On Wed, Nov 01, 2017 at 05:02:55PM +0200, Amir Goldstein wrote: > On Wed, Nov 1, 2017 at 4:42 PM, Vivek Goyal <vgoyal@xxxxxxxxxx> wrote: > > On Mon, Oct 30, 2017 at 10:27:25PM +0200, Amir Goldstein wrote: > >> From: Chandan Rajendra <chandan@xxxxxxxxxxxxxxxxxx> > >> > >> For stat(2) on lowerdir non-dir entries in non-samefs case, this commit > >> provides unique values for st_dev. The unique values are obtained by > >> allocating anonymous bdevs for each of the lowerdirs in the overlayfs > >> instance. > > > > Hi Amir, Chandan, > > > > In the commit message, can we also mention what's the current behavior > > and why this new behavior beneficial/desirable. > > > > This is the blurb from the uptodate patch on my branch: > > For non-samefs setup, to make sure that st_dev/st_ino pair > is unique across the system, we return a unique anonymous > st_dev for stat(2) of lower layer inode. > > A bit fatter, but not fat enough... > > Actually, it is not accurate, because st_dev/st_ino pair of pure > upper is still same values as underlying inode for non-samefs so the > values are not unique among all inodes in the system. Hi Amir, So as of now for non-samefs non-dir case we return st_dev/st_ino of lower inode. And with this change we will return st_dev of overlayfs while inode of lower, right? What does unique mean in this context. IIUC, st_dev/st_inode of lower will be unique in the system, isn't it. Which other inode can have same st_dev/st_ino pair. Or is it the case that if same inode is accessed through overlayfs, we want to report a different st_dev. > > I can't remember if there was a reason for not allocating anonymous bdev > for upper That's a good point. > or if it just because we did not need it to guaranty uniqueness > of st_dev/st_ino *among* overlay inodes Even for lower, st_dev will be unique for different lower on non same-fs, right. IOW, when it come to uniqueness of st_dev/st_ino pair, among overlay inodes, lower and upper should have same requirements. > while guarantying constant > st_dev/st_ino across copy up. Hmm..., I did not get this point. Over copy up, atleast st_ino will change for non-samefs case. I will spend more time on patch. Vivek > > I will update commit message. > > 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
