linux-kernel - Re: [PATCH v3 1/1] bcachefs: Move BCACHEFS_STATFS

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Message-ID: <20240508211759.GA209026@pevik>
Date: Wed, 8 May 2024 23:17:59 +0200
From: Petr Vorel <pvorel@...e.cz>
To: Glass Su <glass.su@...e.com>
Cc: linux-bcachefs@...r.kernel.org,
	Kent Overstreet <kent.overstreet@...ux.dev>, Su Yue <l@...enly.org>,
	Brian Foster <bfoster@...hat.com>, Coly Li <colyli@...e.de>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v3 1/1] bcachefs: Move BCACHEFS_STATFS_MAGIC value to
 UAPI magic.h

HI Su, Kent,

> > On May 7, 2024, at 23:37, Petr Vorel <pvorel@...e.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@...enly.org>

> Would you kindly amend it to Su Yue <glass.su@...e.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).

> > Signed-off-by: Petr Vorel <pvorel@...e.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@...e.com> 

And also without your RBT.

Kind regards,
Petr

> — 
> Su