Commit ba1e563c authored Jul 24, 2017 by Chandan Rajendra Committed by Miklos Szeredi Nov 09, 2017

ovl: return anonymous st_dev for lower inodes



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 following patch is going to fix constant st_dev/st_ino across copy up
by returning origin st_dev/st_ino for copied up objects.

If the st_dev/st_ino for copied up object would have been the same as
that of the real underlying lower file, running diff on underlying lower
file and overlay copied up file would result in diff reporting that the
2 files are equal when in fact, they may have different content.

[amir: simplify ovl_get_pseudo_dev()
       split from allocate anonymous bdev patch]

Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
Signed-off-by: Amir Goldstein <amir73il@gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>

parent 2a9c6d06

fs/overlayfs/inode.c

+15 −0

Original line number	Original line	Diff line number	Diff line
	@@ -15,6 +15,14 @@
	#include <linux/ratelimit.h>		#include <linux/ratelimit.h>
	#include "overlayfs.h"		#include "overlayfs.h"


			static dev_t ovl_get_pseudo_dev(struct dentry *dentry)
			{
			struct ovl_entry *oe = dentry->d_fsdata;

			return oe->lowerstack[0].layer->pseudo_dev;
			}

	int ovl_setattr(struct dentry dentry, struct iattr attr)		int ovl_setattr(struct dentry dentry, struct iattr attr)
	{		{
	int err;		int err;
	@@ -121,6 +129,13 @@ int ovl_getattr(const struct path path, struct kstat stat,
	*/		*/
	stat->dev = dentry->d_sb->s_dev;		stat->dev = dentry->d_sb->s_dev;
	stat->ino = dentry->d_inode->i_ino;		stat->ino = dentry->d_inode->i_ino;
			} else if (!OVL_TYPE_UPPER(type)) {
			/*
			* For non-samefs setup, to make sure that st_dev/st_ino pair
			* is unique across the system, we use a unique anonymous
			* st_dev for lower layer inode.
			*/
			stat->dev = ovl_get_pseudo_dev(dentry);
	}		}

	/*		/*

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