| BUG: Bad page state in process kworker/u8:0 pfn:5c001
| page:00000000bfda61c8 refcount:0 mapcount:0 mapping:0000000000000000 index:0x20001 pfn:0x5c001
| head:0000000011409842 order:9 entire_mapcount:0 nr_pages_mapped:0 pincount:1
| anon flags: 0x3fffc00000b0004(uptodate|head|mappedtodisk|swapbacked|node=0|zone=0|lastcpupid=0xffff)
| raw: 03fffc0000000000 fffffc0000700001 ffffffff00700903 0000000100000000
| raw: 0000000000000200 0000000000000000 00000000ffffffff 0000000000000000
| head: 03fffc00000b0004 dead000000000100 dead000000000122 ffff00000a809dc1
| head: 0000000000020000 0000000000000000 00000000ffffffff 0000000000000000
| page dumped because: nonzero pincount
| CPU: 3 PID: 9 Comm: kworker/u8:0 Not tainted 6.3.0-rc2-00001-gc6811bf0cd87 #1
| Hardware name: linux,dummy-virt (DT)
| Workqueue: events_unbound io_ring_exit_work
| Call trace:
| dump_backtrace+0x13c/0x208
| show_stack+0x34/0x58
| dump_stack_lvl+0x150/0x1a8
| dump_stack+0x20/0x30
| bad_page+0xec/0x238
| free_tail_pages_check+0x280/0x350
| free_pcp_prepare+0x60c/0x830
| free_unref_page+0x50/0x498
| free_compound_page+0xcc/0x100
| free_transhuge_page+0x1f0/0x2b8
| destroy_large_folio+0x80/0xc8
| __folio_put+0xc4/0xf8
| gup_put_folio+0xd0/0x250
| unpin_user_page+0xcc/0x128
| io_buffer_unmap+0xec/0x2c0
| __io_sqe_buffers_unregister+0xa4/0x1e0
| io_ring_exit_work+0x68c/0x1188
| process_one_work+0x91c/0x1a58
| worker_thread+0x48c/0xe30
| kthread+0x278/0x2f0
| ret_from_fork+0x10/0x20
Mark reports an issue with the recent patches coalescing compound pages
while registering them in io_uring. The reason is that we try to drop
excessive references with folio_put_refs(), but pages were acquired
with pin_user_pages(), which has extra accounting and so should be put
down with matching unpin_user_pages() or at least gup_put_folio().
As a fix unpin_user_pages() all but first page instead, and let's figure
out a better API after.
Fixes: 57bebf807e2abcf8 ("io_uring/rsrc: optimise registered huge pages")
Reported-by: Mark Rutland <mark.rutland@xxxxxxx>
Reviewed-by: Jens Axboe <axboe@xxxxxxxxx>
Tested-by: Jens Axboe <axboe@xxxxxxxxx>
Signed-off-by: Pavel Begunkov <asml.silence@xxxxxxxxx>
---
io_uring/rsrc.c | 8 +++++++-
1 file changed, 7 insertions(+), 1 deletion(-)
diff --git a/io_uring/rsrc.c b/io_uring/rsrc.c
index 056f40946ff6..3c5ab0360317 100644
--- a/io_uring/rsrc.c
+++ b/io_uring/rsrc.c
@@ -1235,7 +1235,13 @@ static int io_sqe_buffer_register(struct io_ring_ctx *ctx, struct iovec *iov,
}
}
if (folio) {
- folio_put_refs(folio, nr_pages - 1);
+ /*
+ * The pages are bound to the folio, it doesn't
+ * actually unpin them but drops all but one reference,
+ * which is usually put down by io_buffer_unmap().
+ * Note, needs a better helper.
+ */
+ unpin_user_pages(&pages[1], nr_pages - 1);
nr_pages = 1;
}
}
--
2.39.1
