[RFC 3/5] io_uring: add infra and support for IORING_OP_URING_CMD

[Kanchan Joshi]

>>>> +	struct io_kiocb *req = container_of(ioucmd, struct io_kiocb, uring_cmd);
>>>> +
>>>> +	if (ret < 0)
>>>> +		req_set_fail(req);
>>>> +	io_req_complete(req, ret);
>>>> +}
>>>> +EXPORT_SYMBOL_GPL(io_uring_cmd_done);
>>>
>>> It seems like all callers of io_req_complete actually call req_set_fail
>>> on failure.  So maybe it would be nice pre-cleanup to handle the
>>> req_set_fail call from ĩo_req_complete?
>>
>> Interpretation of the result is different, e.g. io_tee(), that was the
>> reason it was left in the callers.
>
>Yes, there is about two of them that would then need to be open coded
>using __io_req_complete.

And this is how it looks. 
Pavel, Jens: would you prefer this as independent patch?

commit 2be578326b80f7a9e603b2a3224644b0cb620e25
Author: Kanchan Joshi <joshi.k at samsung.com>
Date:   Wed Apr 6 11:22:07 2022 +0530

    io_uring: cleanup error handling

    Move common error handling to io_req_complete, so that various callers
    avoid repeating that.
    Callers requiring different handling still keep that outside, and call
    __io_req_complete instead.

    Suggested-by: Christoph Hellwig <hch at lst.de>
    Signed-off-by: Kanchan Joshi <joshi.k at samsung.com>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 7445084e48ce..7df465bd489a 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -2162,6 +2162,8 @@ static inline void __io_req_complete(struct io_kiocb *req, unsigned issue_flags,

 static inline void io_req_complete(struct io_kiocb *req, s32 res)
 {
+       if (res < 0)
+               req_set_fail(req);
        __io_req_complete(req, 0, res, 0);
 }

@@ -4100,8 +4102,6 @@ static int io_renameat(struct io_kiocb *req, unsigned int issue_flags)
                                ren->newpath, ren->flags);

        req->flags &= ~REQ_F_NEED_CLEANUP;
-       if (ret < 0)
-               req_set_fail(req);
        io_req_complete(req, ret);
        return 0;
 }
@@ -4122,8 +4122,6 @@ static void io_xattr_finish(struct io_kiocb *req, int ret)
        req->flags &= ~REQ_F_NEED_CLEANUP;

        __io_xattr_finish(req);
-       if (ret < 0)
-               req_set_fail(req);

        io_req_complete(req, ret);
 }
@@ -4443,8 +4441,6 @@ static int io_mkdirat(struct io_kiocb *req, unsigned int issue_flags)
        ret = do_mkdirat(mkd->dfd, mkd->filename, mkd->mode);

        req->flags &= ~REQ_F_NEED_CLEANUP;
-       if (ret < 0)
-               req_set_fail(req);
        io_req_complete(req, ret);
        return 0;
 }
@@ -4492,8 +4488,6 @@ static int io_symlinkat(struct io_kiocb *req, unsigned int issue_flags)
        ret = do_symlinkat(sl->oldpath, sl->new_dfd, sl->newpath);

        req->flags &= ~REQ_F_NEED_CLEANUP;
-       if (ret < 0)
-               req_set_fail(req);
        io_req_complete(req, ret);
        return 0;
 }
@@ -4543,8 +4537,6 @@ static int io_linkat(struct io_kiocb *req, unsigned int issue_flags)
                                lnk->newpath, lnk->flags);

        req->flags &= ~REQ_F_NEED_CLEANUP;
-       if (ret < 0)
-               req_set_fail(req);
        io_req_complete(req, ret);
        return 0;
 }
@@ -4580,8 +4572,6 @@ static int io_shutdown(struct io_kiocb *req, unsigned int issue_flags)
                return -ENOTSOCK;

        ret = __sys_shutdown_sock(sock, req->shutdown.how);
-       if (ret < 0)
-               req_set_fail(req);
        io_req_complete(req, ret);
        return 0;
 #else
@@ -4641,7 +4631,7 @@ static int io_tee(struct io_kiocb *req, unsigned int issue_flags)
 done:
        if (ret != sp->len)
                req_set_fail(req);
-       io_req_complete(req, ret);
+       __io_req_complete(req, 0, ret, 0);
        return 0;
 }

@@ -4685,7 +4675,7 @@ static int io_splice(struct io_kiocb *req, unsigned int issue_flags)
 done:
        if (ret != sp->len)
                req_set_fail(req);
-       io_req_complete(req, ret);
+       __io_req_complete(req, 0, ret, 0);
        return 0;
 }

@@ -4777,8 +4767,6 @@ static int io_fsync(struct io_kiocb *req, unsigned int issue_flags)
        ret = vfs_fsync_range(req->file, req->sync.off,
                                end > 0 ? end : LLONG_MAX,
                                req->sync.flags & IORING_FSYNC_DATASYNC);
-       if (ret < 0)
-               req_set_fail(req);
        io_req_complete(req, ret);
        return 0;
 }
@@ -4807,9 +4795,7 @@ static int io_fallocate(struct io_kiocb *req, unsigned int issue_flags)
                return -EAGAIN;
        ret = vfs_fallocate(req->file, req->sync.mode, req->sync.off,
                                req->sync.len);
-       if (ret < 0)
-               req_set_fail(req);
-       else
+       if (ret >= 0)
                fsnotify_modify(req->file);
        io_req_complete(req, ret);
        return 0;
@@ -5221,8 +5207,6 @@ static int io_madvise(struct io_kiocb *req, unsigned int issue_flags)
                return -EAGAIN;

        ret = do_madvise(current->mm, ma->addr, ma->len, ma->advice);
-       if (ret < 0)
-               req_set_fail(req);
        io_req_complete(req, ret);
        return 0;
 #else
@@ -5309,8 +5293,6 @@ static int io_statx(struct io_kiocb *req, unsigned int issue_flags)
        ret = do_statx(ctx->dfd, ctx->filename, ctx->flags, ctx->mask,
                       ctx->buffer);

-       if (ret < 0)
-               req_set_fail(req);
        io_req_complete(req, ret);
        return 0;
 }
@@ -5410,8 +5392,6 @@ static int io_sync_file_range(struct io_kiocb *req, unsigned int issue_flags)

        ret = sync_file_range(req->file, req->sync.off, req->sync.len,
                                req->sync.flags);
-       if (ret < 0)
-               req_set_fail(req);
        io_req_complete(req, ret);
        return 0;