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

[Greg KH <greg@kroah.com>]

On Wed, Sep 02, 2026 at 07:42:36PM +0800, Gao Xiang wrote:
> On Wed, Sep 02, 2026 at 01:38:16PM +0200, Greg KH wrote:
> > On Wed, Sep 02, 2026 at 06:53:16PM +0800, Gao Xiang wrote:
> > > 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+
> > 
> > Ok, but as this has not been present for a very long time, did anyone
> > even notice and need this now in stable kernels?  :)
> 
> I think Jingbo needs it (btw, I'm no longer in Alibaba Cloud
> anymore).
> 
> Also it would be better to port this into stable kernels so
> that users can get the supported on-disk features in a more
> unique obvious way.

Ok, that makes more sense, sorry for the noise!

greg k-h