// SPDX-License-Identifier: GPL-2.0-only
/*
 *
 * Copyright (C) 2011 Novell Inc.
 */

#include <linux/module.h>
#include <linux/fs.h>
#include <linux/slab.h>
#include <linux/file.h>
#include <linux/splice.h>
#include <linux/xattr.h>
#include <linux/security.h>
#include <linux/uaccess.h>
#include <linux/sched/signal.h>
#include <linux/cred.h>
#include <linux/namei.h>
#include <linux/fdtable.h>
#include <linux/ratelimit.h>
#include <linux/exportfs.h>
#include "overlayfs.h"

#define OVL_COPY_UP_CHUNK_SIZE (1 << 20)

static int ovl_ccup_set(const char *buf, const struct kernel_param *param)
{
        pr_warn("overlayfs: \"check_copy_up\" module option is obsolete\n");
        return 0;
}

static int ovl_ccup_get(char *buf, const struct kernel_param *param)
{
        return sprintf(buf, "N\n");
}

module_param_call(check_copy_up, ovl_ccup_set, ovl_ccup_get, NULL, 0644);
MODULE_PARM_DESC(check_copy_up, "Obsolete; does nothing");

int ovl_copy_xattr(struct dentry *old, struct dentry *new)
{
        ssize_t list_size, size, value_size = 0;
        char *buf, *name, *value = NULL;
        int uninitialized_var(error);
        size_t slen;

        if (!(old->d_inode->i_opflags & IOP_XATTR) ||
            !(new->d_inode->i_opflags & IOP_XATTR))
                return 0;

        list_size = vfs_listxattr(old, NULL, 0);
        if (list_size <= 0) {
                if (list_size == -EOPNOTSUPP)
                        return 0;
                return list_size;
        }

        buf = kzalloc(list_size, GFP_KERNEL);
        if (!buf)
                return -ENOMEM;

        list_size = vfs_listxattr(old, buf, list_size);
        if (list_size <= 0) {
                error = list_size;
                goto out;
        }

        for (name = buf; list_size; name += slen) {
                slen = strnlen(name, list_size) + 1;

                /* underlying fs providing us with an broken xattr list? */
                if (WARN_ON(slen > list_size)) {
                        error = -EIO;
                        break;
                }
                list_size -= slen;

                if (ovl_is_private_xattr(name))
                        continue;
retry:
                size = vfs_getxattr(old, name, value, value_size);
                if (size == -ERANGE)
                        size = vfs_getxattr(old, name, NULL, 0);

                if (size < 0) {
                        error = size;
                        break;
                }

                if (size > value_size) {
                        void *new;

                        new = krealloc(value, size, GFP_KERNEL);
                        if (!new) {
                                error = -ENOMEM;
                                break;
                        }
                        value = new;
                        value_size = size;
                        goto retry;
                }

                error = security_inode_copy_up_xattr(name);
                if (error < 0 && error != -EOPNOTSUPP)
                        break;
                if (error == 1) {
                        error = 0;
                        continue; /* Discard */
                }
                error = vfs_setxattr(new, name, value, size, 0);
                if (error)
                        break;
        }
        kfree(value);
out:
        kfree(buf);
        return error;
}

static int ovl_copy_up_data(struct path *old, struct path *new, loff_t len)
{
        struct file *old_file;
        struct file *new_file;
        loff_t old_pos = 0;
        loff_t new_pos = 0;
        loff_t cloned;
        int error = 0;

        if (len == 0)
                return 0;

        old_file = ovl_path_open(old, O_LARGEFILE | O_RDONLY);
        if (IS_ERR(old_file))
                return PTR_ERR(old_file);

        new_file = ovl_path_open(new, O_LARGEFILE | O_WRONLY);
        if (IS_ERR(new_file)) {
                error = PTR_ERR(new_file);
                goto out_fput;
        }

        /* Try to use clone_file_range to clone up within the same fs */
        cloned = do_clone_file_range(old_file, 0, new_file, 0, len, 0);
        if (cloned == len)
                goto out;
        /* Couldn't clone, so now we try to copy the data */

        /* FIXME: copy up sparse files efficiently */
        while (len) {
                size_t this_len = OVL_COPY_UP_CHUNK_SIZE;
                long bytes;

                if (len < this_len)
                        this_len = len;

                if (signal_pending_state(TASK_KILLABLE, current)) {
                        error = -EINTR;
                        break;
                }

                bytes = do_splice_direct(old_file, &old_pos,
                                         new_file, &new_pos,
                                         this_len, SPLICE_F_MOVE);
                if (bytes <= 0) {
                        error = bytes;
                        break;
                }
                WARN_ON(old_pos != new_pos);

                len -= bytes;
        }
out:
        if (!error)
                error = vfs_fsync(new_file, 0);
        fput(new_file);
out_fput:
        fput(old_file);
        return error;
}

static int ovl_set_size(struct dentry *upperdentry, struct kstat *stat)
{
        struct iattr attr = {
                .ia_valid = ATTR_SIZE,
                .ia_size = stat->size,
        };

        return notify_change(upperdentry, &attr, NULL);
}

static int ovl_set_timestamps(struct dentry *upperdentry, struct kstat *stat)
{
        struct iattr attr = {
                .ia_valid =
                     ATTR_ATIME | ATTR_MTIME | ATTR_ATIME_SET | ATTR_MTIME_SET,
                .ia_atime = stat->atime,
                .ia_mtime = stat->mtime,
        };

        return notify_change(upperdentry, &attr, NULL);
}

int ovl_set_attr(struct dentry *upperdentry, struct kstat *stat)
{
        int err = 0;

        if (!S_ISLNK(stat->mode)) {
                struct iattr attr = {
                        .ia_valid = ATTR_MODE,
                        .ia_mode = stat->mode,
                };
                err = notify_change(upperdentry, &attr, NULL);
        }
        if (!err) {
                struct iattr attr = {
                        .ia_valid = ATTR_UID | ATTR_GID,
                        .ia_uid = stat->uid,
                        .ia_gid = stat->gid,
                };
                err = notify_change(upperdentry, &attr, NULL);
        }
        if (!err)
                ovl_set_timestamps(upperdentry, stat);

        return err;
}

struct ovl_fh *ovl_encode_real_fh(struct dentry *real, bool is_upper)
{
        struct ovl_fh *fh;
        int fh_type, fh_len, dwords;
        void *buf;
        int buflen = MAX_HANDLE_SZ;
        uuid_t *uuid = &real->d_sb->s_uuid;

        buf = kmalloc(buflen, GFP_KERNEL);
        if (!buf)
                return ERR_PTR(-ENOMEM);

        /*
         * We encode a non-connectable file handle for non-dir, because we
         * only need to find the lower inode number and we don't want to pay
         * the price or reconnecting the dentry.
         */
        dwords = buflen >> 2;
        fh_type = exportfs_encode_fh(real, buf, &dwords, 0);
        buflen = (dwords << 2);

        fh = ERR_PTR(-EIO);
        if (WARN_ON(fh_type < 0) ||
            WARN_ON(buflen > MAX_HANDLE_SZ) ||
            WARN_ON(fh_type == FILEID_INVALID))
                goto out;

        BUILD_BUG_ON(MAX_HANDLE_SZ + offsetof(struct ovl_fh, fid) > 255);
        fh_len = offsetof(struct ovl_fh, fid) + buflen;
        fh = kmalloc(fh_len, GFP_KERNEL);
        if (!fh) {
                fh = ERR_PTR(-ENOMEM);
                goto out;
        }

        fh->version = OVL_FH_VERSION;
        fh->magic = OVL_FH_MAGIC;
        fh->type = fh_type;
        fh->flags = OVL_FH_FLAG_CPU_ENDIAN;
        /*
         * When we will want to decode an overlay dentry from this handle
         * and all layers are on the same fs, if we get a disconncted real
         * dentry when we decode fid, the only way to tell if we should assign
         * it to upperdentry or to lowerstack is by checking this flag.
         */
        if (is_upper)
                fh->flags |= OVL_FH_FLAG_PATH_UPPER;
        fh->len = fh_len;
        fh->uuid = *uuid;
        memcpy(fh->fid, buf, buflen);

out:
        kfree(buf);
        return fh;
}

int ovl_set_origin(struct dentry *dentry, struct dentry *lower,
                   struct dentry *upper)
{
        const struct ovl_fh *fh = NULL;
        int err;

        /*
         * When lower layer doesn't support export operations store a 'null' fh,
         * so we can use the overlay.origin xattr to distignuish between a copy
         * up and a pure upper inode.
         */
        if (ovl_can_decode_fh(lower->d_sb)) {
                fh = ovl_encode_real_fh(lower, false);
                if (IS_ERR(fh))
                        return PTR_ERR(fh);
        }

        /*
         * Do not fail when upper doesn't support xattrs.
         */
        err = ovl_check_setxattr(dentry, upper, OVL_XATTR_ORIGIN, fh,
                                 fh ? fh->len : 0, 0);
        kfree(fh);

        return err;
}

/* Store file handle of @upper dir in @index dir entry */
static int ovl_set_upper_fh(struct dentry *upper, struct dentry *index)
{
        const struct ovl_fh *fh;
        int err;

        fh = ovl_encode_real_fh(upper, true);
        if (IS_ERR(fh))
                return PTR_ERR(fh);

        err = ovl_do_setxattr(index, OVL_XATTR_UPPER, fh, fh->len, 0);

        kfree(fh);
        return err;
}

/*
 * Create and install index entry.
 *
 * Caller must hold i_mutex on indexdir.
 */
static int ovl_create_index(struct dentry *dentry, struct dentry *origin,
                            struct dentry *upper)
{
        struct dentry *indexdir = ovl_indexdir(dentry->d_sb);
        struct inode *dir = d_inode(indexdir);
        struct dentry *index = NULL;
        struct dentry *temp = NULL;
        struct qstr name = { };
        int err;

        /*
         * For now this is only used for creating index entry for directories,
         * because non-dir are copied up directly to index and then hardlinked
         * to upper dir.
         *
         * TODO: implement create index for non-dir, so we can call it when
         * encoding file handle for non-dir in case index does not exist.
         */
        if (WARN_ON(!d_is_dir(dentry)))
                return -EIO;

        /* Directory not expected to be indexed before copy up */
        if (WARN_ON(ovl_test_flag(OVL_INDEX, d_inode(dentry))))
                return -EIO;

        err = ovl_get_index_name(origin, &name);
        if (err)
                return err;

        temp = ovl_create_temp(indexdir, OVL_CATTR(S_IFDIR | 0));
        err = PTR_ERR(temp);
        if (IS_ERR(temp))
                goto free_name;

        err = ovl_set_upper_fh(upper, temp);
        if (err)
                goto out;

        index = lookup_one_len(name.name, indexdir, name.len);
        if (IS_ERR(index)) {
                err = PTR_ERR(index);
        } else {
                err = ovl_do_rename(dir, temp, dir, index, 0);
                dput(index);
        }
out:
        if (err)
                ovl_cleanup(dir, temp);
        dput(temp);
free_name:
        kfree(name.name);
        return err;
}

struct ovl_copy_up_ctx {
        struct dentry *parent;
        struct dentry *dentry;
        struct path lowerpath;
        struct kstat stat;
        struct kstat pstat;
        const char *link;
        struct dentry *destdir;
        struct qstr destname;
        struct dentry *workdir;
        bool origin;
        bool indexed;
        bool metacopy;
};

static int ovl_link_up(struct ovl_copy_up_ctx *c)
{
        int err;
        struct dentry *upper;
        struct dentry *upperdir = ovl_dentry_upper(c->parent);
        struct inode *udir = d_inode(upperdir);

        /* Mark parent "impure" because it may now contain non-pure upper */
        err = ovl_set_impure(c->parent, upperdir);
        if (err)
                return err;

        err = ovl_set_nlink_lower(c->dentry);
        if (err)
                return err;

        inode_lock_nested(udir, I_MUTEX_PARENT);
        upper = lookup_one_len(c->dentry->d_name.name, upperdir,
                               c->dentry->d_name.len);
        err = PTR_ERR(upper);
        if (!IS_ERR(upper)) {
                err = ovl_do_link(ovl_dentry_upper(c->dentry), udir, upper);
                dput(upper);

                if (!err) {
                        /* Restore timestamps on parent (best effort) */
                        ovl_set_timestamps(upperdir, &c->pstat);
                        ovl_dentry_set_upper_alias(c->dentry);
                }
        }
        inode_unlock(udir);
        if (err)
                return err;

        err = ovl_set_nlink_upper(c->dentry);

        return err;
}

static int ovl_copy_up_inode(struct ovl_copy_up_ctx *c, struct dentry *temp)
{
        int err;

        /*
         * Copy up data first and then xattrs. Writing data after
         * xattrs will remove security.capability xattr automatically.
         */
        if (S_ISREG(c->stat.mode) && !c->metacopy) {
                struct path upperpath, datapath;

                ovl_path_upper(c->dentry, &upperpath);
                if (WARN_ON(upperpath.dentry != NULL))
                        return -EIO;
                upperpath.dentry = temp;

                ovl_path_lowerdata(c->dentry, &datapath);
                err = ovl_copy_up_data(&datapath, &upperpath, c->stat.size);
                if (err)
                        return err;
        }

        err = ovl_copy_xattr(c->lowerpath.dentry, temp);
        if (err)
                return err;

        /*
         * Store identifier of lower inode in upper inode xattr to
         * allow lookup of the copy up origin inode.
         *
         * Don't set origin when we are breaking the association with a lower
         * hard link.
         */
        if (c->origin) {
                err = ovl_set_origin(c->dentry, c->lowerpath.dentry, temp);
                if (err)
                        return err;
        }

        if (c->metacopy) {
                err = ovl_check_setxattr(c->dentry, temp, OVL_XATTR_METACOPY,
                                         NULL, 0, -EOPNOTSUPP);
                if (err)
                        return err;
        }

        inode_lock(temp->d_inode);
        if (c->metacopy)
                err = ovl_set_size(temp, &c->stat);
        if (!err)
                err = ovl_set_attr(temp, &c->stat);
        inode_unlock(temp->d_inode);

        return err;
}

struct ovl_cu_creds {
        const struct cred *old;
        struct cred *new;
};

static int ovl_prep_cu_creds(struct dentry *dentry, struct ovl_cu_creds *cc)
{
        int err;

        cc->old = cc->new = NULL;
        err = security_inode_copy_up(dentry, &cc->new);
        if (err < 0)
                return err;

        if (cc->new)
                cc->old = override_creds(cc->new);

        return 0;
}

static void ovl_revert_cu_creds(struct ovl_cu_creds *cc)
{
        if (cc->new) {
                revert_creds(cc->old);
                put_cred(cc->new);
        }
}

/*
 * Copyup using workdir to prepare temp file.  Used when copying up directories,
 * special files or when upper fs doesn't support O_TMPFILE.
 */
static int ovl_copy_up_workdir(struct ovl_copy_up_ctx *c)
{
        struct inode *inode;
        struct inode *udir = d_inode(c->destdir), *wdir = d_inode(c->workdir);
        struct dentry *temp, *upper;
        struct ovl_cu_creds cc;
        int err;
        struct ovl_cattr cattr = {
                /* Can't properly set mode on creation because of the umask */
                .mode = c->stat.mode & S_IFMT,
                .rdev = c->stat.rdev,
                .link = c->link
        };

        err = ovl_lock_rename_workdir(c->workdir, c->destdir);
        if (err)
                return err;

        err = ovl_prep_cu_creds(c->dentry, &cc);
        if (err)
                goto unlock;

        temp = ovl_create_temp(c->workdir, &cattr);
        ovl_revert_cu_creds(&cc);

        err = PTR_ERR(temp);
        if (IS_ERR(temp))
                goto unlock;

        err = ovl_copy_up_inode(c, temp);
        if (err)
                goto cleanup;

        if (S_ISDIR(c->stat.mode) && c->indexed) {
                err = ovl_create_index(c->dentry, c->lowerpath.dentry, temp);
                if (err)
                        goto cleanup;
        }

        upper = lookup_one_len(c->destname.name, c->destdir, c->destname.len);
        err = PTR_ERR(upper);
        if (IS_ERR(upper))
                goto cleanup;

        err = ovl_do_rename(wdir, temp, udir, upper, 0);
        dput(upper);
        if (err)
                goto cleanup;

        if (!c->metacopy)
                ovl_set_upperdata(d_inode(c->dentry));
        inode = d_inode(c->dentry);
        ovl_inode_update(inode, temp);
        if (S_ISDIR(inode->i_mode))
                ovl_set_flag(OVL_WHITEOUTS, inode);
unlock:
        unlock_rename(c->workdir, c->destdir);

        return err;

cleanup:
        ovl_cleanup(wdir, temp);
        dput(temp);
        goto unlock;
}

/* Copyup using O_TMPFILE which does not require cross dir locking */
static int ovl_copy_up_tmpfile(struct ovl_copy_up_ctx *c)
{
        struct inode *udir = d_inode(c->destdir);
        struct dentry *temp, *upper;
        struct ovl_cu_creds cc;
        int err;

        err = ovl_prep_cu_creds(c->dentry, &cc);
        if (err)
                return err;

        temp = ovl_do_tmpfile(c->workdir, c->stat.mode);
        ovl_revert_cu_creds(&cc);

        if (IS_ERR(temp))
                return PTR_ERR(temp);

        err = ovl_copy_up_inode(c, temp);
        if (err)
                goto out_dput;

        inode_lock_nested(udir, I_MUTEX_PARENT);

        upper = lookup_one_len(c->destname.name, c->destdir, c->destname.len);
        err = PTR_ERR(upper);
        if (!IS_ERR(upper)) {
                err = ovl_do_link(temp, udir, upper);
                dput(upper);
        }
        inode_unlock(udir);

        if (err)
                goto out_dput;

        if (!c->metacopy)
                ovl_set_upperdata(d_inode(c->dentry));
        ovl_inode_update(d_inode(c->dentry), temp);

        return 0;

out_dput:
        dput(temp);
        return err;
}

/*
 * Copy up a single dentry
 *
 * All renames start with copy up of source if necessary.  The actual
 * rename will only proceed once the copy up was successful.  Copy up uses
 * upper parent i_mutex for exclusion.  Since rename can change d_parent it
 * is possible that the copy up will lock the old parent.  At that point
 * the file will have already been copied up anyway.
 */
static int ovl_do_copy_up(struct ovl_copy_up_ctx *c)
{
        int err;
        struct ovl_fs *ofs = c->dentry->d_sb->s_fs_info;
        bool to_index = false;

        /*
         * Indexed non-dir is copied up directly to the index entry and then
         * hardlinked to upper dir. Indexed dir is copied up to indexdir,
         * then index entry is created and then copied up dir installed.
         * Copying dir up to indexdir instead of workdir simplifies locking.
         */
        if (ovl_need_index(c->dentry)) {
                c->indexed = true;
                if (S_ISDIR(c->stat.mode))
                        c->workdir = ovl_indexdir(c->dentry->d_sb);
                else
                        to_index = true;
        }

        if (S_ISDIR(c->stat.mode) || c->stat.nlink == 1 || to_index)
                c->origin = true;

        if (to_index) {
                c->destdir = ovl_indexdir(c->dentry->d_sb);
                err = ovl_get_index_name(c->lowerpath.dentry, &c->destname);
                if (err)
                        return err;
        } else if (WARN_ON(!c->parent)) {
                /* Disconnected dentry must be copied up to index dir */
                return -EIO;
        } else {
                /*
                 * Mark parent "impure" because it may now contain non-pure
                 * upper
                 */
                err = ovl_set_impure(c->parent, c->destdir);
                if (err)
                        return err;
        }

        /* Should we copyup with O_TMPFILE or with workdir? */
        if (S_ISREG(c->stat.mode) && ofs->tmpfile)
                err = ovl_copy_up_tmpfile(c);
        else
                err = ovl_copy_up_workdir(c);
        if (err)
                goto out;

        if (c->indexed)
                ovl_set_flag(OVL_INDEX, d_inode(c->dentry));

        if (to_index) {
                /* Initialize nlink for copy up of disconnected dentry */
                err = ovl_set_nlink_upper(c->dentry);
        } else {
                struct inode *udir = d_inode(c->destdir);

                /* Restore timestamps on parent (best effort) */
                inode_lock(udir);
                ovl_set_timestamps(c->destdir, &c->pstat);
                inode_unlock(udir);

                ovl_dentry_set_upper_alias(c->dentry);
        }

out:
        if (to_index)
                kfree(c->destname.name);
        return err;
}

static bool ovl_need_meta_copy_up(struct dentry *dentry, umode_t mode,
                                  int flags)
{
        struct ovl_fs *ofs = dentry->d_sb->s_fs_info;

        if (!ofs->config.metacopy)
                return false;

        if (!S_ISREG(mode))
                return false;

        if (flags && ((OPEN_FMODE(flags) & FMODE_WRITE) || (flags & O_TRUNC)))
                return false;

        return true;
}

/* Copy up data of an inode which was copied up metadata only in the past. */
static int ovl_copy_up_meta_inode_data(struct ovl_copy_up_ctx *c)
{
        struct path upperpath, datapath;
        int err;
        char *capability = NULL;
        ssize_t uninitialized_var(cap_size);

        ovl_path_upper(c->dentry, &upperpath);
        if (WARN_ON(upperpath.dentry == NULL))
                return -EIO;

        ovl_path_lowerdata(c->dentry, &datapath);
        if (WARN_ON(datapath.dentry == NULL))
                return -EIO;

        if (c->stat.size) {
                err = cap_size = ovl_getxattr(upperpath.dentry, XATTR_NAME_CAPS,
                                              &capability, 0);
                if (err < 0 && err != -ENODATA)
                        goto out;
        }

        err = ovl_copy_up_data(&datapath, &upperpath, c->stat.size);
        if (err)
                goto out_free;

        /*
         * Writing to upper file will clear security.capability xattr. We
         * don't want that to happen for normal copy-up operation.
         */
        if (capability) {
                err = ovl_do_setxattr(upperpath.dentry, XATTR_NAME_CAPS,
                                      capability, cap_size, 0);
                if (err)
                        goto out_free;
        }


        err = vfs_removexattr(upperpath.dentry, OVL_XATTR_METACOPY);
        if (err)
                goto out_free;

        ovl_set_upperdata(d_inode(c->dentry));
out_free:
        kfree(capability);
out:
        return err;
}

static int ovl_copy_up_one(struct dentry *parent, struct dentry *dentry,
                           int flags)
{
        int err;
        DEFINE_DELAYED_CALL(done);
        struct path parentpath;
        struct ovl_copy_up_ctx ctx = {
                .parent = parent,
                .dentry = dentry,
                .workdir = ovl_workdir(dentry),
        };

        if (WARN_ON(!ctx.workdir))
                return -EROFS;

        ovl_path_lower(dentry, &ctx.lowerpath);
        err = vfs_getattr(&ctx.lowerpath, &ctx.stat,
                          STATX_BASIC_STATS, AT_STATX_SYNC_AS_STAT);
        if (err)
                return err;

        ctx.metacopy = ovl_need_meta_copy_up(dentry, ctx.stat.mode, flags);

        if (parent) {
                ovl_path_upper(parent, &parentpath);
                ctx.destdir = parentpath.dentry;
                ctx.destname = dentry->d_name;

                err = vfs_getattr(&parentpath, &ctx.pstat,
                                  STATX_ATIME | STATX_MTIME,
                                  AT_STATX_SYNC_AS_STAT);
                if (err)
                        return err;
        }

        /* maybe truncate regular file. this has no effect on dirs */
        if (flags & O_TRUNC)
                ctx.stat.size = 0;

        if (S_ISLNK(ctx.stat.mode)) {
                ctx.link = vfs_get_link(ctx.lowerpath.dentry, &done);
                if (IS_ERR(ctx.link))
                        return PTR_ERR(ctx.link);
        }

        err = ovl_copy_up_start(dentry, flags);
        /* err < 0: interrupted, err > 0: raced with another copy-up */
        if (unlikely(err)) {
                if (err > 0)
                        err = 0;
        } else {
                if (!ovl_dentry_upper(dentry))
                        err = ovl_do_copy_up(&ctx);
                if (!err && parent && !ovl_dentry_has_upper_alias(dentry))
                        err = ovl_link_up(&ctx);
                if (!err && ovl_dentry_needs_data_copy_up_locked(dentry, flags))
                        err = ovl_copy_up_meta_inode_data(&ctx);
                ovl_copy_up_end(dentry);
        }
        do_delayed_call(&done);

        return err;
}

int ovl_copy_up_flags(struct dentry *dentry, int flags)
{
        int err = 0;
        const struct cred *old_cred = ovl_override_creds(dentry->d_sb);
        bool disconnected = (dentry->d_flags & DCACHE_DISCONNECTED);

        /*
         * With NFS export, copy up can get called for a disconnected non-dir.
         * In this case, we will copy up lower inode to index dir without
         * linking it to upper dir.
         */
        if (WARN_ON(disconnected && d_is_dir(dentry)))
                return -EIO;

        while (!err) {
                struct dentry *next;
                struct dentry *parent = NULL;

                if (ovl_already_copied_up(dentry, flags))
                        break;

                next = dget(dentry);
                /* find the topmost dentry not yet copied up */
                for (; !disconnected;) {
                        parent = dget_parent(next);

                        if (ovl_dentry_upper(parent))
                                break;

                        dput(next);
                        next = parent;
                }

                err = ovl_copy_up_one(parent, next, flags);

                dput(parent);
                dput(next);
        }
        revert_creds(old_cred);

        return err;
}

static bool ovl_open_need_copy_up(struct dentry *dentry, int flags)
{
        /* Copy up of disconnected dentry does not set upper alias */
        if (ovl_already_copied_up(dentry, flags))
                return false;

        if (special_file(d_inode(dentry)->i_mode))
                return false;

        if (!ovl_open_flags_need_copy_up(flags))
                return false;

        return true;
}

int ovl_maybe_copy_up(struct dentry *dentry, int flags)
{
        int err = 0;

        if (ovl_open_need_copy_up(dentry, flags)) {
                err = ovl_want_write(dentry);
                if (!err) {
                        err = ovl_copy_up_flags(dentry, flags);
                        ovl_drop_write(dentry);
                }
        }

        return err;
}

int ovl_copy_up_with_data(struct dentry *dentry)
{
        return ovl_copy_up_flags(dentry, O_WRONLY);
}

int ovl_copy_up(struct dentry *dentry)
{
        return ovl_copy_up_flags(dentry, 0);
}