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

[ Upstream commit 38cfdd9dd279473a73814df9fd7e6e716951d361 ]

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>
Signed-off-by: Sasha Levin <sashal@kernel.org>

diff --git a/io_uring/fdinfo.c b/io_uring/fdinfo.c
index 294c75a8a3bdbc6eb01b125b7b45c5c013aa4120..3585ad8308504aa99c190e7f240cbfa600e0915c 100644 (file)
--- a/io_uring/fdinfo.c
+++ b/io_uring/fdinfo.c
@@ -65,7 +65,7 @@ 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;
@@ -119,9 +119,11 @@ 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;
 
@@ -136,8 +138,11 @@ 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) {