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vfs: update ovl inode before relatime check

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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underlying inode only, so they will be out-of-date on the overlay inode.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@redhat.com>
This commit is contained in:
Miklos Szeredi 2016-09-16 12:44:20 +02:00
parent f2b20f6ee8
commit 598e3c8f72
4 changed files with 37 additions and 8 deletions
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33
fs/inode.c
View File

@ -1535,17 +1535,37 @@ 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))

9
fs/internal.h
View File

@ -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
*/

2
fs/namei.c
View File

@ -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);

1
include/linux/fs.h
View File

@ -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)
{