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Diffstat (limited to 'fs/overlayfs/inode.c')
-rw-r--r--fs/overlayfs/inode.c103
1 files changed, 100 insertions, 3 deletions
diff --git a/fs/overlayfs/inode.c b/fs/overlayfs/inode.c
index f8fe6bf2036d..ad9547f82da5 100644
--- a/fs/overlayfs/inode.c
+++ b/fs/overlayfs/inode.c
@@ -57,18 +57,78 @@ out:
return err;
}
-static int ovl_getattr(const struct path *path, struct kstat *stat,
- u32 request_mask, unsigned int flags)
+int ovl_getattr(const struct path *path, struct kstat *stat,
+ u32 request_mask, unsigned int flags)
{
struct dentry *dentry = path->dentry;
+ enum ovl_path_type type;
struct path realpath;
const struct cred *old_cred;
+ bool is_dir = S_ISDIR(dentry->d_inode->i_mode);
int err;
- ovl_path_real(dentry, &realpath);
+ type = ovl_path_real(dentry, &realpath);
old_cred = ovl_override_creds(dentry->d_sb);
err = vfs_getattr(&realpath, stat, request_mask, flags);
+ if (err)
+ goto out;
+
+ /*
+ * When all layers are on the same fs, all real inode number are
+ * unique, so we use the overlay st_dev, which is friendly to du -x.
+ *
+ * We also use st_ino of the copy up origin, if we know it.
+ * This guaranties constant st_dev/st_ino across copy up.
+ *
+ * If filesystem supports NFS export ops, this also guaranties
+ * persistent st_ino across mount cycle.
+ */
+ if (ovl_same_sb(dentry->d_sb)) {
+ if (OVL_TYPE_ORIGIN(type)) {
+ struct kstat lowerstat;
+ u32 lowermask = STATX_INO | (!is_dir ? STATX_NLINK : 0);
+
+ ovl_path_lower(dentry, &realpath);
+ err = vfs_getattr(&realpath, &lowerstat,
+ lowermask, flags);
+ if (err)
+ goto out;
+
+ WARN_ON_ONCE(stat->dev != lowerstat.dev);
+ /*
+ * Lower hardlinks are broken on copy up to different
+ * upper files, so we cannot use the lower origin st_ino
+ * for those different files, even for the same fs case.
+ */
+ if (is_dir || lowerstat.nlink == 1)
+ stat->ino = lowerstat.ino;
+ }
+ stat->dev = dentry->d_sb->s_dev;
+ } else if (is_dir) {
+ /*
+ * If not all layers are on the same fs the pair {real st_ino;
+ * overlay st_dev} is not unique, so use the non persistent
+ * overlay st_ino.
+ *
+ * Always use the overlay st_dev for directories, so 'find
+ * -xdev' will scan the entire overlay mount and won't cross the
+ * overlay mount boundaries.
+ */
+ stat->dev = dentry->d_sb->s_dev;
+ stat->ino = dentry->d_inode->i_ino;
+ }
+
+ /*
+ * It's probably not worth it to count subdirs to get the
+ * correct link count. nlink=1 seems to pacify 'find' and
+ * other utilities.
+ */
+ if (is_dir && OVL_TYPE_MERGE(type))
+ stat->nlink = 1;
+
+out:
revert_creds(old_cred);
+
return err;
}
@@ -303,6 +363,41 @@ static const struct inode_operations ovl_symlink_inode_operations = {
.update_time = ovl_update_time,
};
+/*
+ * It is possible to stack overlayfs instance on top of another
+ * overlayfs instance as lower layer. We need to annonate the
+ * stackable i_mutex locks according to stack level of the super
+ * block instance. An overlayfs instance can never be in stack
+ * depth 0 (there is always a real fs below it). An overlayfs
+ * inode lock will use the lockdep annotaion ovl_i_mutex_key[depth].
+ *
+ * For example, here is a snip from /proc/lockdep_chains after
+ * dir_iterate of nested overlayfs:
+ *
+ * [...] &ovl_i_mutex_dir_key[depth] (stack_depth=2)
+ * [...] &ovl_i_mutex_dir_key[depth]#2 (stack_depth=1)
+ * [...] &type->i_mutex_dir_key (stack_depth=0)
+ */
+#define OVL_MAX_NESTING FILESYSTEM_MAX_STACK_DEPTH
+
+static inline void ovl_lockdep_annotate_inode_mutex_key(struct inode *inode)
+{
+#ifdef CONFIG_LOCKDEP
+ static struct lock_class_key ovl_i_mutex_key[OVL_MAX_NESTING];
+ static struct lock_class_key ovl_i_mutex_dir_key[OVL_MAX_NESTING];
+
+ int depth = inode->i_sb->s_stack_depth - 1;
+
+ if (WARN_ON_ONCE(depth < 0 || depth >= OVL_MAX_NESTING))
+ depth = 0;
+
+ if (S_ISDIR(inode->i_mode))
+ lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_dir_key[depth]);
+ else
+ lockdep_set_class(&inode->i_rwsem, &ovl_i_mutex_key[depth]);
+#endif
+}
+
static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
{
inode->i_ino = get_next_ino();
@@ -312,6 +407,8 @@ static void ovl_fill_inode(struct inode *inode, umode_t mode, dev_t rdev)
inode->i_acl = inode->i_default_acl = ACL_DONT_CACHE;
#endif
+ ovl_lockdep_annotate_inode_mutex_key(inode);
+
switch (mode & S_IFMT) {
case S_IFREG:
inode->i_op = &ovl_file_inode_operations;