io_uring/fdinfo: be a bit nicer when looping a lot of SQEs/CQEs

Add cond_resched() in those dump loops, just in case a lot of entries
are being dumped. And detect invalid CQ ring head/tail entries, to avoid
iterating more than what is necessary. Generally not an issue, but can be
if things like KASAN or other debugging metrics are enabled.

Reported-by: 是参差 <shicenci@gmail.com>
Link: https://lore.kernel.org/all/PS1PPF7E1D7501FE5631002D242DD89403FAB9BA@PS1PPF7E1D7501F.apcprd02.prod.outlook.com/
Reviewed-by: Keith Busch <kbusch@kernel.org>
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c
index 4f12e98b22c3005ac59dd3aac824a9b6245c8f25..80178b69e05a25209924cc9eb1c16e256f1b4962 100644 (file)
--- a/io_uring/fdinfo.c
+++ b/io_uring/fdinfo.c
@@ -67,7 +67,7 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
        unsigned int cq_head = READ_ONCE(r->cq.head);
        unsigned int cq_tail = READ_ONCE(r->cq.tail);
        unsigned int sq_shift = 0;
-       unsigned int sq_entries;
+       unsigned int cq_entries, sq_entries;
        int sq_pid = -1, sq_cpu = -1;
        u64 sq_total_time = 0, sq_work_time = 0;
        unsigned int i;
@@ -146,9 +146,11 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
                        }
                }
                seq_printf(m, "\n");
+               cond_resched();
        }
        seq_printf(m, "CQEs:\t%u\n", cq_tail - cq_head);
-       while (cq_head < cq_tail) {
+       cq_entries = min(cq_tail - cq_head, ctx->cq_entries);
+       for (i = 0; i < cq_entries; i++) {
                struct io_uring_cqe *cqe;
                bool cqe32 = false;
 
@@ -163,8 +165,11 @@ static void __io_uring_show_fdinfo(struct io_ring_ctx *ctx, struct seq_file *m)
                                        cqe->big_cqe[0], cqe->big_cqe[1]);
                seq_printf(m, "\n");
                cq_head++;
-               if (cqe32)
+               if (cqe32) {
                        cq_head++;
+                       i++;
+               }
+               cond_resched();
        }
 
        if (ctx->flags & IORING_SETUP_SQPOLL) {