[PATCH 1/1] io-wq: close cancel gap for hashed linked work

[PATCH 1/1] io-wq: close cancel gap for hashed linked work

[Pavel Begunkov]

After io_assign_current_work() of a linked work, it can be decided to
offloaded to another thread so doing io_wqe_enqueue(). However, until
next io_assign_current_work() it can be cancelled, that isn't handled.

Don't assign it, if it's not going to be executed.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io-wq.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 9541df2729de..b3fb61ec0870 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -485,7 +485,7 @@ static void io_worker_handle_work(struct io_worker *worker)
 	struct io_wq *wq = wqe->wq;
 
 	do {
-		struct io_wq_work *work;
+		struct io_wq_work *work, *assign_work;
 		unsigned int hash;
 get_next:
 		/*
@@ -522,10 +522,14 @@ static void io_worker_handle_work(struct io_worker *worker)
 			hash = io_get_work_hash(work);
 			work->func(&work);
 			work = (old_work == work) ? NULL : work;
-			io_assign_current_work(worker, work);
+
+			assign_work = work;
+			if (work && io_wq_is_hashed(work))
+				assign_work = NULL;
+			io_assign_current_work(worker, assign_work);
 			wq->free_work(old_work);
 
-			if (work && io_wq_is_hashed(work)) {
+			if (work && !assign_work) {
 				io_wqe_enqueue(wqe, work);
 				work = NULL;
 			}
-- 
2.24.0

Re: [PATCH 1/1] io-wq: close cancel gap for hashed linked work

[Jens Axboe]

On 3/22/20 10:14 AM, Pavel Begunkov wrote:
> After io_assign_current_work() of a linked work, it can be decided to
> offloaded to another thread so doing io_wqe_enqueue(). However, until
> next io_assign_current_work() it can be cancelled, that isn't handled.
> 
> Don't assign it, if it's not going to be executed.

This needs a Fixes: line as well. I'm guessing like this:

Fixes: 60cf46ae6054 ("io-wq: hash dependent work")

but I didn't look too closely yet... Fix looks good, though.

-- 
Jens Axboe

Re: [PATCH 1/1] io-wq: close cancel gap for hashed linked work

[Pavel Begunkov]

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On 22/03/2020 20:04, Jens Axboe wrote:
> On 3/22/20 10:14 AM, Pavel Begunkov wrote:
>> After io_assign_current_work() of a linked work, it can be decided to
>> offloaded to another thread so doing io_wqe_enqueue(). However, until
>> next io_assign_current_work() it can be cancelled, that isn't handled.
>>
>> Don't assign it, if it's not going to be executed.
> 
> This needs a Fixes: line as well. I'm guessing like this:
> 
> Fixes: 60cf46ae6054 ("io-wq: hash dependent work")
> 
> but I didn't look too closely yet... Fix looks good, though.

Yep, this one

-- 
Pavel Begunkov


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[PATCH v2] io-wq: close cancel gap for hashed linked work

[Pavel Begunkov]

After io_assign_current_work() of a linked work, it can be decided to
offloaded to another thread so doing io_wqe_enqueue(). However, until
next io_assign_current_work() it can be cancelled, that isn't handled.

Don't assign it, if it's not going to be executed.

Fixes: 60cf46ae605446feb0c43c472c0 ("io-wq: hash dependent work")
Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
---
 fs/io-wq.c | 10 +++++++---
 1 file changed, 7 insertions(+), 3 deletions(-)

diff --git a/fs/io-wq.c b/fs/io-wq.c
index 9541df2729de..b3fb61ec0870 100644
--- a/fs/io-wq.c
+++ b/fs/io-wq.c
@@ -485,7 +485,7 @@ static void io_worker_handle_work(struct io_worker *worker)
 	struct io_wq *wq = wqe->wq;
 
 	do {
-		struct io_wq_work *work;
+		struct io_wq_work *work, *assign_work;
 		unsigned int hash;
 get_next:
 		/*
@@ -522,10 +522,14 @@ static void io_worker_handle_work(struct io_worker *worker)
 			hash = io_get_work_hash(work);
 			work->func(&work);
 			work = (old_work == work) ? NULL : work;
-			io_assign_current_work(worker, work);
+
+			assign_work = work;
+			if (work && io_wq_is_hashed(work))
+				assign_work = NULL;
+			io_assign_current_work(worker, assign_work);
 			wq->free_work(old_work);
 
-			if (work && io_wq_is_hashed(work)) {
+			if (work && !assign_work) {
 				io_wqe_enqueue(wqe, work);
 				work = NULL;
 			}
-- 
2.24.0