[PATCH 5.13 032/104] io_uring: dont block level reissue off completion path

Greg Kroah-Hartman
2021-08-02T14:05:10Z

From: Jens Axboe <axboe@kernel.dk>

commit ef04688871f3386b6d40ade8f5c664290420f819 upstream.

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>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
fs/io_uring.c | 6 ++++++
1 file changed, 6 insertions(+)

--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2457,6 +2457,12 @@ static bool io_rw_should_reissue(struct
*/
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