fs/overlayfs/file.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 2017 Red Hat, Inc.
  */

 #include <linux/cred.h>
 #include <linux/file.h>
 #include <linux/mount.h>
 #include <linux/xattr.h>
 #include <linux/uio.h>
 #include <linux/uaccess.h>
 #include <linux/splice.h>
 #include <linux/security.h>
 #include <linux/mm.h>
 #include <linux/fs.h>
 #include "overlayfs.h"

 struct ovl_aio_req {
 	struct kiocb iocb;
 	struct kiocb *orig_iocb;
 	struct fd fd;
 };

 static struct kmem_cache *ovl_aio_request_cachep;

 static char ovl_whatisit(struct inode *inode, struct inode *realinode)
 {
 	if (realinode != ovl_inode_upper(inode))
 		return 'l';
 	if (ovl_has_upperdata(inode))
 		return 'u';
 	else
 		return 'm';
 }

 /* No atime modificaton nor notify on underlying */
 #define OVL_OPEN_FLAGS (O_NOATIME | FMODE_NONOTIFY)

 static struct file *ovl_open_realfile(const struct file *file,
 				      struct inode *realinode)
 {
 	struct inode *inode = file_inode(file);
 	struct file *realfile;
 	const struct cred *old_cred;
 	int flags = file->f_flags | OVL_OPEN_FLAGS;
 	int acc_mode = ACC_MODE(flags);
 	int err;

 	if (flags & O_APPEND)
 		acc_mode |= MAY_APPEND;

 	old_cred = ovl_override_creds(inode->i_sb);
 	err = inode_permission(&init_user_ns, realinode, MAY_OPEN | acc_mode);
 	if (err) {
 		realfile = ERR_PTR(err);
 	} else {
 		if (!inode_owner_or_capable(&init_user_ns, realinode))
 			flags &= ~O_NOATIME;

 		realfile = open_with_fake_path(&file->f_path, flags, realinode,
 					       current_cred());
 	}
 	revert_creds(old_cred);

 	pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
 		 file, file, ovl_whatisit(inode, realinode), file->f_flags,
 		 realfile, IS_ERR(realfile) ? 0 : realfile->f_flags);

 	return realfile;
 }

 #define OVL_SETFL_MASK (O_APPEND | O_NONBLOCK | O_NDELAY | O_DIRECT)

 static int ovl_change_flags(struct file *file, unsigned int flags)
 {
 	struct inode *inode = file_inode(file);
 	int err;

 	flags &= OVL_SETFL_MASK;

 	if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode))
 		return -EPERM;

 	if (flags & O_DIRECT) {
 		if (!file->f_mapping->a_ops ||
 		    !file->f_mapping->a_ops->direct_IO)
 			return -EINVAL;
 	}

 	if (file->f_op->check_flags) {
 		err = file->f_op->check_flags(flags);
 		if (err)
 			return err;
 	}

 	spin_lock(&file->f_lock);
 	file->f_flags = (file->f_flags & ~OVL_SETFL_MASK) | flags;
 	spin_unlock(&file->f_lock);

 	return 0;
 }

 static int ovl_real_fdget_meta(const struct file *file, struct fd *real,
 			       bool allow_meta)
 {
 	struct inode *inode = file_inode(file);
 	struct inode *realinode;

 	real->flags = 0;
 	real->file = file->private_data;

 	if (allow_meta)
 		realinode = ovl_inode_real(inode);
 	else
 		realinode = ovl_inode_realdata(inode);

 	/* Has it been copied up since we'd opened it? */
 	if (unlikely(file_inode(real->file) != realinode)) {
 		real->flags = FDPUT_FPUT;
 		real->file = ovl_open_realfile(file, realinode);

 		return PTR_ERR_OR_ZERO(real->file);
 	}

 	/* Did the flags change since open? */
 	if (unlikely((file->f_flags ^ real->file->f_flags) & ~OVL_OPEN_FLAGS))
 		return ovl_change_flags(real->file, file->f_flags);

 	return 0;
 }

 static int ovl_real_fdget(const struct file *file, struct fd *real)
 {
 	if (d_is_dir(file_dentry(file))) {
 		real->flags = 0;
 		real->file = ovl_dir_real_file(file, false);

 		return PTR_ERR_OR_ZERO(real->file);
 	}

 	return ovl_real_fdget_meta(file, real, false);
 }

 static int ovl_open(struct inode *inode, struct file *file)
 {
 	struct file *realfile;
 	int err;

 	err = ovl_maybe_copy_up(file_dentry(file), file->f_flags);
 	if (err)
 		return err;

 	/* No longer need these flags, so don't pass them on to underlying fs */
 	file->f_flags &= ~(O_CREAT | O_EXCL | O_NOCTTY | O_TRUNC);

 	realfile = ovl_open_realfile(file, ovl_inode_realdata(inode));
 	if (IS_ERR(realfile))
 		return PTR_ERR(realfile);

 	file->private_data = realfile;

 	return 0;
 }

 static int ovl_release(struct inode *inode, struct file *file)
 {
 	fput(file->private_data);

 	return 0;
 }

 static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
 {
 	struct inode *inode = file_inode(file);
 	struct fd real;
 	const struct cred *old_cred;
 	loff_t ret;

 	/*
 	 * The two special cases below do not need to involve real fs,
 	 * so we can optimizing concurrent callers.
 	 */
 	if (offset == 0) {
 		if (whence == SEEK_CUR)
 			return file->f_pos;

 		if (whence == SEEK_SET)
 			return vfs_setpos(file, 0, 0);
 	}

 	ret = ovl_real_fdget(file, &real);
 	if (ret)
 		return ret;

 	/*
 	 * Overlay file f_pos is the master copy that is preserved
 	 * through copy up and modified on read/write, but only real
 	 * fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose
 	 * limitations that are more strict than ->s_maxbytes for specific
 	 * files, so we use the real file to perform seeks.
 	 */
 	ovl_inode_lock(inode);
 	real.file->f_pos = file->f_pos;

 	old_cred = ovl_override_creds(inode->i_sb);
 	ret = vfs_llseek(real.file, offset, whence);
 	revert_creds(old_cred);

 	file->f_pos = real.file->f_pos;
 	ovl_inode_unlock(inode);

 	fdput(real);

 	return ret;
 }

 static void ovl_file_accessed(struct file *file)
 {
 	struct inode *inode, *upperinode;

 	if (file->f_flags & O_NOATIME)
 		return;

 	inode = file_inode(file);
 	upperinode = ovl_inode_upper(inode);

 	if (!upperinode)
 		return;

 	if ((!timespec64_equal(&inode->i_mtime, &upperinode->i_mtime) ||
 	     !timespec64_equal(&inode->i_ctime, &upperinode->i_ctime))) {
 		inode->i_mtime = upperinode->i_mtime;
 		inode->i_ctime = upperinode->i_ctime;
 	}

 	touch_atime(&file->f_path);
 }

 static rwf_t ovl_iocb_to_rwf(int ifl)
 {
 	rwf_t flags = 0;

 	if (ifl & IOCB_NOWAIT)
 		flags |= RWF_NOWAIT;
 	if (ifl & IOCB_HIPRI)
 		flags |= RWF_HIPRI;
 	if (ifl & IOCB_DSYNC)
 		flags |= RWF_DSYNC;
 	if (ifl & IOCB_SYNC)
 		flags |= RWF_SYNC;

 	return flags;
 }

 static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
 {
 	struct kiocb *iocb = &aio_req->iocb;
 	struct kiocb *orig_iocb = aio_req->orig_iocb;

 	if (iocb->ki_flags & IOCB_WRITE) {
 		struct inode *inode = file_inode(orig_iocb->ki_filp);

 		/* Actually acquired in ovl_write_iter() */
 		__sb_writers_acquired(file_inode(iocb->ki_filp)->i_sb,
 				      SB_FREEZE_WRITE);
 		file_end_write(iocb->ki_filp);
 		ovl_copyattr(ovl_inode_real(inode), inode);
 	}

 	orig_iocb->ki_pos = iocb->ki_pos;
 	fdput(aio_req->fd);
 	kmem_cache_free(ovl_aio_request_cachep, aio_req);
 }

 static void ovl_aio_rw_complete(struct kiocb *iocb, long res, long res2)
 {
 	struct ovl_aio_req *aio_req = container_of(iocb,
 						   struct ovl_aio_req, iocb);
 	struct kiocb *orig_iocb = aio_req->orig_iocb;

 	ovl_aio_cleanup_handler(aio_req);
 	orig_iocb->ki_complete(orig_iocb, res, res2);
 }

 static ssize_t ovl_read_iter(struct kiocb *iocb, struct iov_iter *iter)
 {
 	struct file *file = iocb->ki_filp;
 	struct fd real;
 	const struct cred *old_cred;
 	ssize_t ret;

 	if (!iov_iter_count(iter))
 		return 0;

 	ret = ovl_real_fdget(file, &real);
 	if (ret)
 		return ret;

 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	if (is_sync_kiocb(iocb)) {
 		ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
 				    ovl_iocb_to_rwf(iocb->ki_flags));
 	} else {
 		struct ovl_aio_req *aio_req;

 		ret = -ENOMEM;
 		aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
 		if (!aio_req)
 			goto out;

 		aio_req->fd = real;
 		real.flags = 0;
 		aio_req->orig_iocb = iocb;
 		kiocb_clone(&aio_req->iocb, iocb, real.file);
 		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
 		ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
 		if (ret != -EIOCBQUEUED)
 			ovl_aio_cleanup_handler(aio_req);
 	}
 out:
 	revert_creds(old_cred);
 	ovl_file_accessed(file);

 	fdput(real);

 	return ret;
 }

 static ssize_t ovl_write_iter(struct kiocb *iocb, struct iov_iter *iter)
 {
 	struct file *file = iocb->ki_filp;
 	struct inode *inode = file_inode(file);
 	struct fd real;
 	const struct cred *old_cred;
 	ssize_t ret;
 	int ifl = iocb->ki_flags;

 	if (!iov_iter_count(iter))
 		return 0;

 	inode_lock(inode);
 	/* Update mode */
 	ovl_copyattr(ovl_inode_real(inode), inode);
 	ret = file_remove_privs(file);
 	if (ret)
 		goto out_unlock;

 	ret = ovl_real_fdget(file, &real);
 	if (ret)
 		goto out_unlock;

 	if (!ovl_should_sync(OVL_FS(inode->i_sb)))
 		ifl &= ~(IOCB_DSYNC | IOCB_SYNC);

 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	if (is_sync_kiocb(iocb)) {
 		file_start_write(real.file);
 		ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
 				     ovl_iocb_to_rwf(ifl));
 		file_end_write(real.file);
 		/* Update size */
 		ovl_copyattr(ovl_inode_real(inode), inode);
 	} else {
 		struct ovl_aio_req *aio_req;

 		ret = -ENOMEM;
 		aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
 		if (!aio_req)
 			goto out;

 		file_start_write(real.file);
 		/* Pacify lockdep, same trick as done in aio_write() */
 		__sb_writers_release(file_inode(real.file)->i_sb,
 				     SB_FREEZE_WRITE);
 		aio_req->fd = real;
 		real.flags = 0;
 		aio_req->orig_iocb = iocb;
 		kiocb_clone(&aio_req->iocb, iocb, real.file);
 		aio_req->iocb.ki_flags = ifl;
 		aio_req->iocb.ki_complete = ovl_aio_rw_complete;
 		ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
 		if (ret != -EIOCBQUEUED)
 			ovl_aio_cleanup_handler(aio_req);
 	}
 out:
 	revert_creds(old_cred);
 	fdput(real);

 out_unlock:
 	inode_unlock(inode);

 	return ret;
 }

 /*
  * Calling iter_file_splice_write() directly from overlay's f_op may deadlock
  * due to lock order inversion between pipe->mutex in iter_file_splice_write()
  * and file_start_write(real.file) in ovl_write_iter().
  *
  * So do everything ovl_write_iter() does and call iter_file_splice_write() on
  * the real file.
  */
 static ssize_t ovl_splice_write(struct pipe_inode_info *pipe, struct file *out,
 				loff_t *ppos, size_t len, unsigned int flags)
 {
 	struct fd real;
 	const struct cred *old_cred;
 	struct inode *inode = file_inode(out);
 	struct inode *realinode = ovl_inode_real(inode);
 	ssize_t ret;

 	inode_lock(inode);
 	/* Update mode */
 	ovl_copyattr(realinode, inode);
 	ret = file_remove_privs(out);
 	if (ret)
 		goto out_unlock;

 	ret = ovl_real_fdget(out, &real);
 	if (ret)
 		goto out_unlock;

 	old_cred = ovl_override_creds(inode->i_sb);
 	file_start_write(real.file);

 	ret = iter_file_splice_write(pipe, real.file, ppos, len, flags);

 	file_end_write(real.file);
 	/* Update size */
 	ovl_copyattr(realinode, inode);
 	revert_creds(old_cred);
 	fdput(real);

 out_unlock:
 	inode_unlock(inode);

 	return ret;
 }

 static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
 {
 	struct fd real;
 	const struct cred *old_cred;
 	int ret;

 	ret = ovl_sync_status(OVL_FS(file_inode(file)->i_sb));
 	if (ret <= 0)
 		return ret;

 	ret = ovl_real_fdget_meta(file, &real, !datasync);
 	if (ret)
 		return ret;

 	/* Don't sync lower file for fear of receiving EROFS error */
 	if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) {
 		old_cred = ovl_override_creds(file_inode(file)->i_sb);
 		ret = vfs_fsync_range(real.file, start, end, datasync);
 		revert_creds(old_cred);
 	}

 	fdput(real);

 	return ret;
 }

 static int ovl_mmap(struct file *file, struct vm_area_struct *vma)
 {
 	struct file *realfile = file->private_data;
 	const struct cred *old_cred;
 	int ret;

 	if (!realfile->f_op->mmap)
 		return -ENODEV;

 	if (WARN_ON(file != vma->vm_file))
 		return -EIO;

 	vma_set_file(vma, realfile);

 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	ret = call_mmap(vma->vm_file, vma);
 	revert_creds(old_cred);
 	ovl_file_accessed(file);

 	return ret;
 }

 static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
 {
 	struct inode *inode = file_inode(file);
 	struct fd real;
 	const struct cred *old_cred;
 	int ret;

 	ret = ovl_real_fdget(file, &real);
 	if (ret)
 		return ret;

 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	ret = vfs_fallocate(real.file, mode, offset, len);
 	revert_creds(old_cred);

 	/* Update size */
 	ovl_copyattr(ovl_inode_real(inode), inode);

 	fdput(real);

 	return ret;
 }

 static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
 {
 	struct fd real;
 	const struct cred *old_cred;
 	int ret;

 	ret = ovl_real_fdget(file, &real);
 	if (ret)
 		return ret;

 	old_cred = ovl_override_creds(file_inode(file)->i_sb);
 	ret = vfs_fadvise(real.file, offset, len, advice);
 	revert_creds(old_cred);

 	fdput(real);

 	return ret;
 }

 enum ovl_copyop {
 	OVL_COPY,
 	OVL_CLONE,
 	OVL_DEDUPE,
 };

 static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
 			    struct file *file_out, loff_t pos_out,
 			    loff_t len, unsigned int flags, enum ovl_copyop op)
 {
 	struct inode *inode_out = file_inode(file_out);
 	struct fd real_in, real_out;
 	const struct cred *old_cred;
 	loff_t ret;

 	ret = ovl_real_fdget(file_out, &real_out);
 	if (ret)
 		return ret;

 	ret = ovl_real_fdget(file_in, &real_in);
 	if (ret) {
 		fdput(real_out);
 		return ret;
 	}

 	old_cred = ovl_override_creds(file_inode(file_out)->i_sb);
 	switch (op) {
 	case OVL_COPY:
 		ret = vfs_copy_file_range(real_in.file, pos_in,
 					  real_out.file, pos_out, len, flags);
 		break;

 	case OVL_CLONE:
 		ret = vfs_clone_file_range(real_in.file, pos_in,
 					   real_out.file, pos_out, len, flags);
 		break;

 	case OVL_DEDUPE:
 		ret = vfs_dedupe_file_range_one(real_in.file, pos_in,
 						real_out.file, pos_out, len,
 						flags);
 		break;
 	}
 	revert_creds(old_cred);

 	/* Update size */
 	ovl_copyattr(ovl_inode_real(inode_out), inode_out);

 	fdput(real_in);
 	fdput(real_out);

 	return ret;
 }

 static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
 				   struct file *file_out, loff_t pos_out,
 				   size_t len, unsigned int flags)
 {
 	return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
 			    OVL_COPY);
 }

 static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in,
 				   struct file *file_out, loff_t pos_out,
 				   loff_t len, unsigned int remap_flags)
 {
 	enum ovl_copyop op;

 	if (remap_flags & ~(REMAP_FILE_DEDUP | REMAP_FILE_ADVISORY))
 		return -EINVAL;

 	if (remap_flags & REMAP_FILE_DEDUP)
 		op = OVL_DEDUPE;
 	else
 		op = OVL_CLONE;

 	/*
 	 * Don't copy up because of a dedupe request, this wouldn't make sense
 	 * most of the time (data would be duplicated instead of deduplicated).
 	 */
 	if (op == OVL_DEDUPE &&
 	    (!ovl_inode_upper(file_inode(file_in)) ||
 	     !ovl_inode_upper(file_inode(file_out))))
 		return -EPERM;

 	return ovl_copyfile(file_in, pos_in, file_out, pos_out, len,
 			    remap_flags, op);
 }

 static int ovl_flush(struct file *file, fl_owner_t id)
 {
 	struct fd real;
 	const struct cred *old_cred;
 	int err;

 	err = ovl_real_fdget(file, &real);
 	if (err)
 		return err;

 	if (real.file->f_op->flush) {
 		old_cred = ovl_override_creds(file_inode(file)->i_sb);
 		err = real.file->f_op->flush(real.file, id);
 		revert_creds(old_cred);
 	}
 	fdput(real);

 	return err;
 }

 const struct file_operations ovl_file_operations = {
 	.open		= ovl_open,
 	.release	= ovl_release,
 	.llseek		= ovl_llseek,
 	.read_iter	= ovl_read_iter,
 	.write_iter	= ovl_write_iter,
 	.fsync		= ovl_fsync,
 	.mmap		= ovl_mmap,
 	.fallocate	= ovl_fallocate,
 	.fadvise	= ovl_fadvise,
 	.flush		= ovl_flush,
 	.splice_read    = generic_file_splice_read,
 	.splice_write   = ovl_splice_write,

 	.copy_file_range	= ovl_copy_file_range,
 	.remap_file_range	= ovl_remap_file_range,
 };

 int __init ovl_aio_request_cache_init(void)
 {
 	ovl_aio_request_cachep = kmem_cache_create("ovl_aio_req",
 						   sizeof(struct ovl_aio_req),
 						   0, SLAB_HWCACHE_ALIGN, NULL);
 	if (!ovl_aio_request_cachep)
 		return -ENOMEM;

 	return 0;
 }

 void ovl_aio_request_cache_destroy(void)
 {
 	kmem_cache_destroy(ovl_aio_request_cachep);
 }
	// SPDX-License-Identifier: GPL-2.0-only
	/*
	* Copyright (C) 2017 Red Hat, Inc.
	*/

	#include <linux/cred.h>
	#include <linux/file.h>
	#include <linux/mount.h>
	#include <linux/xattr.h>
	#include <linux/uio.h>
	#include <linux/uaccess.h>
	#include <linux/splice.h>
	#include <linux/security.h>
	#include <linux/mm.h>
	#include <linux/fs.h>
	#include "overlayfs.h"

	struct ovl_aio_req {
	struct kiocb iocb;
	struct kiocb *orig_iocb;
	struct fd fd;
	};

	static struct kmem_cache *ovl_aio_request_cachep;

	static char ovl_whatisit(struct inode inode, struct inode realinode)
	{
	if (realinode != ovl_inode_upper(inode))
	return 'l';
	if (ovl_has_upperdata(inode))
	return 'u';
	else
	return 'm';
	}

	/* No atime modificaton nor notify on underlying */
	#define OVL_OPEN_FLAGS (O_NOATIME \| FMODE_NONOTIFY)

	static struct file ovl_open_realfile(const struct file file,
	struct inode *realinode)
	{
	struct inode *inode = file_inode(file);
	struct file *realfile;
	const struct cred *old_cred;
	int flags = file->f_flags \| OVL_OPEN_FLAGS;
	int acc_mode = ACC_MODE(flags);
	int err;

	if (flags & O_APPEND)
	acc_mode \|= MAY_APPEND;

	old_cred = ovl_override_creds(inode->i_sb);
	err = inode_permission(&init_user_ns, realinode, MAY_OPEN \| acc_mode);
	if (err) {
	realfile = ERR_PTR(err);
	} else {
	if (!inode_owner_or_capable(&init_user_ns, realinode))
	flags &= ~O_NOATIME;

	realfile = open_with_fake_path(&file->f_path, flags, realinode,
	current_cred());
	}
	revert_creds(old_cred);

	pr_debug("open(%p[%pD2/%c], 0%o) -> (%p, 0%o)\n",
	file, file, ovl_whatisit(inode, realinode), file->f_flags,
	realfile, IS_ERR(realfile) ? 0 : realfile->f_flags);

	return realfile;
	}

	#define OVL_SETFL_MASK (O_APPEND \| O_NONBLOCK \| O_NDELAY \| O_DIRECT)

	static int ovl_change_flags(struct file *file, unsigned int flags)
	{
	struct inode *inode = file_inode(file);
	int err;

	flags &= OVL_SETFL_MASK;

	if (((flags ^ file->f_flags) & O_APPEND) && IS_APPEND(inode))
	return -EPERM;

	if (flags & O_DIRECT) {
	if (!file->f_mapping->a_ops \|\|
	!file->f_mapping->a_ops->direct_IO)
	return -EINVAL;
	}

	if (file->f_op->check_flags) {
	err = file->f_op->check_flags(flags);
	if (err)
	return err;
	}

	spin_lock(&file->f_lock);
	file->f_flags = (file->f_flags & ~OVL_SETFL_MASK) \| flags;
	spin_unlock(&file->f_lock);

	return 0;
	}

	static int ovl_real_fdget_meta(const struct file file, struct fd real,
	bool allow_meta)
	{
	struct inode *inode = file_inode(file);
	struct inode *realinode;

	real->flags = 0;
	real->file = file->private_data;

	if (allow_meta)
	realinode = ovl_inode_real(inode);
	else
	realinode = ovl_inode_realdata(inode);

	/* Has it been copied up since we'd opened it? */
	if (unlikely(file_inode(real->file) != realinode)) {
	real->flags = FDPUT_FPUT;
	real->file = ovl_open_realfile(file, realinode);

	return PTR_ERR_OR_ZERO(real->file);
	}

	/* Did the flags change since open? */
	if (unlikely((file->f_flags ^ real->file->f_flags) & ~OVL_OPEN_FLAGS))
	return ovl_change_flags(real->file, file->f_flags);

	return 0;
	}

	static int ovl_real_fdget(const struct file file, struct fd real)
	{
	if (d_is_dir(file_dentry(file))) {
	real->flags = 0;
	real->file = ovl_dir_real_file(file, false);

	return PTR_ERR_OR_ZERO(real->file);
	}

	return ovl_real_fdget_meta(file, real, false);
	}

	static int ovl_open(struct inode inode, struct file file)
	{
	struct file *realfile;
	int err;

	err = ovl_maybe_copy_up(file_dentry(file), file->f_flags);
	if (err)
	return err;

	/* No longer need these flags, so don't pass them on to underlying fs */
	file->f_flags &= ~(O_CREAT \| O_EXCL \| O_NOCTTY \| O_TRUNC);

	realfile = ovl_open_realfile(file, ovl_inode_realdata(inode));
	if (IS_ERR(realfile))
	return PTR_ERR(realfile);

	file->private_data = realfile;

	return 0;
	}

	static int ovl_release(struct inode inode, struct file file)
	{
	fput(file->private_data);

	return 0;
	}

	static loff_t ovl_llseek(struct file *file, loff_t offset, int whence)
	{
	struct inode *inode = file_inode(file);
	struct fd real;
	const struct cred *old_cred;
	loff_t ret;

	/*
	* The two special cases below do not need to involve real fs,
	* so we can optimizing concurrent callers.
	*/
	if (offset == 0) {
	if (whence == SEEK_CUR)
	return file->f_pos;

	if (whence == SEEK_SET)
	return vfs_setpos(file, 0, 0);
	}

	ret = ovl_real_fdget(file, &real);
	if (ret)
	return ret;

	/*
	* Overlay file f_pos is the master copy that is preserved
	* through copy up and modified on read/write, but only real
	* fs knows how to SEEK_HOLE/SEEK_DATA and real fs may impose
	* limitations that are more strict than ->s_maxbytes for specific
	* files, so we use the real file to perform seeks.
	*/
	ovl_inode_lock(inode);
	real.file->f_pos = file->f_pos;

	old_cred = ovl_override_creds(inode->i_sb);
	ret = vfs_llseek(real.file, offset, whence);
	revert_creds(old_cred);

	file->f_pos = real.file->f_pos;
	ovl_inode_unlock(inode);

	fdput(real);

	return ret;
	}

	static void ovl_file_accessed(struct file *file)
	{
	struct inode inode, upperinode;

	if (file->f_flags & O_NOATIME)
	return;

	inode = file_inode(file);
	upperinode = ovl_inode_upper(inode);

	if (!upperinode)
	return;

	if ((!timespec64_equal(&inode->i_mtime, &upperinode->i_mtime) \|\|
	!timespec64_equal(&inode->i_ctime, &upperinode->i_ctime))) {
	inode->i_mtime = upperinode->i_mtime;
	inode->i_ctime = upperinode->i_ctime;
	}

	touch_atime(&file->f_path);
	}

	static rwf_t ovl_iocb_to_rwf(int ifl)
	{
	rwf_t flags = 0;

	if (ifl & IOCB_NOWAIT)
	flags \|= RWF_NOWAIT;
	if (ifl & IOCB_HIPRI)
	flags \|= RWF_HIPRI;
	if (ifl & IOCB_DSYNC)
	flags \|= RWF_DSYNC;
	if (ifl & IOCB_SYNC)
	flags \|= RWF_SYNC;

	return flags;
	}

	static void ovl_aio_cleanup_handler(struct ovl_aio_req *aio_req)
	{
	struct kiocb *iocb = &aio_req->iocb;
	struct kiocb *orig_iocb = aio_req->orig_iocb;

	if (iocb->ki_flags & IOCB_WRITE) {
	struct inode *inode = file_inode(orig_iocb->ki_filp);

	/* Actually acquired in ovl_write_iter() */
	__sb_writers_acquired(file_inode(iocb->ki_filp)->i_sb,
	SB_FREEZE_WRITE);
	file_end_write(iocb->ki_filp);
	ovl_copyattr(ovl_inode_real(inode), inode);
	}

	orig_iocb->ki_pos = iocb->ki_pos;
	fdput(aio_req->fd);
	kmem_cache_free(ovl_aio_request_cachep, aio_req);
	}

	static void ovl_aio_rw_complete(struct kiocb *iocb, long res, long res2)
	{
	struct ovl_aio_req *aio_req = container_of(iocb,
	struct ovl_aio_req, iocb);
	struct kiocb *orig_iocb = aio_req->orig_iocb;

	ovl_aio_cleanup_handler(aio_req);
	orig_iocb->ki_complete(orig_iocb, res, res2);
	}

	static ssize_t ovl_read_iter(struct kiocb iocb, struct iov_iter iter)
	{
	struct file *file = iocb->ki_filp;
	struct fd real;
	const struct cred *old_cred;
	ssize_t ret;

	if (!iov_iter_count(iter))
	return 0;

	ret = ovl_real_fdget(file, &real);
	if (ret)
	return ret;

	old_cred = ovl_override_creds(file_inode(file)->i_sb);
	if (is_sync_kiocb(iocb)) {
	ret = vfs_iter_read(real.file, iter, &iocb->ki_pos,
	ovl_iocb_to_rwf(iocb->ki_flags));
	} else {
	struct ovl_aio_req *aio_req;

	ret = -ENOMEM;
	aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
	if (!aio_req)
	goto out;

	aio_req->fd = real;
	real.flags = 0;
	aio_req->orig_iocb = iocb;
	kiocb_clone(&aio_req->iocb, iocb, real.file);
	aio_req->iocb.ki_complete = ovl_aio_rw_complete;
	ret = vfs_iocb_iter_read(real.file, &aio_req->iocb, iter);
	if (ret != -EIOCBQUEUED)
	ovl_aio_cleanup_handler(aio_req);
	}
	out:
	revert_creds(old_cred);
	ovl_file_accessed(file);

	fdput(real);

	return ret;
	}

	static ssize_t ovl_write_iter(struct kiocb iocb, struct iov_iter iter)
	{
	struct file *file = iocb->ki_filp;
	struct inode *inode = file_inode(file);
	struct fd real;
	const struct cred *old_cred;
	ssize_t ret;
	int ifl = iocb->ki_flags;

	if (!iov_iter_count(iter))
	return 0;

	inode_lock(inode);
	/* Update mode */
	ovl_copyattr(ovl_inode_real(inode), inode);
	ret = file_remove_privs(file);
	if (ret)
	goto out_unlock;

	ret = ovl_real_fdget(file, &real);
	if (ret)
	goto out_unlock;

	if (!ovl_should_sync(OVL_FS(inode->i_sb)))
	ifl &= ~(IOCB_DSYNC \| IOCB_SYNC);

	old_cred = ovl_override_creds(file_inode(file)->i_sb);
	if (is_sync_kiocb(iocb)) {
	file_start_write(real.file);
	ret = vfs_iter_write(real.file, iter, &iocb->ki_pos,
	ovl_iocb_to_rwf(ifl));
	file_end_write(real.file);
	/* Update size */
	ovl_copyattr(ovl_inode_real(inode), inode);
	} else {
	struct ovl_aio_req *aio_req;

	ret = -ENOMEM;
	aio_req = kmem_cache_zalloc(ovl_aio_request_cachep, GFP_KERNEL);
	if (!aio_req)
	goto out;

	file_start_write(real.file);
	/* Pacify lockdep, same trick as done in aio_write() */
	__sb_writers_release(file_inode(real.file)->i_sb,
	SB_FREEZE_WRITE);
	aio_req->fd = real;
	real.flags = 0;
	aio_req->orig_iocb = iocb;
	kiocb_clone(&aio_req->iocb, iocb, real.file);
	aio_req->iocb.ki_flags = ifl;
	aio_req->iocb.ki_complete = ovl_aio_rw_complete;
	ret = vfs_iocb_iter_write(real.file, &aio_req->iocb, iter);
	if (ret != -EIOCBQUEUED)
	ovl_aio_cleanup_handler(aio_req);
	}
	out:
	revert_creds(old_cred);
	fdput(real);

	out_unlock:
	inode_unlock(inode);

	return ret;
	}

	/*
	* Calling iter_file_splice_write() directly from overlay's f_op may deadlock
	* due to lock order inversion between pipe->mutex in iter_file_splice_write()
	* and file_start_write(real.file) in ovl_write_iter().
	*
	* So do everything ovl_write_iter() does and call iter_file_splice_write() on
	* the real file.
	*/
	static ssize_t ovl_splice_write(struct pipe_inode_info pipe, struct file out,
	loff_t *ppos, size_t len, unsigned int flags)
	{
	struct fd real;
	const struct cred *old_cred;
	struct inode *inode = file_inode(out);
	struct inode *realinode = ovl_inode_real(inode);
	ssize_t ret;

	inode_lock(inode);
	/* Update mode */
	ovl_copyattr(realinode, inode);
	ret = file_remove_privs(out);
	if (ret)
	goto out_unlock;

	ret = ovl_real_fdget(out, &real);
	if (ret)
	goto out_unlock;

	old_cred = ovl_override_creds(inode->i_sb);
	file_start_write(real.file);

	ret = iter_file_splice_write(pipe, real.file, ppos, len, flags);

	file_end_write(real.file);
	/* Update size */
	ovl_copyattr(realinode, inode);
	revert_creds(old_cred);
	fdput(real);

	out_unlock:
	inode_unlock(inode);

	return ret;
	}

	static int ovl_fsync(struct file *file, loff_t start, loff_t end, int datasync)
	{
	struct fd real;
	const struct cred *old_cred;
	int ret;

	ret = ovl_sync_status(OVL_FS(file_inode(file)->i_sb));
	if (ret <= 0)
	return ret;

	ret = ovl_real_fdget_meta(file, &real, !datasync);
	if (ret)
	return ret;

	/* Don't sync lower file for fear of receiving EROFS error */
	if (file_inode(real.file) == ovl_inode_upper(file_inode(file))) {
	old_cred = ovl_override_creds(file_inode(file)->i_sb);
	ret = vfs_fsync_range(real.file, start, end, datasync);
	revert_creds(old_cred);
	}

	fdput(real);

	return ret;
	}

	static int ovl_mmap(struct file file, struct vm_area_struct vma)
	{
	struct file *realfile = file->private_data;
	const struct cred *old_cred;
	int ret;

	if (!realfile->f_op->mmap)
	return -ENODEV;

	if (WARN_ON(file != vma->vm_file))
	return -EIO;

	vma_set_file(vma, realfile);

	old_cred = ovl_override_creds(file_inode(file)->i_sb);
	ret = call_mmap(vma->vm_file, vma);
	revert_creds(old_cred);
	ovl_file_accessed(file);

	return ret;
	}

	static long ovl_fallocate(struct file *file, int mode, loff_t offset, loff_t len)
	{
	struct inode *inode = file_inode(file);
	struct fd real;
	const struct cred *old_cred;
	int ret;

	ret = ovl_real_fdget(file, &real);
	if (ret)
	return ret;

	old_cred = ovl_override_creds(file_inode(file)->i_sb);
	ret = vfs_fallocate(real.file, mode, offset, len);
	revert_creds(old_cred);

	/* Update size */
	ovl_copyattr(ovl_inode_real(inode), inode);

	fdput(real);

	return ret;
	}

	static int ovl_fadvise(struct file *file, loff_t offset, loff_t len, int advice)
	{
	struct fd real;
	const struct cred *old_cred;
	int ret;

	ret = ovl_real_fdget(file, &real);
	if (ret)
	return ret;

	old_cred = ovl_override_creds(file_inode(file)->i_sb);
	ret = vfs_fadvise(real.file, offset, len, advice);
	revert_creds(old_cred);

	fdput(real);

	return ret;
	}

	enum ovl_copyop {
	OVL_COPY,
	OVL_CLONE,
	OVL_DEDUPE,
	};

	static loff_t ovl_copyfile(struct file *file_in, loff_t pos_in,
	struct file *file_out, loff_t pos_out,
	loff_t len, unsigned int flags, enum ovl_copyop op)
	{
	struct inode *inode_out = file_inode(file_out);
	struct fd real_in, real_out;
	const struct cred *old_cred;
	loff_t ret;

	ret = ovl_real_fdget(file_out, &real_out);
	if (ret)
	return ret;

	ret = ovl_real_fdget(file_in, &real_in);
	if (ret) {
	fdput(real_out);
	return ret;
	}

	old_cred = ovl_override_creds(file_inode(file_out)->i_sb);
	switch (op) {
	case OVL_COPY:
	ret = vfs_copy_file_range(real_in.file, pos_in,
	real_out.file, pos_out, len, flags);
	break;

	case OVL_CLONE:
	ret = vfs_clone_file_range(real_in.file, pos_in,
	real_out.file, pos_out, len, flags);
	break;

	case OVL_DEDUPE:
	ret = vfs_dedupe_file_range_one(real_in.file, pos_in,
	real_out.file, pos_out, len,
	flags);
	break;
	}
	revert_creds(old_cred);

	/* Update size */
	ovl_copyattr(ovl_inode_real(inode_out), inode_out);

	fdput(real_in);
	fdput(real_out);

	return ret;
	}

	static ssize_t ovl_copy_file_range(struct file *file_in, loff_t pos_in,
	struct file *file_out, loff_t pos_out,
	size_t len, unsigned int flags)
	{
	return ovl_copyfile(file_in, pos_in, file_out, pos_out, len, flags,
	OVL_COPY);
	}

	static loff_t ovl_remap_file_range(struct file *file_in, loff_t pos_in,
	struct file *file_out, loff_t pos_out,
	loff_t len, unsigned int remap_flags)
	{
	enum ovl_copyop op;

	if (remap_flags & ~(REMAP_FILE_DEDUP \| REMAP_FILE_ADVISORY))
	return -EINVAL;

	if (remap_flags & REMAP_FILE_DEDUP)
	op = OVL_DEDUPE;
	else
	op = OVL_CLONE;

	/*
	* Don't copy up because of a dedupe request, this wouldn't make sense
	* most of the time (data would be duplicated instead of deduplicated).
	*/
	if (op == OVL_DEDUPE &&
	(!ovl_inode_upper(file_inode(file_in)) \|\|
	!ovl_inode_upper(file_inode(file_out))))
	return -EPERM;

	return ovl_copyfile(file_in, pos_in, file_out, pos_out, len,
	remap_flags, op);
	}

	static int ovl_flush(struct file *file, fl_owner_t id)
	{
	struct fd real;
	const struct cred *old_cred;
	int err;

	err = ovl_real_fdget(file, &real);
	if (err)
	return err;

	if (real.file->f_op->flush) {
	old_cred = ovl_override_creds(file_inode(file)->i_sb);
	err = real.file->f_op->flush(real.file, id);
	revert_creds(old_cred);
	}
	fdput(real);

	return err;
	}

	const struct file_operations ovl_file_operations = {
	.open = ovl_open,
	.release = ovl_release,
	.llseek = ovl_llseek,
	.read_iter = ovl_read_iter,
	.write_iter = ovl_write_iter,
	.fsync = ovl_fsync,
	.mmap = ovl_mmap,
	.fallocate = ovl_fallocate,
	.fadvise = ovl_fadvise,
	.flush = ovl_flush,
	.splice_read = generic_file_splice_read,
	.splice_write = ovl_splice_write,

	.copy_file_range = ovl_copy_file_range,
	.remap_file_range = ovl_remap_file_range,
	};

	int __init ovl_aio_request_cache_init(void)
	{
	ovl_aio_request_cachep = kmem_cache_create("ovl_aio_req",
	sizeof(struct ovl_aio_req),
	0, SLAB_HWCACHE_ALIGN, NULL);
	if (!ovl_aio_request_cachep)
	return -ENOMEM;

	return 0;
	}

	void ovl_aio_request_cache_destroy(void)
	{
	kmem_cache_destroy(ovl_aio_request_cachep);
	}