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-rw-r--r--fs/overlayfs/super.c1567
1 files changed, 1567 insertions, 0 deletions
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
new file mode 100644
index 0000000000..c71d185980
--- /dev/null
+++ b/fs/overlayfs/super.c
@@ -0,0 +1,1567 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *
+ * Copyright (C) 2011 Novell Inc.
+ */
+
+#include <uapi/linux/magic.h>
+#include <linux/fs.h>
+#include <linux/namei.h>
+#include <linux/xattr.h>
+#include <linux/mount.h>
+#include <linux/parser.h>
+#include <linux/module.h>
+#include <linux/statfs.h>
+#include <linux/seq_file.h>
+#include <linux/posix_acl_xattr.h>
+#include <linux/exportfs.h>
+#include <linux/file.h>
+#include <linux/fs_context.h>
+#include <linux/fs_parser.h>
+#include "overlayfs.h"
+#include "params.h"
+
+MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
+MODULE_DESCRIPTION("Overlay filesystem");
+MODULE_LICENSE("GPL");
+
+
+struct ovl_dir_cache;
+
+static struct dentry *ovl_d_real(struct dentry *dentry,
+ const struct inode *inode)
+{
+ struct dentry *real = NULL, *lower;
+ int err;
+
+ /* It's an overlay file */
+ if (inode && d_inode(dentry) == inode)
+ return dentry;
+
+ if (!d_is_reg(dentry)) {
+ if (!inode || inode == d_inode(dentry))
+ return dentry;
+ goto bug;
+ }
+
+ real = ovl_dentry_upper(dentry);
+ if (real && (inode == d_inode(real)))
+ return real;
+
+ if (real && !inode && ovl_has_upperdata(d_inode(dentry)))
+ return real;
+
+ /*
+ * Best effort lazy lookup of lowerdata for !inode case to return
+ * the real lowerdata dentry. The only current caller of d_real() with
+ * NULL inode is d_real_inode() from trace_uprobe and this caller is
+ * likely going to be followed reading from the file, before placing
+ * uprobes on offset within the file, so lowerdata should be available
+ * when setting the uprobe.
+ */
+ err = ovl_verify_lowerdata(dentry);
+ if (err)
+ goto bug;
+ lower = ovl_dentry_lowerdata(dentry);
+ if (!lower)
+ goto bug;
+ real = lower;
+
+ /* Handle recursion */
+ real = d_real(real, inode);
+
+ if (!inode || inode == d_inode(real))
+ return real;
+bug:
+ WARN(1, "%s(%pd4, %s:%lu): real dentry (%p/%lu) not found\n",
+ __func__, dentry, inode ? inode->i_sb->s_id : "NULL",
+ inode ? inode->i_ino : 0, real,
+ real && d_inode(real) ? d_inode(real)->i_ino : 0);
+ return dentry;
+}
+
+static int ovl_revalidate_real(struct dentry *d, unsigned int flags, bool weak)
+{
+ int ret = 1;
+
+ if (!d)
+ return 1;
+
+ if (weak) {
+ if (d->d_flags & DCACHE_OP_WEAK_REVALIDATE)
+ ret = d->d_op->d_weak_revalidate(d, flags);
+ } else if (d->d_flags & DCACHE_OP_REVALIDATE) {
+ ret = d->d_op->d_revalidate(d, flags);
+ if (!ret) {
+ if (!(flags & LOOKUP_RCU))
+ d_invalidate(d);
+ ret = -ESTALE;
+ }
+ }
+ return ret;
+}
+
+static int ovl_dentry_revalidate_common(struct dentry *dentry,
+ unsigned int flags, bool weak)
+{
+ struct ovl_entry *oe;
+ struct ovl_path *lowerstack;
+ struct inode *inode = d_inode_rcu(dentry);
+ struct dentry *upper;
+ unsigned int i;
+ int ret = 1;
+
+ /* Careful in RCU mode */
+ if (!inode)
+ return -ECHILD;
+
+ oe = OVL_I_E(inode);
+ lowerstack = ovl_lowerstack(oe);
+ upper = ovl_i_dentry_upper(inode);
+ if (upper)
+ ret = ovl_revalidate_real(upper, flags, weak);
+
+ for (i = 0; ret > 0 && i < ovl_numlower(oe); i++)
+ ret = ovl_revalidate_real(lowerstack[i].dentry, flags, weak);
+
+ return ret;
+}
+
+static int ovl_dentry_revalidate(struct dentry *dentry, unsigned int flags)
+{
+ return ovl_dentry_revalidate_common(dentry, flags, false);
+}
+
+static int ovl_dentry_weak_revalidate(struct dentry *dentry, unsigned int flags)
+{
+ return ovl_dentry_revalidate_common(dentry, flags, true);
+}
+
+static const struct dentry_operations ovl_dentry_operations = {
+ .d_real = ovl_d_real,
+ .d_revalidate = ovl_dentry_revalidate,
+ .d_weak_revalidate = ovl_dentry_weak_revalidate,
+};
+
+static struct kmem_cache *ovl_inode_cachep;
+
+static struct inode *ovl_alloc_inode(struct super_block *sb)
+{
+ struct ovl_inode *oi = alloc_inode_sb(sb, ovl_inode_cachep, GFP_KERNEL);
+
+ if (!oi)
+ return NULL;
+
+ oi->cache = NULL;
+ oi->redirect = NULL;
+ oi->version = 0;
+ oi->flags = 0;
+ oi->__upperdentry = NULL;
+ oi->lowerdata_redirect = NULL;
+ oi->oe = NULL;
+ mutex_init(&oi->lock);
+
+ return &oi->vfs_inode;
+}
+
+static void ovl_free_inode(struct inode *inode)
+{
+ struct ovl_inode *oi = OVL_I(inode);
+
+ kfree(oi->redirect);
+ kfree(oi->oe);
+ mutex_destroy(&oi->lock);
+ kmem_cache_free(ovl_inode_cachep, oi);
+}
+
+static void ovl_destroy_inode(struct inode *inode)
+{
+ struct ovl_inode *oi = OVL_I(inode);
+
+ dput(oi->__upperdentry);
+ ovl_stack_put(ovl_lowerstack(oi->oe), ovl_numlower(oi->oe));
+ if (S_ISDIR(inode->i_mode))
+ ovl_dir_cache_free(inode);
+ else
+ kfree(oi->lowerdata_redirect);
+}
+
+static void ovl_put_super(struct super_block *sb)
+{
+ struct ovl_fs *ofs = OVL_FS(sb);
+
+ if (ofs)
+ ovl_free_fs(ofs);
+}
+
+/* Sync real dirty inodes in upper filesystem (if it exists) */
+static int ovl_sync_fs(struct super_block *sb, int wait)
+{
+ struct ovl_fs *ofs = OVL_FS(sb);
+ struct super_block *upper_sb;
+ int ret;
+
+ ret = ovl_sync_status(ofs);
+ /*
+ * We have to always set the err, because the return value isn't
+ * checked in syncfs, and instead indirectly return an error via
+ * the sb's writeback errseq, which VFS inspects after this call.
+ */
+ if (ret < 0) {
+ errseq_set(&sb->s_wb_err, -EIO);
+ return -EIO;
+ }
+
+ if (!ret)
+ return ret;
+
+ /*
+ * Not called for sync(2) call or an emergency sync (SB_I_SKIP_SYNC).
+ * All the super blocks will be iterated, including upper_sb.
+ *
+ * If this is a syncfs(2) call, then we do need to call
+ * sync_filesystem() on upper_sb, but enough if we do it when being
+ * called with wait == 1.
+ */
+ if (!wait)
+ return 0;
+
+ upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
+
+ down_read(&upper_sb->s_umount);
+ ret = sync_filesystem(upper_sb);
+ up_read(&upper_sb->s_umount);
+
+ return ret;
+}
+
+/**
+ * ovl_statfs
+ * @dentry: The dentry to query
+ * @buf: The struct kstatfs to fill in with stats
+ *
+ * Get the filesystem statistics. As writes always target the upper layer
+ * filesystem pass the statfs to the upper filesystem (if it exists)
+ */
+static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf)
+{
+ struct super_block *sb = dentry->d_sb;
+ struct ovl_fs *ofs = OVL_FS(sb);
+ struct dentry *root_dentry = sb->s_root;
+ struct path path;
+ int err;
+
+ ovl_path_real(root_dentry, &path);
+
+ err = vfs_statfs(&path, buf);
+ if (!err) {
+ buf->f_namelen = ofs->namelen;
+ buf->f_type = OVERLAYFS_SUPER_MAGIC;
+ if (ovl_has_fsid(ofs))
+ buf->f_fsid = uuid_to_fsid(sb->s_uuid.b);
+ }
+
+ return err;
+}
+
+static const struct super_operations ovl_super_operations = {
+ .alloc_inode = ovl_alloc_inode,
+ .free_inode = ovl_free_inode,
+ .destroy_inode = ovl_destroy_inode,
+ .drop_inode = generic_delete_inode,
+ .put_super = ovl_put_super,
+ .sync_fs = ovl_sync_fs,
+ .statfs = ovl_statfs,
+ .show_options = ovl_show_options,
+};
+
+#define OVL_WORKDIR_NAME "work"
+#define OVL_INDEXDIR_NAME "index"
+
+static struct dentry *ovl_workdir_create(struct ovl_fs *ofs,
+ const char *name, bool persist)
+{
+ struct inode *dir = ofs->workbasedir->d_inode;
+ struct vfsmount *mnt = ovl_upper_mnt(ofs);
+ struct dentry *work;
+ int err;
+ bool retried = false;
+
+ inode_lock_nested(dir, I_MUTEX_PARENT);
+retry:
+ work = ovl_lookup_upper(ofs, name, ofs->workbasedir, strlen(name));
+
+ if (!IS_ERR(work)) {
+ struct iattr attr = {
+ .ia_valid = ATTR_MODE,
+ .ia_mode = S_IFDIR | 0,
+ };
+
+ if (work->d_inode) {
+ err = -EEXIST;
+ if (retried)
+ goto out_dput;
+
+ if (persist)
+ goto out_unlock;
+
+ retried = true;
+ err = ovl_workdir_cleanup(ofs, dir, mnt, work, 0);
+ dput(work);
+ if (err == -EINVAL) {
+ work = ERR_PTR(err);
+ goto out_unlock;
+ }
+ goto retry;
+ }
+
+ err = ovl_mkdir_real(ofs, dir, &work, attr.ia_mode);
+ if (err)
+ goto out_dput;
+
+ /* Weird filesystem returning with hashed negative (kernfs)? */
+ err = -EINVAL;
+ if (d_really_is_negative(work))
+ goto out_dput;
+
+ /*
+ * Try to remove POSIX ACL xattrs from workdir. We are good if:
+ *
+ * a) success (there was a POSIX ACL xattr and was removed)
+ * b) -ENODATA (there was no POSIX ACL xattr)
+ * c) -EOPNOTSUPP (POSIX ACL xattrs are not supported)
+ *
+ * There are various other error values that could effectively
+ * mean that the xattr doesn't exist (e.g. -ERANGE is returned
+ * if the xattr name is too long), but the set of filesystems
+ * allowed as upper are limited to "normal" ones, where checking
+ * for the above two errors is sufficient.
+ */
+ err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_DEFAULT);
+ if (err && err != -ENODATA && err != -EOPNOTSUPP)
+ goto out_dput;
+
+ err = ovl_do_remove_acl(ofs, work, XATTR_NAME_POSIX_ACL_ACCESS);
+ if (err && err != -ENODATA && err != -EOPNOTSUPP)
+ goto out_dput;
+
+ /* Clear any inherited mode bits */
+ inode_lock(work->d_inode);
+ err = ovl_do_notify_change(ofs, work, &attr);
+ inode_unlock(work->d_inode);
+ if (err)
+ goto out_dput;
+ } else {
+ err = PTR_ERR(work);
+ goto out_err;
+ }
+out_unlock:
+ inode_unlock(dir);
+ return work;
+
+out_dput:
+ dput(work);
+out_err:
+ pr_warn("failed to create directory %s/%s (errno: %i); mounting read-only\n",
+ ofs->config.workdir, name, -err);
+ work = NULL;
+ goto out_unlock;
+}
+
+static int ovl_check_namelen(const struct path *path, struct ovl_fs *ofs,
+ const char *name)
+{
+ struct kstatfs statfs;
+ int err = vfs_statfs(path, &statfs);
+
+ if (err)
+ pr_err("statfs failed on '%s'\n", name);
+ else
+ ofs->namelen = max(ofs->namelen, statfs.f_namelen);
+
+ return err;
+}
+
+static int ovl_lower_dir(const char *name, struct path *path,
+ struct ovl_fs *ofs, int *stack_depth)
+{
+ int fh_type;
+ int err;
+
+ err = ovl_check_namelen(path, ofs, name);
+ if (err)
+ return err;
+
+ *stack_depth = max(*stack_depth, path->mnt->mnt_sb->s_stack_depth);
+
+ /*
+ * The inodes index feature and NFS export need to encode and decode
+ * file handles, so they require that all layers support them.
+ */
+ fh_type = ovl_can_decode_fh(path->dentry->d_sb);
+ if ((ofs->config.nfs_export ||
+ (ofs->config.index && ofs->config.upperdir)) && !fh_type) {
+ ofs->config.index = false;
+ ofs->config.nfs_export = false;
+ pr_warn("fs on '%s' does not support file handles, falling back to index=off,nfs_export=off.\n",
+ name);
+ }
+ ofs->nofh |= !fh_type;
+ /*
+ * Decoding origin file handle is required for persistent st_ino.
+ * Without persistent st_ino, xino=auto falls back to xino=off.
+ */
+ if (ofs->config.xino == OVL_XINO_AUTO &&
+ ofs->config.upperdir && !fh_type) {
+ ofs->config.xino = OVL_XINO_OFF;
+ pr_warn("fs on '%s' does not support file handles, falling back to xino=off.\n",
+ name);
+ }
+
+ /* Check if lower fs has 32bit inode numbers */
+ if (fh_type != FILEID_INO32_GEN)
+ ofs->xino_mode = -1;
+
+ return 0;
+}
+
+/* Workdir should not be subdir of upperdir and vice versa */
+static bool ovl_workdir_ok(struct dentry *workdir, struct dentry *upperdir)
+{
+ bool ok = false;
+
+ if (workdir != upperdir) {
+ ok = (lock_rename(workdir, upperdir) == NULL);
+ unlock_rename(workdir, upperdir);
+ }
+ return ok;
+}
+
+static int ovl_own_xattr_get(const struct xattr_handler *handler,
+ struct dentry *dentry, struct inode *inode,
+ const char *name, void *buffer, size_t size)
+{
+ return -EOPNOTSUPP;
+}
+
+static int ovl_own_xattr_set(const struct xattr_handler *handler,
+ struct mnt_idmap *idmap,
+ struct dentry *dentry, struct inode *inode,
+ const char *name, const void *value,
+ size_t size, int flags)
+{
+ return -EOPNOTSUPP;
+}
+
+static int ovl_other_xattr_get(const struct xattr_handler *handler,
+ struct dentry *dentry, struct inode *inode,
+ const char *name, void *buffer, size_t size)
+{
+ return ovl_xattr_get(dentry, inode, name, buffer, size);
+}
+
+static int ovl_other_xattr_set(const struct xattr_handler *handler,
+ struct mnt_idmap *idmap,
+ struct dentry *dentry, struct inode *inode,
+ const char *name, const void *value,
+ size_t size, int flags)
+{
+ return ovl_xattr_set(dentry, inode, name, value, size, flags);
+}
+
+static const struct xattr_handler ovl_own_trusted_xattr_handler = {
+ .prefix = OVL_XATTR_TRUSTED_PREFIX,
+ .get = ovl_own_xattr_get,
+ .set = ovl_own_xattr_set,
+};
+
+static const struct xattr_handler ovl_own_user_xattr_handler = {
+ .prefix = OVL_XATTR_USER_PREFIX,
+ .get = ovl_own_xattr_get,
+ .set = ovl_own_xattr_set,
+};
+
+static const struct xattr_handler ovl_other_xattr_handler = {
+ .prefix = "", /* catch all */
+ .get = ovl_other_xattr_get,
+ .set = ovl_other_xattr_set,
+};
+
+static const struct xattr_handler *ovl_trusted_xattr_handlers[] = {
+ &ovl_own_trusted_xattr_handler,
+ &ovl_other_xattr_handler,
+ NULL
+};
+
+static const struct xattr_handler *ovl_user_xattr_handlers[] = {
+ &ovl_own_user_xattr_handler,
+ &ovl_other_xattr_handler,
+ NULL
+};
+
+static int ovl_setup_trap(struct super_block *sb, struct dentry *dir,
+ struct inode **ptrap, const char *name)
+{
+ struct inode *trap;
+ int err;
+
+ trap = ovl_get_trap_inode(sb, dir);
+ err = PTR_ERR_OR_ZERO(trap);
+ if (err) {
+ if (err == -ELOOP)
+ pr_err("conflicting %s path\n", name);
+ return err;
+ }
+
+ *ptrap = trap;
+ return 0;
+}
+
+/*
+ * Determine how we treat concurrent use of upperdir/workdir based on the
+ * index feature. This is papering over mount leaks of container runtimes,
+ * for example, an old overlay mount is leaked and now its upperdir is
+ * attempted to be used as a lower layer in a new overlay mount.
+ */
+static int ovl_report_in_use(struct ovl_fs *ofs, const char *name)
+{
+ if (ofs->config.index) {
+ pr_err("%s is in-use as upperdir/workdir of another mount, mount with '-o index=off' to override exclusive upperdir protection.\n",
+ name);
+ return -EBUSY;
+ } else {
+ pr_warn("%s is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.\n",
+ name);
+ return 0;
+ }
+}
+
+static int ovl_get_upper(struct super_block *sb, struct ovl_fs *ofs,
+ struct ovl_layer *upper_layer,
+ const struct path *upperpath)
+{
+ struct vfsmount *upper_mnt;
+ int err;
+
+ /* Upperdir path should not be r/o */
+ if (__mnt_is_readonly(upperpath->mnt)) {
+ pr_err("upper fs is r/o, try multi-lower layers mount\n");
+ err = -EINVAL;
+ goto out;
+ }
+
+ err = ovl_check_namelen(upperpath, ofs, ofs->config.upperdir);
+ if (err)
+ goto out;
+
+ err = ovl_setup_trap(sb, upperpath->dentry, &upper_layer->trap,
+ "upperdir");
+ if (err)
+ goto out;
+
+ upper_mnt = clone_private_mount(upperpath);
+ err = PTR_ERR(upper_mnt);
+ if (IS_ERR(upper_mnt)) {
+ pr_err("failed to clone upperpath\n");
+ goto out;
+ }
+
+ /* Don't inherit atime flags */
+ upper_mnt->mnt_flags &= ~(MNT_NOATIME | MNT_NODIRATIME | MNT_RELATIME);
+ upper_layer->mnt = upper_mnt;
+ upper_layer->idx = 0;
+ upper_layer->fsid = 0;
+
+ /*
+ * Inherit SB_NOSEC flag from upperdir.
+ *
+ * This optimization changes behavior when a security related attribute
+ * (suid/sgid/security.*) is changed on an underlying layer. This is
+ * okay because we don't yet have guarantees in that case, but it will
+ * need careful treatment once we want to honour changes to underlying
+ * filesystems.
+ */
+ if (upper_mnt->mnt_sb->s_flags & SB_NOSEC)
+ sb->s_flags |= SB_NOSEC;
+
+ if (ovl_inuse_trylock(ovl_upper_mnt(ofs)->mnt_root)) {
+ ofs->upperdir_locked = true;
+ } else {
+ err = ovl_report_in_use(ofs, "upperdir");
+ if (err)
+ goto out;
+ }
+
+ err = 0;
+out:
+ return err;
+}
+
+/*
+ * Returns 1 if RENAME_WHITEOUT is supported, 0 if not supported and
+ * negative values if error is encountered.
+ */
+static int ovl_check_rename_whiteout(struct ovl_fs *ofs)
+{
+ struct dentry *workdir = ofs->workdir;
+ struct inode *dir = d_inode(workdir);
+ struct dentry *temp;
+ struct dentry *dest;
+ struct dentry *whiteout;
+ struct name_snapshot name;
+ int err;
+
+ inode_lock_nested(dir, I_MUTEX_PARENT);
+
+ temp = ovl_create_temp(ofs, workdir, OVL_CATTR(S_IFREG | 0));
+ err = PTR_ERR(temp);
+ if (IS_ERR(temp))
+ goto out_unlock;
+
+ dest = ovl_lookup_temp(ofs, workdir);
+ err = PTR_ERR(dest);
+ if (IS_ERR(dest)) {
+ dput(temp);
+ goto out_unlock;
+ }
+
+ /* Name is inline and stable - using snapshot as a copy helper */
+ take_dentry_name_snapshot(&name, temp);
+ err = ovl_do_rename(ofs, dir, temp, dir, dest, RENAME_WHITEOUT);
+ if (err) {
+ if (err == -EINVAL)
+ err = 0;
+ goto cleanup_temp;
+ }
+
+ whiteout = ovl_lookup_upper(ofs, name.name.name, workdir, name.name.len);
+ err = PTR_ERR(whiteout);
+ if (IS_ERR(whiteout))
+ goto cleanup_temp;
+
+ err = ovl_is_whiteout(whiteout);
+
+ /* Best effort cleanup of whiteout and temp file */
+ if (err)
+ ovl_cleanup(ofs, dir, whiteout);
+ dput(whiteout);
+
+cleanup_temp:
+ ovl_cleanup(ofs, dir, temp);
+ release_dentry_name_snapshot(&name);
+ dput(temp);
+ dput(dest);
+
+out_unlock:
+ inode_unlock(dir);
+
+ return err;
+}
+
+static struct dentry *ovl_lookup_or_create(struct ovl_fs *ofs,
+ struct dentry *parent,
+ const char *name, umode_t mode)
+{
+ size_t len = strlen(name);
+ struct dentry *child;
+
+ inode_lock_nested(parent->d_inode, I_MUTEX_PARENT);
+ child = ovl_lookup_upper(ofs, name, parent, len);
+ if (!IS_ERR(child) && !child->d_inode)
+ child = ovl_create_real(ofs, parent->d_inode, child,
+ OVL_CATTR(mode));
+ inode_unlock(parent->d_inode);
+ dput(parent);
+
+ return child;
+}
+
+/*
+ * Creates $workdir/work/incompat/volatile/dirty file if it is not already
+ * present.
+ */
+static int ovl_create_volatile_dirty(struct ovl_fs *ofs)
+{
+ unsigned int ctr;
+ struct dentry *d = dget(ofs->workbasedir);
+ static const char *const volatile_path[] = {
+ OVL_WORKDIR_NAME, "incompat", "volatile", "dirty"
+ };
+ const char *const *name = volatile_path;
+
+ for (ctr = ARRAY_SIZE(volatile_path); ctr; ctr--, name++) {
+ d = ovl_lookup_or_create(ofs, d, *name, ctr > 1 ? S_IFDIR : S_IFREG);
+ if (IS_ERR(d))
+ return PTR_ERR(d);
+ }
+ dput(d);
+ return 0;
+}
+
+static int ovl_make_workdir(struct super_block *sb, struct ovl_fs *ofs,
+ const struct path *workpath)
+{
+ struct vfsmount *mnt = ovl_upper_mnt(ofs);
+ struct dentry *workdir;
+ struct file *tmpfile;
+ bool rename_whiteout;
+ bool d_type;
+ int fh_type;
+ int err;
+
+ err = mnt_want_write(mnt);
+ if (err)
+ return err;
+
+ workdir = ovl_workdir_create(ofs, OVL_WORKDIR_NAME, false);
+ err = PTR_ERR(workdir);
+ if (IS_ERR_OR_NULL(workdir))
+ goto out;
+
+ ofs->workdir = workdir;
+
+ err = ovl_setup_trap(sb, ofs->workdir, &ofs->workdir_trap, "workdir");
+ if (err)
+ goto out;
+
+ /*
+ * Upper should support d_type, else whiteouts are visible. Given
+ * workdir and upper are on same fs, we can do iterate_dir() on
+ * workdir. This check requires successful creation of workdir in
+ * previous step.
+ */
+ err = ovl_check_d_type_supported(workpath);
+ if (err < 0)
+ goto out;
+
+ d_type = err;
+ if (!d_type)
+ pr_warn("upper fs needs to support d_type.\n");
+
+ /* Check if upper/work fs supports O_TMPFILE */
+ tmpfile = ovl_do_tmpfile(ofs, ofs->workdir, S_IFREG | 0);
+ ofs->tmpfile = !IS_ERR(tmpfile);
+ if (ofs->tmpfile)
+ fput(tmpfile);
+ else
+ pr_warn("upper fs does not support tmpfile.\n");
+
+
+ /* Check if upper/work fs supports RENAME_WHITEOUT */
+ err = ovl_check_rename_whiteout(ofs);
+ if (err < 0)
+ goto out;
+
+ rename_whiteout = err;
+ if (!rename_whiteout)
+ pr_warn("upper fs does not support RENAME_WHITEOUT.\n");
+
+ /*
+ * Check if upper/work fs supports (trusted|user).overlay.* xattr
+ */
+ err = ovl_setxattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE, "0", 1);
+ if (err) {
+ pr_warn("failed to set xattr on upper\n");
+ ofs->noxattr = true;
+ if (ovl_redirect_follow(ofs)) {
+ ofs->config.redirect_mode = OVL_REDIRECT_NOFOLLOW;
+ pr_warn("...falling back to redirect_dir=nofollow.\n");
+ }
+ if (ofs->config.metacopy) {
+ ofs->config.metacopy = false;
+ pr_warn("...falling back to metacopy=off.\n");
+ }
+ if (ofs->config.index) {
+ ofs->config.index = false;
+ pr_warn("...falling back to index=off.\n");
+ }
+ if (ovl_has_fsid(ofs)) {
+ ofs->config.uuid = OVL_UUID_NULL;
+ pr_warn("...falling back to uuid=null.\n");
+ }
+ /*
+ * xattr support is required for persistent st_ino.
+ * Without persistent st_ino, xino=auto falls back to xino=off.
+ */
+ if (ofs->config.xino == OVL_XINO_AUTO) {
+ ofs->config.xino = OVL_XINO_OFF;
+ pr_warn("...falling back to xino=off.\n");
+ }
+ if (err == -EPERM && !ofs->config.userxattr)
+ pr_info("try mounting with 'userxattr' option\n");
+ err = 0;
+ } else {
+ ovl_removexattr(ofs, ofs->workdir, OVL_XATTR_OPAQUE);
+ }
+
+ /*
+ * We allowed sub-optimal upper fs configuration and don't want to break
+ * users over kernel upgrade, but we never allowed remote upper fs, so
+ * we can enforce strict requirements for remote upper fs.
+ */
+ if (ovl_dentry_remote(ofs->workdir) &&
+ (!d_type || !rename_whiteout || ofs->noxattr)) {
+ pr_err("upper fs missing required features.\n");
+ err = -EINVAL;
+ goto out;
+ }
+
+ /*
+ * For volatile mount, create a incompat/volatile/dirty file to keep
+ * track of it.
+ */
+ if (ofs->config.ovl_volatile) {
+ err = ovl_create_volatile_dirty(ofs);
+ if (err < 0) {
+ pr_err("Failed to create volatile/dirty file.\n");
+ goto out;
+ }
+ }
+
+ /* Check if upper/work fs supports file handles */
+ fh_type = ovl_can_decode_fh(ofs->workdir->d_sb);
+ if (ofs->config.index && !fh_type) {
+ ofs->config.index = false;
+ pr_warn("upper fs does not support file handles, falling back to index=off.\n");
+ }
+ ofs->nofh |= !fh_type;
+
+ /* Check if upper fs has 32bit inode numbers */
+ if (fh_type != FILEID_INO32_GEN)
+ ofs->xino_mode = -1;
+
+ /* NFS export of r/w mount depends on index */
+ if (ofs->config.nfs_export && !ofs->config.index) {
+ pr_warn("NFS export requires \"index=on\", falling back to nfs_export=off.\n");
+ ofs->config.nfs_export = false;
+ }
+out:
+ mnt_drop_write(mnt);
+ return err;
+}
+
+static int ovl_get_workdir(struct super_block *sb, struct ovl_fs *ofs,
+ const struct path *upperpath,
+ const struct path *workpath)
+{
+ int err;
+
+ err = -EINVAL;
+ if (upperpath->mnt != workpath->mnt) {
+ pr_err("workdir and upperdir must reside under the same mount\n");
+ return err;
+ }
+ if (!ovl_workdir_ok(workpath->dentry, upperpath->dentry)) {
+ pr_err("workdir and upperdir must be separate subtrees\n");
+ return err;
+ }
+
+ ofs->workbasedir = dget(workpath->dentry);
+
+ if (ovl_inuse_trylock(ofs->workbasedir)) {
+ ofs->workdir_locked = true;
+ } else {
+ err = ovl_report_in_use(ofs, "workdir");
+ if (err)
+ return err;
+ }
+
+ err = ovl_setup_trap(sb, ofs->workbasedir, &ofs->workbasedir_trap,
+ "workdir");
+ if (err)
+ return err;
+
+ return ovl_make_workdir(sb, ofs, workpath);
+}
+
+static int ovl_get_indexdir(struct super_block *sb, struct ovl_fs *ofs,
+ struct ovl_entry *oe, const struct path *upperpath)
+{
+ struct vfsmount *mnt = ovl_upper_mnt(ofs);
+ struct dentry *indexdir;
+ int err;
+
+ err = mnt_want_write(mnt);
+ if (err)
+ return err;
+
+ /* Verify lower root is upper root origin */
+ err = ovl_verify_origin(ofs, upperpath->dentry,
+ ovl_lowerstack(oe)->dentry, true);
+ if (err) {
+ pr_err("failed to verify upper root origin\n");
+ goto out;
+ }
+
+ /* index dir will act also as workdir */
+ iput(ofs->workdir_trap);
+ ofs->workdir_trap = NULL;
+ dput(ofs->workdir);
+ ofs->workdir = NULL;
+ indexdir = ovl_workdir_create(ofs, OVL_INDEXDIR_NAME, true);
+ if (IS_ERR(indexdir)) {
+ err = PTR_ERR(indexdir);
+ } else if (indexdir) {
+ ofs->indexdir = indexdir;
+ ofs->workdir = dget(indexdir);
+
+ err = ovl_setup_trap(sb, ofs->indexdir, &ofs->indexdir_trap,
+ "indexdir");
+ if (err)
+ goto out;
+
+ /*
+ * Verify upper root is exclusively associated with index dir.
+ * Older kernels stored upper fh in ".overlay.origin"
+ * xattr. If that xattr exists, verify that it is a match to
+ * upper dir file handle. In any case, verify or set xattr
+ * ".overlay.upper" to indicate that index may have
+ * directory entries.
+ */
+ if (ovl_check_origin_xattr(ofs, ofs->indexdir)) {
+ err = ovl_verify_set_fh(ofs, ofs->indexdir,
+ OVL_XATTR_ORIGIN,
+ upperpath->dentry, true, false);
+ if (err)
+ pr_err("failed to verify index dir 'origin' xattr\n");
+ }
+ err = ovl_verify_upper(ofs, ofs->indexdir, upperpath->dentry,
+ true);
+ if (err)
+ pr_err("failed to verify index dir 'upper' xattr\n");
+
+ /* Cleanup bad/stale/orphan index entries */
+ if (!err)
+ err = ovl_indexdir_cleanup(ofs);
+ }
+ if (err || !ofs->indexdir)
+ pr_warn("try deleting index dir or mounting with '-o index=off' to disable inodes index.\n");
+
+out:
+ mnt_drop_write(mnt);
+ return err;
+}
+
+static bool ovl_lower_uuid_ok(struct ovl_fs *ofs, const uuid_t *uuid)
+{
+ unsigned int i;
+
+ if (!ofs->config.nfs_export && !ovl_upper_mnt(ofs))
+ return true;
+
+ /*
+ * We allow using single lower with null uuid for index and nfs_export
+ * for example to support those features with single lower squashfs.
+ * To avoid regressions in setups of overlay with re-formatted lower
+ * squashfs, do not allow decoding origin with lower null uuid unless
+ * user opted-in to one of the new features that require following the
+ * lower inode of non-dir upper.
+ */
+ if (ovl_allow_offline_changes(ofs) && uuid_is_null(uuid))
+ return false;
+
+ for (i = 0; i < ofs->numfs; i++) {
+ /*
+ * We use uuid to associate an overlay lower file handle with a
+ * lower layer, so we can accept lower fs with null uuid as long
+ * as all lower layers with null uuid are on the same fs.
+ * if we detect multiple lower fs with the same uuid, we
+ * disable lower file handle decoding on all of them.
+ */
+ if (ofs->fs[i].is_lower &&
+ uuid_equal(&ofs->fs[i].sb->s_uuid, uuid)) {
+ ofs->fs[i].bad_uuid = true;
+ return false;
+ }
+ }
+ return true;
+}
+
+/* Get a unique fsid for the layer */
+static int ovl_get_fsid(struct ovl_fs *ofs, const struct path *path)
+{
+ struct super_block *sb = path->mnt->mnt_sb;
+ unsigned int i;
+ dev_t dev;
+ int err;
+ bool bad_uuid = false;
+ bool warn = false;
+
+ for (i = 0; i < ofs->numfs; i++) {
+ if (ofs->fs[i].sb == sb)
+ return i;
+ }
+
+ if (!ovl_lower_uuid_ok(ofs, &sb->s_uuid)) {
+ bad_uuid = true;
+ if (ofs->config.xino == OVL_XINO_AUTO) {
+ ofs->config.xino = OVL_XINO_OFF;
+ warn = true;
+ }
+ if (ofs->config.index || ofs->config.nfs_export) {
+ ofs->config.index = false;
+ ofs->config.nfs_export = false;
+ warn = true;
+ }
+ if (warn) {
+ pr_warn("%s uuid detected in lower fs '%pd2', falling back to xino=%s,index=off,nfs_export=off.\n",
+ uuid_is_null(&sb->s_uuid) ? "null" :
+ "conflicting",
+ path->dentry, ovl_xino_mode(&ofs->config));
+ }
+ }
+
+ err = get_anon_bdev(&dev);
+ if (err) {
+ pr_err("failed to get anonymous bdev for lowerpath\n");
+ return err;
+ }
+
+ ofs->fs[ofs->numfs].sb = sb;
+ ofs->fs[ofs->numfs].pseudo_dev = dev;
+ ofs->fs[ofs->numfs].bad_uuid = bad_uuid;
+
+ return ofs->numfs++;
+}
+
+/*
+ * The fsid after the last lower fsid is used for the data layers.
+ * It is a "null fs" with a null sb, null uuid, and no pseudo dev.
+ */
+static int ovl_get_data_fsid(struct ovl_fs *ofs)
+{
+ return ofs->numfs;
+}
+
+
+static int ovl_get_layers(struct super_block *sb, struct ovl_fs *ofs,
+ struct ovl_fs_context *ctx, struct ovl_layer *layers)
+{
+ int err;
+ unsigned int i;
+ size_t nr_merged_lower;
+
+ ofs->fs = kcalloc(ctx->nr + 2, sizeof(struct ovl_sb), GFP_KERNEL);
+ if (ofs->fs == NULL)
+ return -ENOMEM;
+
+ /*
+ * idx/fsid 0 are reserved for upper fs even with lower only overlay
+ * and the last fsid is reserved for "null fs" of the data layers.
+ */
+ ofs->numfs++;
+
+ /*
+ * All lower layers that share the same fs as upper layer, use the same
+ * pseudo_dev as upper layer. Allocate fs[0].pseudo_dev even for lower
+ * only overlay to simplify ovl_fs_free().
+ * is_lower will be set if upper fs is shared with a lower layer.
+ */
+ err = get_anon_bdev(&ofs->fs[0].pseudo_dev);
+ if (err) {
+ pr_err("failed to get anonymous bdev for upper fs\n");
+ return err;
+ }
+
+ if (ovl_upper_mnt(ofs)) {
+ ofs->fs[0].sb = ovl_upper_mnt(ofs)->mnt_sb;
+ ofs->fs[0].is_lower = false;
+ }
+
+ nr_merged_lower = ctx->nr - ctx->nr_data;
+ for (i = 0; i < ctx->nr; i++) {
+ struct ovl_fs_context_layer *l = &ctx->lower[i];
+ struct vfsmount *mnt;
+ struct inode *trap;
+ int fsid;
+
+ if (i < nr_merged_lower)
+ fsid = ovl_get_fsid(ofs, &l->path);
+ else
+ fsid = ovl_get_data_fsid(ofs);
+ if (fsid < 0)
+ return fsid;
+
+ /*
+ * Check if lower root conflicts with this overlay layers before
+ * checking if it is in-use as upperdir/workdir of "another"
+ * mount, because we do not bother to check in ovl_is_inuse() if
+ * the upperdir/workdir is in fact in-use by our
+ * upperdir/workdir.
+ */
+ err = ovl_setup_trap(sb, l->path.dentry, &trap, "lowerdir");
+ if (err)
+ return err;
+
+ if (ovl_is_inuse(l->path.dentry)) {
+ err = ovl_report_in_use(ofs, "lowerdir");
+ if (err) {
+ iput(trap);
+ return err;
+ }
+ }
+
+ mnt = clone_private_mount(&l->path);
+ err = PTR_ERR(mnt);
+ if (IS_ERR(mnt)) {
+ pr_err("failed to clone lowerpath\n");
+ iput(trap);
+ return err;
+ }
+
+ /*
+ * Make lower layers R/O. That way fchmod/fchown on lower file
+ * will fail instead of modifying lower fs.
+ */
+ mnt->mnt_flags |= MNT_READONLY | MNT_NOATIME;
+
+ layers[ofs->numlayer].trap = trap;
+ layers[ofs->numlayer].mnt = mnt;
+ layers[ofs->numlayer].idx = ofs->numlayer;
+ layers[ofs->numlayer].fsid = fsid;
+ layers[ofs->numlayer].fs = &ofs->fs[fsid];
+ /* Store for printing lowerdir=... in ovl_show_options() */
+ ofs->config.lowerdirs[ofs->numlayer] = l->name;
+ l->name = NULL;
+ ofs->numlayer++;
+ ofs->fs[fsid].is_lower = true;
+ }
+
+ /*
+ * When all layers on same fs, overlay can use real inode numbers.
+ * With mount option "xino=<on|auto>", mounter declares that there are
+ * enough free high bits in underlying fs to hold the unique fsid.
+ * If overlayfs does encounter underlying inodes using the high xino
+ * bits reserved for fsid, it emits a warning and uses the original
+ * inode number or a non persistent inode number allocated from a
+ * dedicated range.
+ */
+ if (ofs->numfs - !ovl_upper_mnt(ofs) == 1) {
+ if (ofs->config.xino == OVL_XINO_ON)
+ pr_info("\"xino=on\" is useless with all layers on same fs, ignore.\n");
+ ofs->xino_mode = 0;
+ } else if (ofs->config.xino == OVL_XINO_OFF) {
+ ofs->xino_mode = -1;
+ } else if (ofs->xino_mode < 0) {
+ /*
+ * This is a roundup of number of bits needed for encoding
+ * fsid, where fsid 0 is reserved for upper fs (even with
+ * lower only overlay) +1 extra bit is reserved for the non
+ * persistent inode number range that is used for resolving
+ * xino lower bits overflow.
+ */
+ BUILD_BUG_ON(ilog2(OVL_MAX_STACK) > 30);
+ ofs->xino_mode = ilog2(ofs->numfs - 1) + 2;
+ }
+
+ if (ofs->xino_mode > 0) {
+ pr_info("\"xino\" feature enabled using %d upper inode bits.\n",
+ ofs->xino_mode);
+ }
+
+ return 0;
+}
+
+static struct ovl_entry *ovl_get_lowerstack(struct super_block *sb,
+ struct ovl_fs_context *ctx,
+ struct ovl_fs *ofs,
+ struct ovl_layer *layers)
+{
+ int err;
+ unsigned int i;
+ size_t nr_merged_lower;
+ struct ovl_entry *oe;
+ struct ovl_path *lowerstack;
+
+ struct ovl_fs_context_layer *l;
+
+ if (!ofs->config.upperdir && ctx->nr == 1) {
+ pr_err("at least 2 lowerdir are needed while upperdir nonexistent\n");
+ return ERR_PTR(-EINVAL);
+ }
+
+ err = -EINVAL;
+ for (i = 0; i < ctx->nr; i++) {
+ l = &ctx->lower[i];
+
+ err = ovl_lower_dir(l->name, &l->path, ofs, &sb->s_stack_depth);
+ if (err)
+ return ERR_PTR(err);
+ }
+
+ err = -EINVAL;
+ sb->s_stack_depth++;
+ if (sb->s_stack_depth > FILESYSTEM_MAX_STACK_DEPTH) {
+ pr_err("maximum fs stacking depth exceeded\n");
+ return ERR_PTR(err);
+ }
+
+ err = ovl_get_layers(sb, ofs, ctx, layers);
+ if (err)
+ return ERR_PTR(err);
+
+ err = -ENOMEM;
+ /* Data-only layers are not merged in root directory */
+ nr_merged_lower = ctx->nr - ctx->nr_data;
+ oe = ovl_alloc_entry(nr_merged_lower);
+ if (!oe)
+ return ERR_PTR(err);
+
+ lowerstack = ovl_lowerstack(oe);
+ for (i = 0; i < nr_merged_lower; i++) {
+ l = &ctx->lower[i];
+ lowerstack[i].dentry = dget(l->path.dentry);
+ lowerstack[i].layer = &ofs->layers[i + 1];
+ }
+ ofs->numdatalayer = ctx->nr_data;
+
+ return oe;
+}
+
+/*
+ * Check if this layer root is a descendant of:
+ * - another layer of this overlayfs instance
+ * - upper/work dir of any overlayfs instance
+ */
+static int ovl_check_layer(struct super_block *sb, struct ovl_fs *ofs,
+ struct dentry *dentry, const char *name,
+ bool is_lower)
+{
+ struct dentry *next = dentry, *parent;
+ int err = 0;
+
+ if (!dentry)
+ return 0;
+
+ parent = dget_parent(next);
+
+ /* Walk back ancestors to root (inclusive) looking for traps */
+ while (!err && parent != next) {
+ if (is_lower && ovl_lookup_trap_inode(sb, parent)) {
+ err = -ELOOP;
+ pr_err("overlapping %s path\n", name);
+ } else if (ovl_is_inuse(parent)) {
+ err = ovl_report_in_use(ofs, name);
+ }
+ next = parent;
+ parent = dget_parent(next);
+ dput(next);
+ }
+
+ dput(parent);
+
+ return err;
+}
+
+/*
+ * Check if any of the layers or work dirs overlap.
+ */
+static int ovl_check_overlapping_layers(struct super_block *sb,
+ struct ovl_fs *ofs)
+{
+ int i, err;
+
+ if (ovl_upper_mnt(ofs)) {
+ err = ovl_check_layer(sb, ofs, ovl_upper_mnt(ofs)->mnt_root,
+ "upperdir", false);
+ if (err)
+ return err;
+
+ /*
+ * Checking workbasedir avoids hitting ovl_is_inuse(parent) of
+ * this instance and covers overlapping work and index dirs,
+ * unless work or index dir have been moved since created inside
+ * workbasedir. In that case, we already have their traps in
+ * inode cache and we will catch that case on lookup.
+ */
+ err = ovl_check_layer(sb, ofs, ofs->workbasedir, "workdir",
+ false);
+ if (err)
+ return err;
+ }
+
+ for (i = 1; i < ofs->numlayer; i++) {
+ err = ovl_check_layer(sb, ofs,
+ ofs->layers[i].mnt->mnt_root,
+ "lowerdir", true);
+ if (err)
+ return err;
+ }
+
+ return 0;
+}
+
+static struct dentry *ovl_get_root(struct super_block *sb,
+ struct dentry *upperdentry,
+ struct ovl_entry *oe)
+{
+ struct dentry *root;
+ struct ovl_path *lowerpath = ovl_lowerstack(oe);
+ unsigned long ino = d_inode(lowerpath->dentry)->i_ino;
+ int fsid = lowerpath->layer->fsid;
+ struct ovl_inode_params oip = {
+ .upperdentry = upperdentry,
+ .oe = oe,
+ };
+
+ root = d_make_root(ovl_new_inode(sb, S_IFDIR, 0));
+ if (!root)
+ return NULL;
+
+ if (upperdentry) {
+ /* Root inode uses upper st_ino/i_ino */
+ ino = d_inode(upperdentry)->i_ino;
+ fsid = 0;
+ ovl_dentry_set_upper_alias(root);
+ if (ovl_is_impuredir(sb, upperdentry))
+ ovl_set_flag(OVL_IMPURE, d_inode(root));
+ }
+
+ /* Root is always merge -> can have whiteouts */
+ ovl_set_flag(OVL_WHITEOUTS, d_inode(root));
+ ovl_dentry_set_flag(OVL_E_CONNECTED, root);
+ ovl_set_upperdata(d_inode(root));
+ ovl_inode_init(d_inode(root), &oip, ino, fsid);
+ ovl_dentry_init_flags(root, upperdentry, oe, DCACHE_OP_WEAK_REVALIDATE);
+ /* root keeps a reference of upperdentry */
+ dget(upperdentry);
+
+ return root;
+}
+
+int ovl_fill_super(struct super_block *sb, struct fs_context *fc)
+{
+ struct ovl_fs *ofs = sb->s_fs_info;
+ struct ovl_fs_context *ctx = fc->fs_private;
+ struct dentry *root_dentry;
+ struct ovl_entry *oe;
+ struct ovl_layer *layers;
+ struct cred *cred;
+ int err;
+
+ err = -EIO;
+ if (WARN_ON(fc->user_ns != current_user_ns()))
+ goto out_err;
+
+ sb->s_d_op = &ovl_dentry_operations;
+
+ err = -ENOMEM;
+ ofs->creator_cred = cred = prepare_creds();
+ if (!cred)
+ goto out_err;
+
+ err = ovl_fs_params_verify(ctx, &ofs->config);
+ if (err)
+ goto out_err;
+
+ err = -EINVAL;
+ if (ctx->nr == 0) {
+ if (!(fc->sb_flags & SB_SILENT))
+ pr_err("missing 'lowerdir'\n");
+ goto out_err;
+ }
+
+ err = -ENOMEM;
+ layers = kcalloc(ctx->nr + 1, sizeof(struct ovl_layer), GFP_KERNEL);
+ if (!layers)
+ goto out_err;
+
+ ofs->config.lowerdirs = kcalloc(ctx->nr + 1, sizeof(char *), GFP_KERNEL);
+ if (!ofs->config.lowerdirs) {
+ kfree(layers);
+ goto out_err;
+ }
+ ofs->layers = layers;
+ /*
+ * Layer 0 is reserved for upper even if there's no upper.
+ * For consistency, config.lowerdirs[0] is NULL.
+ */
+ ofs->numlayer = 1;
+
+ sb->s_stack_depth = 0;
+ sb->s_maxbytes = MAX_LFS_FILESIZE;
+ atomic_long_set(&ofs->last_ino, 1);
+ /* Assume underlying fs uses 32bit inodes unless proven otherwise */
+ if (ofs->config.xino != OVL_XINO_OFF) {
+ ofs->xino_mode = BITS_PER_LONG - 32;
+ if (!ofs->xino_mode) {
+ pr_warn("xino not supported on 32bit kernel, falling back to xino=off.\n");
+ ofs->config.xino = OVL_XINO_OFF;
+ }
+ }
+
+ /* alloc/destroy_inode needed for setting up traps in inode cache */
+ sb->s_op = &ovl_super_operations;
+
+ if (ofs->config.upperdir) {
+ struct super_block *upper_sb;
+
+ err = -EINVAL;
+ if (!ofs->config.workdir) {
+ pr_err("missing 'workdir'\n");
+ goto out_err;
+ }
+
+ err = ovl_get_upper(sb, ofs, &layers[0], &ctx->upper);
+ if (err)
+ goto out_err;
+
+ upper_sb = ovl_upper_mnt(ofs)->mnt_sb;
+ if (!ovl_should_sync(ofs)) {
+ ofs->errseq = errseq_sample(&upper_sb->s_wb_err);
+ if (errseq_check(&upper_sb->s_wb_err, ofs->errseq)) {
+ err = -EIO;
+ pr_err("Cannot mount volatile when upperdir has an unseen error. Sync upperdir fs to clear state.\n");
+ goto out_err;
+ }
+ }
+
+ err = ovl_get_workdir(sb, ofs, &ctx->upper, &ctx->work);
+ if (err)
+ goto out_err;
+
+ if (!ofs->workdir)
+ sb->s_flags |= SB_RDONLY;
+
+ sb->s_stack_depth = upper_sb->s_stack_depth;
+ sb->s_time_gran = upper_sb->s_time_gran;
+ }
+ oe = ovl_get_lowerstack(sb, ctx, ofs, layers);
+ err = PTR_ERR(oe);
+ if (IS_ERR(oe))
+ goto out_err;
+
+ /* If the upper fs is nonexistent, we mark overlayfs r/o too */
+ if (!ovl_upper_mnt(ofs))
+ sb->s_flags |= SB_RDONLY;
+
+ if (!ovl_origin_uuid(ofs) && ofs->numfs > 1) {
+ pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=null.\n");
+ ofs->config.uuid = OVL_UUID_NULL;
+ } else if (ovl_has_fsid(ofs) && ovl_upper_mnt(ofs)) {
+ /* Use per instance persistent uuid/fsid */
+ ovl_init_uuid_xattr(sb, ofs, &ctx->upper);
+ }
+
+ if (!ovl_force_readonly(ofs) && ofs->config.index) {
+ err = ovl_get_indexdir(sb, ofs, oe, &ctx->upper);
+ if (err)
+ goto out_free_oe;
+
+ /* Force r/o mount with no index dir */
+ if (!ofs->indexdir)
+ sb->s_flags |= SB_RDONLY;
+ }
+
+ err = ovl_check_overlapping_layers(sb, ofs);
+ if (err)
+ goto out_free_oe;
+
+ /* Show index=off in /proc/mounts for forced r/o mount */
+ if (!ofs->indexdir) {
+ ofs->config.index = false;
+ if (ovl_upper_mnt(ofs) && ofs->config.nfs_export) {
+ pr_warn("NFS export requires an index dir, falling back to nfs_export=off.\n");
+ ofs->config.nfs_export = false;
+ }
+ }
+
+ if (ofs->config.metacopy && ofs->config.nfs_export) {
+ pr_warn("NFS export is not supported with metadata only copy up, falling back to nfs_export=off.\n");
+ ofs->config.nfs_export = false;
+ }
+
+ /*
+ * Support encoding decodable file handles with nfs_export=on
+ * and encoding non-decodable file handles with nfs_export=off
+ * if all layers support file handles.
+ */
+ if (ofs->config.nfs_export)
+ sb->s_export_op = &ovl_export_operations;
+ else if (!ofs->nofh)
+ sb->s_export_op = &ovl_export_fid_operations;
+
+ /* Never override disk quota limits or use reserved space */
+ cap_lower(cred->cap_effective, CAP_SYS_RESOURCE);
+
+ sb->s_magic = OVERLAYFS_SUPER_MAGIC;
+ sb->s_xattr = ofs->config.userxattr ? ovl_user_xattr_handlers :
+ ovl_trusted_xattr_handlers;
+ sb->s_fs_info = ofs;
+ sb->s_flags |= SB_POSIXACL;
+ sb->s_iflags |= SB_I_SKIP_SYNC;
+
+ err = -ENOMEM;
+ root_dentry = ovl_get_root(sb, ctx->upper.dentry, oe);
+ if (!root_dentry)
+ goto out_free_oe;
+
+ sb->s_root = root_dentry;
+
+ return 0;
+
+out_free_oe:
+ ovl_free_entry(oe);
+out_err:
+ ovl_free_fs(ofs);
+ sb->s_fs_info = NULL;
+ return err;
+}
+
+struct file_system_type ovl_fs_type = {
+ .owner = THIS_MODULE,
+ .name = "overlay",
+ .init_fs_context = ovl_init_fs_context,
+ .parameters = ovl_parameter_spec,
+ .fs_flags = FS_USERNS_MOUNT,
+ .kill_sb = kill_anon_super,
+};
+MODULE_ALIAS_FS("overlay");
+
+static void ovl_inode_init_once(void *foo)
+{
+ struct ovl_inode *oi = foo;
+
+ inode_init_once(&oi->vfs_inode);
+}
+
+static int __init ovl_init(void)
+{
+ int err;
+
+ ovl_inode_cachep = kmem_cache_create("ovl_inode",
+ sizeof(struct ovl_inode), 0,
+ (SLAB_RECLAIM_ACCOUNT|
+ SLAB_MEM_SPREAD|SLAB_ACCOUNT),
+ ovl_inode_init_once);
+ if (ovl_inode_cachep == NULL)
+ return -ENOMEM;
+
+ err = ovl_aio_request_cache_init();
+ if (!err) {
+ err = register_filesystem(&ovl_fs_type);
+ if (!err)
+ return 0;
+
+ ovl_aio_request_cache_destroy();
+ }
+ kmem_cache_destroy(ovl_inode_cachep);
+
+ return err;
+}
+
+static void __exit ovl_exit(void)
+{
+ unregister_filesystem(&ovl_fs_type);
+
+ /*
+ * Make sure all delayed rcu free inodes are flushed before we
+ * destroy cache.
+ */
+ rcu_barrier();
+ kmem_cache_destroy(ovl_inode_cachep);
+ ovl_aio_request_cache_destroy();
+}
+
+module_init(ovl_init);
+module_exit(ovl_exit);