty_writeback_interval * 10);
- spin_lock_bh(&wb->work_lock);
+ spin_lock_irq(&wb->work_lock);
if (test_bit(WB_registered, &wb->state))
queue_delayed_work(bdi_wq, &wb->dwork, timeout);
- spin_unlock_bh(&wb->work_lock);
+ spin_unlock_irq(&wb->work_lock);
}

static void wb_update_bandwidth_workfn(struct work_struct *work)
@@ -334,12 +334,12 @@ static void cgwb_remove_from_bdi_list(struct bdi_writeback *wb);
static void wb_shutdown(struct bdi_writeback *wb)
{
/* Make sure nobody queues further work */
- spin_lock_bh(&wb->work_lock);
+ spin_lock_irq(&wb->work_lock);
if (!test_and_clear_bit(WB_registered, &wb->state)) {
- spin_unlock_bh(&wb->work_lock);
+ spin_unlock_irq(&wb->work_lock);
return;
}
- spin_unlock_bh(&wb->work_lock);
+ spin_unlock_irq(&wb->work_lock);

cgwb_remove_from_bdi_list(wb);
/*
diff --git a/mm/page-writeback.c b/mm/page-writeback.c
index 55c2776ae699..3c34db15cf70 100644
--- a/mm/page-writeback.c
+++ b/mm/page-writeback.c
@@ -2867,6 +2867,7 @@ static void wb_inode_writeback_start(struct bdi_writeback *wb)

static void wb_inode_writeback_end(struct bdi_writeback *wb)
{
+ unsigned long flags;
atomic_dec(&wb->writeback_inodes);
/*
* Make sure estimate of writeback throughput gets updated after
@@ -2875,7 +2876,10 @@ static void wb_inode_writeback_end(struct bdi_writeback *wb)
* that if multiple inodes end writeback at a similar time, they get
* batched into one bandwidth update.
*/
- queue_delayed_work(bdi_wq, &wb->bw_dwork, BANDWIDTH_INTERVAL);
+ spin_lock_irqsave(&wb->work_lock, flags);
+ if (test_bit(WB_registered, &wb->state))
+ queue_delayed_work(bdi_wq, &wb->bw_dwork, BANDWIDTH_INTERVAL);
+ spin_unlock_irqrestore(&wb->work_lock, flags);
}

bool __folio_end_writeback(struct folio *folio)
--
2.37.1.455.g008518b4e5-goog
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