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

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Date: Wed, 8 May 2024 10:08:01 +0800
From: Glass Su <glass.su@...e.com>
To: Petr Vorel <pvorel@...e.cz>
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



> 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.

> Signed-off-by: Petr Vorel <pvorel@...e.cz>
> ---
> Changes v2->v3:
> * Align tab with other entries.
> 
> Changes v1->v2 (all suggested by Brian Foster - thanks!):
> * rename constant to BCACHEFS_SUPER_MAGIC,
> * keep BCACHEFS_STATFS_MAGIC in bcachefs_format.h, just include
> <uapi/linux/magic.h> and use BCACHEFS_SUPER_MAGIC definition,
> * move the constant to the first chunk.
> 
> Kind regards,
> Petr
> 
> fs/bcachefs/bcachefs_format.h | 3 ++-
> include/uapi/linux/magic.h    | 1 +
> 2 files changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/fs/bcachefs/bcachefs_format.h b/fs/bcachefs/bcachefs_format.h
> index f7fbfccd2b1e..3b831415409b 100644
> --- a/fs/bcachefs/bcachefs_format.h
> +++ b/fs/bcachefs/bcachefs_format.h
> @@ -76,6 +76,7 @@
> #include <asm/byteorder.h>
> #include <linux/kernel.h>
> #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.

Anyway, it looks good to me so far:
Reviewed-by: Su Yue <glass.su@...e.com> 

— 
Su

> #define MINIX_SUPER_MAGIC 0x137F /* minix v1 fs, 14 char names */
> #define MINIX_SUPER_MAGIC2 0x138F /* minix v1 fs, 30 char names */
> -- 
> 2.43.0
> 
>