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ublk: make sure io cmd handled in submitter task context

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In well-done ublk server implementation, ublk io command won't be
linked into any link chain. Meantime they are always handled in no-wait
style, so basically io cmd is always handled in submitter task context.

However, the server may set IOSQE_ASYNC, or io command is linked to one
chain mistakenly, then we may still run into io-wq context and
ctx->uring_lock isn't held.

So in case of IO_URING_F_UNLOCKED, schedule this command by
io_uring_cmd_complete_in_task to force running it in submitter task. Then
ublk_ch_uring_cmd_local() is guaranteed to run with context uring_lock held,
and we needn't to worry about sync among submission code path any more.

Signed-off-by: Ming Lei <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Jens Axboe <[email protected]>
This commit is contained in:
Ming Lei authored and Jens Axboe committed 2023-10-17 08:27:55 -06:00
1 parent 8ed90e370f
commit 3421c7f68b
1 file changed
+21 -1
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drivers/block/ublk_drv.c
+21 -1
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@@ -1811,7 +1811,8 @@ fail_put:
return NULL;
}
static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
static inline int ublk_ch_uring_cmd_local(struct io_uring_cmd *cmd,
unsigned int issue_flags)
{
/*
* Not necessary for async retry, but let's keep it simple and always
@@ -1825,9 +1826,28 @@ static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
.addr = READ_ONCE(ub_src->addr)
};
WARN_ON_ONCE(issue_flags & IO_URING_F_UNLOCKED);
return __ublk_ch_uring_cmd(cmd, issue_flags, &ub_cmd);
}
static void ublk_ch_uring_cmd_cb(struct io_uring_cmd *cmd,
unsigned int issue_flags)
{
ublk_ch_uring_cmd_local(cmd, issue_flags);
}
static int ublk_ch_uring_cmd(struct io_uring_cmd *cmd, unsigned int issue_flags)
{
/* well-implemented server won't run into unlocked */
if (unlikely(issue_flags & IO_URING_F_UNLOCKED)) {
io_uring_cmd_complete_in_task(cmd, ublk_ch_uring_cmd_cb);
return -EIOCBQUEUED;
}
return ublk_ch_uring_cmd_local(cmd, issue_flags);
}
static inline bool ublk_check_ubuf_dir(const struct request *req,
int ubuf_dir)
{