lkml.org 
[lkml]   [2019]   [Jan]   [2]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
SubjectRe: INFO: task hung in generic_file_write_iter
From
Date
On 2019/01/03 2:26, Jan Kara wrote:
> On Thu 03-01-19 01:07:25, Tetsuo Handa wrote:
>> On 2019/01/02 23:40, Jan Kara wrote:
>>> I had a look into this and the only good explanation for this I have is
>>> that sb->s_blocksize is different from (1 << sb->s_bdev->bd_inode->i_blkbits).
>>> If that would happen, we'd get exactly the behavior syzkaller observes
>>> because grow_buffers() would populate different page than
>>> __find_get_block() then looks up.
>>>
>>> However I don't see how that's possible since the filesystem has the block
>>> device open exclusively and blkdev_bszset() makes sure we also have
>>> exclusive access to the block device before changing the block device size.
>>> So changing block device block size after filesystem gets access to the
>>> device should be impossible.
>>>
>>> Anyway, could you perhaps add to your debug patch a dump of 'size' passed
>>> to __getblk_slow() and bdev->bd_inode->i_blkbits? That should tell us
>>> whether my theory is right or not. Thanks!
>>>
>>
>> OK. Andrew, will you add (or fold into) this change?
>>
>> From e6f334380ad2c87457bfc2a4058316c47f75824a Mon Sep 17 00:00:00 2001
>> From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
>> Date: Thu, 3 Jan 2019 01:03:35 +0900
>> Subject: [PATCH] fs/buffer.c: dump more info for __getblk_gfp() stall problem
>>
>> We need to dump more variables on top of
>> "fs/buffer.c: add debug print for __getblk_gfp() stall problem".
>>
>> Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
>> Cc: Jan Kara <jack@suse.cz>
>> ---
>> fs/buffer.c | 9 +++++++--
>> 1 file changed, 7 insertions(+), 2 deletions(-)
>>
>> diff --git a/fs/buffer.c b/fs/buffer.c
>> index 580fda0..a50acac 100644
>> --- a/fs/buffer.c
>> +++ b/fs/buffer.c
>> @@ -1066,9 +1066,14 @@ static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
>> #ifdef CONFIG_DEBUG_AID_FOR_SYZBOT
>> if (!time_after(jiffies, current->getblk_stamp + 3 * HZ))
>> continue;
>> - printk(KERN_ERR "%s(%u): getblk(): executed=%x bh_count=%d bh_state=%lx\n",
>> + printk(KERN_ERR "%s(%u): getblk(): executed=%x bh_count=%d bh_state=%lx "
>> + "bdev_super_blocksize=%lu size=%u "
>> + "bdev_super_blocksize_bits=%u bdev_inode_blkbits=%u\n",
>> current->comm, current->pid, current->getblk_executed,
>> - current->getblk_bh_count, current->getblk_bh_state);
>> + current->getblk_bh_count, current->getblk_bh_state,
>> + bdev->bd_super->s_blocksize, size,
>> + bdev->bd_super->s_blocksize_bits,
>> + bdev->bd_inode->i_blkbits);
>
> Well, bd_super may be NULL if there's no filesystem mounted so it would be
> safer to check for this rather than blindly dereferencing it... Otherwise
> the change looks good to me.

I see. Let's be cautious here.

From 317a0d0002b3d2cadae606055ad50f2926ca62d2 Mon Sep 17 00:00:00 2001
From: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Date: Thu, 3 Jan 2019 09:42:02 +0900
Subject: [PATCH v2] fs/buffer.c: dump more info for __getblk_gfp() stall problem

We need to dump more variables on top of
"fs/buffer.c: add debug print for __getblk_gfp() stall problem".

Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Cc: Jan Kara <jack@suse.cz>
---
fs/buffer.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/fs/buffer.c b/fs/buffer.c
index 580fda0..784de3d 100644
--- a/fs/buffer.c
+++ b/fs/buffer.c
@@ -1066,9 +1066,15 @@ static sector_t blkdev_max_block(struct block_device *bdev, unsigned int size)
#ifdef CONFIG_DEBUG_AID_FOR_SYZBOT
if (!time_after(jiffies, current->getblk_stamp + 3 * HZ))
continue;
- printk(KERN_ERR "%s(%u): getblk(): executed=%x bh_count=%d bh_state=%lx\n",
+ printk(KERN_ERR "%s(%u): getblk(): executed=%x bh_count=%d bh_state=%lx bdev_super_blocksize=%ld size=%u bdev_super_blocksize_bits=%d bdev_inode_blkbits=%d\n",
current->comm, current->pid, current->getblk_executed,
- current->getblk_bh_count, current->getblk_bh_state);
+ current->getblk_bh_count, current->getblk_bh_state,
+ IS_ERR_OR_NULL(bdev->bd_super) ? -1L :
+ bdev->bd_super->s_blocksize, size,
+ IS_ERR_OR_NULL(bdev->bd_super) ? -1 :
+ bdev->bd_super->s_blocksize_bits,
+ IS_ERR_OR_NULL(bdev->bd_inode) ? -1 :
+ bdev->bd_inode->i_blkbits);
current->getblk_executed = 0;
current->getblk_bh_count = 0;
current->getblk_bh_state = 0;
--
1.8.3.1
\
 
 \ /
  Last update: 2019-01-03 01:47    [W:0.097 / U:18.548 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site