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    SubjectRe: [f2fs-dev] [RFC PATCH 10/10] f2fs: fs-verity support
    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 <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?

    No, it was reserved by f2fs-tools, and I think this should be aligned to the
    encryption bit. Moreover, we guarantee i_flags less strictly from power-cut than
    i_advise.

    >
    > 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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    > > _______________________________________________
    > > Linux-f2fs-devel mailing list
    > > Linux-f2fs-devel@lists.sourceforge.net
    > > https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
    > >

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