diff options
Diffstat (limited to 'fs/overlayfs/util.c')
| -rw-r--r-- | fs/overlayfs/util.c | 26 |
1 files changed, 25 insertions, 1 deletions
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c index 25d202b47326..43235294e77b 100644 --- a/fs/overlayfs/util.c +++ b/fs/overlayfs/util.c @@ -377,13 +377,37 @@ struct file *ovl_path_open(struct path *path, int flags) return dentry_open(path, flags | O_NOATIME, current_cred()); } +bool ovl_already_copied_up(struct dentry *dentry) +{ + bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED; + + /* + * Check if copy-up has happened as well as for upper alias (in + * case of hard links) is there. + * + * Both checks are lockless: + * - false negatives: will recheck under oi->lock + * - false positives: + * + ovl_dentry_upper() uses memory barriers to ensure the + * upper dentry is up-to-date + * + ovl_dentry_has_upper_alias() relies on locking of + * upper parent i_rwsem to prevent reordering copy-up + * with rename. + */ + if (ovl_dentry_upper(dentry) && + (ovl_dentry_has_upper_alias(dentry) || disconnected)) + return true; + + return false; +} + int ovl_copy_up_start(struct dentry *dentry) { struct ovl_inode *oi = OVL_I(d_inode(dentry)); int err; err = mutex_lock_interruptible(&oi->lock); - if (!err && ovl_dentry_has_upper_alias(dentry)) { + if (!err && ovl_already_copied_up(dentry)) { err = 1; /* Already copied up */ mutex_unlock(&oi->lock); } |