re: [PATCH -next] io_uring: add support for fchmod

re: [PATCH -next] io_uring: add support for fchmod

[lizetao]

Hi,

>On 11/23/24 5:23 AM, lizetao wrote:
>> Hi
>> 
>>>> On 11/19/24 1:12 AM, lizetao wrote:
>>>> Adds support for doing chmod through io_uring. IORING_OP_FCHMOD 
>>>> behaves like fchmod(2) and takes the same arguments.
>> 
>>> Looks pretty straight forward. The only downside is the forced use of REQ_F_FORCE_ASYNC - did you look into how feasible it would be to allow non-blocking issue of this? Would imagine the majority of fchmod calls end up not blocking in the first place.
>> 
>> Yes, I considered fchmod to allow asynchronous execution and wrote a test case to test it, the results are as follows:
>> 
>> fchmod:
>> real	0m1.413s
>> user	0m0.253s
>> sys	0m1.079s
>> 
>> io_uring + fchmod:
>> real	0m1.268s
>> user	0m0.015s
>> sys	0m5.739s
>> 
>> There is about a 10% improvement.

> And that makes sense if you're keeping some fchmod inflight, as you'd generally just have one io-wq processing them and running things in parallel with submission. But what you you keep an indepth count of 1, eg do sync fchmod? Then it'd be considerably slower than the syscall.
Indeed, When performing REQ_F_FORCE_ASYNC operations at depth 1, performance is degraded. The results are as follows:

fchmod:
real	0m2.285s
user	0m0.050s
sys	0m1.996s

io_uring + fchmod:
real	0m2.541s
user	0m0.013s
sys	0m2.379s

>This isn't necessarily something to worry about, but fact is that if you can do a nonblock issue and have it succeed most of the time, that'll be more efficient (and faster for low/sync fchmod) than something that just offloads to io-wq. You can see that from your results too, comparing the sys number netween the two.
However, when I remove REQ_F_FORCE_ASYNC and use IO_URING_F_NONBLOCK, the performance is not improved. The measured results are as follows:
fchmod:
real	0m2.132s
user	0m0.048s
sys	0m1.845s

io_uring + fchmod:
real	0m2.196s
user	0m0.005s
sys	0m2.097s

>Hence why I'm asking if you looked into doing a nonblocking issue at all. This won't necessarily gate the inclusion of the patch, and it is something that can be changed down the line, I'm mostly just curious.
Does this result meet expectations? Or maybe I missed something, please let me know

>--
>Jens Axboe

---
Li Zetao

[PATCH -next] io_uring: add support for fchmod

[lizetao]

Adds support for doing chmod through io_uring. IORING_OP_FCHMOD behaves like fchmod(2) and takes the same arguments.

Signed-off-by: Li Zetao <lizetao1@huawei.com>
---
 include/uapi/linux/io_uring.h |  1 +
 io_uring/fs.c                 | 32 ++++++++++++++++++++++++++++++++
 io_uring/fs.h                 |  3 +++
 io_uring/opdef.c              |  8 ++++++++
 4 files changed, 44 insertions(+)

diff --git a/include/uapi/linux/io_uring.h b/include/uapi/linux/io_uring.h index 5d08435b95a8..de5cce11f937 100644
--- a/include/uapi/linux/io_uring.h
+++ b/include/uapi/linux/io_uring.h
@@ -262,6 +262,7 @@ enum io_uring_op {
 	IORING_OP_FTRUNCATE,
 	IORING_OP_BIND,
 	IORING_OP_LISTEN,
+	IORING_OP_FCHMOD,
 
 	/* this goes last, obviously */
 	IORING_OP_LAST,
diff --git a/io_uring/fs.c b/io_uring/fs.c index eccea851dd5a..835f66fb75ff 100644
--- a/io_uring/fs.c
+++ b/io_uring/fs.c
@@ -47,6 +47,11 @@ struct io_link {
 	int				flags;
 };
 
+struct io_fchmod {
+	struct file			*file;
+	umode_t				mode;
+};
+
 int io_renameat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe)  {
 	struct io_rename *ren = io_kiocb_to_cmd(req, struct io_rename); @@ -291,3 +296,30 @@ void io_link_cleanup(struct io_kiocb *req)
 	putname(sl->oldpath);
 	putname(sl->newpath);
 }
+
+int io_fchmod_prep(struct io_kiocb *req, const struct io_uring_sqe 
+*sqe) {
+	struct io_fchmod *fc = io_kiocb_to_cmd(req, struct io_fchmod);
+
+	if (unlikely(sqe->off || sqe->addr || sqe->rw_flags ||
+		     sqe->buf_index || sqe->splice_fd_in))
+		return -EINVAL;
+	if (unlikely(req->flags & REQ_F_FIXED_FILE))
+		return -EBADF;
+
+	fc->mode = READ_ONCE(sqe->len);
+	req->flags |= REQ_F_FORCE_ASYNC;
+	return 0;
+}
+
+int io_fchmod(struct io_kiocb *req, unsigned int issue_flags) {
+	struct io_fchmod *fc = io_kiocb_to_cmd(req, struct io_fchmod);
+	int ret;
+
+	WARN_ON_ONCE(issue_flags & IO_URING_F_NONBLOCK);
+
+	ret = vfs_fchmod(req->file, fc->mode);
+	io_req_set_res(req, ret, 0);
+	return IOU_OK;
+}
diff --git a/io_uring/fs.h b/io_uring/fs.h index 0bb5efe3d6bb..bc7d95e77b2f 100644
--- a/io_uring/fs.h
+++ b/io_uring/fs.h
@@ -18,3 +18,6 @@ int io_symlinkat(struct io_kiocb *req, unsigned int issue_flags);  int io_linkat_prep(struct io_kiocb *req, const struct io_uring_sqe *sqe);  int io_linkat(struct io_kiocb *req, unsigned int issue_flags);  void io_link_cleanup(struct io_kiocb *req);
+
+int io_fchmod_prep(struct io_kiocb *req, const struct io_uring_sqe 
+*sqe); int io_fchmod(struct io_kiocb *req, unsigned int issue_flags);
diff --git a/io_uring/opdef.c b/io_uring/opdef.c index 3de75eca1c92..eb5bf831513c 100644
--- a/io_uring/opdef.c
+++ b/io_uring/opdef.c
@@ -515,6 +515,11 @@ const struct io_issue_def io_issue_defs[] = {
 		.prep			= io_eopnotsupp_prep,
 #endif
 	},
+	[IORING_OP_FCHMOD] = {
+		.needs_file		= 1,
+		.prep			= io_fchmod_prep,
+		.issue			= io_fchmod,
+	},
 };
 
 const struct io_cold_def io_cold_defs[] = { @@ -744,6 +749,9 @@ const struct io_cold_def io_cold_defs[] = {
 	[IORING_OP_LISTEN] = {
 		.name			= "LISTEN",
 	},
+	[IORING_OP_FCHMOD] = {
+		.name			= "FCHMOD",
+	},
 };
 
 const char *io_uring_get_opcode(u8 opcode)
--
2.34.1

Re: [PATCH -next] io_uring: add support for fchmod

[Jens Axboe]

On 11/19/24 1:12 AM, lizetao wrote:
> Adds support for doing chmod through io_uring. IORING_OP_FCHMOD
> behaves like fchmod(2) and takes the same arguments.

Looks pretty straight forward. The only downside is the forced use of 
REQ_F_FORCE_ASYNC - did you look into how feasible it would be to allow
non-blocking issue of this? Would imagine the majority of fchmod calls
end up not blocking in the first place.

-- 
Jens Axboe