v4.19.13 snapshot.
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
new file mode 100644
index 0000000..ace4fe4
--- /dev/null
+++ b/fs/overlayfs/util.c
@@ -0,0 +1,918 @@
+/*
+ * Copyright (C) 2011 Novell Inc.
+ * Copyright (C) 2016 Red Hat, Inc.
+ *
+ * This program is free software; you can redistribute it and/or modify it
+ * under the terms of the GNU General Public License version 2 as published by
+ * the Free Software Foundation.
+ */
+
+#include <linux/fs.h>
+#include <linux/mount.h>
+#include <linux/slab.h>
+#include <linux/cred.h>
+#include <linux/xattr.h>
+#include <linux/exportfs.h>
+#include <linux/uuid.h>
+#include <linux/namei.h>
+#include <linux/ratelimit.h>
+#include "overlayfs.h"
+
+int ovl_want_write(struct dentry *dentry)
+{
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+ return mnt_want_write(ofs->upper_mnt);
+}
+
+void ovl_drop_write(struct dentry *dentry)
+{
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+ mnt_drop_write(ofs->upper_mnt);
+}
+
+struct dentry *ovl_workdir(struct dentry *dentry)
+{
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+ return ofs->workdir;
+}
+
+const struct cred *ovl_override_creds(struct super_block *sb)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+
+ return override_creds(ofs->creator_cred);
+}
+
+struct super_block *ovl_same_sb(struct super_block *sb)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+
+ if (!ofs->numlowerfs)
+ return ofs->upper_mnt->mnt_sb;
+ else if (ofs->numlowerfs == 1 && !ofs->upper_mnt)
+ return ofs->lower_fs[0].sb;
+ else
+ return NULL;
+}
+
+/*
+ * Check if underlying fs supports file handles and try to determine encoding
+ * type, in order to deduce maximum inode number used by fs.
+ *
+ * Return 0 if file handles are not supported.
+ * Return 1 (FILEID_INO32_GEN) if fs uses the default 32bit inode encoding.
+ * Return -1 if fs uses a non default encoding with unknown inode size.
+ */
+int ovl_can_decode_fh(struct super_block *sb)
+{
+ if (!sb->s_export_op || !sb->s_export_op->fh_to_dentry ||
+ uuid_is_null(&sb->s_uuid))
+ return 0;
+
+ return sb->s_export_op->encode_fh ? -1 : FILEID_INO32_GEN;
+}
+
+struct dentry *ovl_indexdir(struct super_block *sb)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+
+ return ofs->indexdir;
+}
+
+/* Index all files on copy up. For now only enabled for NFS export */
+bool ovl_index_all(struct super_block *sb)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+
+ return ofs->config.nfs_export && ofs->config.index;
+}
+
+/* Verify lower origin on lookup. For now only enabled for NFS export */
+bool ovl_verify_lower(struct super_block *sb)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+
+ return ofs->config.nfs_export && ofs->config.index;
+}
+
+struct ovl_entry *ovl_alloc_entry(unsigned int numlower)
+{
+ size_t size = offsetof(struct ovl_entry, lowerstack[numlower]);
+ struct ovl_entry *oe = kzalloc(size, GFP_KERNEL);
+
+ if (oe)
+ oe->numlower = numlower;
+
+ return oe;
+}
+
+bool ovl_dentry_remote(struct dentry *dentry)
+{
+ return dentry->d_flags &
+ (DCACHE_OP_REVALIDATE | DCACHE_OP_WEAK_REVALIDATE |
+ DCACHE_OP_REAL);
+}
+
+bool ovl_dentry_weird(struct dentry *dentry)
+{
+ return dentry->d_flags & (DCACHE_NEED_AUTOMOUNT |
+ DCACHE_MANAGE_TRANSIT |
+ DCACHE_OP_HASH |
+ DCACHE_OP_COMPARE);
+}
+
+enum ovl_path_type ovl_path_type(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+ enum ovl_path_type type = 0;
+
+ if (ovl_dentry_upper(dentry)) {
+ type = __OVL_PATH_UPPER;
+
+ /*
+ * Non-dir dentry can hold lower dentry of its copy up origin.
+ */
+ if (oe->numlower) {
+ if (ovl_test_flag(OVL_CONST_INO, d_inode(dentry)))
+ type |= __OVL_PATH_ORIGIN;
+ if (d_is_dir(dentry) ||
+ !ovl_has_upperdata(d_inode(dentry)))
+ type |= __OVL_PATH_MERGE;
+ }
+ } else {
+ if (oe->numlower > 1)
+ type |= __OVL_PATH_MERGE;
+ }
+ return type;
+}
+
+void ovl_path_upper(struct dentry *dentry, struct path *path)
+{
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+
+ path->mnt = ofs->upper_mnt;
+ path->dentry = ovl_dentry_upper(dentry);
+}
+
+void ovl_path_lower(struct dentry *dentry, struct path *path)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ if (oe->numlower) {
+ path->mnt = oe->lowerstack[0].layer->mnt;
+ path->dentry = oe->lowerstack[0].dentry;
+ } else {
+ *path = (struct path) { };
+ }
+}
+
+void ovl_path_lowerdata(struct dentry *dentry, struct path *path)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ if (oe->numlower) {
+ path->mnt = oe->lowerstack[oe->numlower - 1].layer->mnt;
+ path->dentry = oe->lowerstack[oe->numlower - 1].dentry;
+ } else {
+ *path = (struct path) { };
+ }
+}
+
+enum ovl_path_type ovl_path_real(struct dentry *dentry, struct path *path)
+{
+ enum ovl_path_type type = ovl_path_type(dentry);
+
+ if (!OVL_TYPE_UPPER(type))
+ ovl_path_lower(dentry, path);
+ else
+ ovl_path_upper(dentry, path);
+
+ return type;
+}
+
+struct dentry *ovl_dentry_upper(struct dentry *dentry)
+{
+ return ovl_upperdentry_dereference(OVL_I(d_inode(dentry)));
+}
+
+struct dentry *ovl_dentry_lower(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ return oe->numlower ? oe->lowerstack[0].dentry : NULL;
+}
+
+struct ovl_layer *ovl_layer_lower(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ return oe->numlower ? oe->lowerstack[0].layer : NULL;
+}
+
+/*
+ * ovl_dentry_lower() could return either a data dentry or metacopy dentry
+ * dependig on what is stored in lowerstack[0]. At times we need to find
+ * lower dentry which has data (and not metacopy dentry). This helper
+ * returns the lower data dentry.
+ */
+struct dentry *ovl_dentry_lowerdata(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ return oe->numlower ? oe->lowerstack[oe->numlower - 1].dentry : NULL;
+}
+
+struct dentry *ovl_dentry_real(struct dentry *dentry)
+{
+ return ovl_dentry_upper(dentry) ?: ovl_dentry_lower(dentry);
+}
+
+struct dentry *ovl_i_dentry_upper(struct inode *inode)
+{
+ return ovl_upperdentry_dereference(OVL_I(inode));
+}
+
+struct inode *ovl_inode_upper(struct inode *inode)
+{
+ struct dentry *upperdentry = ovl_i_dentry_upper(inode);
+
+ return upperdentry ? d_inode(upperdentry) : NULL;
+}
+
+struct inode *ovl_inode_lower(struct inode *inode)
+{
+ return OVL_I(inode)->lower;
+}
+
+struct inode *ovl_inode_real(struct inode *inode)
+{
+ return ovl_inode_upper(inode) ?: ovl_inode_lower(inode);
+}
+
+/* Return inode which contains lower data. Do not return metacopy */
+struct inode *ovl_inode_lowerdata(struct inode *inode)
+{
+ if (WARN_ON(!S_ISREG(inode->i_mode)))
+ return NULL;
+
+ return OVL_I(inode)->lowerdata ?: ovl_inode_lower(inode);
+}
+
+/* Return real inode which contains data. Does not return metacopy inode */
+struct inode *ovl_inode_realdata(struct inode *inode)
+{
+ struct inode *upperinode;
+
+ upperinode = ovl_inode_upper(inode);
+ if (upperinode && ovl_has_upperdata(inode))
+ return upperinode;
+
+ return ovl_inode_lowerdata(inode);
+}
+
+struct ovl_dir_cache *ovl_dir_cache(struct inode *inode)
+{
+ return OVL_I(inode)->cache;
+}
+
+void ovl_set_dir_cache(struct inode *inode, struct ovl_dir_cache *cache)
+{
+ OVL_I(inode)->cache = cache;
+}
+
+void ovl_dentry_set_flag(unsigned long flag, struct dentry *dentry)
+{
+ set_bit(flag, &OVL_E(dentry)->flags);
+}
+
+void ovl_dentry_clear_flag(unsigned long flag, struct dentry *dentry)
+{
+ clear_bit(flag, &OVL_E(dentry)->flags);
+}
+
+bool ovl_dentry_test_flag(unsigned long flag, struct dentry *dentry)
+{
+ return test_bit(flag, &OVL_E(dentry)->flags);
+}
+
+bool ovl_dentry_is_opaque(struct dentry *dentry)
+{
+ return ovl_dentry_test_flag(OVL_E_OPAQUE, dentry);
+}
+
+bool ovl_dentry_is_whiteout(struct dentry *dentry)
+{
+ return !dentry->d_inode && ovl_dentry_is_opaque(dentry);
+}
+
+void ovl_dentry_set_opaque(struct dentry *dentry)
+{
+ ovl_dentry_set_flag(OVL_E_OPAQUE, dentry);
+}
+
+/*
+ * For hard links and decoded file handles, it's possible for ovl_dentry_upper()
+ * to return positive, while there's no actual upper alias for the inode.
+ * Copy up code needs to know about the existence of the upper alias, so it
+ * can't use ovl_dentry_upper().
+ */
+bool ovl_dentry_has_upper_alias(struct dentry *dentry)
+{
+ return ovl_dentry_test_flag(OVL_E_UPPER_ALIAS, dentry);
+}
+
+void ovl_dentry_set_upper_alias(struct dentry *dentry)
+{
+ ovl_dentry_set_flag(OVL_E_UPPER_ALIAS, dentry);
+}
+
+static bool ovl_should_check_upperdata(struct inode *inode)
+{
+ if (!S_ISREG(inode->i_mode))
+ return false;
+
+ if (!ovl_inode_lower(inode))
+ return false;
+
+ return true;
+}
+
+bool ovl_has_upperdata(struct inode *inode)
+{
+ if (!ovl_should_check_upperdata(inode))
+ return true;
+
+ if (!ovl_test_flag(OVL_UPPERDATA, inode))
+ return false;
+ /*
+ * Pairs with smp_wmb() in ovl_set_upperdata(). Main user of
+ * ovl_has_upperdata() is ovl_copy_up_meta_inode_data(). Make sure
+ * if setting of OVL_UPPERDATA is visible, then effects of writes
+ * before that are visible too.
+ */
+ smp_rmb();
+ return true;
+}
+
+void ovl_set_upperdata(struct inode *inode)
+{
+ /*
+ * Pairs with smp_rmb() in ovl_has_upperdata(). Make sure
+ * if OVL_UPPERDATA flag is visible, then effects of write operations
+ * before it are visible as well.
+ */
+ smp_wmb();
+ ovl_set_flag(OVL_UPPERDATA, inode);
+}
+
+/* Caller should hold ovl_inode->lock */
+bool ovl_dentry_needs_data_copy_up_locked(struct dentry *dentry, int flags)
+{
+ if (!ovl_open_flags_need_copy_up(flags))
+ return false;
+
+ return !ovl_test_flag(OVL_UPPERDATA, d_inode(dentry));
+}
+
+bool ovl_dentry_needs_data_copy_up(struct dentry *dentry, int flags)
+{
+ if (!ovl_open_flags_need_copy_up(flags))
+ return false;
+
+ return !ovl_has_upperdata(d_inode(dentry));
+}
+
+bool ovl_redirect_dir(struct super_block *sb)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+
+ return ofs->config.redirect_dir && !ofs->noxattr;
+}
+
+const char *ovl_dentry_get_redirect(struct dentry *dentry)
+{
+ return OVL_I(d_inode(dentry))->redirect;
+}
+
+void ovl_dentry_set_redirect(struct dentry *dentry, const char *redirect)
+{
+ struct ovl_inode *oi = OVL_I(d_inode(dentry));
+
+ kfree(oi->redirect);
+ oi->redirect = redirect;
+}
+
+void ovl_inode_init(struct inode *inode, struct dentry *upperdentry,
+ struct dentry *lowerdentry, struct dentry *lowerdata)
+{
+ struct inode *realinode = d_inode(upperdentry ?: lowerdentry);
+
+ if (upperdentry)
+ OVL_I(inode)->__upperdentry = upperdentry;
+ if (lowerdentry)
+ OVL_I(inode)->lower = igrab(d_inode(lowerdentry));
+ if (lowerdata)
+ OVL_I(inode)->lowerdata = igrab(d_inode(lowerdata));
+
+ ovl_copyattr(realinode, inode);
+ ovl_copyflags(realinode, inode);
+ if (!inode->i_ino)
+ inode->i_ino = realinode->i_ino;
+}
+
+void ovl_inode_update(struct inode *inode, struct dentry *upperdentry)
+{
+ struct inode *upperinode = d_inode(upperdentry);
+
+ WARN_ON(OVL_I(inode)->__upperdentry);
+
+ /*
+ * Make sure upperdentry is consistent before making it visible
+ */
+ smp_wmb();
+ OVL_I(inode)->__upperdentry = upperdentry;
+ if (inode_unhashed(inode)) {
+ if (!inode->i_ino)
+ inode->i_ino = upperinode->i_ino;
+ inode->i_private = upperinode;
+ __insert_inode_hash(inode, (unsigned long) upperinode);
+ }
+}
+
+static void ovl_dentry_version_inc(struct dentry *dentry, bool impurity)
+{
+ struct inode *inode = d_inode(dentry);
+
+ WARN_ON(!inode_is_locked(inode));
+ /*
+ * Version is used by readdir code to keep cache consistent. For merge
+ * dirs all changes need to be noted. For non-merge dirs, cache only
+ * contains impure (ones which have been copied up and have origins)
+ * entries, so only need to note changes to impure entries.
+ */
+ if (OVL_TYPE_MERGE(ovl_path_type(dentry)) || impurity)
+ OVL_I(inode)->version++;
+}
+
+void ovl_dir_modified(struct dentry *dentry, bool impurity)
+{
+ /* Copy mtime/ctime */
+ ovl_copyattr(d_inode(ovl_dentry_upper(dentry)), d_inode(dentry));
+
+ ovl_dentry_version_inc(dentry, impurity);
+}
+
+u64 ovl_dentry_version_get(struct dentry *dentry)
+{
+ struct inode *inode = d_inode(dentry);
+
+ WARN_ON(!inode_is_locked(inode));
+ return OVL_I(inode)->version;
+}
+
+bool ovl_is_whiteout(struct dentry *dentry)
+{
+ struct inode *inode = dentry->d_inode;
+
+ return inode && IS_WHITEOUT(inode);
+}
+
+struct file *ovl_path_open(struct path *path, int flags)
+{
+ return dentry_open(path, flags | O_NOATIME, current_cred());
+}
+
+/* Caller should hold ovl_inode->lock */
+static bool ovl_already_copied_up_locked(struct dentry *dentry, int flags)
+{
+ bool disconnected = dentry->d_flags & DCACHE_DISCONNECTED;
+
+ if (ovl_dentry_upper(dentry) &&
+ (ovl_dentry_has_upper_alias(dentry) || disconnected) &&
+ !ovl_dentry_needs_data_copy_up_locked(dentry, flags))
+ return true;
+
+ return false;
+}
+
+bool ovl_already_copied_up(struct dentry *dentry, int flags)
+{
+ 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) &&
+ !ovl_dentry_needs_data_copy_up(dentry, flags))
+ return true;
+
+ return false;
+}
+
+int ovl_copy_up_start(struct dentry *dentry, int flags)
+{
+ struct ovl_inode *oi = OVL_I(d_inode(dentry));
+ int err;
+
+ err = mutex_lock_interruptible(&oi->lock);
+ if (!err && ovl_already_copied_up_locked(dentry, flags)) {
+ err = 1; /* Already copied up */
+ mutex_unlock(&oi->lock);
+ }
+
+ return err;
+}
+
+void ovl_copy_up_end(struct dentry *dentry)
+{
+ mutex_unlock(&OVL_I(d_inode(dentry))->lock);
+}
+
+bool ovl_check_origin_xattr(struct dentry *dentry)
+{
+ int res;
+
+ res = vfs_getxattr(dentry, OVL_XATTR_ORIGIN, NULL, 0);
+
+ /* Zero size value means "copied up but origin unknown" */
+ if (res >= 0)
+ return true;
+
+ return false;
+}
+
+bool ovl_check_dir_xattr(struct dentry *dentry, const char *name)
+{
+ int res;
+ char val;
+
+ if (!d_is_dir(dentry))
+ return false;
+
+ res = vfs_getxattr(dentry, name, &val, 1);
+ if (res == 1 && val == 'y')
+ return true;
+
+ return false;
+}
+
+int ovl_check_setxattr(struct dentry *dentry, struct dentry *upperdentry,
+ const char *name, const void *value, size_t size,
+ int xerr)
+{
+ int err;
+ struct ovl_fs *ofs = dentry->d_sb->s_fs_info;
+
+ if (ofs->noxattr)
+ return xerr;
+
+ err = ovl_do_setxattr(upperdentry, name, value, size, 0);
+
+ if (err == -EOPNOTSUPP) {
+ pr_warn("overlayfs: cannot set %s xattr on upper\n", name);
+ ofs->noxattr = true;
+ return xerr;
+ }
+
+ return err;
+}
+
+int ovl_set_impure(struct dentry *dentry, struct dentry *upperdentry)
+{
+ int err;
+
+ if (ovl_test_flag(OVL_IMPURE, d_inode(dentry)))
+ return 0;
+
+ /*
+ * Do not fail when upper doesn't support xattrs.
+ * Upper inodes won't have origin nor redirect xattr anyway.
+ */
+ err = ovl_check_setxattr(dentry, upperdentry, OVL_XATTR_IMPURE,
+ "y", 1, 0);
+ if (!err)
+ ovl_set_flag(OVL_IMPURE, d_inode(dentry));
+
+ return err;
+}
+
+void ovl_set_flag(unsigned long flag, struct inode *inode)
+{
+ set_bit(flag, &OVL_I(inode)->flags);
+}
+
+void ovl_clear_flag(unsigned long flag, struct inode *inode)
+{
+ clear_bit(flag, &OVL_I(inode)->flags);
+}
+
+bool ovl_test_flag(unsigned long flag, struct inode *inode)
+{
+ return test_bit(flag, &OVL_I(inode)->flags);
+}
+
+/**
+ * Caller must hold a reference to inode to prevent it from being freed while
+ * it is marked inuse.
+ */
+bool ovl_inuse_trylock(struct dentry *dentry)
+{
+ struct inode *inode = d_inode(dentry);
+ bool locked = false;
+
+ spin_lock(&inode->i_lock);
+ if (!(inode->i_state & I_OVL_INUSE)) {
+ inode->i_state |= I_OVL_INUSE;
+ locked = true;
+ }
+ spin_unlock(&inode->i_lock);
+
+ return locked;
+}
+
+void ovl_inuse_unlock(struct dentry *dentry)
+{
+ if (dentry) {
+ struct inode *inode = d_inode(dentry);
+
+ spin_lock(&inode->i_lock);
+ WARN_ON(!(inode->i_state & I_OVL_INUSE));
+ inode->i_state &= ~I_OVL_INUSE;
+ spin_unlock(&inode->i_lock);
+ }
+}
+
+/*
+ * Does this overlay dentry need to be indexed on copy up?
+ */
+bool ovl_need_index(struct dentry *dentry)
+{
+ struct dentry *lower = ovl_dentry_lower(dentry);
+
+ if (!lower || !ovl_indexdir(dentry->d_sb))
+ return false;
+
+ /* Index all files for NFS export and consistency verification */
+ if (ovl_index_all(dentry->d_sb))
+ return true;
+
+ /* Index only lower hardlinks on copy up */
+ if (!d_is_dir(lower) && d_inode(lower)->i_nlink > 1)
+ return true;
+
+ return false;
+}
+
+/* Caller must hold OVL_I(inode)->lock */
+static void ovl_cleanup_index(struct dentry *dentry)
+{
+ struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
+ struct inode *dir = indexdir->d_inode;
+ struct dentry *lowerdentry = ovl_dentry_lower(dentry);
+ struct dentry *upperdentry = ovl_dentry_upper(dentry);
+ struct dentry *index = NULL;
+ struct inode *inode;
+ struct qstr name = { };
+ int err;
+
+ err = ovl_get_index_name(lowerdentry, &name);
+ if (err)
+ goto fail;
+
+ inode = d_inode(upperdentry);
+ if (!S_ISDIR(inode->i_mode) && inode->i_nlink != 1) {
+ pr_warn_ratelimited("overlayfs: cleanup linked index (%pd2, ino=%lu, nlink=%u)\n",
+ upperdentry, inode->i_ino, inode->i_nlink);
+ /*
+ * We either have a bug with persistent union nlink or a lower
+ * hardlink was added while overlay is mounted. Adding a lower
+ * hardlink and then unlinking all overlay hardlinks would drop
+ * overlay nlink to zero before all upper inodes are unlinked.
+ * As a safety measure, when that situation is detected, set
+ * the overlay nlink to the index inode nlink minus one for the
+ * index entry itself.
+ */
+ set_nlink(d_inode(dentry), inode->i_nlink - 1);
+ ovl_set_nlink_upper(dentry);
+ goto out;
+ }
+
+ inode_lock_nested(dir, I_MUTEX_PARENT);
+ index = lookup_one_len(name.name, indexdir, name.len);
+ err = PTR_ERR(index);
+ if (IS_ERR(index)) {
+ index = NULL;
+ } else if (ovl_index_all(dentry->d_sb)) {
+ /* Whiteout orphan index to block future open by handle */
+ err = ovl_cleanup_and_whiteout(indexdir, dir, index);
+ } else {
+ /* Cleanup orphan index entries */
+ err = ovl_cleanup(dir, index);
+ }
+
+ inode_unlock(dir);
+ if (err)
+ goto fail;
+
+out:
+ kfree(name.name);
+ dput(index);
+ return;
+
+fail:
+ pr_err("overlayfs: cleanup index of '%pd2' failed (%i)\n", dentry, err);
+ goto out;
+}
+
+/*
+ * Operations that change overlay inode and upper inode nlink need to be
+ * synchronized with copy up for persistent nlink accounting.
+ */
+int ovl_nlink_start(struct dentry *dentry, bool *locked)
+{
+ struct ovl_inode *oi = OVL_I(d_inode(dentry));
+ const struct cred *old_cred;
+ int err;
+
+ if (!d_inode(dentry))
+ return 0;
+
+ /*
+ * With inodes index is enabled, we store the union overlay nlink
+ * in an xattr on the index inode. When whiting out an indexed lower,
+ * we need to decrement the overlay persistent nlink, but before the
+ * first copy up, we have no upper index inode to store the xattr.
+ *
+ * As a workaround, before whiteout/rename over an indexed lower,
+ * copy up to create the upper index. Creating the upper index will
+ * initialize the overlay nlink, so it could be dropped if unlink
+ * or rename succeeds.
+ *
+ * TODO: implement metadata only index copy up when called with
+ * ovl_copy_up_flags(dentry, O_PATH).
+ */
+ if (ovl_need_index(dentry) && !ovl_dentry_has_upper_alias(dentry)) {
+ err = ovl_copy_up(dentry);
+ if (err)
+ return err;
+ }
+
+ err = mutex_lock_interruptible(&oi->lock);
+ if (err)
+ return err;
+
+ if (d_is_dir(dentry) || !ovl_test_flag(OVL_INDEX, d_inode(dentry)))
+ goto out;
+
+ old_cred = ovl_override_creds(dentry->d_sb);
+ /*
+ * The overlay inode nlink should be incremented/decremented IFF the
+ * upper operation succeeds, along with nlink change of upper inode.
+ * Therefore, before link/unlink/rename, we store the union nlink
+ * value relative to the upper inode nlink in an upper inode xattr.
+ */
+ err = ovl_set_nlink_upper(dentry);
+ revert_creds(old_cred);
+
+out:
+ if (err)
+ mutex_unlock(&oi->lock);
+ else
+ *locked = true;
+
+ return err;
+}
+
+void ovl_nlink_end(struct dentry *dentry, bool locked)
+{
+ if (locked) {
+ if (ovl_test_flag(OVL_INDEX, d_inode(dentry)) &&
+ d_inode(dentry)->i_nlink == 0) {
+ const struct cred *old_cred;
+
+ old_cred = ovl_override_creds(dentry->d_sb);
+ ovl_cleanup_index(dentry);
+ revert_creds(old_cred);
+ }
+
+ mutex_unlock(&OVL_I(d_inode(dentry))->lock);
+ }
+}
+
+int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir)
+{
+ /* Workdir should not be the same as upperdir */
+ if (workdir == upperdir)
+ goto err;
+
+ /* Workdir should not be subdir of upperdir and vice versa */
+ if (lock_rename(workdir, upperdir) != NULL)
+ goto err_unlock;
+
+ return 0;
+
+err_unlock:
+ unlock_rename(workdir, upperdir);
+err:
+ pr_err("overlayfs: failed to lock workdir+upperdir\n");
+ return -EIO;
+}
+
+/* err < 0, 0 if no metacopy xattr, 1 if metacopy xattr found */
+int ovl_check_metacopy_xattr(struct dentry *dentry)
+{
+ int res;
+
+ /* Only regular files can have metacopy xattr */
+ if (!S_ISREG(d_inode(dentry)->i_mode))
+ return 0;
+
+ res = vfs_getxattr(dentry, OVL_XATTR_METACOPY, NULL, 0);
+ if (res < 0) {
+ if (res == -ENODATA || res == -EOPNOTSUPP)
+ return 0;
+ goto out;
+ }
+
+ return 1;
+out:
+ pr_warn_ratelimited("overlayfs: failed to get metacopy (%i)\n", res);
+ return res;
+}
+
+bool ovl_is_metacopy_dentry(struct dentry *dentry)
+{
+ struct ovl_entry *oe = dentry->d_fsdata;
+
+ if (!d_is_reg(dentry))
+ return false;
+
+ if (ovl_dentry_upper(dentry)) {
+ if (!ovl_has_upperdata(d_inode(dentry)))
+ return true;
+ return false;
+ }
+
+ return (oe->numlower > 1);
+}
+
+char *ovl_get_redirect_xattr(struct dentry *dentry, int padding)
+{
+ int res;
+ char *s, *next, *buf = NULL;
+
+ res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, NULL, 0);
+ if (res < 0) {
+ if (res == -ENODATA || res == -EOPNOTSUPP)
+ return NULL;
+ goto fail;
+ }
+
+ buf = kzalloc(res + padding + 1, GFP_KERNEL);
+ if (!buf)
+ return ERR_PTR(-ENOMEM);
+
+ if (res == 0)
+ goto invalid;
+
+ res = vfs_getxattr(dentry, OVL_XATTR_REDIRECT, buf, res);
+ if (res < 0)
+ goto fail;
+ if (res == 0)
+ goto invalid;
+
+ if (buf[0] == '/') {
+ for (s = buf; *s++ == '/'; s = next) {
+ next = strchrnul(s, '/');
+ if (s == next)
+ goto invalid;
+ }
+ } else {
+ if (strchr(buf, '/') != NULL)
+ goto invalid;
+ }
+
+ return buf;
+
+err_free:
+ kfree(buf);
+ return ERR_PTR(res);
+fail:
+ pr_warn_ratelimited("overlayfs: failed to get redirect (%i)\n", res);
+ goto err_free;
+invalid:
+ pr_warn_ratelimited("overlayfs: invalid redirect (%s)\n", buf);
+ res = -EINVAL;
+ goto err_free;
+}