On Fri, Oct 05, 2018 at 08:10:32PM +0200, Adam Borowski wrote: > On Fri, Oct 05, 2018 at 09:06:00AM -0700, Darrick J. Wong wrote: > > On Fri, Oct 05, 2018 at 02:27:41PM +0200, Adam Borowski wrote: > > > Needed by users of fstatfs(). > > > > NAK. > > > > The XFS superblock magic number is part of the on-disk format definition > > of XFS. It belongs with all the other on-disk format definitions in this > > file. > > > > I don't think it's a good idea for userspace to associate s_magic with > > userspace API feature sets, though the cat's long escaped the bag on > > that one. > > > > With that being reality, "the XFS superblock magic number" has a > > different semantic meaning than "the agreed upon statfs.f_type value for > > XFS", which means the latter should have a different symbol name to > > reflect that difference. > > Ie, you'd be ok with the same value to be defined in two places -- do I > understand this right? I'd be fine with it, but let's see what the other XFS maintainers think. I still don't like the practice of inferring behaviors from magic numbers, but at least we'd decouple the disk format from the UABI. :) > > > --- a/fs/xfs/libxfs/xfs_format.h > > > -#define XFS_SB_MAGIC 0x58465342 /* 'XFSB' */ > > > +#define XFS_SB_MAGIC XFS_SUPER_MAGIC /* 0x58465342 = 'XFSB' */ > > > --- a/include/uapi/linux/magic.h > > > #define JFFS2_SUPER_MAGIC 0x72b6 > > > +#define XFS_SUPER_MAGIC 0x58465342 /* "XFSB" */ > > > #define PSTOREFS_MAGIC 0x6165676C You'd change xfs_fs_fill_super and xfs_fs_statfs too, right? --D > > > Meow! > -- > ⢀⣴⠾⠻⢶⣦⠀ > ⣾⠁⢰⠒⠀⣿⡁ 10 people enter a bar: 1 who understands binary, > ⢿⡄⠘⠷⠚⠋⠀ 1 who doesn't, D who prefer to write it as hex, > ⠈⠳⣄⠀⠀⠀⠀ and 1 who narrowly avoided an off-by-one error.
