[PATCH V4 2/2] io_uring: cancelable uring_cmd

Ming Lei
2023-09-23T02:52:07Z

uring_cmd may never complete, such as ublk, in which uring cmd isn't
completed until one new block request is coming from ublk block device.

Add cancelable uring_cmd to provide mechanism to driver for cancelling
pending commands in its own way.

Add API of io_uring_cmd_mark_cancelable() for driver to mark one command as
cancelable, then io_uring will cancel this command in
io_uring_cancel_generic(). ->uring_cmd() callback is reused for canceling
command in driver's way, then driver gets notified with the cancelling
from io_uring.

Add API of io_uring_cmd_get_task() to help driver cancel handler
deal with the canceling.

Cc: Gabriel Krisman Bertazi <krisman@suse.de>
Suggested-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Ming Lei <ming.lei@redhat.com>
---
include/linux/io_uring.h | 16 +++++++++++
include/linux/io_uring_types.h | 6 +++++
io_uring/io_uring.c | 36 +++++++++++++++++++++++++
io_uring/uring_cmd.c | 49 ++++++++++++++++++++++++++++++++++
4 files changed, 107 insertions(+)

diff --git a/include/linux/io_uring.h b/include/linux/io_uring.h
index ae08d6f66e62..a0307289bdc7 100644
--- a/include/linux/io_uring.h
+++ b/include/linux/io_uring.h
@@ -20,9 +20,13 @@ enum io_uring_cmd_flags {
IO_URING_F_SQE128 = (1 << 8),
IO_URING_F_CQE32 = (1 << 9),
IO_URING_F_IOPOLL = (1 << 10),
+
+ /* set when uring wants to cancel one issued command */
+ IO_URING_F_CANCEL = (1 << 11),
};

/* only top 8 bits of sqe->uring_cmd_flags for kernel internal use */
+#define IORING_URING_CMD_CANCELABLE (1U << 30)
#define IORING_URING_CMD_POLLED (1U << 31)

struct io_uring_cmd {
@@ -85,6 +89,9 @@ static inline void io_uring_free(struct task_struct *tsk)
__io_uring_free(tsk);
}
int io_uring_cmd_sock(struct io_uring_cmd *cmd, unsigned int issue_flags);
+int io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
+ unsigned int issue_flags);
+struct task_struct *io_uring_cmd_get_task(struct io_uring_cmd *cmd);
#else
static inline int io_uring_cmd_import_fixed(u64 ubuf, unsigned long len, int rw,
struct iov_iter *iter, void *ioucmd)
@@ -125,6 +132,15 @@ static inline int io_uring_cmd_sock(struct io_uring_cmd *cmd,
{
return -EOPNOTSUPP;
}
+static inline int io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
+ unsigned int issue_flags)
+{
+ return -EOPNOTSUPP;
+}
+static inline struct task_struct *io_uring_cmd_get_task(struct io_uring_cmd *cmd)
+{
+ return NULL;
+}
#endif

#endif
diff --git a/include/linux/io_uring_types.h b/include/linux/io_uring_types.h
index 13d19b9be9f4..1571db76bec1 100644
--- a/include/linux/io_uring_types.h
+++ b/include/linux/io_uring_types.h
@@ -265,6 +265,12 @@ struct io_ring_ctx {
*/
struct io_wq_work_list iopoll_list;
bool poll_multi_queue;
+
+ /*
+ * Any cancelable uring_cmd is added to this list in
+ * ->uring_cmd() by io_uring_cmd_insert_cancelable()
+ */
+ struct hlist_head cancelable_uring_cmd;
} ____cacheline_aligned_in_smp;

struct {
diff --git a/io_uring/io_uring.c b/io_uring/io_uring.c
index 9aedb7202403..9c90cad39059 100644
--- a/io_uring/io_uring.c
+++ b/io_uring/io_uring.c
@@ -350,6 +350,7 @@ static __cold struct io_ring_ctx *io_ring_ctx_alloc(struct io_uring_params *p)
INIT_WQ_LIST(&ctx->locked_free_list);
INIT_DELAYED_WORK(&ctx->fallback_work, io_fallback_req_func);
INIT_WQ_LIST(&ctx->submit_state.compl_reqs);
+ INIT_HLIST_HEAD(&ctx->cancelable_uring_cmd);
return ctx;
err:
kfree(ctx->cancel_table.hbs);
@@ -3256,6 +3257,40 @@ static __cold bool io_uring_try_cancel_iowq(struct io_ring_ctx *ctx)
return ret;
}

+static bool io_uring_try_cancel_uring_cmd(struct io_ring_ctx *ctx,
+ struct task_struct *task, bool cancel_all)
+{
+ struct hlist_node *tmp;
+ struct io_kiocb *req;
+ bool ret = false;
+
+ lockdep_assert_held(&ctx->uring_lock);
+
+ hlist_for_each_entry_safe(req, tmp, &ctx->cancelable_uring_cmd,
+ hash_node) {
+ struct io_uring_cmd *cmd = io_kiocb_to_cmd(req,
+ struct io_uring_cmd);
+ struct file *file = req->file;
+
+ if (WARN_ON_ONCE(!file->f_op->uring_cmd))
+ continue;
+
+ if (!cancel_all && req->task != task)
+ continue;
+
+ if (cmd->flags & IORING_URING_CMD_CANCELABLE) {
+ /* ->sqe isn't available if no async data */
+ if (!req_has_async_data(req))
+ cmd->sqe = NULL;
+ file->f_op->uring_cmd(cmd, IO_URING_F_CANCEL);
+ ret = true;
+ }
+ }
+ io_submit_flush_completions(ctx);
+
+ return ret;
+}
+
static __cold bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
struct task_struct *task,
bool cancel_all)
@@ -3303,6 +3338,7 @@ static __cold bool io_uring_try_cancel_requests(struct io_ring_ctx *ctx,
ret |= io_cancel_defer_files(ctx, task, cancel_all);
mutex_lock(&ctx->uring_lock);
ret |= io_poll_remove_all(ctx, task, cancel_all);
+ ret |= io_uring_try_cancel_uring_cmd(ctx, task, cancel_all);
mutex_unlock(&ctx->uring_lock);
ret |= io_kill_timeouts(ctx, task, cancel_all);
if (task)
diff --git a/io_uring/uring_cmd.c b/io_uring/uring_cmd.c
index a0b0ec5473bf..f2cbfa7f1f7f 100644
--- a/io_uring/uring_cmd.c
+++ b/io_uring/uring_cmd.c
@@ -13,6 +13,53 @@
#include "rsrc.h"
#include "uring_cmd.h"

+static void io_uring_cmd_del_cancelable(struct io_uring_cmd *cmd,
+ unsigned int issue_flags)
+{
+ struct io_kiocb *req = cmd_to_io_kiocb(cmd);
+ struct io_ring_ctx *ctx = req->ctx;
+
+ if (!(cmd->flags & IORING_URING_CMD_CANCELABLE))
+ return;
+
+ cmd->flags &= ~IORING_URING_CMD_CANCELABLE;
+ io_ring_submit_lock(ctx, issue_flags);
+ hlist_del(&req->hash_node);
+ io_ring_submit_unlock(ctx, issue_flags);
+}
+
+/*
+ * Mark this command as concelable, then io_uring_try_cancel_uring_cmd()
+ * will try to cancel this issued command by sending ->uring_cmd() with
+ * issue_flags of IO_URING_F_CANCEL.
+ *
+ * The command is guaranteed to not be done when calling ->uring_cmd()
+ * with IO_URING_F_CANCEL, but it is driver's responsibility to deal
+ * with race between io_uring canceling and normal completion.
+ */
+int io_uring_cmd_mark_cancelable(struct io_uring_cmd *cmd,
+ unsigned int issue_flags)
+{
+ struct io_kiocb *req = cmd_to_io_kiocb(cmd);
+ struct io_ring_ctx *ctx = req->ctx;
+
+ if (!(cmd->flags & IORING_URING_CMD_CANCELABLE)) {
+ cmd->flags |= IORING_URING_CMD_CANCELABLE;
+ io_ring_submit_lock(ctx, issue_flags);
+ hlist_add_head(&req->hash_node, &ctx->cancelable_uring_cmd);
+ io_ring_submit_unlock(ctx, issue_flags);
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_mark_cancelable);
+
+struct task_struct *io_uring_cmd_get_task(struct io_uring_cmd *cmd)
+{
+ return cmd_to_io_kiocb(cmd)->task;
+}
+EXPORT_SYMBOL_GPL(io_uring_cmd_get_task);
+
static void io_uring_cmd_work(struct io_kiocb *req, struct io_tw_state *ts)
{
struct io_uring_cmd *ioucmd = io_kiocb_to_cmd(req, struct io_uring_cmd);
@@ -56,6 +103,8 @@ void io_uring_cmd_done(struct io_uring_cmd *ioucmd, ssize_t ret, ssize_t res2,
{
struct io_kiocb *req = cmd_to_io_kiocb(ioucmd);

+ io_uring_cmd_del_cancelable(ioucmd, issue_flags);
+
if (ret < 0)
req_set_fail(req);

--
2.41.0