Hi,all:
I found two problemes about overlayfs, please let me know what you think:
1. Cannot update upper dir's access time.
Reproduce:
# mkdir lower upper worker merger
# mkdir upper/dir
# mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=worker overlayfs merger
# ls mrger/dir
# stat mrger/dir
Access: 2017-08-07 11:03:56.364771584 -0400
Modify: 2017-08-07 11:01:52.319771584 -0400
Change: 2017-08-07 11:01:52.319771584 -0400
# touch mrger/dir/aa
# stat mrger/dir
Access: 2017-08-07 11:03:56.364771584 -0400
Modify: 2017-08-07 11:05:33.969771584 -0400
Change: 2017-08-07 11:05:33.969771584 -0400
# ls mrger/dir
# stat mrger/dir
Access: 2017-08-07 11:03:56.364771584 -0400
Modify: 2017-08-07 11:05:33.969771584 -0400
Change: 2017-08-07 11:05:33.969771584 -0400
I find the reason of this problem is in update_ovl_inode_times():
(598e3c8f7 "vfs: update ovl inode before relatime check")
static void update_ovl_inode_times(struct dentry *dentry, struct inode *inode,
bool rcu)
{
if (!rcu) {
struct inode *realinode = d_real_inode(dentry);
*d_real_inode() cannot get dir's real inode, so i_mtime always equal to i_ctime*
*an not updated*
if (unlikely(inode != realinode) &&
(!timespec_equal(&inode->i_mtime, &realinode->i_mtime) ||
!timespec_equal(&inode->i_ctime, &realinode->i_ctime))) {
inode->i_mtime = realinode->i_mtime;
inode->i_ctime = realinode->i_ctime;
}
}
}
2. Chattr will modify lower file's attributes directly.
Reproduce:
# mkdir lower upper worker merger
# touch lower/aa
# lsattr -p lower/aa
0 --------------e---- lower/aa
# mount -t overlay -o lowerdir=lower,upperdir=upper,workdir=worker overlayfs merger
# chattr -p 123 merger/aa #set project id
# lsattr -p lower/aa
123 --------------e---- lower/aa
If we try to set "immutable" or any other attributes, the result are consistent.
Because chattr open file in RDONLY mode, so it will not trigger copyup, and then,
FS_IOC_SETFLAGS ioctl will get the lower inode and modify it. By the way,
ovl's directory not support ioctl now, so we fail to change dir's attributes.
Do you think these two "problemes" need to fix or should avoid ?
Thanks,
ZhangYi.
--
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
