Re: [PATCH v3] erofs: add sysfs feature entry for xattr prefixes

[Gao Xiang <xiang@kernel.org>]

Hi Greg,

On Wed, Sep 02, 2026 at 07:36:13AM +0200, Greg KH wrote:
> On Wed, Sep 02, 2026 at 09:50:39AM +0800, Jingbo Xu wrote:
> > Let /sys/fs/erofs/features/xattr_prefixes advertise that this kernel
> > supports the EROFS_FEATURE_INCOMPAT_XATTR_PREFIXES on-disk format.
> > 
> > Fixes: 6a318ccd7e08 ("erofs: enable long extended attribute name prefixes")
> > Cc: <stable@vger.kernel.org> # 6.4+
> > Reviewed-by: Gao Xiang <xiang@kernel.org>
> > Signed-off-by: Jingbo Xu <jefflexu@linux.alibaba.com>
> > ---
> > changes since v2:
> > - add Reviewed-by tag (Gao Xiang)
> > - update list in Documentation/ABI/testing/sysfs-fs-erofs
> > (https://sashiko.dev/#/patchset/20260901062243.109172-1-jefflexu%40linux.alibaba.com)
> > ---
> >  Documentation/ABI/testing/sysfs-fs-erofs | 2 +-
> >  fs/erofs/sysfs.c                         | 2 ++
> >  2 files changed, 3 insertions(+), 1 deletion(-)
> 
> Why is adding a new feature a stable thing?

It's not a new feature (Also, this patch has 3 lines diff):
This is a bugfix to address the missing part of
commit 6a318ccd7e08 ("erofs: enable long extended
attribute name prefixes"") since every on-disk features
should be shown in `/sys/fs/erofs/features/*` according to
the definition of:

What:           /sys/fs/erofs/features/
Date:           November 2021
Contact:        "Huang Jianan" <huangjianan@oppo.com>
Description:    Shows all enabled kernel features.
...

IOWs, this sysfs entry should be part of commit 6a318ccd7e08
to indicate this feature is supported since Linux 6.4+

Thanks,
Gao Xiang

> 
> confused,
> 
> greg k-h
>