path: root/fs/ext4/file.c

// 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/filelock.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"

/*
 * Returns %true if the given DIO request should be attempted with DIO, or
 * %false if it should fall back to buffered I/O.
 *
 * DIO isn't well specified; when it's unsupported (either due to the request
 * being misaligned, or due to the file not supporting DIO at all), filesystems
 * either fall back to buffered I/O or return EINVAL.  For files that don't use
 * any special features like encryption or verity, ext4 has traditionally
 * returned EINVAL for misaligned DIO.  iomap_dio_rw() uses this convention too.
 * In this case, we should attempt the DIO, *not* fall back to buffered I/O.
 *
 * In contrast, in cases where DIO is unsupported due to ext4 features, ext4
 * traditionally falls back to buffered I/O.
 *
 * This function implements the traditional ext4 behavior in all these cases.
 */
static bool ext4_should_use_dio(struct kiocb *iocb, struct iov_iter *iter)
{
	struct inode *inode = file_inode(iocb->ki_filp);
	u32 dio_align = ext4_dio_alignment(inode);

	if (dio_align == 0)
		return false;

	if (dio_align == 1)
		return true;

	return IS_ALIGNED(iocb->ki_pos | iov_iter_alignment(iter), dio_align);
}

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_should_use_dio(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, 0, NULL, 0);
	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(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);
}

static ssize_t ext4_file_splice_read(struct file *in, loff_t *ppos,
				     struct pipe_inode_info *pipe,
				     size_t len, unsigned int flags)
{
	struct inode *inode = file_inode(in);

	if (unlikely(ext4_forced_shutdown(inode->i_sb)))
		return -EIO;
	return filemap_splice_read(in, ppos, pipe, len, flags);
}

/*
 * 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))