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| author | Hao Xu <howeyxu@tencent.com> | 2022-06-17 13:04:29 +0800 |
|---|---|---|
| committer | Jens Axboe <axboe@kernel.dk> | 2022-07-24 18:39:14 -0600 |
| commit | f09c8643f0fad0e287b9f737955276000fd76a5d (patch) | |
| tree | d968fe6a0471e999ccfe624763e6bca1eb750c8b | |
| parent | 9ca9fb24d5febccea354089c41f96a8ad0d853f8 (diff) | |
| download | linux-f09c8643f0fad0e287b9f737955276000fd76a5d.tar.gz linux-f09c8643f0fad0e287b9f737955276000fd76a5d.tar.bz2 linux-f09c8643f0fad0e287b9f737955276000fd76a5d.zip | |
io_uring: kbuf: add comments for some tricky code
Add comments to explain why it is always under uring lock when
incrementing head in __io_kbuf_recycle. And rectify one comemnt about
kbuf consuming in iowq case.
Signed-off-by: Hao Xu <howeyxu@tencent.com>
Link: https://lore.kernel.org/r/20220617050429.94293-1-hao.xu@linux.dev
Signed-off-by: Jens Axboe <axboe@kernel.dk>
| -rw-r--r-- | io_uring/kbuf.c | 20 |
1 files changed, 14 insertions, 6 deletions
diff --git a/io_uring/kbuf.c b/io_uring/kbuf.c index b9c7f6e87cc9..59e4fafeb28c 100644 --- a/io_uring/kbuf.c +++ b/io_uring/kbuf.c @@ -52,6 +52,13 @@ void __io_kbuf_recycle(struct io_kiocb *req, unsigned issue_flags) if (req->flags & REQ_F_BUFFER_RING) { if (req->buf_list) { if (req->flags & REQ_F_PARTIAL_IO) { + /* + * If we end up here, then the io_uring_lock has + * been kept held since we retrieved the buffer. + * For the io-wq case, we already cleared + * req->buf_list when the buffer was retrieved, + * hence it cannot be set here for that case. + */ req->buf_list->head++; req->buf_list = NULL; } else { @@ -163,12 +170,13 @@ static void __user *io_ring_buffer_select(struct io_kiocb *req, size_t *len, if (issue_flags & IO_URING_F_UNLOCKED || !file_can_poll(req->file)) { /* * If we came in unlocked, we have no choice but to consume the - * buffer here. This does mean it'll be pinned until the IO - * completes. But coming in unlocked means we're in io-wq - * context, hence there should be no further retry. For the - * locked case, the caller must ensure to call the commit when - * the transfer completes (or if we get -EAGAIN and must poll - * or retry). + * buffer here, otherwise nothing ensures that the buffer won't + * get used by others. This does mean it'll be pinned until the + * IO completes, coming in unlocked means we're being called from + * io-wq context and there may be further retries in async hybrid + * mode. For the locked case, the caller must call commit when + * the transfer completes (or if we get -EAGAIN and must poll of + * retry). */ req->buf_list = NULL; bl->head++; |