On overlayfs relatime_need_update() needs inode times to be correct on
overlay inode. But i_mtime and i_ctime are updated by filesystem code on
underlying inode only, so they will be out-of-date on the overlay inode.
This patch copies the times from the underlying inode if needed. This
can't be done if called from RCU lookup (link following) but link m/ctime
are not updated by fs, so this is all right.
This patch doesn't change functionality for anything but overlayfs.
Signed-off-by: Miklos Szeredi <mszeredi@xxxxxxxxxx>
---
fs/inode.c | 33 +++++++++++++++++++++++++++------
fs/internal.h | 9 +++++++++
fs/namei.c | 2 +-
include/linux/fs.h | 1 -
4 files changed, 37 insertions(+), 8 deletions(-)
diff --git a/fs/inode.c b/fs/inode.c
index 7e3ef3af3db9..4a1fc1631e00 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -1536,16 +1536,36 @@ sector_t bmap(struct inode *inode, sector_t block)
EXPORT_SYMBOL(bmap);
/*
+ * Update times in overlayed inode from underlying real inode
+ */
+static void update_ovl_inode_times(struct dentry *dentry, struct inode *inode,
+ bool rcu)
+{
+ if (!rcu) {
+ struct inode *realinode = d_real_inode(dentry);
+
+ 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;
+ }
+ }
+}
+
+/*
* With relative atime, only update atime if the previous atime is
* earlier than either the ctime or mtime or if at least a day has
* passed since the last atime update.
*/
-static int relatime_need_update(struct vfsmount *mnt, struct inode *inode,
- struct timespec now)
+static int relatime_need_update(const struct path *path, struct inode *inode,
+ struct timespec now, bool rcu)
{
- if (!(mnt->mnt_flags & MNT_RELATIME))
+ if (!(path->mnt->mnt_flags & MNT_RELATIME))
return 1;
+
+ update_ovl_inode_times(path->dentry, inode, rcu);
/*
* Is mtime younger than atime? If yes, update atime:
*/
@@ -1612,7 +1632,8 @@ static int update_time(struct inode *inode, struct timespec *time, int flags)
* This function automatically handles read only file systems and media,
* as well as the "noatime" flag and inode specific "noatime" markers.
*/
-bool atime_needs_update(const struct path *path, struct inode *inode)
+bool __atime_needs_update(const struct path *path, struct inode *inode,
+ bool rcu)
{
struct vfsmount *mnt = path->mnt;
struct timespec now;
@@ -1638,7 +1659,7 @@ bool atime_needs_update(const struct path *path, struct inode *inode)
now = current_fs_time(inode->i_sb);
- if (!relatime_need_update(mnt, inode, now))
+ if (!relatime_need_update(path, inode, now, rcu))
return false;
if (timespec_equal(&inode->i_atime, &now))
@@ -1653,7 +1674,7 @@ void touch_atime(const struct path *path)
struct inode *inode = d_inode(path->dentry);
struct timespec now;
- if (!atime_needs_update(path, inode))
+ if (!__atime_needs_update(path, inode, false))
return;
if (!sb_start_write_trylock(inode->i_sb))
diff --git a/fs/internal.h b/fs/internal.h
index ba0737649d4a..a63da5e96148 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -120,6 +120,15 @@ extern long prune_icache_sb(struct super_block *sb, struct shrink_control *sc);
extern void inode_add_lru(struct inode *inode);
extern int dentry_needs_remove_privs(struct dentry *dentry);
+extern bool __atime_needs_update(const struct path *, struct inode *, bool);
+static inline bool atime_needs_update_rcu(const struct path *path,
+ struct inode *inode)
+{
+ return __atime_needs_update(path, inode, true);
+}
+
+extern bool atime_needs_update_rcu(const struct path *, struct inode *);
+
/*
* fs-writeback.c
*/
diff --git a/fs/namei.c b/fs/namei.c
index adb04146df09..4bbcae1ba58e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -1015,7 +1015,7 @@ const char *get_link(struct nameidata *nd)
if (!(nd->flags & LOOKUP_RCU)) {
touch_atime(&last->link);
cond_resched();
- } else if (atime_needs_update(&last->link, inode)) {
+ } else if (atime_needs_update_rcu(&last->link, inode)) {
if (unlikely(unlazy_walk(nd, NULL, 0)))
return ERR_PTR(-ECHILD);
touch_atime(&last->link);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index 7c391366fb43..7db097d673a8 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -2007,7 +2007,6 @@ enum file_time_flags {
S_VERSION = 8,
};
-extern bool atime_needs_update(const struct path *, struct inode *);
extern void touch_atime(const struct path *);
static inline void file_accessed(struct file *file)
{
--
2.5.5
--
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