1 files changed, 1083 insertions, 0 deletions

diff --git a/fs/exfat/file.c b/fs/exfat/file.c
new file mode 100644
index 000000000..a2a9ee1a2
--- /dev/null
+++ b/fs/exfat/file.c
@@ -0,0 +1,1083 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ * Copyright (C) 2012-2013 Samsung Electronics Co., Ltd.
+ */
+
+#include <linux/slab.h>
+#include <linux/compat.h>
+#include <linux/cred.h>
+#include <linux/buffer_head.h>
+#include <linux/blkdev.h>
+#include <linux/fsnotify.h>
+#include <linux/security.h>
+#include <linux/msdos_fs.h>
+#include <linux/writeback.h>
+#include <linux/filelock.h>
+#include <linux/falloc.h>
+#include <linux/fileattr.h>
+#include <linux/iomap.h>
+#include <linux/pagemap.h>
+
+#include "exfat_raw.h"
+#include "exfat_fs.h"
+#include "iomap.h"
+
+static int exfat_cont_expand(struct inode *inode, loff_t size)
+{
+	int ret;
+	unsigned int num_clusters, new_num_clusters, last_clu;
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+	struct super_block *sb = inode->i_sb;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+	struct exfat_chain clu;
+	loff_t oldsize = i_size_read(inode);
+
+	truncate_pagecache(inode, oldsize);
+
+	ret = inode_newsize_ok(inode, size);
+	if (ret)
+		return ret;
+
+	num_clusters = exfat_bytes_to_cluster(sbi, exfat_ondisk_size(inode));
+	/* integer overflow is already checked in inode_newsize_ok(). */
+	new_num_clusters = exfat_bytes_to_cluster_round_up(sbi, size);
+
+	if (new_num_clusters == num_clusters)
+		goto out;
+
+	if (num_clusters) {
+		exfat_chain_set(&clu, ei->start_clu, num_clusters, ei->flags);
+		ret = exfat_find_last_cluster(sb, &clu, &last_clu);
+		if (ret)
+			return ret;
+
+		clu.dir = last_clu + 1;
+	} else {
+		last_clu = EXFAT_EOF_CLUSTER;
+		clu.dir = EXFAT_EOF_CLUSTER;
+	}
+
+	clu.size = 0;
+	clu.flags = ei->flags;
+
+	ret = exfat_alloc_cluster(inode, new_num_clusters - num_clusters,
+			&clu, inode_needs_sync(inode), false);
+	if (ret)
+		return ret;
+
+	/* Append new clusters to chain */
+	if (num_clusters) {
+		if (clu.flags != ei->flags)
+			if (exfat_chain_cont_cluster(sb, ei->start_clu, num_clusters))
+				goto free_clu;
+
+		if (clu.flags == ALLOC_FAT_CHAIN)
+			if (exfat_ent_set(sb, last_clu, clu.dir))
+				goto free_clu;
+	} else
+		ei->start_clu = clu.dir;
+
+	ei->flags = clu.flags;
+
+out:
+	inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
+	/* Expanded range not zeroed, do not update valid_size */
+	i_size_write(inode, size);
+	/*
+	 * When extending file size, call truncate_pagecache() first,
+	 * then update i_size, and call pagecache_isize_extended()
+	 * to ensures the straddling folio is properly marked RO so
+	 * page_mkwrite() is called and post-EOF area is zeroed.
+	 */
+	pagecache_isize_extended(inode, oldsize, inode->i_size);
+
+	inode->i_blocks = round_up(size, sbi->cluster_size) >> 9;
+	mark_inode_dirty(inode);
+
+	if (IS_SYNC(inode))
+		return write_inode_now(inode, 1);
+
+	return 0;
+
+free_clu:
+	exfat_free_cluster(inode, &clu);
+	return -EIO;
+}
+
+/*
+ * Preallocate space for a file. This implements exfat's fallocate file
+ * operation, which gets called from sys_fallocate system call. User space
+ * requests len bytes at offset. In contrary to fat, we only support
+ * FALLOC_FL_ALLOCATE_RANGE because by leaving the valid data length(VDL)
+ * field, it is unnecessary to zero out the newly allocated clusters.
+ */
+static long exfat_fallocate(struct file *file, int mode,
+			  loff_t offset, loff_t len)
+{
+	struct inode *inode = file->f_mapping->host;
+	loff_t newsize = offset + len;
+	int err = 0;
+
+	/* No support for other modes */
+	if (mode != FALLOC_FL_ALLOCATE_RANGE)
+		return -EOPNOTSUPP;
+
+	/* No support for dir */
+	if (!S_ISREG(inode->i_mode))
+		return -EOPNOTSUPP;
+
+	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
+		return -EIO;
+
+	inode_lock(inode);
+
+	if (newsize <= i_size_read(inode))
+		goto error;
+
+	/* This is just an expanding truncate */
+	err = exfat_cont_expand(inode, newsize);
+
+error:
+	inode_unlock(inode);
+
+	return err;
+}
+
+static bool exfat_allow_set_time(struct mnt_idmap *idmap,
+				 struct exfat_sb_info *sbi, struct inode *inode)
+{
+	mode_t allow_utime = sbi->options.allow_utime;
+
+	if (!vfsuid_eq_kuid(i_uid_into_vfsuid(idmap, inode),
+			    current_fsuid())) {
+		if (vfsgid_in_group_p(i_gid_into_vfsgid(idmap, inode)))
+			allow_utime >>= 3;
+		if (allow_utime & MAY_WRITE)
+			return true;
+	}
+
+	/* use a default check */
+	return false;
+}
+
+static int exfat_sanitize_mode(const struct exfat_sb_info *sbi,
+		struct inode *inode, umode_t *mode_ptr)
+{
+	mode_t i_mode, mask, perm;
+
+	i_mode = inode->i_mode;
+
+	mask = (S_ISREG(i_mode) || S_ISLNK(i_mode)) ?
+		sbi->options.fs_fmask : sbi->options.fs_dmask;
+	perm = *mode_ptr & ~(S_IFMT | mask);
+
+	/* Of the r and x bits, all (subject to umask) must be present.*/
+	if ((perm & 0555) != (i_mode & 0555))
+		return -EPERM;
+
+	if (exfat_mode_can_hold_ro(inode)) {
+		/*
+		 * Of the w bits, either all (subject to umask) or none must
+		 * be present.
+		 */
+		if ((perm & 0222) && ((perm & 0222) != (0222 & ~mask)))
+			return -EPERM;
+	} else {
+		/*
+		 * If exfat_mode_can_hold_ro(inode) is false, can't change
+		 * w bits.
+		 */
+		if ((perm & 0222) != (0222 & ~mask))
+			return -EPERM;
+	}
+
+	*mode_ptr &= S_IFMT | perm;
+
+	return 0;
+}
+
+/* resize the file length */
+int __exfat_truncate(struct inode *inode)
+{
+	unsigned int num_clusters_new, num_clusters_phys;
+	unsigned int last_clu = EXFAT_FREE_CLUSTER;
+	struct exfat_chain clu;
+	struct super_block *sb = inode->i_sb;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+
+	/* check if the given file ID is opened */
+	if (ei->type != TYPE_FILE && ei->type != TYPE_DIR)
+		return -EPERM;
+
+	exfat_set_volume_dirty(sb);
+
+	num_clusters_new = exfat_bytes_to_cluster_round_up(sbi, i_size_read(inode));
+	num_clusters_phys = exfat_bytes_to_cluster(sbi, exfat_ondisk_size(inode));
+
+	exfat_chain_set(&clu, ei->start_clu, num_clusters_phys, ei->flags);
+
+	if (i_size_read(inode) > 0) {
+		/*
+		 * Truncate FAT chain num_clusters after the first cluster
+		 * num_clusters = min(new, phys);
+		 */
+		unsigned int num_clusters =
+			min(num_clusters_new, num_clusters_phys);
+
+		/*
+		 * Follow FAT chain
+		 * (defensive coding - works fine even with corrupted FAT table
+		 */
+		if (clu.flags == ALLOC_NO_FAT_CHAIN) {
+			clu.dir += num_clusters;
+			clu.size -= num_clusters;
+		} else {
+			while (num_clusters > 0) {
+				last_clu = clu.dir;
+				if (exfat_get_next_cluster(sb, &(clu.dir)))
+					return -EIO;
+
+				num_clusters--;
+				clu.size--;
+			}
+		}
+	} else {
+		ei->flags = ALLOC_NO_FAT_CHAIN;
+		ei->start_clu = EXFAT_EOF_CLUSTER;
+	}
+
+	if (i_size_read(inode) < ei->valid_size)
+		ei->valid_size = ei->zeroed_size = i_size_read(inode);
+
+	if (ei->type == TYPE_FILE)
+		ei->attr |= EXFAT_ATTR_ARCHIVE;
+
+	/*
+	 * update the directory entry
+	 *
+	 * If the directory entry is updated by mark_inode_dirty(), the
+	 * directory entry will be written after a writeback cycle of
+	 * updating the bitmap/FAT, which may result in clusters being
+	 * freed but referenced by the directory entry in the event of a
+	 * sudden power failure.
+	 * __exfat_write_inode() is called for directory entry, bitmap
+	 * and FAT to be written in a same writeback.
+	 */
+	if (__exfat_write_inode(inode, inode_needs_sync(inode)))
+		return -EIO;
+
+	/* cut off from the FAT chain */
+	if (ei->flags == ALLOC_FAT_CHAIN && last_clu != EXFAT_FREE_CLUSTER &&
+			last_clu != EXFAT_EOF_CLUSTER) {
+		if (exfat_ent_set(sb, last_clu, EXFAT_EOF_CLUSTER))
+			return -EIO;
+	}
+
+	/* invalidate cache and free the clusters */
+	/* clear exfat cache */
+	exfat_cache_inval_inode(inode);
+
+	/* hint information */
+	ei->hint_bmap.off = EXFAT_EOF_CLUSTER;
+	ei->hint_bmap.clu = EXFAT_EOF_CLUSTER;
+
+	/* hint_stat will be used if this is directory. */
+	ei->hint_stat.eidx = 0;
+	ei->hint_stat.clu = ei->start_clu;
+	ei->hint_femp.eidx = EXFAT_HINT_NONE;
+
+	/* free the clusters */
+	if (exfat_free_cluster(inode, &clu))
+		return -EIO;
+
+	return 0;
+}
+
+static void exfat_truncate(struct inode *inode)
+{
+	struct super_block *sb = inode->i_sb;
+	struct exfat_sb_info *sbi = EXFAT_SB(sb);
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+	int err;
+
+	mutex_lock(&sbi->s_lock);
+	if (ei->start_clu == 0) {
+		/*
+		 * Empty start_clu != ~0 (not allocated)
+		 */
+		exfat_fs_error(sb, "tried to truncate zeroed cluster.");
+		goto write_size;
+	}
+
+	err = __exfat_truncate(inode);
+	if (err)
+		goto write_size;
+
+	inode->i_blocks = round_up(i_size_read(inode), sbi->cluster_size) >> 9;
+write_size:
+	mutex_unlock(&sbi->s_lock);
+}
+
+int exfat_getattr(struct mnt_idmap *idmap, const struct path *path,
+		  struct kstat *stat, unsigned int request_mask,
+		  unsigned int query_flags)
+{
+	struct inode *inode = d_backing_inode(path->dentry);
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+
+	generic_fillattr(idmap, request_mask, inode, stat);
+	exfat_truncate_atime(&stat->atime);
+	stat->result_mask |= STATX_BTIME;
+	stat->btime.tv_sec = ei->i_crtime.tv_sec;
+	stat->btime.tv_nsec = ei->i_crtime.tv_nsec;
+	stat->blksize = EXFAT_SB(inode->i_sb)->cluster_size;
+	return 0;
+}
+
+int exfat_fileattr_get(struct dentry *dentry, struct file_kattr *fa)
+{
+	/*
+	 * exFAT compares filenames through an upcase table, so lookup
+	 * is always case-insensitive. Long names are stored in UTF-16
+	 * with case intact; CASENONPRESERVING stays clear.
+	 */
+	fa->fsx_xflags |= FS_XFLAG_CASEFOLD;
+	fa->flags |= FS_CASEFOLD_FL;
+	return 0;
+}
+
+int exfat_setattr(struct mnt_idmap *idmap, struct dentry *dentry,
+		  struct iattr *attr)
+{
+	struct exfat_sb_info *sbi = EXFAT_SB(dentry->d_sb);
+	struct inode *inode = dentry->d_inode;
+	unsigned int ia_valid;
+	int error;
+
+	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
+		return -EIO;
+
+	if ((attr->ia_valid & ATTR_SIZE) &&
+	    attr->ia_size > i_size_read(inode)) {
+		error = exfat_cont_expand(inode, attr->ia_size);
+		if (error || attr->ia_valid == ATTR_SIZE)
+			return error;
+		attr->ia_valid &= ~ATTR_SIZE;
+	}
+
+	/* Check for setting the inode time. */
+	ia_valid = attr->ia_valid;
+	if ((ia_valid & (ATTR_MTIME_SET | ATTR_ATIME_SET | ATTR_TIMES_SET)) &&
+	    exfat_allow_set_time(idmap, sbi, inode)) {
+		attr->ia_valid &= ~(ATTR_MTIME_SET | ATTR_ATIME_SET |
+				ATTR_TIMES_SET);
+	}
+
+	error = setattr_prepare(idmap, dentry, attr);
+	attr->ia_valid = ia_valid;
+	if (error)
+		goto out;
+
+	if (((attr->ia_valid & ATTR_UID) &&
+	      (!uid_eq(from_vfsuid(idmap, i_user_ns(inode), attr->ia_vfsuid),
+	       sbi->options.fs_uid))) ||
+	    ((attr->ia_valid & ATTR_GID) &&
+	      (!gid_eq(from_vfsgid(idmap, i_user_ns(inode), attr->ia_vfsgid),
+	       sbi->options.fs_gid))) ||
+	    ((attr->ia_valid & ATTR_MODE) &&
+	     (attr->ia_mode & ~(S_IFREG | S_IFLNK | S_IFDIR | 0777)))) {
+		error = -EPERM;
+		goto out;
+	}
+
+	/*
+	 * We don't return -EPERM here. Yes, strange, but this is too
+	 * old behavior.
+	 */
+	if (attr->ia_valid & ATTR_MODE) {
+		if (exfat_sanitize_mode(sbi, inode, &attr->ia_mode) < 0)
+			attr->ia_valid &= ~ATTR_MODE;
+	}
+
+	if (attr->ia_valid & ATTR_SIZE)
+		inode_set_mtime_to_ts(inode, inode_set_ctime_current(inode));
+
+	setattr_copy(idmap, inode, attr);
+	exfat_truncate_inode_atime(inode);
+
+	if (attr->ia_valid & ATTR_SIZE) {
+		/*
+		 * Wait for any in-flight DIO to finish before truncating to
+		 * prevent a concurrent DIO from writing to clusters that are
+		 * about to be freed.
+		 */
+		inode_dio_wait(inode);
+		truncate_setsize(inode, attr->ia_size);
+
+		/*
+		 * __exfat_write_inode() is called from exfat_truncate(), inode
+		 * is already written by it, so mark_inode_dirty() is unneeded.
+		 */
+		exfat_truncate(inode);
+	} else
+		mark_inode_dirty(inode);
+
+out:
+	return error;
+}
+
+/*
+ * modified ioctls from fat/file.c by Welmer Almesberger
+ */
+static int exfat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
+{
+	u32 attr;
+
+	inode_lock_shared(inode);
+	attr = exfat_make_attr(inode);
+	inode_unlock_shared(inode);
+
+	return put_user(attr, user_attr);
+}
+
+static int exfat_ioctl_set_attributes(struct file *file, u32 __user *user_attr)
+{
+	struct inode *inode = file_inode(file);
+	struct exfat_sb_info *sbi = EXFAT_SB(inode->i_sb);
+	int is_dir = S_ISDIR(inode->i_mode);
+	u32 attr, oldattr;
+	struct iattr ia;
+	int err;
+
+	err = get_user(attr, user_attr);
+	if (err)
+		goto out;
+
+	err = mnt_want_write_file(file);
+	if (err)
+		goto out;
+	inode_lock(inode);
+
+	oldattr = exfat_make_attr(inode);
+
+	/*
+	 * Mask attributes so we don't set reserved fields.
+	 */
+	attr &= (EXFAT_ATTR_READONLY | EXFAT_ATTR_HIDDEN | EXFAT_ATTR_SYSTEM |
+		 EXFAT_ATTR_ARCHIVE);
+	attr |= (is_dir ? EXFAT_ATTR_SUBDIR : 0);
+
+	/* Equivalent to a chmod() */
+	ia.ia_valid = ATTR_MODE | ATTR_CTIME;
+	ia.ia_ctime = current_time(inode);
+	if (is_dir)
+		ia.ia_mode = exfat_make_mode(sbi, attr, 0777);
+	else
+		ia.ia_mode = exfat_make_mode(sbi, attr, 0666 | (inode->i_mode & 0111));
+
+	/* The root directory has no attributes */
+	if (inode->i_ino == EXFAT_ROOT_INO && attr != EXFAT_ATTR_SUBDIR) {
+		err = -EINVAL;
+		goto out_unlock_inode;
+	}
+
+	if (((attr | oldattr) & EXFAT_ATTR_SYSTEM) &&
+	    !capable(CAP_LINUX_IMMUTABLE)) {
+		err = -EPERM;
+		goto out_unlock_inode;
+	}
+
+	/*
+	 * The security check is questionable...  We single
+	 * out the RO attribute for checking by the security
+	 * module, just because it maps to a file mode.
+	 */
+	err = security_inode_setattr(file_mnt_idmap(file),
+				     file->f_path.dentry, &ia);
+	if (err)
+		goto out_unlock_inode;
+
+	/* This MUST be done before doing anything irreversible... */
+	err = exfat_setattr(file_mnt_idmap(file), file->f_path.dentry, &ia);
+	if (err)
+		goto out_unlock_inode;
+
+	fsnotify_change(file->f_path.dentry, ia.ia_valid);
+
+	exfat_save_attr(inode, attr);
+	mark_inode_dirty(inode);
+out_unlock_inode:
+	inode_unlock(inode);
+	mnt_drop_write_file(file);
+out:
+	return err;
+}
+
+static int exfat_ioctl_fitrim(struct inode *inode, unsigned long arg)
+{
+	struct fstrim_range range;
+	int ret = 0;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (!bdev_max_discard_sectors(inode->i_sb->s_bdev))
+		return -EOPNOTSUPP;
+
+	if (copy_from_user(&range, (struct fstrim_range __user *)arg, sizeof(range)))
+		return -EFAULT;
+
+	range.minlen = max_t(unsigned int, range.minlen,
+				bdev_discard_granularity(inode->i_sb->s_bdev));
+
+	ret = exfat_trim_fs(inode, &range);
+	if (ret < 0)
+		return ret;
+
+	if (copy_to_user((struct fstrim_range __user *)arg, &range, sizeof(range)))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int exfat_ioctl_shutdown(struct super_block *sb, unsigned long arg)
+{
+	u32 flags;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (get_user(flags, (__u32 __user *)arg))
+		return -EFAULT;
+
+	return exfat_force_shutdown(sb, flags);
+}
+
+static int exfat_ioctl_get_volume_label(struct super_block *sb, unsigned long arg)
+{
+	int ret;
+	char label[FSLABEL_MAX] = {0};
+	struct exfat_uni_name uniname;
+
+	ret = exfat_read_volume_label(sb, &uniname);
+	if (ret < 0)
+		return ret;
+
+	ret = exfat_utf16_to_nls(sb, &uniname, label, sizeof(label));
+	if (ret < 0)
+		return ret;
+
+	if (copy_to_user((char __user *)arg, label, ret + 1))
+		return -EFAULT;
+
+	return 0;
+}
+
+static int exfat_ioctl_set_volume_label(struct super_block *sb,
+					unsigned long arg)
+{
+	int ret = 0, lossy, label_len;
+	char label[FSLABEL_MAX] = {0};
+	struct exfat_uni_name uniname;
+
+	if (!capable(CAP_SYS_ADMIN))
+		return -EPERM;
+
+	if (copy_from_user(label, (char __user *)arg, FSLABEL_MAX))
+		return -EFAULT;
+
+	memset(&uniname, 0, sizeof(uniname));
+	label_len = strnlen(label, FSLABEL_MAX - 1);
+	if (label[0]) {
+		ret = exfat_nls_to_utf16(sb, label, label_len,
+					 &uniname, &lossy);
+		if (ret < 0)
+			return ret;
+		else if (lossy & NLS_NAME_LOSSY)
+			return -EINVAL;
+	}
+
+	uniname.name_len = ret;
+
+	return exfat_write_volume_label(sb, &uniname);
+}
+
+long exfat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	struct inode *inode = file_inode(filp);
+	u32 __user *user_attr = (u32 __user *)arg;
+
+	switch (cmd) {
+	case FAT_IOCTL_GET_ATTRIBUTES:
+		return exfat_ioctl_get_attributes(inode, user_attr);
+	case FAT_IOCTL_SET_ATTRIBUTES:
+		return exfat_ioctl_set_attributes(filp, user_attr);
+	case EXFAT_IOC_SHUTDOWN:
+		return exfat_ioctl_shutdown(inode->i_sb, arg);
+	case FITRIM:
+		return exfat_ioctl_fitrim(inode, arg);
+	case FS_IOC_GETFSLABEL:
+		return exfat_ioctl_get_volume_label(inode->i_sb, arg);
+	case FS_IOC_SETFSLABEL:
+		return exfat_ioctl_set_volume_label(inode->i_sb, arg);
+	default:
+		return -ENOTTY;
+	}
+}
+
+#ifdef CONFIG_COMPAT
+long exfat_compat_ioctl(struct file *filp, unsigned int cmd,
+				unsigned long arg)
+{
+	return exfat_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
+}
+#endif
+
+int exfat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
+{
+	struct inode *inode = filp->f_mapping->host;
+	int err;
+
+	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
+		return -EIO;
+
+	err = simple_fsync_noflush(filp, start, end, datasync);
+	if (err)
+		return err;
+
+	err = sync_blockdev(inode->i_sb->s_bdev);
+	if (err)
+		return err;
+
+	return blkdev_issue_flush(inode->i_sb->s_bdev);
+}
+
+/*
+ * exfat_zero_new_range - zero [start, end) without overwriting uptodate blocks
+ *
+ * Uptodate blocks may contain data written through a shared mapping beyond
+ * valid_size.
+ */
+static int exfat_zero_new_range(struct inode *inode, loff_t start, loff_t end)
+{
+	struct address_space *mapping = inode->i_mapping;
+	unsigned int blocksize = i_blocksize(inode);
+	loff_t pos = start;
+	int err;
+
+	while (pos < end) {
+		loff_t next = min_t(loff_t,
+				round_down(pos, PAGE_SIZE) + PAGE_SIZE, end);
+		struct folio *folio;
+		loff_t bpos;
+
+		folio = filemap_get_folio(mapping, pos >> PAGE_SHIFT);
+		if (IS_ERR(folio)) {
+			err = iomap_zero_range(inode, pos, next - pos, NULL,
+					       &exfat_iomap_ops, NULL, NULL);
+			if (err < 0)
+				return err;
+			pos = next;
+			continue;
+		}
+
+		if (folio_test_uptodate(folio)) {
+			folio_lock(folio);
+			if (folio->mapping == mapping)
+				folio_mark_dirty(folio);
+			folio_unlock(folio);
+			folio_put(folio);
+			pos = next;
+			continue;
+		}
+
+		/*
+		 * Zero not-uptodate block runs. iomap_zero_range() requires an
+		 * unlocked folio, so recheck ->mapping after each call.
+		 */
+		folio_lock(folio);
+		bpos = pos;
+		while (bpos < next) {
+			loff_t rstart, rend;
+
+			if (folio->mapping != mapping) {
+				folio_unlock(folio);
+				err = iomap_zero_range(inode, bpos, next - bpos,
+						NULL, &exfat_iomap_ops, NULL, NULL);
+				if (err < 0) {
+					folio_put(folio);
+					return err;
+				}
+				folio_lock(folio);
+				break;
+			}
+
+			if (iomap_is_partially_uptodate(folio,
+					offset_in_folio(folio, bpos), blocksize)) {
+				bpos += blocksize;
+				continue;
+			}
+
+			rstart = bpos;
+			rend = min_t(loff_t, bpos + blocksize, next);
+			while (rend < next &&
+			       !iomap_is_partially_uptodate(folio,
+					offset_in_folio(folio, rend), blocksize))
+				rend = min_t(loff_t, rend + blocksize, next);
+
+			folio_unlock(folio);
+			err = iomap_zero_range(inode, rstart, rend - rstart,
+					NULL, &exfat_iomap_ops, NULL, NULL);
+			if (err < 0) {
+				folio_put(folio);
+				return err;
+			}
+			folio_lock(folio);
+			bpos = rend;
+		}
+
+		/*
+		 * Dirty only a fully uptodate folio. Dirtying a partial folio could
+		 * write uninitialised cache contents over valid on-disk blocks.
+		 */
+		if (folio->mapping == mapping && folio_test_uptodate(folio))
+			folio_mark_dirty(folio);
+		folio_unlock(folio);
+		folio_put(folio);
+		pos = next;
+	}
+
+	return 0;
+}
+
+static int exfat_extend_valid_size(struct inode *inode, loff_t new_valid_size)
+{
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+	loff_t old_valid_size = ei->valid_size;
+	int ret = 0;
+
+	if (old_valid_size < new_valid_size) {
+		/* Do not re-zero blocks already covered by zeroed_size. */
+		loff_t gap_start = max(old_valid_size, ei->zeroed_size);
+
+		if (i_size_read(inode) < new_valid_size) {
+			/*
+			 * Allocate clusters before increasing i_size. The gap
+			 * may already be zeroed, so the subsequent zeroing
+			 * can be skipped.
+			 */
+			ret = exfat_cont_expand(inode, new_valid_size);
+			if (ret)
+				return ret;
+		}
+
+		/*
+		 * Revoke writable PTEs while zeroing the gap. A racing mmap
+		 * store re-faults through exfat_page_mkwrite() after valid_size
+		 * is updated.
+		 */
+		filemap_invalidate_lock(inode->i_mapping);
+		if (gap_start < new_valid_size)
+			unmap_mapping_range(inode->i_mapping, gap_start,
+					new_valid_size - gap_start, 0);
+		ret = exfat_zero_new_range(inode, gap_start, new_valid_size);
+		filemap_invalidate_unlock(inode->i_mapping);
+		if (ret) {
+			truncate_setsize(inode, old_valid_size);
+			exfat_truncate(inode);
+			return ret;
+		}
+
+		ei->valid_size = new_valid_size;
+		if (ei->zeroed_size < round_up(new_valid_size, i_blocksize(inode)))
+			ei->zeroed_size = round_up(new_valid_size, i_blocksize(inode));
+		mark_inode_dirty(inode);
+	}
+
+	return ret;
+}
+
+static ssize_t exfat_fallback_buffered_write(struct kiocb *iocb,
+		struct iov_iter *from)
+{
+	loff_t offset = iocb->ki_pos, end;
+	ssize_t written;
+	int ret;
+
+	iocb->ki_flags &= ~IOCB_DIRECT;
+
+	written = iomap_file_buffered_write(iocb, from, &exfat_write_iomap_ops,
+			NULL, NULL);
+	if (written < 0)
+		return written;
+
+	end = iocb->ki_pos + written - 1;
+	ret = filemap_write_and_wait_range(iocb->ki_filp->f_mapping,
+			offset, end);
+	if (ret)
+		return -EIO;
+
+	invalidate_mapping_pages(iocb->ki_filp->f_mapping,
+			offset >> PAGE_SHIFT,
+			end >> PAGE_SHIFT);
+
+	return written;
+}
+
+static ssize_t exfat_dio_write_iter(struct kiocb *iocb, struct iov_iter *from)
+{
+	ssize_t ret;
+
+	ret = iomap_dio_rw(iocb, from, &exfat_write_iomap_ops,
+			&exfat_write_dio_ops, 0, NULL, 0);
+	if (ret == -ENOTBLK)
+		ret = 0;
+	else if (ret < 0)
+		return ret;
+
+	if (iov_iter_count(from)) {
+		ssize_t written;
+
+		written = exfat_fallback_buffered_write(iocb, from);
+		if (written < 0)
+			return written;
+		ret += written;
+	}
+
+	return ret;
+}
+
+static ssize_t exfat_file_write_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+	ssize_t ret;
+	struct file *file = iocb->ki_filp;
+	struct inode *inode = file_inode(file);
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+	loff_t pos = iocb->ki_pos;
+	loff_t valid_size;
+	int err;
+
+	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
+		return -EIO;
+
+	inode_lock(inode);
+
+	if (pos > i_size_read(inode))
+		truncate_pagecache(inode, i_size_read(inode));
+
+	valid_size = ei->valid_size;
+
+	ret = generic_write_checks(iocb, iter);
+	if (ret <= 0)
+		goto unlock;
+
+	err = file_modified(iocb->ki_filp);
+	if (err) {
+		ret = err;
+		goto unlock;
+	}
+
+	if (pos > valid_size) {
+		ret = exfat_extend_valid_size(inode, pos);
+		if (ret < 0 && ret != -ENOSPC) {
+			exfat_err(inode->i_sb,
+				"write: fail to zero from %llu to %llu(%zd)",
+				valid_size, pos, ret);
+		}
+		if (ret < 0)
+			goto unlock;
+	}
+
+	if (iocb->ki_flags & IOCB_DIRECT)
+		ret = exfat_dio_write_iter(iocb, iter);
+	else
+		ret = iomap_file_buffered_write(iocb, iter,
+				&exfat_write_iomap_ops, NULL, NULL);
+	if (ret < 0)
+		goto unlock;
+
+	inode_unlock(inode);
+
+	if (pos > valid_size)
+		pos = valid_size;
+
+	if (iocb->ki_pos > pos) {
+		ssize_t err = generic_write_sync(iocb, iocb->ki_pos - pos);
+
+		if (err < 0)
+			return err;
+	}
+
+	return ret;
+
+unlock:
+	inode_unlock(inode);
+
+	return ret;
+}
+
+static ssize_t exfat_file_read_iter(struct kiocb *iocb, struct iov_iter *iter)
+{
+	struct inode *inode = file_inode(iocb->ki_filp);
+	ssize_t ret;
+
+	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
+		return -EIO;
+
+	inode_lock_shared(inode);
+
+	if (iocb->ki_flags & IOCB_DIRECT) {
+		file_accessed(iocb->ki_filp);
+		ret = iomap_dio_rw(iocb, iter, &exfat_iomap_ops, NULL, 0,
+				NULL, 0);
+	} else {
+		ret = generic_file_read_iter(iocb, iter);
+	}
+
+	inode_unlock_shared(inode);
+
+	return ret;
+}
+
+static vm_fault_t exfat_page_mkwrite(struct vm_fault *vmf)
+{
+	struct inode *inode = file_inode(vmf->vma->vm_file);
+	struct exfat_inode_info *ei = EXFAT_I(inode);
+	vm_fault_t ret;
+	loff_t new_valid_size, mmap_valid_size, fault_page_start;
+
+	if (!inode_trylock(inode))
+		return VM_FAULT_RETRY;
+
+	mmap_valid_size = ((loff_t)vmf->pgoff + 1) << PAGE_SHIFT;
+	fault_page_start = ((loff_t)vmf->pgoff) << PAGE_SHIFT;
+	new_valid_size = min(mmap_valid_size, i_size_read(inode));
+
+	if (ei->valid_size < new_valid_size) {
+		if (ei->zeroed_size < fault_page_start) {
+			int err;
+
+			/*
+			 * Zero only the gap below the faulting page. The read
+			 * fault populated its folio and iomap_page_mkwrite()
+			 * will dirty it.
+			 */
+			err = exfat_zero_new_range(inode, ei->zeroed_size,
+					fault_page_start);
+			if (err < 0) {
+				inode_unlock(inode);
+				return vmf_fs_error(err);
+			}
+		}
+
+		/*
+		 * Track zeroed_size by block, not page, because writeback stops
+		 * at i_size recording blocks wholly beyond it could skip a
+		 * later required zeroing.
+		 */
+		if (ei->zeroed_size < round_up(new_valid_size, i_blocksize(inode)))
+			ei->zeroed_size = round_up(new_valid_size, i_blocksize(inode));
+		ei->valid_size = new_valid_size;
+		mark_inode_dirty(inode);
+	}
+
+	sb_start_pagefault(inode->i_sb);
+	file_update_time(vmf->vma->vm_file);
+
+	filemap_invalidate_lock_shared(inode->i_mapping);
+	ret = iomap_page_mkwrite(vmf, &exfat_iomap_ops, NULL);
+	filemap_invalidate_unlock_shared(inode->i_mapping);
+	sb_end_pagefault(inode->i_sb);
+	inode_unlock(inode);
+
+	return ret;
+}
+
+static const struct vm_operations_struct exfat_file_vm_ops = {
+	.fault		= filemap_fault,
+	.page_mkwrite	= exfat_page_mkwrite,
+};
+
+static int exfat_file_mmap_prepare(struct vm_area_desc *desc)
+{
+	struct file *file = desc->file;
+
+	if (unlikely(exfat_forced_shutdown(file_inode(desc->file)->i_sb)))
+		return -EIO;
+
+	file_accessed(file);
+	desc->vm_ops = &exfat_file_vm_ops;
+	return 0;
+}
+
+static ssize_t exfat_splice_read(struct file *in, loff_t *ppos,
+		struct pipe_inode_info *pipe, size_t len, unsigned int flags)
+{
+	if (unlikely(exfat_forced_shutdown(file_inode(in)->i_sb)))
+		return -EIO;
+
+	return filemap_splice_read(in, ppos, pipe, len, flags);
+}
+
+static int exfat_file_open(struct inode *inode, struct file *filp)
+{
+	int err;
+
+	if (unlikely(exfat_forced_shutdown(inode->i_sb)))
+		return -EIO;
+
+	err = generic_file_open(inode, filp);
+	if (err)
+		return err;
+
+	filp->f_mode |= FMODE_CAN_ODIRECT;
+
+	return 0;
+}
+
+static loff_t exfat_file_llseek(struct file *file, loff_t offset, int whence)
+{
+	struct inode *inode = file->f_mapping->host;
+
+	switch (whence) {
+	case SEEK_HOLE:
+		inode_lock_shared(inode);
+		offset = iomap_seek_hole(inode, offset, &exfat_iomap_ops);
+		inode_unlock_shared(inode);
+		break;
+	case SEEK_DATA:
+		inode_lock_shared(inode);
+		offset = iomap_seek_data(inode, offset, &exfat_iomap_ops);
+		inode_unlock_shared(inode);
+		break;
+	default:
+		return generic_file_llseek(file, offset, whence);
+	}
+	if (offset < 0)
+		return offset;
+	return vfs_setpos(file, offset, inode->i_sb->s_maxbytes);
+}
+
+const struct file_operations exfat_file_operations = {
+	.open		= exfat_file_open,
+	.llseek		= exfat_file_llseek,
+	.read_iter	= exfat_file_read_iter,
+	.write_iter	= exfat_file_write_iter,
+	.unlocked_ioctl = exfat_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl = exfat_compat_ioctl,
+#endif
+	.mmap_prepare	= exfat_file_mmap_prepare,
+	.fsync		= exfat_file_fsync,
+	.splice_read	= exfat_splice_read,
+	.splice_write	= iter_file_splice_write,
+	.fallocate	= exfat_fallocate,
+	.setlease	= generic_setlease,
+};
+
+const struct inode_operations exfat_file_inode_operations = {
+	.setattr	= exfat_setattr,
+	.getattr	= exfat_getattr,
+	.fileattr_get	= exfat_fileattr_get,
+};