io_uring: track request creds with a flag

Currently, if req->creds is not NULL, then there are creds assigned.
Track the invariant with a new flag in req->flags. No need to clear the
field at init, and also cleanup can be efficiently moved into
io_clean_op().

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/5f8baeb8d3b909487f555542350e2eac97005556.1623949695.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 1b8d0ad..af93f79 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -718,6 +718,7 @@ enum {
        REQ_F_COMPLETE_INLINE_BIT,
        REQ_F_REISSUE_BIT,
        REQ_F_DONT_REISSUE_BIT,
+       REQ_F_CREDS_BIT,
        /* keep async read/write and isreg together and in order */
        REQ_F_ASYNC_READ_BIT,
        REQ_F_ASYNC_WRITE_BIT,
@@ -771,6 +772,8 @@ enum {
        REQ_F_ASYNC_WRITE       = BIT(REQ_F_ASYNC_WRITE_BIT),
        /* regular file */
        REQ_F_ISREG             = BIT(REQ_F_ISREG_BIT),
+       /* has creds assigned */
+       REQ_F_CREDS             = BIT(REQ_F_CREDS_BIT),
 };
 
 struct async_poll {
@@ -1236,8 +1239,10 @@ static void io_prep_async_work(struct io_kiocb *req)
        const struct io_op_def *def = &io_op_defs[req->opcode];
        struct io_ring_ctx *ctx = req->ctx;
 
-       if (!req->creds)
+       if (!(req->flags & REQ_F_CREDS)) {
+               req->flags |= REQ_F_CREDS;
                req->creds = get_current_cred();
+       }
 
        req->work.list.next = NULL;
        req->work.flags = 0;
@@ -1623,7 +1628,7 @@ static void io_req_complete_post(struct io_kiocb *req, long res,
 static inline bool io_req_needs_clean(struct io_kiocb *req)
 {
        return req->flags & (REQ_F_BUFFER_SELECTED | REQ_F_NEED_CLEANUP |
-                               REQ_F_POLLED | REQ_F_INFLIGHT);
+                               REQ_F_POLLED | REQ_F_INFLIGHT | REQ_F_CREDS);
 }
 
 static void io_req_complete_state(struct io_kiocb *req, long res,
@@ -1747,10 +1752,6 @@ static void io_dismantle_req(struct io_kiocb *req)
                percpu_ref_put(req->fixed_rsrc_refs);
        if (req->async_data)
                kfree(req->async_data);
-       if (req->creds) {
-               put_cred(req->creds);
-               req->creds = NULL;
-       }
 }
 
 /* must to be called somewhat shortly after putting a request */
@@ -6133,6 +6134,10 @@ static void io_clean_op(struct io_kiocb *req)
                atomic_dec(&tctx->inflight_tracked);
                req->flags &= ~REQ_F_INFLIGHT;
        }
+       if (req->flags & REQ_F_CREDS) {
+               put_cred(req->creds);
+               req->flags &= ~REQ_F_CREDS;
+       }
 }
 
 static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
@@ -6141,7 +6146,7 @@ static int io_issue_sqe(struct io_kiocb *req, unsigned int issue_flags)
        const struct cred *creds = NULL;
        int ret;
 
-       if (req->creds && req->creds != current_cred())
+       if ((req->flags & REQ_F_CREDS) && req->creds != current_cred())
                creds = override_creds(req->creds);
 
        switch (req->opcode) {
@@ -6534,7 +6539,6 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
        atomic_set(&req->refs, 2);
        req->task = current;
        req->result = 0;
-       req->creds = NULL;
 
        /* enforce forwards compatibility on users */
        if (unlikely(sqe_flags & ~SQE_VALID_FLAGS))
@@ -6556,6 +6560,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
                if (!req->creds)
                        return -EINVAL;
                get_cred(req->creds);
+               req->flags |= REQ_F_CREDS;
        }
        state = &ctx->submit_state;