Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>
于2025年7月25日周五 09:03写道：
>
> It provides a way to disable linear lookup fallback during mkfs.
>
> Behavior summary:
> Android Distro
> By default disabled enabled
> Tune w/ [no]hashonly no yes
>
> Android case:
>
> 1.1) Disable linear lookup:
> mkfs.f2fs -f -g android -O casefold -C utf8:hashonly /dev/vdb
> dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
> s_encoding_flags [0x 2 : 2]
>
> 1.2) Enable linear lookup:
> mkfs.f2fs -f -g android -O casefold -C utf8:nohashonly /dev/vdb
> dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
> s_encoding_flags [0x 2 : 2]
Hi Chao,
Seems like a typo here? should be:
s_encoding_flags [0x 0 : 0] ?
thanks!
>
> 1.3) By default:
> mkfs.f2fs -f -g android -O casefold -C utf8 /dev/vdb
> dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
> s_encoding_flags [0x 2 : 2]
>
> Distro case:
>
> 2.1) Disable linear lookup:
> mkfs.f2fs -f -O casefold -C utf8:hashonly /dev/vdb
> dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
> s_encoding_flags [0x 2 : 2]
>
> 2.2) Enable linear lookup:
> mkfs.f2fs -f -O casefold -C utf8:nohashonly /dev/vdb
> dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
> s_encoding_flags [0x 0 : 0]
>
> 2.3) By default:
> mkfs.f2fs -f -O casefold -C utf8 /dev/vdb
> dump.f2fs -d3 /dev/vdb |grep s_encoding_flags
> s_encoding_flags [0x 0 : 0]
>
> Signed-off-by: Chao Yu <c...@kernel.org>
> ---
> v2:
> - disable linear lookup by default for Android case
> include/f2fs_fs.h | 3 ++-
> lib/libf2fs.c | 1 +
> man/mkfs.f2fs.8 | 10 ++++++++--
> mkfs/f2fs_format.c | 3 +++
> mkfs/f2fs_format_main.c | 3 ++-
> 5 files changed, 16 insertions(+), 4 deletions(-)
>
> diff --git a/include/f2fs_fs.h b/include/f2fs_fs.h
> index f7268d1..a8da8fa 100644
> --- a/include/f2fs_fs.h
> +++ b/include/f2fs_fs.h
> @@ -1478,7 +1478,8 @@ enum {
>
> /* feature list in Android */
> enum {
> - F2FS_FEATURE_NAT_BITS = 0x0001,
> + F2FS_FEATURE_NAT_BITS = 0x0001,
> + F2FS_FEATURE_LINEAR_LOOKUP = 0x0002,
> };
>
> /* nolinear lookup tune */
> diff --git a/lib/libf2fs.c b/lib/libf2fs.c
> index 2f012c8..0e3e62a 100644
> --- a/lib/libf2fs.c
> +++ b/lib/libf2fs.c
> @@ -1424,6 +1424,7 @@ static const struct enc_flags {
> char *param;
> } encoding_flags[] = {
> { F2FS_ENC_STRICT_MODE_FL, "strict" },
> + { F2FS_ENC_NO_COMPAT_FALLBACK_FL, "hashonly"}
> };
>
> /* Return a positive number < 0xff indicating the encoding magic number
> diff --git a/man/mkfs.f2fs.8 b/man/mkfs.f2fs.8
> index 8b3b0cc..8cb7d32 100644
> --- a/man/mkfs.f2fs.8
> +++ b/man/mkfs.f2fs.8
> @@ -232,9 +232,15 @@ Use UTF-8 for casefolding.
> .I flags:
> .RS 1.2i
> .TP 1.2i
> -.B strict
> +.B [no]strict
> This flag specifies that invalid strings should be rejected by the
> filesystem.
> -Default is disabled.
> +For android case, it will disable linear lookup by default.
> +.RE
> +.RS 1.2i
> +.TP 1.2i
> +.B [no]hashonly
> +This flag specifies that there is no linear lookup fallback during lookup.
> +By default, linear lookup fallback is enabled.
> .RE
> .RE
> .TP
> diff --git a/mkfs/f2fs_format.c b/mkfs/f2fs_format.c
> index 2680bd3..a45bbcb 100644
> --- a/mkfs/f2fs_format.c
> +++ b/mkfs/f2fs_format.c
> @@ -671,6 +671,9 @@ static int f2fs_prepare_super_block(void)
> memcpy(sb->init_version, c.version, VERSION_LEN);
>
> if (c.feature & F2FS_FEATURE_CASEFOLD) {
> + if (!(c.s_encoding_flags & F2FS_ENC_NO_COMPAT_FALLBACK_FL) &&
> + (c.disabled_feature & F2FS_FEATURE_LINEAR_LOOKUP))
> + c.s_encoding_flags |= F2FS_ENC_NO_COMPAT_FALLBACK_FL;
> set_sb(s_encoding, c.s_encoding);
> set_sb(s_encoding_flags, c.s_encoding_flags);
> }
> diff --git a/mkfs/f2fs_format_main.c b/mkfs/f2fs_format_main.c
> index f0bec4f..8f8e975 100644
> --- a/mkfs/f2fs_format_main.c
> +++ b/mkfs/f2fs_format_main.c
> @@ -143,7 +143,8 @@ static void add_default_options(void)
> force_overwrite = 1;
> c.wanted_sector_size = F2FS_BLKSIZE;
> c.root_uid = c.root_gid = 0;
> - c.disabled_feature |= F2FS_FEATURE_NAT_BITS;
> + c.disabled_feature |= F2FS_FEATURE_NAT_BITS |
> + F2FS_FEATURE_LINEAR_LOOKUP;
>
> /* RO doesn't need any other features */
> if (c.feature & F2FS_FEATURE_RO)
> --
> 2.49.0
>
>
>
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