io_uring: fix cached_sq_head in io_timeout()

io_timeout() can be executed asynchronously by a worker and without
holding ctx->uring_lock

1. using ctx->cached_sq_head there is racy there
2. it should count events from a moment of timeout's submission, but
not execution

Use req->sequence.

Signed-off-by: Pavel Begunkov <asml.silence@gmail.com>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/fs/io_uring.c b/fs/io_uring.c
index 32cbace..9325ac6 100644 (file)
--- a/fs/io_uring.c
+++ b/fs/io_uring.c
@@ -4714,6 +4714,7 @@ static int io_timeout(struct io_kiocb *req)
        struct io_timeout_data *data;
        struct list_head *entry;
        unsigned span = 0;
+       u32 seq = req->sequence;
 
        data = &req->io->timeout;
 
@@ -4730,7 +4731,7 @@ static int io_timeout(struct io_kiocb *req)
                goto add;
        }
 
-       req->sequence = ctx->cached_sq_head + count - 1;
+       req->sequence = seq + count;
        data->seq_offset = count;
 
        /*
@@ -4740,7 +4741,7 @@ static int io_timeout(struct io_kiocb *req)
        spin_lock_irq(&ctx->completion_lock);
        list_for_each_prev(entry, &ctx->timeout_list) {
                struct io_kiocb *nxt = list_entry(entry, struct io_kiocb, list);
-               unsigned nxt_sq_head;
+               unsigned nxt_seq;
                long long tmp, tmp_nxt;
                u32 nxt_offset = nxt->io->timeout.seq_offset;
 
@@ -4748,18 +4749,18 @@ static int io_timeout(struct io_kiocb *req)
                        continue;
 
                /*
-                * Since cached_sq_head + count - 1 can overflow, use type long
+                * Since seq + count can overflow, use type long
                 * long to store it.
                 */
-               tmp = (long long)ctx->cached_sq_head + count - 1;
-               nxt_sq_head = nxt->sequence - nxt_offset + 1;
-               tmp_nxt = (long long)nxt_sq_head + nxt_offset - 1;
+               tmp = (long long)seq + count;
+               nxt_seq = nxt->sequence - nxt_offset;
+               tmp_nxt = (long long)nxt_seq + nxt_offset;
 
                /*
                 * cached_sq_head may overflow, and it will never overflow twice
                 * once there is some timeout req still be valid.
                 */
-               if (ctx->cached_sq_head < nxt_sq_head)
+               if (seq < nxt_seq)
                        tmp += UINT_MAX;
 
                if (tmp > tmp_nxt)