On 2018/07/21 5:06, Andrew Morton wrote: > On Fri, 20 Jul 2018 19:36:23 +0900 Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> wrote: > >>> >>> This report is stalling after mount() completed and process used remap_file_pages(). >>> I think that we might need to use debug printk(). But I don't know what to examine. >>> >> >> Andrew, can you pick up this debug printk() patch? >> I guess we can get the result within one week. > > Sure, let's toss it in -next for a while. > >> >From 8f55e00b21fefffbc6abd9085ac503c52a302464 Mon Sep 17 00:00:00 2001 >> From: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> >> Date: Fri, 20 Jul 2018 19:29:06 +0900 >> Subject: [PATCH] fs/buffer.c: add debug print for __getblk_gfp() stall problem >> >> Among syzbot's unresolved hung task reports, 18 out of 65 reports contain >> __getblk_gfp() line in the backtrace. Since there is a comment block that >> says that __getblk_gfp() will lock up the machine if try_to_free_buffers() >> attempt from grow_dev_page() is failing, let's start from checking whether >> syzbot is hitting that case. This change will be removed after the bug is >> fixed. > > I'm not sure that grow_dev_page() is hanging. It has often been > suspected, but always is proven innocent. Lets see. syzbot reproduced this problem ( https://syzkaller.appspot.com/text?tag=CrashLog&x=11f2fc44400000 ) . It says that grow_dev_page() is returning 1 but __find_get_block() is failing forever. Any idea?
