Hi Chao
Chao Yu via Linux-f2fs-devel <linux-f2fs-devel@lists.sourceforge.net>
于2025年7月25日周五 13:51写道：
>
> It provides a way to disable linear lookup fallback during mkfs.
>
> Behavior summary:
> Android Distro
> By default disabled enabled
>
> 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 0 : 0]
>
> 1.3) By default:
> - mkfs.f2fs -f -g android -O casefold -C utf8 /dev/vdb
> Info: set default linear_lookup option: disable
> - 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]
>
It is very clear and easy to understand.
> Signed-off-by: Chao Yu <c...@kernel.org>
> ---
> v3:
> - honor [no]hashonly flag for Android case
> - update testcase and output
> include/f2fs_fs.h | 3 ++-
> lib/libf2fs.c | 6 ++++++
> man/mkfs.f2fs.8 | 9 ++++++++-
> mkfs/f2fs_format.c | 11 +++++++++++
> mkfs/f2fs_format_main.c | 3 ++-
> 5 files changed, 29 insertions(+), 3 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..1a496b7 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
> @@ -1485,6 +1486,11 @@ int f2fs_str2encoding_flags(char **param, __u16 *flags)
> *flags |= fl->flag;
> }
>
> + if (fl->flag ==
> F2FS_ENC_NO_COMPAT_FALLBACK_FL)
> + c.nolinear_lookup = neg ?
> + LINEAR_LOOKUP_ENABLE :
> + LINEAR_LOOKUP_DISABLE;
> +
> goto next_flag;
> }
> }
> diff --git a/man/mkfs.f2fs.8 b/man/mkfs.f2fs.8
> index 8b3b0cc..fcb227c 100644
> --- a/man/mkfs.f2fs.8
> +++ b/man/mkfs.f2fs.8
> @@ -232,10 +232,17 @@ 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.
> .RE
> +.RS 1.2i
> +.TP 1.2i
> +.B [no]hashonly
> +This flag specifies that linear lookup fallback is off during lookup, to turn
> +off linear lookup fallback, use nohashonly flag.
here should "to turn off linear lookup fallback, use hashonly flag"?
or "to turn on linear lookup fallback, use nohashonly flag"
1.1) Disable linear lookup:
- mkfs.f2fs -f -g android -O casefold -C utf8:hashonly /dev/vdb
> +For android case, it will disable linear lookup by default.
> +.RE
> .RE
> .TP
> .BI \-q
> diff --git a/mkfs/f2fs_format.c b/mkfs/f2fs_format.c
> index 2680bd3..04dfc20 100644
> --- a/mkfs/f2fs_format.c
> +++ b/mkfs/f2fs_format.c
> @@ -671,6 +671,17 @@ static int f2fs_prepare_super_block(void)
> memcpy(sb->init_version, c.version, VERSION_LEN);
>
> if (c.feature & F2FS_FEATURE_CASEFOLD) {
> + /*
> + * if [no]hashonly option is not assigned, let's disable
> + * linear lookup fallback by default for Android case.
> + */
> + if ((c.nolinear_lookup == LINEAR_LOOKUP_DEFAULT) &&
> + (c.disabled_feature & F2FS_FEATURE_LINEAR_LOOKUP)) {
> + c.s_encoding_flags |= F2FS_ENC_NO_COMPAT_FALLBACK_FL;
> + MSG(0, "Info: set default linear_lookup option: %s\n",
> + c.s_encoding_flags &
> F2FS_ENC_NO_COMPAT_FALLBACK_FL ?
> + "disable" : "enable");
> + }
> 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)
others look OK to me,so
Reviewed-by: Zhiguo Niu <zhiguo....@unisoc.com>
> --
> 2.49.0
>
>
>
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