From: Jaegeuk Kim Subject: Re: [f2fs-dev] [RFC PATCH 10/10] f2fs: fs-verity support Date: Tue, 28 Aug 2018 10:01:42 -0700 Message-ID: <20180828170142.GB62482@jaegeuk-macbookpro.roam.corp.google.com> References: <20180824161642.1144-1-ebiggers@kernel.org> <20180824161642.1144-11-ebiggers@kernel.org> <20180826173507.GC728@sol.localdomain> <20180828072756.GC29049@jaegeuk-macbookpro.roam.corp.google.com> <63a19512-e938-d239-9e3c-f6ecc479478c@huawei.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Chao Yu , Eric Biggers , Dmitry Kasatkin , Michael Halcrow , 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 , Victor Hsieh To: Chao Yu Return-path: Content-Disposition: inline In-Reply-To: <63a19512-e938-d239-9e3c-f6ecc479478c@huawei.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On 08/28, Chao Yu wrote: > On 2018/8/28 15:27, Jaegeuk Kim wrote: > > On 08/27, Chao Yu wrote: > >> 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 > >>>>> #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? > > > > No, it was reserved by f2fs-tools, > > That's not a problem, since we didn't use that reserved bit in any of images > now, there is no backward compatibility issue. We're using that. > > > and I think this should be aligned to the encryption bit. > > Alright, we could, but if so, i_advise will run out of space earlier, after that > we have to add real advice bit into i_inline or i_flags, that would be a little > weird. > > For encryption bit, as a common vfs feature flag, in the beginning of encryption > development, it will be better to set it into i_flags, IMO, but now, we have to > keep it as it was. > > > Moreover, we guarantee i_flags less strictly from power-cut than i_advise. > > IMO, in power-cut scenario, it needs to keep both i_flags and i_advise being > recoverable strictly. Any condition that we can not recover i_flags? In __f2fs_ioc_setflags, f2fs_mark_inode_dirty_sync(inode, false); > > Thanks, > > > > >> > >> 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 > >>> > >>> ------------------------------------------------------------------------------ > >>> Check out the vibrant tech community on one of the world's most > >>> engaging tech sites, Slashdot.org! http://sdm.link/slashdot > >>> _______________________________________________ > >>> Linux-f2fs-devel mailing list > >>> Linux-f2fs-devel@lists.sourceforge.net > >>> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel > >>> > > > > . > >