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io_uring/cmd: expose iowq to cmds

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When an io_uring request needs blocking context we offload it to the
io_uring's thread pool called io-wq. We can get there off ->uring_cmd
by returning -EAGAIN, but there is no straightforward way of doing that
from an asynchronous callback. Add a helper that would transfer a
command to a blocking context.

Note, we do an extra hop via task_work before io_queue_iowq(), that's a
limitation of io_uring infra we have that can likely be lifted later
if that would ever become a problem.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Link: https://lore.kernel.org/r/f735f807d7c8ba50c9452c69dfe5d3e9e535037b.1726072086.git.asml.silence@gmail.com
Signed-off-by: Jens Axboe <axboe@kernel.dk>
This commit is contained in:
Pavel Begunkov 2024-09-11 17:34:37 +01:00 committed by Jens Axboe
parent 6d0f8dcb3a
commit 6746ee4c3a
4 changed files with 25 additions and 0 deletions
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6
include/linux/io_uring/cmd.h
View File

@ -48,6 +48,9 @@ void __io_uring_cmd_do_in_task(struct io_uring_cmd *ioucmd,
void io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
unsigned int issue_flags);
/* Execute the request from a blocking context */
void io_uring_cmd_issue_blocking(struct io_uring_cmd *ioucmd);
#else
static inline int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
struct iov_iter *iter, void *ioucmd)
@ -67,6 +70,9 @@ static inline void io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
unsigned int issue_flags)
{
}
static inline void io_uring_cmd_issue_blocking(struct io_uring_cmd *ioucmd)
{
}
#endif
/*

11
io_uring/io_uring.c
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@ -533,6 +533,17 @@ static void io_queue_iowq(struct io_kiocb *req)
io_queue_linked_timeout(link);
}
static void io_req_queue_iowq_tw(struct io_kiocb *req, struct io_tw_state *ts)
{
io_queue_iowq(req);
}
void io_req_queue_iowq(struct io_kiocb *req)
{
req->io_task_work.func = io_req_queue_iowq_tw;
io_req_task_work_add(req);
}
static __cold void io_queue_deferred(struct io_ring_ctx *ctx)
{
while (!list_empty(&ctx->defer_list)) {

1
io_uring/io_uring.h
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@ -94,6 +94,7 @@ int io_uring_alloc_task_context(struct task_struct *task,
int io_ring_add_registered_file(struct io_uring_task *tctx, struct file *file,
int start, int end);
void io_req_queue_iowq(struct io_kiocb *req);
int io_poll_issue(struct io_kiocb *req, struct io_tw_state *ts);
int io_submit_sqes(struct io_ring_ctx *ctx, unsigned int nr);

7
io_uring/uring_cmd.c
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@ -277,6 +277,13 @@ int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
}
EXPORT_SYMBOL_GPL(io_uring_cmd_import_fixed);
void io_uring_cmd_issue_blocking(struct io_uring_cmd *ioucmd)
{
struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);
io_req_queue_iowq(req);
}
static inline int io_uring_cmd_getsockopt(struct socket *sock,
struct io_uring_cmd *cmd,
unsigned int issue_flags)