On Mon, Apr 2, 2018 at 4:56 PM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > On Fri, Mar 30, 2018 at 07:52:17AM +0300, Amir Goldstein wrote: >> On Thu, Mar 29, 2018 at 10:38 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. >> > >> > metacopy feature requires redirect_dir=on when upper is present. Otherwise, >> > it requires redirect_dir=follow atleast. >> > >> > Like index feature, we verify on mount that upper root is not being >> > reused with a different lower root. >> >> I don't see that in the patch > > Oh.., this is leftover from previous patches. Will remove this comment. > I have completely got rid of dealing with ORIGIN when moving to > REDIRECT based lookup. > >> >> > 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. >> > >> > Reviewed-by: Amir Goldstein <amir73il@xxxxxxxxx> >> > Signed-off-by: Vivek Goyal <vgoyal@xxxxxxxxxx> >> > --- >> > Documentation/filesystems/overlayfs.txt | 30 ++++++++++++++++++++++++- >> > fs/overlayfs/Kconfig | 19 ++++++++++++++++ >> > fs/overlayfs/ovl_entry.h | 1 + >> > fs/overlayfs/super.c | 40 ++++++++++++++++++++++++++++++++- >> > 4 files changed, 88 insertions(+), 2 deletions(-) >> > >> > diff --git a/Documentation/filesystems/overlayfs.txt b/Documentation/filesystems/overlayfs.txt >> > index 6ea1e64d1464..b7720e61973c 100644 >> > --- a/Documentation/filesystems/overlayfs.txt >> > +++ b/Documentation/filesystems/overlayfs.txt >> > @@ -249,6 +249,30 @@ rightmost one and going left. In the above example lower1 will be the >> > top, lower2 the middle and lower3 the bottom layer. >> > >> > >> > +Metadata only copyup >> > +-------------------- >> > + >> > +When metadata only copy up feature is enabled, overlayfs will only copy >> > +up metadata (as opposed to whole file), when a metadata specific operation >> > +like chown/chmod is performed. Full file will be copied up later when >> > +file is opened for WRITE operation. >> > + >> > +IOW, this is delayed data copy up operation and data is copied up when >> > +there is a need to actually modify data. >> > + Vivek, Some nick picking here. This is document is about the only decent documentation for overlayfs. I always try to live up to the standards set by Neil who started it. Abbreviations (IOW) doesn't seem right to me in this context. Also, you'll notice that the form "copyup" does not appear in this document. It may sound petty, but if people wish to read a coherent document about overlayfs, we would be wise to maintain coherency in the phrases we use throughout the document. Thanks, 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
