On Tue, Nov 28, 2017 at 5:59 PM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > By default metadata only copy up is disabled. Provide a mount option so > that users can choose one way or other. > > Also provide a kernel config and module option to enable/disable > metacopy feature. > > Like index feature, we verify on mount that upper root is not being > reused with a different lower root. This hopes to get the configuration > right and detect the copied layers use case. But this does only so > much as we don't verify all the lowers. So it is possible that a lower is > missing and later data copy up fails. > > Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx> Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx> > --- > fs/overlayfs/Kconfig | 8 ++++++++ > fs/overlayfs/ovl_entry.h | 1 + > fs/overlayfs/super.c | 40 +++++++++++++++++++++++++++++++++++++--- > 3 files changed, 46 insertions(+), 3 deletions(-) > > diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig > index cbfc196e5dc5..17a0b17ad14c 100644 > --- a/fs/overlayfs/Kconfig > +++ b/fs/overlayfs/Kconfig > @@ -43,3 +43,11 @@ config OVERLAY_FS_INDEX > outcomes. However, mounting the same overlay with an old kernel > read-write and then mounting it again with a new kernel, will have > unexpected results. > + > +config OVERLAY_FS_METACOPY > + bool "Overlayfs: turn on metadata only copy up feature by default" > + depends on OVERLAY_FS > + help > + If this config option is enabled then overlay filesystems will > + copy up only metadata where appropriate and data copy up will > + happen when a file is opended for WRITE operation. Just add some scary stuff about mounting with old kernel. And the text about module/mount option. Use the gist version like in REDIRECT_DIR, not like I did... Amir. -- To unsubscribe from this list: send the line "unsubscribe linux-unionfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
