io_uring: don't block level reissue off completion path

Some setups, like SCSI, can throw spurious -EAGAIN off the softirq
completion path. Normally we expect this to happen inline as part
of submission, but apparently SCSI has a weird corner case where it
can happen as part of normal completions.

This should be solved by having the -EAGAIN bubble back up the stack
as part of submission, but previous attempts at this failed and we're
not just quite there yet. Instead we currently use REQ_F_REISSUE to
handle this case.

For now, catch it in io_rw_should_reissue() and prevent a reissue
from a bogus path.

Cc: stable@vger.kernel.org
Reported-by: Fabian Ebner <f.ebner@proxmox.com>
Tested-by: Fabian Ebner <f.ebner@proxmox.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 6ba101cd46618c53334c146e29852a50f4d34265..83f67d33bf67319f2eb0287e0636e649155acde1 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2447,6 +2447,12 @@ static bool io_rw_should_reissue(struct io_kiocb *req)
         */
        if (percpu_ref_is_dying(&ctx->refs))
                return false;
+       /*
+        * Play it safe and assume not safe to re-import and reissue if we're
+        * not in the original thread group (or in task context).
+        */
+       if (!same_thread_group(req->task, current) || !in_task())
+               return false;
        return true;
 }
 #else