READV cannot recycle buffers as it would lose some of the data required to
reimport that buffer.
Reported-by: Ammar Faizi <ammarfaizi2@xxxxxxxxxxx>
Fixes: b66e65f41426 ("io_uring: never call io_buffer_select() for a buffer re-select")
Signed-off-by: Dylan Yudaken <dylany@xxxxxx>
---
I think going forward we can probably re-enable recycling for READV, or perhaps stick
it in the opdef to make it a bit more general. However since it is late in the merge
cycle I thought the simplest approach is best.
Worth noting the initial discussed approach of stashing the data in `struct io_rw` would not
have worked as that struct is full already apparently.
Dylan
fs/io_uring.c | 8 ++++++++
1 file changed, 8 insertions(+)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index a01ea49f3017..b0180679584f 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -1737,6 +1737,14 @@ static void io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags)
(req->flags & REQ_F_PARTIAL_IO))
return;
+ /*
+ * READV uses fields in `struct io_rw` (len/addr) to stash the selected
+ * buffer data. However if that buffer is recycled the original request
+ * data stored in addr is lost. Therefore forbid recycling for now.
+ */
+ if (req->opcode == IORING_OP_READV)
+ return;
+
/*
* We don't need to recycle for REQ_F_BUFFER_RING, we can just clear
* the flag and hence ensure that bl->head doesn't get incremented.
base-commit: ff6992735ade75aae3e35d16b17da1008d753d28
--
2.30.2
