[PATCH 5.17 093/219] io_uring: stop using io_wq_work as an fd placeholder

Greg Kroah-Hartman
2022-04-18T12:23:54Z

From: Jens Axboe <axboe@kernel.dk>

[ Upstream commit 82733d168cbd3fe9dab603f05894316b99008924 ]

There are two reasons why this isn't the best idea:

- It's an odd area to grab a bit of storage space, hence it's an odd area
to grab storage from.
- It puts the 3rd io_kiocb cacheline into the hot path, where normal hot
path just needs the first two.

Use 'cflags' for joint fd/cflags storage. We only need fd until we
successfully issue, and we only need cflags once a request is done and is
completed.

Fixes: 6bf9c47a3989 ("io_uring: defer file assignment")
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
fs/io-wq.h | 1 -
fs/io_uring.c | 12 ++++++++----
2 files changed, 8 insertions(+), 5 deletions(-)

diff --git a/fs/io-wq.h b/fs/io-wq.h
index 04d374e65e54..dbecd27656c7 100644
--- a/fs/io-wq.h
+++ b/fs/io-wq.h
@@ -155,7 +155,6 @@ struct io_wq_work_node *wq_stack_extract(struct io_wq_work_node *stack)
struct io_wq_work {
struct io_wq_work_node list;
unsigned flags;
- int fd;
};

static inline struct io_wq_work *wq_next_work(struct io_wq_work *work)
diff --git a/fs/io_uring.c b/fs/io_uring.c
index d13f142793f2..d05394b0c1e6 100644
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -864,7 +864,11 @@ struct io_kiocb {

u64 user_data;
u32 result;
- u32 cflags;
+ /* fd initially, then cflags for completion */
+ union {
+ u32 cflags;
+ int fd;
+ };

struct io_ring_ctx *ctx;
struct task_struct *task;
@@ -6708,9 +6712,9 @@ static bool io_assign_file(struct io_kiocb *req, unsigned int issue_flags)
return true;

if (req->flags & REQ_F_FIXED_FILE)
- req->file = io_file_get_fixed(req, req->work.fd, issue_flags);
+ req->file = io_file_get_fixed(req, req->fd, issue_flags);
else
- req->file = io_file_get_normal(req, req->work.fd);
+ req->file = io_file_get_normal(req, req->fd);
if (req->file)
return true;

@@ -7243,7 +7247,7 @@ static int io_init_req(struct io_ring_ctx *ctx, struct io_kiocb *req,
if (io_op_defs[opcode].needs_file) {
struct io_submit_state *state = &ctx->submit_state;

- req->work.fd = READ_ONCE(sqe->fd);
+ req->fd = READ_ONCE(sqe->fd);

/*
* Plug now if we have more than 2 IO left after this, and the
--
2.35.1