Re: [PATCH v9 05/10] erofs: support user-defined fingerprint name

[Gao Xiang <hsiangkao@linux.alibaba.com>]

On 2025/11/17 21:25, Hongbo Li wrote:
> From: Hongzhen Luo <hongzhen@linux.alibaba.com>
> 
> When creating the EROFS image, users can specify the fingerprint name.
> This is to prepare for the upcoming inode page cache share.
> 
> Signed-off-by: Hongzhen Luo <hongzhen@linux.alibaba.com>
> Signed-off-by: Hongbo Li <lihongbo22@huawei.com>
> ---
>   fs/erofs/Kconfig    |  9 +++++++++
>   fs/erofs/erofs_fs.h |  6 ++++--
>   fs/erofs/internal.h |  2 ++
>   fs/erofs/super.c    |  5 +++--
>   fs/erofs/xattr.c    | 15 +++++++++++++++
>   5 files changed, 33 insertions(+), 4 deletions(-)
> 
> diff --git a/fs/erofs/Kconfig b/fs/erofs/Kconfig
> index d81f3318417d..c88b6d0714a4 100644
> --- a/fs/erofs/Kconfig
> +++ b/fs/erofs/Kconfig
> @@ -194,3 +194,12 @@ config EROFS_FS_PCPU_KTHREAD_HIPRI
>   	  at higher priority.
>   
>   	  If unsure, say N.
> +
> +config EROFS_FS_PAGE_CACHE_SHARE
> +	bool "EROFS page cache share support (experimental)"
> +	depends on EROFS_FS && EROFS_FS_XATTR && !EROFS_FS_ONDEMAND
> +	help
> +	  This enables page cache sharing among inodes with identical
> +	  content fingerprints on the same device.
> +
> +	  If unsure, say N.
> diff --git a/fs/erofs/erofs_fs.h b/fs/erofs/erofs_fs.h
> index 3d5738f80072..9b9fe1abe0b9 100644
> --- a/fs/erofs/erofs_fs.h
> +++ b/fs/erofs/erofs_fs.h
> @@ -35,8 +35,9 @@
>   #define EROFS_FEATURE_INCOMPAT_XATTR_PREFIXES	0x00000040
>   #define EROFS_FEATURE_INCOMPAT_48BIT		0x00000080
>   #define EROFS_FEATURE_INCOMPAT_METABOX		0x00000100
> +#define EROFS_FEATURE_INCOMPAT_ISHARE_KEY	0x00000200

It seems that you didn't address this part I
mentioned in the previous reply:
https://lore.kernel.org/r/a3b0bac9-d08f-44dc-8adb-7cc85cae7b13@linux.alibaba.com

>   #define EROFS_ALL_FEATURE_INCOMPAT		\
> -	((EROFS_FEATURE_INCOMPAT_METABOX << 1) - 1)
> +	((EROFS_FEATURE_INCOMPAT_ISHARE_KEY << 1) - 1)
>   
>   #define EROFS_SB_EXTSLOT_SIZE	16
>   
> @@ -83,7 +84,8 @@ struct erofs_super_block {
>   	__le32 xattr_prefix_start;	/* start of long xattr prefixes */
>   	__le64 packed_nid;	/* nid of the special packed inode */
>   	__u8 xattr_filter_reserved; /* reserved for xattr name filter */
> -	__u8 reserved[3];
> +	__u8 ishare_xattr_prefix_id;	/* indice the ishare key in prefix xattr */

/* indexes the ishare key in prefix xattres */ ?

> +	__u8 reserved[2];
>   	__le32 build_time;	/* seconds added to epoch for mkfs time */
>   	__le64 rootnid_8b;	/* (48BIT on) nid of root directory */
>   	__le64 reserved2;
> diff --git a/fs/erofs/internal.h b/fs/erofs/internal.h
> index 98fe652aea33..3033252211ba 100644
> --- a/fs/erofs/internal.h
> +++ b/fs/erofs/internal.h
> @@ -134,6 +134,7 @@ struct erofs_sb_info {
>   	u32 xattr_blkaddr;
>   	u32 xattr_prefix_start;
>   	u8 xattr_prefix_count;
> +	u8 ishare_xattr_pfx;	/* ishare prefix xattr index */

I think either giving a meaningful comment or just
get rid of the comment entirely.

>   	struct erofs_xattr_prefix_item *xattr_prefixes;
>   	unsigned int xattr_filter_reserved;
>   #endif
> @@ -234,6 +235,7 @@ EROFS_FEATURE_FUNCS(dedupe, incompat, INCOMPAT_DEDUPE)
>   EROFS_FEATURE_FUNCS(xattr_prefixes, incompat, INCOMPAT_XATTR_PREFIXES)
>   EROFS_FEATURE_FUNCS(48bit, incompat, INCOMPAT_48BIT)
>   EROFS_FEATURE_FUNCS(metabox, incompat, INCOMPAT_METABOX)
> +EROFS_FEATURE_FUNCS(ishare_key, incompat, INCOMPAT_ISHARE_KEY)
>   EROFS_FEATURE_FUNCS(sb_chksum, compat, COMPAT_SB_CHKSUM)
>   EROFS_FEATURE_FUNCS(xattr_filter, compat, COMPAT_XATTR_FILTER)
>   EROFS_FEATURE_FUNCS(shared_ea_in_metabox, compat, COMPAT_SHARED_EA_IN_METABOX)
> diff --git a/fs/erofs/super.c b/fs/erofs/super.c
> index 0d88c04684b9..80f032cb2cc3 100644
> --- a/fs/erofs/super.c
> +++ b/fs/erofs/super.c
> @@ -298,6 +298,9 @@ static int erofs_read_superblock(struct super_block *sb)
>   		if (ret)
>   			goto out;
>   	}
> +	if (erofs_sb_has_ishare_key(sbi))
> +		sbi->ishare_xattr_pfx =
> +			dsb->ishare_xattr_prefix_id & EROFS_XATTR_LONG_PREFIX_MASK;
>   
>   	ret = -EINVAL;
>   	sbi->feature_incompat = le32_to_cpu(dsb->feature_incompat);
> @@ -339,7 +342,6 @@ static int erofs_read_superblock(struct super_block *sb)
>   			return -EFSCORRUPTED;	/* self-loop detection */
>   	}
>   	sbi->inos = le64_to_cpu(dsb->inos);
> -

Unnecessary change here.

>   	sbi->epoch = (s64)le64_to_cpu(dsb->epoch);
>   	sbi->fixed_nsec = le32_to_cpu(dsb->fixed_nsec);
>   	super_set_uuid(sb, (void *)dsb->uuid, sizeof(dsb->uuid));
> @@ -737,7 +739,6 @@ static int erofs_fc_fill_super(struct super_block *sb, struct fs_context *fc)
>   	err = erofs_xattr_prefixes_init(sb);
>   	if (err)
>   		return err;
> -

Unnecessary change here.

>   	erofs_set_sysfs_name(sb);
>   	err = erofs_register_sysfs(sb);
>   	if (err)
> diff --git a/fs/erofs/xattr.c b/fs/erofs/xattr.c
> index 396536d9a862..6cb76313c14c 100644
> --- a/fs/erofs/xattr.c
> +++ b/fs/erofs/xattr.c
> @@ -519,6 +519,21 @@ int erofs_xattr_prefixes_init(struct super_block *sb)
>   	}
>   
>   	erofs_put_metabuf(&buf);
> +	if (!ret && erofs_sb_has_ishare_key(sbi)) {
> +		struct erofs_xattr_long_prefix *new_pfx, *pfx =
> +					pfs[sbi->ishare_xattr_pfx].prefix;

		struct erofs_xattr_prefix_item *pf = pfs + sbi->ishare_xattr_pfx;
		struct erofs_xattr_long_prefix *newpfx;

		newpfx = krealloc(pf->prefix,
				sizeof(*newpfx) + pf->infix_len + 1, GFP_KERNEL);
		if (newpfx) {
			newpfx->infix[pf->infix_len] = '\0';
			pf->prefix = newpfx;
		} else {
			ret = -ENOMEM;
		}

Thanks,
Gao Xiang

> +
> +		new_pfx = krealloc(pfx,
> +				   sizeof(struct erofs_xattr_long_prefix) +
> +				   pfs[sbi->ishare_xattr_pfx].infix_len + 1,
> +				   GFP_KERNEL);
> +		if (new_pfx) {
> +			new_pfx->infix[pfs[sbi->ishare_xattr_pfx].infix_len] = '\0';
> +			pfs[sbi->ishare_xattr_pfx].prefix = new_pfx;
> +		} else {
> +			ret = -ENOMEM;
> +		}
> +	}
>   	sbi->xattr_prefixes = pfs;
>   	if (ret)
>   		erofs_xattr_prefixes_cleanup(sb);