// SPDX-License-Identifier: GPL-2.0

  /*

   *  linux/fs/ext4/file.c

   *
   * Copyright (C) 1992, 1993, 1994, 1995
   * Remy Card (card@masi.ibp.fr)
   * Laboratoire MASI - Institut Blaise Pascal
   * Universite Pierre et Marie Curie (Paris VI)
   *
   *  from
   *
   *  linux/fs/minix/file.c
   *
   *  Copyright (C) 1991, 1992  Linus Torvalds
   *

   *  ext4 fs regular file handling primitives

   *
   *  64-bit file support on 64-bit platforms by Jakub Jelinek
   *	(jj@sunsite.ms.mff.cuni.cz)
   */
  
  #include <linux/time.h>
  #include <linux/fs.h>

  #include <linux/iomap.h>

  #include <linux/mount.h>
  #include <linux/path.h>

  #include <linux/dax.h>

  #include <linux/quotaops.h>

  #include <linux/pagevec.h>

  #include <linux/uio.h>

  #include <linux/mman.h>

  #include <linux/backing-dev.h>

  #include "ext4.h"
  #include "ext4_jbd2.h"

  #include "xattr.h"
  #include "acl.h"

  #include "truncate.h"

  static bool ext4_dio_supported(struct kiocb *iocb, struct iov_iter *iter)

  {

  	struct inode *inode = file_inode(iocb->ki_filp);

  	if (!fscrypt_dio_supported(iocb, iter))
  		return false;

  	if (fsverity_active(inode))
  		return false;
  	if (ext4_should_journal_data(inode))
  		return false;
  	if (ext4_has_inline_data(inode))
  		return false;
  	return true;
  }
  
  static ssize_t ext4_dio_read_iter(struct kiocb *iocb, struct iov_iter *to)
  {
  	ssize_t ret;
  	struct inode *inode = file_inode(iocb->ki_filp);
  
  	if (iocb->ki_flags & IOCB_NOWAIT) {
  		if (!inode_trylock_shared(inode))
  			return -EAGAIN;
  	} else {
  		inode_lock_shared(inode);
  	}

  	if (!ext4_dio_supported(iocb, to)) {

  		inode_unlock_shared(inode);
  		/*
  		 * Fallback to buffered I/O if the operation being performed on
  		 * the inode is not supported by direct I/O. The IOCB_DIRECT
  		 * flag needs to be cleared here in order to ensure that the
  		 * direct I/O path within generic_file_read_iter() is not
  		 * taken.
  		 */
  		iocb->ki_flags &= ~IOCB_DIRECT;
  		return generic_file_read_iter(iocb, to);
  	}
  
  	ret = iomap_dio_rw(iocb, to, &ext4_iomap_ops, NULL,
  			   is_sync_kiocb(iocb));
  	inode_unlock_shared(inode);
  
  	file_accessed(iocb->ki_filp);
  	return ret;
  }

  #ifdef CONFIG_FS_DAX
  static ssize_t ext4_dax_read_iter(struct kiocb *iocb, struct iov_iter *to)
  {
  	struct inode *inode = file_inode(iocb->ki_filp);
  	ssize_t ret;

  	if (iocb->ki_flags & IOCB_NOWAIT) {
  		if (!inode_trylock_shared(inode))

  			return -EAGAIN;

  	} else {

  		inode_lock_shared(inode);
  	}

  	/*
  	 * Recheck under inode lock - at this point we are sure it cannot
  	 * change anymore
  	 */
  	if (!IS_DAX(inode)) {
  		inode_unlock_shared(inode);
  		/* Fallback to buffered IO in case we cannot support DAX */
  		return generic_file_read_iter(iocb, to);
  	}
  	ret = dax_iomap_rw(iocb, to, &ext4_iomap_ops);
  	inode_unlock_shared(inode);
  
  	file_accessed(iocb->ki_filp);
  	return ret;
  }
  #endif
  
  static ssize_t ext4_file_read_iter(struct kiocb *iocb, struct iov_iter *to)
  {

  	struct inode *inode = file_inode(iocb->ki_filp);
  
  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))

  		return -EIO;

  	if (!iov_iter_count(to))
  		return 0; /* skip atime */
  
  #ifdef CONFIG_FS_DAX

  	if (IS_DAX(inode))

  		return ext4_dax_read_iter(iocb, to);
  #endif

  	if (iocb->ki_flags & IOCB_DIRECT)
  		return ext4_dio_read_iter(iocb, to);

  	return generic_file_read_iter(iocb, to);
  }

  /*
   * Called when an inode is released. Note that this is different

   * from ext4_file_open: open gets called at every open, but release

   * gets called only when /all/ the files are closed.
   */

  static int ext4_release_file(struct inode *inode, struct file *filp)

  {

  	if (ext4_test_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE)) {

  		ext4_alloc_da_blocks(inode);

  		ext4_clear_inode_state(inode, EXT4_STATE_DA_ALLOC_CLOSE);

  	}

  	/* if we are the last writer on the inode, drop the block reservation */
  	if ((filp->f_mode & FMODE_WRITE) &&

  			(atomic_read(&inode->i_writecount) == 1) &&

  			!EXT4_I(inode)->i_reserved_data_blocks) {

  		down_write(&EXT4_I(inode)->i_data_sem);

  		ext4_discard_preallocations(inode, 0);

  		up_write(&EXT4_I(inode)->i_data_sem);

  	}
  	if (is_dx(inode) && filp->private_data)

  		ext4_htree_free_dir_info(filp->private_data);

  
  	return 0;
  }

  /*
   * This tests whether the IO in question is block-aligned or not.
   * Ext4 utilizes unwritten extents when hole-filling during direct IO, and they
   * are converted to written only after the IO is complete.  Until they are
   * mapped, these blocks appear as holes, so dio_zero_block() will assume that
   * it needs to zero out portions of the start and/or end block.  If 2 AIO
   * threads are at work on the same unwritten block, they must be synchronized
   * or one thread will zero the other's data, causing corruption.
   */

  static bool
  ext4_unaligned_io(struct inode *inode, struct iov_iter *from, loff_t pos)

  {
  	struct super_block *sb = inode->i_sb;

  	unsigned long blockmask = sb->s_blocksize - 1;

  	if ((pos | iov_iter_alignment(from)) & blockmask)

  		return true;

  	return false;
  }
  
  static bool
  ext4_extending_io(struct inode *inode, loff_t offset, size_t len)
  {
  	if (offset + len > i_size_read(inode) ||
  	    offset + len > EXT4_I(inode)->i_disksize)
  		return true;
  	return false;

  }

  /* Is IO overwriting allocated and initialized blocks? */
  static bool ext4_overwrite_io(struct inode *inode, loff_t pos, loff_t len)
  {
  	struct ext4_map_blocks map;
  	unsigned int blkbits = inode->i_blkbits;
  	int err, blklen;
  
  	if (pos + len > i_size_read(inode))
  		return false;
  
  	map.m_lblk = pos >> blkbits;
  	map.m_len = EXT4_MAX_BLOCKS(len, pos, blkbits);
  	blklen = map.m_len;
  
  	err = ext4_map_blocks(NULL, inode, &map, 0);
  	/*
  	 * 'err==len' means that all of the blocks have been preallocated,
  	 * regardless of whether they have been initialized or not. To exclude
  	 * unwritten extents, we need to check m_flags.
  	 */
  	return err == blklen && (map.m_flags & EXT4_MAP_MAPPED);
  }

  static ssize_t ext4_generic_write_checks(struct kiocb *iocb,
  					 struct iov_iter *from)

  {
  	struct inode *inode = file_inode(iocb->ki_filp);
  	ssize_t ret;

  	if (unlikely(IS_IMMUTABLE(inode)))
  		return -EPERM;

  	ret = generic_write_checks(iocb, from);
  	if (ret <= 0)
  		return ret;

  	/*
  	 * If we have encountered a bitmap-format file, the size limit
  	 * is smaller than s_maxbytes, which is for extent-mapped files.
  	 */
  	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS))) {
  		struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  
  		if (iocb->ki_pos >= sbi->s_bitmap_maxbytes)
  			return -EFBIG;
  		iov_iter_truncate(from, sbi->s_bitmap_maxbytes - iocb->ki_pos);
  	}

  	return iov_iter_count(from);
  }
  
  static ssize_t ext4_write_checks(struct kiocb *iocb, struct iov_iter *from)
  {
  	ssize_t ret, count;
  
  	count = ext4_generic_write_checks(iocb, from);
  	if (count <= 0)
  		return count;

  	ret = file_modified(iocb->ki_filp);
  	if (ret)
  		return ret;

  	return count;

  }

  static ssize_t ext4_buffered_write_iter(struct kiocb *iocb,
  					struct iov_iter *from)
  {
  	ssize_t ret;
  	struct inode *inode = file_inode(iocb->ki_filp);
  
  	if (iocb->ki_flags & IOCB_NOWAIT)
  		return -EOPNOTSUPP;

  	ext4_fc_start_update(inode);

  	inode_lock(inode);
  	ret = ext4_write_checks(iocb, from);
  	if (ret <= 0)
  		goto out;
  
  	current->backing_dev_info = inode_to_bdi(inode);
  	ret = generic_perform_write(iocb->ki_filp, from, iocb->ki_pos);
  	current->backing_dev_info = NULL;
  
  out:
  	inode_unlock(inode);

  	ext4_fc_stop_update(inode);

  	if (likely(ret > 0)) {
  		iocb->ki_pos += ret;
  		ret = generic_write_sync(iocb, ret);
  	}
  
  	return ret;
  }

  static ssize_t ext4_handle_inode_extension(struct inode *inode, loff_t offset,
  					   ssize_t written, size_t count)
  {
  	handle_t *handle;
  	bool truncate = false;
  	u8 blkbits = inode->i_blkbits;
  	ext4_lblk_t written_blk, end_blk;

  	int ret;

  
  	/*
  	 * Note that EXT4_I(inode)->i_disksize can get extended up to
  	 * inode->i_size while the I/O was running due to writeback of delalloc
  	 * blocks. But, the code in ext4_iomap_alloc() is careful to use
  	 * zeroed/unwritten extents if this is possible; thus we won't leave
  	 * uninitialized blocks in a file even if we didn't succeed in writing
  	 * as much as we intended.
  	 */
  	WARN_ON_ONCE(i_size_read(inode) < EXT4_I(inode)->i_disksize);
  	if (offset + count <= EXT4_I(inode)->i_disksize) {
  		/*
  		 * We need to ensure that the inode is removed from the orphan
  		 * list if it has been added prematurely, due to writeback of
  		 * delalloc blocks.
  		 */
  		if (!list_empty(&EXT4_I(inode)->i_orphan) && inode->i_nlink) {
  			handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
  
  			if (IS_ERR(handle)) {
  				ext4_orphan_del(NULL, inode);
  				return PTR_ERR(handle);
  			}
  
  			ext4_orphan_del(handle, inode);
  			ext4_journal_stop(handle);
  		}
  
  		return written;
  	}
  
  	if (written < 0)
  		goto truncate;
  
  	handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
  	if (IS_ERR(handle)) {
  		written = PTR_ERR(handle);
  		goto truncate;
  	}

  	if (ext4_update_inode_size(inode, offset + written)) {
  		ret = ext4_mark_inode_dirty(handle, inode);
  		if (unlikely(ret)) {
  			written = ret;
  			ext4_journal_stop(handle);
  			goto truncate;
  		}
  	}

  
  	/*
  	 * We may need to truncate allocated but not written blocks beyond EOF.
  	 */
  	written_blk = ALIGN(offset + written, 1 << blkbits);
  	end_blk = ALIGN(offset + count, 1 << blkbits);
  	if (written_blk < end_blk && ext4_can_truncate(inode))
  		truncate = true;
  
  	/*
  	 * Remove the inode from the orphan list if it has been extended and
  	 * everything went OK.
  	 */
  	if (!truncate && inode->i_nlink)
  		ext4_orphan_del(handle, inode);
  	ext4_journal_stop(handle);
  
  	if (truncate) {
  truncate:
  		ext4_truncate_failed_write(inode);
  		/*
  		 * If the truncate operation failed early, then the inode may
  		 * still be on the orphan list. In that case, we need to try
  		 * remove the inode from the in-memory linked list.
  		 */
  		if (inode->i_nlink)
  			ext4_orphan_del(NULL, inode);
  	}
  
  	return written;
  }

  static int ext4_dio_write_end_io(struct kiocb *iocb, ssize_t size,
  				 int error, unsigned int flags)
  {
  	loff_t offset = iocb->ki_pos;
  	struct inode *inode = file_inode(iocb->ki_filp);
  
  	if (error)
  		return error;
  
  	if (size && flags & IOMAP_DIO_UNWRITTEN)
  		return ext4_convert_unwritten_extents(NULL, inode,
  						      offset, size);
  
  	return 0;
  }
  
  static const struct iomap_dio_ops ext4_dio_write_ops = {
  	.end_io = ext4_dio_write_end_io,
  };

  /*
   * The intention here is to start with shared lock acquired then see if any
   * condition requires an exclusive inode lock. If yes, then we restart the
   * whole operation by releasing the shared lock and acquiring exclusive lock.
   *
   * - For unaligned_io we never take shared lock as it may cause data corruption
   *   when two unaligned IO tries to modify the same block e.g. while zeroing.
   *
   * - For extending writes case we don't take the shared lock, since it requires
   *   updating inode i_disksize and/or orphan handling with exclusive lock.
   *

   * - shared locking will only be true mostly with overwrites. Otherwise we will
   *   switch to exclusive i_rwsem lock.

   */
  static ssize_t ext4_dio_write_checks(struct kiocb *iocb, struct iov_iter *from,
  				     bool *ilock_shared, bool *extend)
  {
  	struct file *file = iocb->ki_filp;
  	struct inode *inode = file_inode(file);
  	loff_t offset;
  	size_t count;
  	ssize_t ret;
  
  restart:
  	ret = ext4_generic_write_checks(iocb, from);
  	if (ret <= 0)
  		goto out;
  
  	offset = iocb->ki_pos;
  	count = ret;
  	if (ext4_extending_io(inode, offset, count))
  		*extend = true;
  	/*
  	 * Determine whether the IO operation will overwrite allocated

  	 * and initialized blocks.

  	 * We need exclusive i_rwsem for changing security info
  	 * in file_modified().
  	 */
  	if (*ilock_shared && (!IS_NOSEC(inode) || *extend ||

  	     !ext4_overwrite_io(inode, offset, count))) {

  		if (iocb->ki_flags & IOCB_NOWAIT) {
  			ret = -EAGAIN;
  			goto out;
  		}

  		inode_unlock_shared(inode);
  		*ilock_shared = false;
  		inode_lock(inode);
  		goto restart;
  	}
  
  	ret = file_modified(file);
  	if (ret < 0)
  		goto out;
  
  	return count;
  out:
  	if (*ilock_shared)
  		inode_unlock_shared(inode);
  	else
  		inode_unlock(inode);
  	return ret;
  }

  static ssize_t ext4_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
  {
  	ssize_t ret;

  	handle_t *handle;
  	struct inode *inode = file_inode(iocb->ki_filp);

  	loff_t offset = iocb->ki_pos;
  	size_t count = iov_iter_count(from);

  	const struct iomap_ops *iomap_ops = &ext4_iomap_ops;

  	bool extend = false, unaligned_io = false;
  	bool ilock_shared = true;
  
  	/*
  	 * We initially start with shared inode lock unless it is
  	 * unaligned IO which needs exclusive lock anyways.
  	 */
  	if (ext4_unaligned_io(inode, from, offset)) {
  		unaligned_io = true;
  		ilock_shared = false;
  	}
  	/*
  	 * Quick check here without any i_rwsem lock to see if it is extending
  	 * IO. A more reliable check is done in ext4_dio_write_checks() with
  	 * proper locking in place.
  	 */
  	if (offset + count > i_size_read(inode))
  		ilock_shared = false;

  
  	if (iocb->ki_flags & IOCB_NOWAIT) {

  		if (ilock_shared) {
  			if (!inode_trylock_shared(inode))
  				return -EAGAIN;
  		} else {
  			if (!inode_trylock(inode))
  				return -EAGAIN;
  		}

  	} else {

  		if (ilock_shared)
  			inode_lock_shared(inode);
  		else
  			inode_lock(inode);

  	}

  	/* Fallback to buffered I/O if the inode does not support direct I/O. */

  	if (!ext4_dio_supported(iocb, from)) {

  		if (ilock_shared)
  			inode_unlock_shared(inode);
  		else
  			inode_unlock(inode);

  		return ext4_buffered_write_iter(iocb, from);
  	}

  	ret = ext4_dio_write_checks(iocb, from, &ilock_shared, &extend);
  	if (ret <= 0)

  		return ret;

  	/* if we're going to block and IOCB_NOWAIT is set, return -EAGAIN */
  	if ((iocb->ki_flags & IOCB_NOWAIT) && (unaligned_io || extend)) {
  		ret = -EAGAIN;
  		goto out;
  	}

  	offset = iocb->ki_pos;

  	count = ret;

  
  	/*

  	 * Unaligned direct IO must be serialized among each other as zeroing
  	 * of partial blocks of two competing unaligned IOs can result in data
  	 * corruption.
  	 *
  	 * So we make sure we don't allow any unaligned IO in flight.
  	 * For IOs where we need not wait (like unaligned non-AIO DIO),
  	 * below inode_dio_wait() may anyway become a no-op, since we start
  	 * with exclusive lock.

  	 */

  	if (unaligned_io)
  		inode_dio_wait(inode);

  	if (extend) {

  		handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
  		if (IS_ERR(handle)) {
  			ret = PTR_ERR(handle);
  			goto out;
  		}

  		ext4_fc_start_update(inode);

  		ret = ext4_orphan_add(handle, inode);

  		ext4_fc_stop_update(inode);

  		if (ret) {
  			ext4_journal_stop(handle);
  			goto out;
  		}

  		ext4_journal_stop(handle);
  	}

  	if (ilock_shared)
  		iomap_ops = &ext4_iomap_overwrite_ops;
  	ret = iomap_dio_rw(iocb, from, iomap_ops, &ext4_dio_write_ops,

  			   is_sync_kiocb(iocb) || unaligned_io || extend);

  	if (ret == -ENOTBLK)
  		ret = 0;

  
  	if (extend)
  		ret = ext4_handle_inode_extension(inode, offset, ret, count);
  
  out:

  	if (ilock_shared)

  		inode_unlock_shared(inode);
  	else
  		inode_unlock(inode);
  
  	if (ret >= 0 && iov_iter_count(from)) {
  		ssize_t err;
  		loff_t endbyte;
  
  		offset = iocb->ki_pos;
  		err = ext4_buffered_write_iter(iocb, from);
  		if (err < 0)
  			return err;
  
  		/*
  		 * We need to ensure that the pages within the page cache for
  		 * the range covered by this I/O are written to disk and
  		 * invalidated. This is in attempt to preserve the expected
  		 * direct I/O semantics in the case we fallback to buffered I/O
  		 * to complete off the I/O request.
  		 */
  		ret += err;
  		endbyte = offset + err - 1;
  		err = filemap_write_and_wait_range(iocb->ki_filp->f_mapping,
  						   offset, endbyte);
  		if (!err)
  			invalidate_mapping_pages(iocb->ki_filp->f_mapping,
  						 offset >> PAGE_SHIFT,
  						 endbyte >> PAGE_SHIFT);
  	}
  
  	return ret;
  }

  #ifdef CONFIG_FS_DAX
  static ssize_t
  ext4_dax_write_iter(struct kiocb *iocb, struct iov_iter *from)
  {

  	ssize_t ret;

  	size_t count;
  	loff_t offset;

  	handle_t *handle;
  	bool extend = false;

  	struct inode *inode = file_inode(iocb->ki_filp);

  	if (iocb->ki_flags & IOCB_NOWAIT) {
  		if (!inode_trylock(inode))

  			return -EAGAIN;

  	} else {

  		inode_lock(inode);
  	}

  	ret = ext4_write_checks(iocb, from);
  	if (ret <= 0)
  		goto out;

  	offset = iocb->ki_pos;
  	count = iov_iter_count(from);

  
  	if (offset + count > EXT4_I(inode)->i_disksize) {
  		handle = ext4_journal_start(inode, EXT4_HT_INODE, 2);
  		if (IS_ERR(handle)) {
  			ret = PTR_ERR(handle);
  			goto out;
  		}
  
  		ret = ext4_orphan_add(handle, inode);
  		if (ret) {
  			ext4_journal_stop(handle);
  			goto out;
  		}
  
  		extend = true;
  		ext4_journal_stop(handle);
  	}

  	ret = dax_iomap_rw(iocb, from, &ext4_iomap_ops);

  
  	if (extend)
  		ret = ext4_handle_inode_extension(inode, offset, ret, count);

  out:

  	inode_unlock(inode);

  	if (ret > 0)
  		ret = generic_write_sync(iocb, ret);
  	return ret;
  }
  #endif

  static ssize_t

  ext4_file_write_iter(struct kiocb *iocb, struct iov_iter *from)

  {

  	struct inode *inode = file_inode(iocb->ki_filp);

  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
  		return -EIO;

  #ifdef CONFIG_FS_DAX
  	if (IS_DAX(inode))
  		return ext4_dax_write_iter(iocb, from);
  #endif

  	if (iocb->ki_flags & IOCB_DIRECT)
  		return ext4_dio_write_iter(iocb, from);

  	else
  		return ext4_buffered_write_iter(iocb, from);

  }

  #ifdef CONFIG_FS_DAX

  static vm_fault_t ext4_dax_huge_fault(struct vm_fault *vmf,

  		enum page_entry_size pe_size)

  {

  	int error = 0;
  	vm_fault_t result;

  	int retries = 0;

  	handle_t *handle = NULL;

  	struct inode *inode = file_inode(vmf->vma->vm_file);

  	struct super_block *sb = inode->i_sb;

  
  	/*
  	 * We have to distinguish real writes from writes which will result in a
  	 * COW page; COW writes should *not* poke the journal (the file will not
  	 * be changed). Doing so would cause unintended failures when mounted
  	 * read-only.
  	 *
  	 * We check for VM_SHARED rather than vmf->cow_page since the latter is
  	 * unset for pe_size != PE_SIZE_PTE (i.e. only in do_cow_fault); for
  	 * other sizes, dax_iomap_fault will handle splitting / fallback so that
  	 * we eventually come back with a COW page.
  	 */
  	bool write = (vmf->flags & FAULT_FLAG_WRITE) &&
  		(vmf->vma->vm_flags & VM_SHARED);

  	pfn_t pfn;

  
  	if (write) {
  		sb_start_pagefault(sb);

  		file_update_time(vmf->vma->vm_file);

  		down_read(&EXT4_I(inode)->i_mmap_sem);

  retry:

  		handle = ext4_journal_start_sb(sb, EXT4_HT_WRITE_PAGE,
  					       EXT4_DATA_TRANS_BLOCKS(sb));

  		if (IS_ERR(handle)) {
  			up_read(&EXT4_I(inode)->i_mmap_sem);
  			sb_end_pagefault(sb);
  			return VM_FAULT_SIGBUS;
  		}

  	} else {
  		down_read(&EXT4_I(inode)->i_mmap_sem);

  	}

  	result = dax_iomap_fault(vmf, pe_size, &pfn, &error, &ext4_iomap_ops);

  	if (write) {

  		ext4_journal_stop(handle);

  
  		if ((result & VM_FAULT_ERROR) && error == -ENOSPC &&
  		    ext4_should_retry_alloc(sb, &retries))
  			goto retry;

  		/* Handling synchronous page fault? */
  		if (result & VM_FAULT_NEEDDSYNC)
  			result = dax_finish_sync_fault(vmf, pe_size, pfn);

  		up_read(&EXT4_I(inode)->i_mmap_sem);

  		sb_end_pagefault(sb);

  	} else {
  		up_read(&EXT4_I(inode)->i_mmap_sem);
  	}

  
  	return result;

  }

  static vm_fault_t ext4_dax_fault(struct vm_fault *vmf)

  {
  	return ext4_dax_huge_fault(vmf, PE_SIZE_PTE);
  }

  static const struct vm_operations_struct ext4_dax_vm_ops = {
  	.fault		= ext4_dax_fault,

  	.huge_fault	= ext4_dax_huge_fault,

  	.page_mkwrite	= ext4_dax_fault,

  	.pfn_mkwrite	= ext4_dax_fault,

  };
  #else
  #define ext4_dax_vm_ops	ext4_file_vm_ops
  #endif

  static const struct vm_operations_struct ext4_file_vm_ops = {

  	.fault		= ext4_filemap_fault,

  	.map_pages	= filemap_map_pages,

  	.page_mkwrite   = ext4_page_mkwrite,
  };
  
  static int ext4_file_mmap(struct file *file, struct vm_area_struct *vma)
  {

  	struct inode *inode = file->f_mapping->host;

  	struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
  	struct dax_device *dax_dev = sbi->s_daxdev;

  	if (unlikely(ext4_forced_shutdown(sbi)))

  		return -EIO;

  	/*

  	 * We don't support synchronous mappings for non-DAX files and
  	 * for DAX files if underneath dax_device is not synchronous.

  	 */

  	if (!daxdev_mapping_supported(vma, dax_dev))

  		return -EOPNOTSUPP;

  	file_accessed(file);

  	if (IS_DAX(file_inode(file))) {
  		vma->vm_ops = &ext4_dax_vm_ops;

  		vma->vm_flags |= VM_HUGEPAGE;

  	} else {
  		vma->vm_ops = &ext4_file_vm_ops;
  	}

  	return 0;
  }

  static int ext4_sample_last_mounted(struct super_block *sb,
  				    struct vfsmount *mnt)

  {

  	struct ext4_sb_info *sbi = EXT4_SB(sb);

  	struct path path;
  	char buf[64], *cp;

  	handle_t *handle;
  	int err;

  	if (likely(ext4_test_mount_flag(sb, EXT4_MF_MNTDIR_SAMPLED)))

  		return 0;

  	if (sb_rdonly(sb) || !sb_start_intwrite_trylock(sb))

  		return 0;

  	ext4_set_mount_flag(sb, EXT4_MF_MNTDIR_SAMPLED);

  	/*
  	 * Sample where the filesystem has been mounted and
  	 * store it in the superblock for sysadmin convenience
  	 * when trying to sort through large numbers of block
  	 * devices or filesystem images.
  	 */
  	memset(buf, 0, sizeof(buf));
  	path.mnt = mnt;
  	path.dentry = mnt->mnt_root;
  	cp = d_path(&path, buf, sizeof(buf));

  	err = 0;

  	if (IS_ERR(cp))

  		goto out;

  
  	handle = ext4_journal_start_sb(sb, EXT4_HT_MISC, 1);

  	err = PTR_ERR(handle);

  	if (IS_ERR(handle))

  		goto out;

  	BUFFER_TRACE(sbi->s_sbh, "get_write_access");
  	err = ext4_journal_get_write_access(handle, sbi->s_sbh);
  	if (err)

  		goto out_journal;

  	strncpy(sbi->s_es->s_last_mounted, cp,

  		sizeof(sbi->s_es->s_last_mounted));
  	ext4_handle_dirty_super(handle, sb);

  out_journal:

  	ext4_journal_stop(handle);

  out:
  	sb_end_intwrite(sb);

  	return err;
  }

  static int ext4_file_open(struct inode *inode, struct file *filp)

  {

  	int ret;

  	if (unlikely(ext4_forced_shutdown(EXT4_SB(inode->i_sb))))
  		return -EIO;

  	ret = ext4_sample_last_mounted(inode->i_sb, filp->f_path.mnt);
  	if (ret)
  		return ret;

  	ret = fscrypt_file_open(inode, filp);
  	if (ret)

  		return ret;
  
  	ret = fsverity_file_open(inode, filp);
  	if (ret)

  		return ret;

  	/*
  	 * Set up the jbd2_inode if we are opening the inode for
  	 * writing and the journal is present
  	 */

  	if (filp->f_mode & FMODE_WRITE) {

  		ret = ext4_inode_attach_jinode(inode);

  		if (ret < 0)
  			return ret;

  	}

  	filp->f_mode |= FMODE_NOWAIT | FMODE_BUF_RASYNC;

  	return dquot_file_open(inode, filp);

  }

  /*

   * ext4_llseek() handles both block-mapped and extent-mapped maxbytes values
   * by calling generic_file_llseek_size() with the appropriate maxbytes
   * value for each.

   */

  loff_t ext4_llseek(struct file *file, loff_t offset, int whence)

  {
  	struct inode *inode = file->f_mapping->host;
  	loff_t maxbytes;
  
  	if (!(ext4_test_inode_flag(inode, EXT4_INODE_EXTENTS)))
  		maxbytes = EXT4_SB(inode->i_sb)->s_bitmap_maxbytes;
  	else
  		maxbytes = inode->i_sb->s_maxbytes;

  	switch (whence) {

  	default:

  		return generic_file_llseek_size(file, offset, whence,

  						maxbytes, i_size_read(inode));

  	case SEEK_HOLE:

  		inode_lock_shared(inode);

  		offset = iomap_seek_hole(inode, offset,
  					 &ext4_iomap_report_ops);

  		inode_unlock_shared(inode);
  		break;
  	case SEEK_DATA:
  		inode_lock_shared(inode);

  		offset = iomap_seek_data(inode, offset,
  					 &ext4_iomap_report_ops);

  		inode_unlock_shared(inode);
  		break;

  	}

  	if (offset < 0)
  		return offset;
  	return vfs_setpos(file, offset, maxbytes);

  }

  const struct file_operations ext4_file_operations = {

  	.llseek		= ext4_llseek,

  	.read_iter	= ext4_file_read_iter,

  	.write_iter	= ext4_file_write_iter,

  	.iopoll		= iomap_dio_iopoll,

  	.unlocked_ioctl = ext4_ioctl,

  #ifdef CONFIG_COMPAT

  	.compat_ioctl	= ext4_compat_ioctl,

  #endif

  	.mmap		= ext4_file_mmap,

  	.mmap_supported_flags = MAP_SYNC,

  	.open		= ext4_file_open,

  	.release	= ext4_release_file,
  	.fsync		= ext4_sync_file,

  	.get_unmapped_area = thp_get_unmapped_area,

  	.splice_read	= generic_file_splice_read,

  	.splice_write	= iter_file_splice_write,

  	.fallocate	= ext4_fallocate,

  };

  const struct inode_operations ext4_file_inode_operations = {

  	.setattr	= ext4_setattr,

  	.getattr	= ext4_file_getattr,

  	.listxattr	= ext4_listxattr,

  	.get_acl	= ext4_get_acl,

  	.set_acl	= ext4_set_acl,

  	.fiemap		= ext4_fiemap,

  };