Re: [f2fs-dev] [PATCH 13/13] f2fs: don't recovery orphan inode on readonly device

[Chao Yu <yuchao0@huawei.com>]

On 2019/4/15 16:10, Ju Hyung Park wrote:
> Hi,
> 
> Thanks for the fix. I'll try this sooner than later.
> 
> One minor request though, can you change
> "JuHyung Park <qkrwngud825@gmail.com>"
> to
> "Park Ju Hyung <qkrwngud825@gmail.com>"?
> 
> That's my preference and I'd like to avoid any inconsistencies.

Sure, will update it in next version. :)

> 
> One additional question from reviewing the code surrounding it:
> does it really makes sense to cleanup orphan inodes even when the "ro"
> mount option is passed?
> It's an explicit request from the user not to write to the block device/image.

Now, f2fs follows the rule that ext4 kept, you can check codes in
ext4_orphan_cleanup()

	if (bdev_read_only(sb->s_bdev)) {
		ext4_msg(sb, KERN_ERR, "write access "
			"unavailable, skipping orphan cleanup");
		return;
	}
...
	if (s_flags & SB_RDONLY) {
		ext4_msg(sb, KERN_INFO, "orphan cleanup on readonly fs");
		sb->s_flags &= ~SB_RDONLY;
	}

There are two points in above codes:
- if block device is readonly, filesystem should not execute any recovery flow
which can trigger write IO.
- if filesystem was mounted as readonly one, and recovery is needed, it will
ignore readonly flag and update data in device for journal recovery during mount.

So IMO, readonly mountoption sematics is only try to restrict data/meta update
behavior that is triggered by user from mountpoint, but filesystem still can do
any updates on a writable device if it needs, mostly like recovery flow.

Anyway, if you want to limit any updates on block device, making it readonly
will be a good choice. :)

Thanks,

> 
> Thanks.
> 
> On Mon, Apr 15, 2019 at 4:31 PM Chao Yu <yuchao0@huawei.com> wrote:
>>
>> As JuHyung Park reported in mailing list:
>>
>> https://sourceforge.net/p/linux-f2fs/mailman/message/36639787/
>>
>> generic_make_request: Trying to write to read-only block-device loop0 (partno 0)
>> WARNING: CPU: 0 PID: 23437 at block/blk-core.c:2174 generic_make_request_checks+0x594/0x630
>>
>>  generic_make_request+0x46/0x3d0
>>  submit_bio+0x30/0x110
>>  __submit_merged_bio+0x68/0x390
>>  f2fs_submit_page_write+0x1bb/0x7f0
>>  f2fs_do_write_meta_page+0x7f/0x160
>>  __f2fs_write_meta_page+0x70/0x140
>>  f2fs_sync_meta_pages+0x140/0x250
>>  f2fs_write_checkpoint+0x5c5/0x17b0
>>  f2fs_sync_fs+0x9c/0x110
>>  sync_filesystem+0x66/0x80
>>  f2fs_recover_fsync_data+0x790/0xa30
>>  f2fs_fill_super+0xe4e/0x1980
>>  mount_bdev+0x518/0x610
>>  mount_fs+0x34/0x13f
>>  vfs_kern_mount.part.11+0x4f/0x120
>>  do_mount+0x2d1/0xe40
>>  __x64_sys_mount+0xbf/0xe0
>>  do_syscall_64+0x4a/0xf0
>>  entry_SYSCALL_64_after_hwframe+0x44/0xa9
>>
>> print_req_error: I/O error, dev loop0, sector 4096
>>
>> If block device is readonly, we should never trigger write IO from
>> filesystem layer, but previously, orphan recovery didn't consider
>> such condition, result in triggering above warning, fix it.
>>
>> Reported-by: JuHyung Park <qkrwngud825@gmail.com>
>> Signed-off-by: Chao Yu <yuchao0@huawei.com>
>> ---
>>  fs/f2fs/checkpoint.c | 6 ++++++
>>  1 file changed, 6 insertions(+)
>>
>> diff --git a/fs/f2fs/checkpoint.c b/fs/f2fs/checkpoint.c
>> index a7ad1b1e5750..90e1bab86269 100644
>> --- a/fs/f2fs/checkpoint.c
>> +++ b/fs/f2fs/checkpoint.c
>> @@ -674,6 +674,12 @@ int f2fs_recover_orphan_inodes(struct f2fs_sb_info *sbi)
>>         if (!is_set_ckpt_flags(sbi, CP_ORPHAN_PRESENT_FLAG))
>>                 return 0;
>>
>> +       if (bdev_read_only(sbi->sb->s_bdev)) {
>> +               f2fs_msg(sbi->sb, KERN_INFO, "write access "
>> +                       "unavailable, skipping orphan cleanup");
>> +               return 0;
>> +       }
>> +
>>         if (s_flags & SB_RDONLY) {
>>                 f2fs_msg(sbi->sb, KERN_INFO, "orphan cleanup on readonly fs");
>>                 sbi->sb->s_flags &= ~SB_RDONLY;
>> --
>> 2.18.0.rc1
>>
>>
>>
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> .
>