Re: [PATCH v3 1/1] bcachefs: Move BCACHEFS_STATFS_MAGIC value to UAPI magic.h

Kent Overstreet
2024-05-08T21:27:56Z

On Wed, May 08, 2024 at 11:17:59PM +0200, Petr Vorel wrote:
> HI Su, Kent,
>
> > > On May 7, 2024, at 23:37, Petr Vorel <pvorel@suse.cz> wrote:
>
> > > Move BCACHEFS_STATFS_MAGIC value to UAPI <linux/magic.h> under
> > > BCACHEFS_SUPER_MAGIC definition (use common approach for name) and reuse the
> > > definition in bcachefs_format.h BCACHEFS_STATFS_MAGIC.
>
> > > There are other bcachefs magic definitions: BCACHE_MAGIC, BCHFS_MAGIC,
> > > which use UUID_INIT() and are used only in libbcachefs. Therefore move
> > > only BCACHEFS_STATFS_MAGIC value, which can be used outside of
> > > libbcachefs for f_type field in struct statfs in statfs() or fstatfs().
>
> > > Suggested-by: Su Yue <l@damenly.org>
>
> > Would you kindly amend it to Su Yue <glass.su@suse.com> or
> > Kent can help if the patch is going to be applied.
>
> Unfortunately Kent was faster, it's already merged without your SUSE address
> (and your RBT you added in the end):
>
> https://evilpiepirate.org/git/bcachefs.git/commit/?h=for-next&id=ce8f9355f23be9756e499682d0d642a741db6c3a
>
> @Kent: Maybe it can be even now amended (with Su Yue's RBT).

...sure, make me invalidate my test results :)

> > > Signed-off-by: Petr Vorel <pvorel@suse.cz>
> > > ---
> > > Changes v2->v3:
> > > * Align tab with other entries.
> ...
> > > #include <linux/uuid.h>
> > > +#include <uapi/linux/magic.h>
> > > #include "vstructs.h"
>
> > > #ifdef __KERNEL__
> > > @@ -1275,7 +1276,7 @@ enum bch_compression_opts {
> > > UUID_INIT(0xc68573f6, 0x66ce, 0x90a9, \
> > > 0xd9, 0x6a, 0x60, 0xcf, 0x80, 0x3d, 0xf7, 0xef)
>
> > > -#define BCACHEFS_STATFS_MAGIC 0xca451a4e
> > > +#define BCACHEFS_STATFS_MAGIC BCACHEFS_SUPER_MAGIC
>
> > > #define JSET_MAGIC __cpu_to_le64(0x245235c1a3625032ULL)
> > > #define BSET_MAGIC __cpu_to_le64(0x90135c78b99e07f5ULL)
> > > diff --git a/include/uapi/linux/magic.h b/include/uapi/linux/magic.h
> > > index 1b40a968ba91..bb575f3ab45e 100644
> > > --- a/include/uapi/linux/magic.h
> > > +++ b/include/uapi/linux/magic.h
> > > @@ -37,6 +37,7 @@
> > > #define HOSTFS_SUPER_MAGIC 0x00c0ffee
> > > #define OVERLAYFS_SUPER_MAGIC 0x794c7630
> > > #define FUSE_SUPER_MAGIC 0x65735546
> > > +#define BCACHEFS_SUPER_MAGIC 0xca451a4e
>
> > IIUC, due to some historical reasons bcachefs used to switched
> > ondisk sb magic from BCACHE_MAGIC to BCHFS_MAGIC.
> > Other major fses uses *_SUPER_MAGIC both for ondisk
> > sb magic, kstatfs::f_type and super_block::s_magic.
> > However, for bcacehfs there are three magic numbers.
>
> Thanks for info. But for struct statfs in statfs() or fstatfs() only 0xca451a4e
> is needed, right? I would not expose the other(s) unless it's really needed.
> Also we'd need to backport UUID_INIT() into UAPI :(.
>
> > Anyway, it looks good to me so far:
> > Reviewed-by: Su Yue <glass.su@suse.com>
>
> And also without your RBT.
>
> Kind regards,
> Petr
>
> > —
> > Su