Re: [f2fs-dev] [RFC PATCH 10/10] f2fs: fs-verity support

From: Chao Yu <chao@kernel.org>
To: Eric Biggers <ebiggers@kernel.org>, Chao Yu <yuchao0@huawei.com>
Cc: Dmitry Kasatkin <dmitry.kasatkin@gmail.com>,
	Michael Halcrow <mhalcrow@google.com>,
	linux-kernel@vger.kernel.org,
	linux-f2fs-devel@lists.sourceforge.net,
	linux-fscrypt@vger.kernel.org, linux-fsdevel@vger.kernel.org,
	linux-integrity@vger.kernel.org, linux-ext4@vger.kernel.org,
	Mimi Zohar <zohar@linux.vnet.ibm.com>,
	Victor Hsieh <victorhsieh@google.com>
Subject: Re: [f2fs-dev] [RFC PATCH 10/10] f2fs: fs-verity support
Date: Mon, 27 Aug 2018 23:54:34 +0800	[thread overview]
Message-ID: <dbc20be8-975d-7bd2-002d-a8f30896da4a@kernel.org> (raw)
In-Reply-To: <20180826173507.GC728@sol.localdomain>

Hi Eric,

On 2018/8/27 1:35, Eric Biggers wrote:
> Hi Chao,
> 
> On Sat, Aug 25, 2018 at 01:54:08PM +0800, Chao Yu wrote:
>> On 2018/8/25 0:16, Eric Biggers wrote:
>>> From: Eric Biggers <ebiggers@google.com>
>>>  #ifdef CONFIG_F2FS_CHECK_FS
>>>  #define f2fs_bug_on(sbi, condition)	BUG_ON(condition)
>>>  #else
>>> @@ -146,7 +149,7 @@ struct f2fs_mount_info {
>>>  #define F2FS_FEATURE_QUOTA_INO		0x0080
>>>  #define F2FS_FEATURE_INODE_CRTIME	0x0100
>>>  #define F2FS_FEATURE_LOST_FOUND		0x0200
>>> -#define F2FS_FEATURE_VERITY		0x0400	/* reserved */
>>> +#define F2FS_FEATURE_VERITY		0x0400
>>>  
>>>  #define F2FS_HAS_FEATURE(sb, mask)					\
>>>  	((F2FS_SB(sb)->raw_super->feature & cpu_to_le32(mask)) != 0)
>>> @@ -598,7 +601,7 @@ enum {
>>>  #define FADVISE_ENC_NAME_BIT	0x08
>>>  #define FADVISE_KEEP_SIZE_BIT	0x10
>>>  #define FADVISE_HOT_BIT		0x20
>>> -#define FADVISE_VERITY_BIT	0x40	/* reserved */
>>> +#define FADVISE_VERITY_BIT	0x40
>>
>> As I suggested before, how about moving f2fs' verity_bit from i_fadvise to more
>> generic i_flags field like ext4, so we can a) remaining more bits for those
>> demands which really need file advise fields. b) using i_flags bits keeping line
>> with ext4. Not sure, if user want to know whether the file is verity one, it
>> will be easy for f2fs to export the status through FS_IOC_SETFLAGS.
>>
>> #define EXT4_VERITY_FL			0x00100000 /* Verity protected inode */
>>
>> #define F2FS_VERITY_FL			0x00100000 /* Verity protected inode */
>>
> 
> I don't like using i_advise much either, but I actually don't see either
> location being much better than the other at the moment.  The real problem is an
> artificial one: the i_flags in f2fs's on-disk format are being assumed to use

Yeah, but since most copied flags from vfs/ext4 are not actually used in f2fs,
also 0x00100000 bit is not used now, so we can just define it now directly for
verity bit.

Cleanup and remapping in ioctl interface for those unused flags, we can do it
latter?

Thanks,

> the same numbering scheme as ext4's on-disk format, which makes it seem that
> they have to be in sync, and that all new ext4 flags (say, EA_INODE) also
> reserve bits in f2fs and vice versa, when they in fact do not.  Instead, f2fs
> should use its own numbering for its i_flags, and it should map them to/from
> whatever is needed for common APIs like FS_IOC_{GET,SET}FLAGS and
> FS_IOC_FS{GET,SET}XATTR.
> 
> So putting the verity flag in *either* location (i_advise or i_flags) is just
> kicking the can down the road.  If I get around to it I will send a patch that
> cleans up the f2fs flags properly...>
> Thanks,
> 
> - Eric
> 
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