io_wq: add get/put_work handlers to io_wq_create()

For cancellation, we need to ensure that the work item stays valid for
as long as ->cur_work is valid. Right now we can't safely dereference
the work item even under the wqe->lock, because while the ->cur_work
pointer will remain valid, the work could be completing and be freed
in parallel.

Only invoke ->get/put_work() on items we know that the caller queued
themselves. Add IO_WQ_WORK_INTERNAL for io-wq to use, which is needed
when we're queueing a flush item, for instance.

Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 6 insertions, 1 deletions

diff --git a/fs/io-wq.h b/fs/io-wq.h
index cc50754d028c..4b29f922f80c 100644
--- a/fs/io-wq.h
+++ b/fs/io-wq.h
@@ -10,6 +10,7 @@ enum {
 	IO_WQ_WORK_NEEDS_USER	= 8,
 	IO_WQ_WORK_NEEDS_FILES	= 16,
 	IO_WQ_WORK_UNBOUND	= 32,
+	IO_WQ_WORK_INTERNAL	= 64,
 
 	IO_WQ_HASH_SHIFT	= 24,	/* upper 8 bits are used for hash key */
 };
@@ -34,8 +35,12 @@ struct io_wq_work {
 		(work)->files = NULL;			\
 	} while (0)					\
 
+typedef void (get_work_fn)(struct io_wq_work *);
+typedef void (put_work_fn)(struct io_wq_work *);
+
 struct io_wq *io_wq_create(unsigned bounded, struct mm_struct *mm,
-				struct user_struct *user);
+				struct user_struct *user,
+				get_work_fn *get_work, put_work_fn *put_work);
 void io_wq_destroy(struct io_wq *wq);
 
 void io_wq_enqueue(struct io_wq *wq, struct io_wq_work *work);