Chao Yu <c...@kernel.org> 于2025年7月25日周五 10:45写道：
>
> On 7/25/2025 10:08 AM, Zhiguo Niu wrote:
> > 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:
>
> Zhiguo,
>
> Not a typo, it's intentional, see above behavior summary.
>
Hi Chao,
Ah, I got it after checking again.^^
> But after rethinking about this, I guess it will be good to honor
> 'nohashonly' for Android case like Distro case.
>
> Anyway, let me update the patch.
Thanks for this and explanation.
>
> Thanks,
>
> > 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
> >>
> >>
> >>
> >> _______________________________________________
> >> Linux-f2fs-devel mailing list
> >> Linux-f2fs-devel@lists.sourceforge.net
> >> https://lists.sourceforge.net/lists/listinfo/linux-f2fs-devel
>
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