From: Jens Axboe axboe@kernel.dk
[ Upstream commit 944d1444d53f5a213457e5096db370cfd06923d4 ]
Any attempt to do path resolution on /proc/self from an async worker will yield -EOPNOTSUPP. We can safely do that resolution from the task itself, and without blocking, so retry it from there.
Ideally io_uring would know this upfront and not have to go through the worker thread to find out, but that doesn't currently seem feasible.
Signed-off-by: Jens Axboe axboe@kernel.dk Signed-off-by: Sasha Levin sashal@kernel.org --- fs/io_uring.c | 19 ++++++++++++++++++- 1 file changed, 18 insertions(+), 1 deletion(-)
diff --git a/fs/io_uring.c b/fs/io_uring.c index 185c206e5683f..5d9f8e40b93d3 100644 --- a/fs/io_uring.c +++ b/fs/io_uring.c @@ -436,6 +436,7 @@ struct io_sr_msg { struct io_open { struct file *file; int dfd; + bool ignore_nonblock; struct filename *filename; struct open_how how; unsigned long nofile; @@ -3591,6 +3592,7 @@ static int __io_openat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe return ret; } req->open.nofile = rlimit(RLIMIT_NOFILE); + req->open.ignore_nonblock = false; req->flags |= REQ_F_NEED_CLEANUP; return 0; } @@ -3638,7 +3640,7 @@ static int io_openat2(struct io_kiocb *req, bool force_nonblock) struct file *file; int ret;
- if (force_nonblock) + if (force_nonblock && !req->open.ignore_nonblock) return -EAGAIN;
ret = build_open_flags(&req->open.how, &op); @@ -3653,6 +3655,21 @@ static int io_openat2(struct io_kiocb *req, bool force_nonblock) if (IS_ERR(file)) { put_unused_fd(ret); ret = PTR_ERR(file); + /* + * A work-around to ensure that /proc/self works that way + * that it should - if we get -EOPNOTSUPP back, then assume + * that proc_self_get_link() failed us because we're in async + * context. We should be safe to retry this from the task + * itself with force_nonblock == false set, as it should not + * block on lookup. Would be nice to know this upfront and + * avoid the async dance, but doesn't seem feasible. + */ + if (ret == -EOPNOTSUPP && io_wq_current_is_worker()) { + req->open.ignore_nonblock = true; + refcount_inc(&req->refs); + io_req_task_queue(req); + return 0; + } } else { fsnotify_open(file); fd_install(ret, file);