[Devel] [PATCH RH7] docker: Revert "vfs: take stat's dev from mnt->sb"

[Pavel Tikhomirov]

This reverts commit ecfa1b0f7ba985e200e807941b5838943b266cb3.

All non-directory objects on overlayfs should report an st_dev from
lower or upper filesystem that is providing the object then call
stat(2) on it(Documentation/filesystems/overlayfs.txt). But in our
case file on overlayfs reports st_dev from overlayfs itself:

e.g.: on VZ7 host device is 57 but should be 64768:
mkdir /lower /upper /merged /work
mount -t overlay overlay -olowerdir=/lower,upperdir=/upper,\
workdir=/work /merged
touch /merged/file
stat /merged/file | grep Device | awk '{print $1$2}'
  Device:39h/57d
cat /proc/self/mountinfo
  63 1 253:0 / / rw,relatime shared:1 - ext4
/dev/mapper/virtuozzo_pcs7-root rw,data=ordered
  149 63 0:57 / /merged rw,relatime shared:81 - overlay overlay
rw,lowerdir=/lower,upperdir=/upper,workdir=/work

Reason is in sys_stat->vfs_stat->vfs_fstatat->vfs_getattr:
1) Call ovl_getattr()->ovl_path_real() - find real object's path
2) Call ovl_getattr()->vfs_getattr() - find real object's s_dev
3) Replace it with overlay's s_dev, which is wrong.

We do not have simfs - remove step (3) and stat will be fine again.

*note: we need it for docker - when stat and fstat give different
s_dev ldconfig in glibc breaks, and thus docker-ui tests break.

https://jira.sw.ru/browse/PSBM-51255
Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
---
 fs/stat.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/fs/stat.c b/fs/stat.c
index a423f63..d0ea7ef 100644
--- a/fs/stat.c
+++ b/fs/stat.c
@@ -14,7 +14,6 @@
 #include <linux/security.h>
 #include <linux/syscalls.h>
 #include <linux/pagemap.h>
-#include <linux/mount.h>
 
 #include <asm/uaccess.h>
 #include <asm/unistd.h>
@@ -48,14 +47,10 @@ int vfs_getattr(struct path *path, struct kstat *stat)
 		return retval;
 
 	if (inode->i_op->getattr)
-		retval = inode->i_op->getattr(path->mnt, path->dentry, stat);
-	else
-		generic_fillattr(inode, stat);
+		return inode->i_op->getattr(path->mnt, path->dentry, stat);
 
-	if (!retval)
-		stat->dev = path->mnt->mnt_sb->s_dev;
-
-	return retval;
+	generic_fillattr(inode, stat);
+	return 0;
 }
 
 EXPORT_SYMBOL(vfs_getattr);
-- 
2.5.5