Re: [f2fs-dev] [PATCH] f2fs: invalidate block device page cache on umount

[Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>]

On 2026/3/12 11:56, Yongpeng Yang wrote:
> 
> On 3/12/26 08:49, Chao Yu via Linux-f2fs-devel wrote:
>> On 2026/2/16 19:27, Yongpeng Yang wrote:
>>> From: Yongpeng Yang <yangyongpeng@xiaomi.com>
>>>
>>> Neither F2FS nor VFS invalidates the block device page cache, which
>>> results in reading stale metadata. An example scenario is shown below:
>>>
>>> Terminal A                  Terminal B
>>> mount /dev/vdb /mnt/f2fs
>>> touch mx // ino = 4
>>> sync
>>> dump.f2fs -i 4 /dev/vdb// block on "[Y/N]"
>>>                               touch mx2 // ino = 5
>>>                               sync
>>>                               umount /mnt/f2fs
>>>                               dump.f2fs -i 5 /dev/vdb // block addr is 0
>>>
>>> After umount, the block device page cache is not purged, causing
>>> `dump.f2fs -i 5 /dev/vdb` to read stale metadata and see inode 5 with
>>> block address 0.
>>>
>>> This patch calls invalidate_bdev during umount to invalidate the block
>>> device page cache, preventing stale metadata from being read.
>>>
>>> Signed-off-by: Yongpeng Yang <yangyongpeng@xiaomi.com>
>>> ---
>>>    fs/f2fs/super.c | 6 ++++++
>>>    1 file changed, 6 insertions(+)
>>>
>>> diff --git a/fs/f2fs/super.c b/fs/f2fs/super.c
>>> index 1a755997aff5..39d3b52ceac1 100644
>>> --- a/fs/f2fs/super.c
>>> +++ b/fs/f2fs/super.c
>>> @@ -2091,6 +2091,12 @@ static void f2fs_put_super(struct super_block *sb)
>>>    #if IS_ENABLED(CONFIG_UNICODE)
>>>        utf8_unload(sb->s_encoding);
>>>    #endif
>>> +    sync_blockdev(sb->s_bdev);
>>
>> We will call sync_blockdev in below path?
>>
>> - kill_f2fs_super
>>   - kill_block_super
>>    - generic_shutdown_super
>>     - put_super
>>    - sync_blockdev
>>
>> 1721 void kill_block_super(struct super_block *sb)
>> 1722 {
>> 1723         struct block_device *bdev = sb->s_bdev;
>> 1724
>> 1725         generic_shutdown_super(sb);
>> 1726         if (bdev) {
>> 1727                 sync_blockdev(bdev);
>> 1728                 bdev_fput(sb->s_bdev_file);
>> 1729         }
>> 1730 }
>>
>>> +    invalidate_bdev(sb->s_bdev);
> 
> This works for an f2fs instance mounted on a single device, but it does
> not work for multi-device configurations, because the vfs cannot be
> aware of FDEV(1).

Yeah, I meant we can avoid duplicated sync_blockdev() for main device in
f2fs_put_super().

> 
>>
>> I guess we can leave the device w/ uptodate cache, in case if there are
>> multiple user on the device?
> 
> The page cache of the block device file may contain data that is not
> uptodate. For example, data may first be read directly through the block
 > device file, and then the same blocks may be written through f2fs. Since> f2fs writes to the block device via the submit_bio path, it does not
> update the page cache of the block device file. As a result, the data in
> the block device file’s page cache may become stale. Therefore, the page
> cache must be invalidated during unmount.

Well, can we call ioctl(fd, BLKFLSBUF) for all devices belong to f2fs img like
you did in ("f2fs-tools: invalidate block device page cache before reading
metadata"), does that fix the issue?

Thanks,

> 
> Thanks
> Yongpeng,
> 
>>
>> Thanks,
>>
>>> +    for (i = 1; i < sbi->s_ndevs; i++) {
>>> +        sync_blockdev(FDEV(i).bdev);
>>> +        invalidate_bdev(FDEV(i).bdev);
>>> +    }
>>>    }
>>>      int f2fs_sync_fs(struct super_block *sb, int sync)
>>
>>
>>
>> _______________________________________________
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>> Linux-f2fs-devel@lists.sourceforge.net
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> 



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