io_uring: do not recycle buffer in READV

READV cannot recycle buffers as it would lose some of the data required to
reimport that buffer.

Reported-by: Ammar Faizi <ammarfaizi2@gnuweeb.org>
Fixes: 0029c288b8c2 ("io_uring: never call io_buffer_select() for a buffer re-select")
Signed-off-by: Dylan Yudaken <dylany@fb.com>
Link: https://lore.kernel.org/r/20220721131325.624788-1-dylany@fb.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 2b7bb62c7805c0fc763ac1d4393159773ae259ac..e8e769be9ed0581238efdbf223ff448922ba52c3 100644 (file)
--- 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.