From: Chao Yu Subject: Re: [f2fs-dev] [RFC PATCH 10/10] f2fs: fs-verity support Date: Wed, 29 Aug 2018 09:22:42 +0800 Message-ID: <8b7f83db-810a-bdd6-85b0-1248dc14f8d7@huawei.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> <20180828170142.GB62482@jaegeuk-macbookpro.roam.corp.google.com> Mime-Version: 1.0 Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit Cc: Chao Yu , Eric Biggers , "Dmitry Kasatkin" , Michael Halcrow , , , , , , , Mimi Zohar , Victor Hsieh To: Jaegeuk Kim Return-path: In-Reply-To: <20180828170142.GB62482@jaegeuk-macbookpro.roam.corp.google.com> Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org On 2018/8/29 1:01, Jaegeuk Kim wrote: > 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. Oops, if it was in production, I agree to keep it in i_advice, otherwise, we still can discuss its location. > >> >>> 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); Ah, that's right, do you remember why we treat them with different recoverable level? Thanks, > >> >> 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 >>>>> >>> >>> . >>> > > . >