io_uring/io-wq: don't use static creds/mm assignments

We currently setup the io_wq with a static set of mm and creds. Even for
a single-use io-wq per io_uring, this is suboptimal as we have may have
multiple enters of the ring. For sharing the io-wq backend, it doesn't
work at all.

Switch to passing in the creds and mm when the work item is setup. This
means that async work is no longer deferred to the io_uring mm and creds,
it is done with the current mm and creds.

Flag this behavior with IORING_FEAT_CUR_PERSONALITY, so applications know
they can rely on the current personality (mm and creds) being the same
for direct issue and async issue.

Reviewed-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

1 files changed, 4 insertions, 3 deletions

diff --git a/fs/io-wq.h b/fs/io-wq.h
index 1cd039af8813..167316ad447e 100644
--- a/fs/io-wq.h
+++ b/fs/io-wq.h
@@ -7,7 +7,6 @@ enum {
 	IO_WQ_WORK_CANCEL	= 1,
 	IO_WQ_WORK_HAS_MM	= 2,
 	IO_WQ_WORK_HASHED	= 4,
-	IO_WQ_WORK_NEEDS_USER	= 8,
 	IO_WQ_WORK_NEEDS_FILES	= 16,
 	IO_WQ_WORK_UNBOUND	= 32,
 	IO_WQ_WORK_INTERNAL	= 64,
@@ -74,6 +73,8 @@ struct io_wq_work {
 	};
 	void (*func)(struct io_wq_work **);
 	struct files_struct *files;
+	struct mm_struct *mm;
+	const struct cred *creds;
 	unsigned flags;
 };
 
@@ -83,15 +84,15 @@ struct io_wq_work {
 		(work)->func = _func;			\
 		(work)->flags = 0;			\
 		(work)->files = NULL;			\
+		(work)->mm = NULL;			\
+		(work)->creds = NULL;			\
 	} while (0)					\
 
 typedef void (get_work_fn)(struct io_wq_work *);
 typedef void (put_work_fn)(struct io_wq_work *);
 
 struct io_wq_data {
-	struct mm_struct *mm;
 	struct user_struct *user;
-	const struct cred *creds;
 
 	get_work_fn *get_work;
 	put_work_fn *put_work;