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SubjectRe: [PATCH 2/3] ovl: fix relatime for directories
On Tue, Sep 5, 2017 at 10:55 AM, Amir Goldstein <amir73il@gmail.com> wrote:
[...]
> Alternatively, update_ovl_inode_times() could use D_REAL_UPPER
> and then we explicitly say that we don't care about lower mtime/ctime
> modifications.

Right, you convinced me that this is the right way to go. Updated patch below
(and pushed to overlayfs-next).

Thanks,
Miklos
---

From: Miklos Szeredi <mszeredi@redhat.com>
Subject: ovl: fix relatime for directories

Need to treat non-regular overlayfs files the same as regular files when
checking for an atime update.

Add a d_real() flag to make it return the upper dentry for all file types.

Reported-by: "zhangyi (F)" <yi.zhang@huawei.com>
Signed-off-by: Miklos Szeredi <mszeredi@redhat.com>
---
fs/inode.c | 21 +++++++++++++++++----
fs/overlayfs/super.c | 3 +++
include/linux/dcache.h | 3 +++
3 files changed, 23 insertions(+), 4 deletions(-)

--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1569,11 +1569,24 @@ EXPORT_SYMBOL(bmap);
static void update_ovl_inode_times(struct dentry *dentry, struct inode *inode,
bool rcu)
{
- if (!rcu) {
- struct inode *realinode = d_real_inode(dentry);
+ struct dentry *upperdentry;

- if (unlikely(inode != realinode) &&
- (!timespec_equal(&inode->i_mtime, &realinode->i_mtime) ||
+ /*
+ * Nothing to do if in rcu or if non-overlayfs
+ */
+ if (rcu || likely(!(dentry->d_flags & DCACHE_OP_REAL)))
+ return;
+
+ upperdentry = d_real(dentry, NULL, 0, D_REAL_UPPER);
+
+ /*
+ * If file is on lower then we can't update atime, so no worries about
+ * stale mtime/ctime.
+ */
+ if (upperdentry) {
+ struct inode *realinode = d_inode(upperdentry);
+
+ if ((!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;
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -75,6 +75,9 @@ static struct dentry *ovl_d_real(struct
struct dentry *real;
int err;

+ if (flags & D_REAL_UPPER)
+ return ovl_dentry_upper(dentry);
+
if (!d_is_reg(dentry)) {
if (!inode || inode == d_inode(dentry))
return dentry;
--- a/include/linux/dcache.h
+++ b/include/linux/dcache.h
@@ -562,6 +562,9 @@ static inline struct dentry *d_backing_d
return upper;
}

+/* d_real() flags */
+#define D_REAL_UPPER 0x2 /* return upper dentry or NULL if non-upper */
+
/**
* d_real - Return the real dentry
* @dentry: the dentry to query
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