Update Linux to v5.4.2

Change-Id: Idf6911045d9d382da2cfe01b1edff026404ac8fd
diff --git a/fs/fat/Kconfig b/fs/fat/Kconfig
index 3ff1772..718163d 100644
--- a/fs/fat/Kconfig
+++ b/fs/fat/Kconfig
@@ -1,3 +1,4 @@
+# SPDX-License-Identifier: GPL-2.0-only
 config FAT_FS
 	tristate
 	select NLS
diff --git a/fs/fat/cache.c b/fs/fat/cache.c
index 78d501c..738e427 100644
--- a/fs/fat/cache.c
+++ b/fs/fat/cache.c
@@ -363,7 +363,7 @@
 
 	*phys = 0;
 	*mapped_blocks = 0;
-	if ((sbi->fat_bits != 32) && (inode->i_ino == MSDOS_ROOT_INO)) {
+	if (!is_fat32(sbi) && (inode->i_ino == MSDOS_ROOT_INO)) {
 		if (sector < (sbi->dir_entries >> sbi->dir_per_block_bits)) {
 			*phys = sector + sbi->dir_start;
 			*mapped_blocks = 1;
diff --git a/fs/fat/dir.c b/fs/fat/dir.c
index 7f5f369..054acd9 100644
--- a/fs/fat/dir.c
+++ b/fs/fat/dir.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/fs/fat/dir.c
  *
@@ -57,7 +58,7 @@
 	if ((iblock & (sbi->sec_per_clus - 1)) || sbi->sec_per_clus == 1)
 		return;
 	/* root dir of FAT12/FAT16 */
-	if ((sbi->fat_bits != 32) && (dir->i_ino == MSDOS_ROOT_INO))
+	if (!is_fat32(sbi) && (dir->i_ino == MSDOS_ROOT_INO))
 		return;
 
 	bh = sb_find_get_block(sb, phys);
@@ -87,9 +88,7 @@
 	int err, offset;
 
 next:
-	if (*bh)
-		brelse(*bh);
-
+	brelse(*bh);
 	*bh = NULL;
 	iblock = *pos >> sb->s_blocksize_bits;
 	err = fat_bmap(dir, iblock, &phys, &mapped_blocks, 0, false);
@@ -369,7 +368,9 @@
 	}
 
 	memcpy(work, de->name, sizeof(work));
-	/* see namei.c, msdos_format_name */
+	/* For an explanation of the special treatment of 0x05 in
+	 * filenames, see msdos_format_name in namei_msdos.c
+	 */
 	if (work[0] == 0x05)
 		work[0] = 0xE5;
 
@@ -803,7 +804,7 @@
 		return fat_generic_ioctl(filp, cmd, arg);
 	}
 
-	if (!access_ok(VERIFY_WRITE, d1, sizeof(struct __fat_dirent[2])))
+	if (!access_ok(d1, sizeof(struct __fat_dirent[2])))
 		return -EFAULT;
 	/*
 	 * Yes, we don't need this put_user() absolutely. However old
@@ -843,7 +844,7 @@
 		return fat_generic_ioctl(filp, cmd, (unsigned long)arg);
 	}
 
-	if (!access_ok(VERIFY_WRITE, d1, sizeof(struct compat_dirent[2])))
+	if (!access_ok(d1, sizeof(struct compat_dirent[2])))
 		return -EFAULT;
 	/*
 	 * Yes, we don't need this put_user() absolutely. However old
@@ -1071,7 +1072,7 @@
 		}
 	}
 
-	dir->i_mtime = dir->i_atime = current_time(dir);
+	fat_truncate_time(dir, NULL, S_ATIME|S_MTIME);
 	if (IS_DIRSYNC(dir))
 		(void)fat_sync_inode(dir);
 	else
@@ -1097,8 +1098,11 @@
 			err = -ENOMEM;
 			goto error;
 		}
+		/* Avoid race with userspace read via bdev */
+		lock_buffer(bhs[n]);
 		memset(bhs[n]->b_data, 0, sb->s_blocksize);
 		set_buffer_uptodate(bhs[n]);
+		unlock_buffer(bhs[n]);
 		mark_buffer_dirty_inode(bhs[n], dir);
 
 		n++;
@@ -1155,6 +1159,8 @@
 	fat_time_unix2fat(sbi, ts, &time, &date, &time_cs);
 
 	de = (struct msdos_dir_entry *)bhs[0]->b_data;
+	/* Avoid race with userspace read via bdev */
+	lock_buffer(bhs[0]);
 	/* filling the new directory slots ("." and ".." entries) */
 	memcpy(de[0].name, MSDOS_DOT, MSDOS_NAME);
 	memcpy(de[1].name, MSDOS_DOTDOT, MSDOS_NAME);
@@ -1177,6 +1183,7 @@
 	de[0].size = de[1].size = 0;
 	memset(de + 2, 0, sb->s_blocksize - 2 * sizeof(*de));
 	set_buffer_uptodate(bhs[0]);
+	unlock_buffer(bhs[0]);
 	mark_buffer_dirty_inode(bhs[0], dir);
 
 	err = fat_zeroed_cluster(dir, blknr, 1, bhs, MAX_BUF_PER_PAGE);
@@ -1234,11 +1241,14 @@
 
 			/* fill the directory entry */
 			copy = min(size, sb->s_blocksize);
+			/* Avoid race with userspace read via bdev */
+			lock_buffer(bhs[n]);
 			memcpy(bhs[n]->b_data, slots, copy);
+			set_buffer_uptodate(bhs[n]);
+			unlock_buffer(bhs[n]);
+			mark_buffer_dirty_inode(bhs[n], dir);
 			slots += copy;
 			size -= copy;
-			set_buffer_uptodate(bhs[n]);
-			mark_buffer_dirty_inode(bhs[n], dir);
 			if (!size)
 				break;
 			n++;
@@ -1311,7 +1321,7 @@
 		}
 	}
 	if (dir->i_ino == MSDOS_ROOT_INO) {
-		if (sbi->fat_bits != 32)
+		if (!is_fat32(sbi))
 			goto error;
 	} else if (MSDOS_I(dir)->i_start == 0) {
 		fat_msg(sb, KERN_ERR, "Corrupted directory (i_pos %lld)",
diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index 9d7d2d5..922a0c6 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -142,6 +142,34 @@
 	return sb->s_fs_info;
 }
 
+/*
+ * Functions that determine the variant of the FAT file system (i.e.,
+ * whether this is FAT12, FAT16 or FAT32.
+ */
+static inline bool is_fat12(const struct msdos_sb_info *sbi)
+{
+	return sbi->fat_bits == 12;
+}
+
+static inline bool is_fat16(const struct msdos_sb_info *sbi)
+{
+	return sbi->fat_bits == 16;
+}
+
+static inline bool is_fat32(const struct msdos_sb_info *sbi)
+{
+	return sbi->fat_bits == 32;
+}
+
+/* Maximum number of clusters */
+static inline u32 max_fat(struct super_block *sb)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	return is_fat32(sbi) ? MAX_FAT32 :
+		is_fat16(sbi) ? MAX_FAT16 : MAX_FAT12;
+}
+
 static inline struct msdos_inode_info *MSDOS_I(struct inode *inode)
 {
 	return container_of(inode, struct msdos_inode_info, vfs_inode);
@@ -257,7 +285,7 @@
 				const struct msdos_dir_entry *de)
 {
 	int cluster = le16_to_cpu(de->start);
-	if (sbi->fat_bits == 32)
+	if (is_fat32(sbi))
 		cluster |= (le16_to_cpu(de->starthi) << 16);
 	return cluster;
 }
@@ -416,6 +444,10 @@
 			      __le16 __time, __le16 __date, u8 time_cs);
 extern void fat_time_unix2fat(struct msdos_sb_info *sbi, struct timespec64 *ts,
 			      __le16 *time, __le16 *date, u8 *time_cs);
+extern int fat_truncate_time(struct inode *inode, struct timespec64 *now,
+			     int flags);
+extern int fat_update_time(struct inode *inode, struct timespec64 *now,
+			   int flags);
 extern int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs);
 
 int fat_cache_init(void);
diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index f58c0ca..3647c65 100644
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -1,6 +1,6 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  * Copyright (C) 2004, OGAWA Hirofumi
- * Released under GPL v2.
  */
 
 #include <linux/blkdev.h>
@@ -290,19 +290,17 @@
 
 	mutex_init(&sbi->fat_lock);
 
-	switch (sbi->fat_bits) {
-	case 32:
+	if (is_fat32(sbi)) {
 		sbi->fatent_shift = 2;
 		sbi->fatent_ops = &fat32_ops;
-		break;
-	case 16:
+	} else if (is_fat16(sbi)) {
 		sbi->fatent_shift = 1;
 		sbi->fatent_ops = &fat16_ops;
-		break;
-	case 12:
+	} else if (is_fat12(sbi)) {
 		sbi->fatent_shift = -1;
 		sbi->fatent_ops = &fat12_ops;
-		break;
+	} else {
+		fat_fs_error(sb, "invalid FAT variant, %u bits", sbi->fat_bits);
 	}
 }
 
@@ -310,7 +308,7 @@
 {
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
 
-	if (sb_rdonly(sb) || sbi->fat_bits != 32)
+	if (sb_rdonly(sb) || !is_fat32(sbi))
 		return;
 
 	__mark_inode_dirty(sbi->fsinfo_inode, I_DIRTY_SYNC);
@@ -327,7 +325,7 @@
 	/* Is this fatent's blocks including this entry? */
 	if (!fatent->nr_bhs || bhs[0]->b_blocknr != blocknr)
 		return 0;
-	if (sbi->fat_bits == 12) {
+	if (is_fat12(sbi)) {
 		if ((offset + 1) < sb->s_blocksize) {
 			/* This entry is on bhs[0]. */
 			if (fatent->nr_bhs == 2) {
@@ -390,8 +388,11 @@
 				err = -ENOMEM;
 				goto error;
 			}
+			/* Avoid race with userspace read via bdev */
+			lock_buffer(c_bh);
 			memcpy(c_bh->b_data, bhs[n]->b_data, sb->s_blocksize);
 			set_buffer_uptodate(c_bh);
+			unlock_buffer(c_bh);
 			mark_buffer_dirty_inode(c_bh, sbi->fat_inode);
 			if (sb->s_flags & SB_SYNCHRONOUS)
 				err = sync_dirty_buffer(c_bh);
diff --git a/fs/fat/file.c b/fs/fat/file.c
index 4f3d72f..4614c0b 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/fs/fat/file.c
  *
@@ -193,12 +194,17 @@
 int fat_file_fsync(struct file *filp, loff_t start, loff_t end, int datasync)
 {
 	struct inode *inode = filp->f_mapping->host;
-	int res, err;
+	int err;
 
-	res = generic_file_fsync(filp, start, end, datasync);
+	err = __generic_file_fsync(filp, start, end, datasync);
+	if (err)
+		return err;
+
 	err = sync_mapping_buffers(MSDOS_SB(inode->i_sb)->fat_inode->i_mapping);
+	if (err)
+		return err;
 
-	return res ? res : err;
+	return blkdev_issue_flush(inode->i_sb->s_bdev, GFP_KERNEL, NULL);
 }
 
 
@@ -214,6 +220,7 @@
 #endif
 	.fsync		= fat_file_fsync,
 	.splice_read	= generic_file_splice_read,
+	.splice_write	= iter_file_splice_write,
 	.fallocate	= fat_fallocate,
 };
 
@@ -227,7 +234,7 @@
 	if (err)
 		goto out;
 
-	inode->i_ctime = inode->i_mtime = current_time(inode);
+	fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
 	mark_inode_dirty(inode);
 	if (IS_SYNC(inode)) {
 		int err2;
@@ -330,7 +337,7 @@
 		MSDOS_I(inode)->i_logstart = 0;
 	}
 	MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
-	inode->i_ctime = inode->i_mtime = current_time(inode);
+	fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
 	if (wait) {
 		err = fat_sync_inode(inode);
 		if (err) {
@@ -542,6 +549,18 @@
 		up_write(&MSDOS_I(inode)->truncate_lock);
 	}
 
+	/*
+	 * setattr_copy can't truncate these appropriately, so we'll
+	 * copy them ourselves
+	 */
+	if (attr->ia_valid & ATTR_ATIME)
+		fat_truncate_time(inode, &attr->ia_atime, S_ATIME);
+	if (attr->ia_valid & ATTR_CTIME)
+		fat_truncate_time(inode, &attr->ia_ctime, S_CTIME);
+	if (attr->ia_valid & ATTR_MTIME)
+		fat_truncate_time(inode, &attr->ia_mtime, S_MTIME);
+	attr->ia_valid &= ~(ATTR_ATIME|ATTR_CTIME|ATTR_MTIME);
+
 	setattr_copy(inode, attr);
 	mark_inode_dirty(inode);
 out:
@@ -552,4 +571,5 @@
 const struct inode_operations fat_file_inode_operations = {
 	.setattr	= fat_setattr,
 	.getattr	= fat_getattr,
+	.update_time	= fat_update_time,
 };
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index d6b81e3..5f04c5c 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/fs/fat/inode.c
  *
@@ -30,6 +31,11 @@
 
 #define KB_IN_SECTORS 2
 
+/* DOS dates from 1980/1/1 through 2107/12/31 */
+#define FAT_DATE_MIN (0<<9 | 1<<5 | 1)
+#define FAT_DATE_MAX (127<<9 | 12<<5 | 31)
+#define FAT_TIME_MAX (23<<11 | 59<<5 | 29)
+
 /*
  * A deserialized copy of the on-disk structure laid out in struct
  * fat_boot_sector.
@@ -244,7 +250,7 @@
 	if (err < len)
 		fat_write_failed(mapping, pos + len);
 	if (!(err < 0) && !(MSDOS_I(inode)->i_attrs & ATTR_ARCH)) {
-		inode->i_mtime = inode->i_ctime = current_time(inode);
+		fat_truncate_time(inode, NULL, S_CTIME|S_MTIME);
 		MSDOS_I(inode)->i_attrs |= ATTR_ARCH;
 		mark_inode_dirty(inode);
 	}
@@ -564,7 +570,7 @@
 				  de->cdate, de->ctime_cs);
 		fat_time_fat2unix(sbi, &inode->i_atime, 0, de->adate, 0);
 	} else
-		inode->i_ctime = inode->i_atime = inode->i_mtime;
+		fat_truncate_time(inode, &inode->i_mtime, S_ATIME|S_CTIME);
 
 	return 0;
 }
@@ -686,7 +692,7 @@
 
 	b = (struct fat_boot_sector *) bh->b_data;
 
-	if (sbi->fat_bits == 32) {
+	if (is_fat32(sbi)) {
 		if (set)
 			b->fat32.state |= FAT_STATE_DIRTY;
 		else
@@ -746,17 +752,11 @@
 	return &ei->vfs_inode;
 }
 
-static void fat_i_callback(struct rcu_head *head)
+static void fat_free_inode(struct inode *inode)
 {
-	struct inode *inode = container_of(head, struct inode, i_rcu);
 	kmem_cache_free(fat_inode_cachep, MSDOS_I(inode));
 }
 
-static void fat_destroy_inode(struct inode *inode)
-{
-	call_rcu(&inode->i_rcu, fat_i_callback);
-}
-
 static void init_once(void *foo)
 {
 	struct msdos_inode_info *ei = (struct msdos_inode_info *)foo;
@@ -920,7 +920,7 @@
 static int fat_show_options(struct seq_file *m, struct dentry *root);
 static const struct super_operations fat_sops = {
 	.alloc_inode	= fat_alloc_inode,
-	.destroy_inode	= fat_destroy_inode,
+	.free_inode	= fat_free_inode,
 	.write_inode	= fat_write_inode,
 	.evict_inode	= fat_evict_inode,
 	.put_super	= fat_put_super,
@@ -1396,7 +1396,7 @@
 	inode->i_mode = fat_make_mode(sbi, ATTR_DIR, S_IRWXUGO);
 	inode->i_op = sbi->dir_ops;
 	inode->i_fop = &fat_dir_operations;
-	if (sbi->fat_bits == 32) {
+	if (is_fat32(sbi)) {
 		MSDOS_I(inode)->i_start = sbi->root_cluster;
 		error = fat_calc_dir_size(inode);
 		if (error < 0)
@@ -1423,7 +1423,7 @@
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
 
 	/* Divide first to avoid overflow */
-	if (sbi->fat_bits != 12) {
+	if (!is_fat12(sbi)) {
 		unsigned long ent_per_sec = sb->s_blocksize * 8 / sbi->fat_bits;
 		return ent_per_sec * sbi->fat_length;
 	}
@@ -1610,6 +1610,7 @@
 	int debug;
 	long error;
 	char buf[50];
+	struct timespec64 ts;
 
 	/*
 	 * GFP_KERNEL is ok here, because while we do hold the
@@ -1626,6 +1627,11 @@
 	sb->s_magic = MSDOS_SUPER_MAGIC;
 	sb->s_op = &fat_sops;
 	sb->s_export_op = &fat_export_ops;
+	/*
+	 * fat timestamps are complex and truncated by fat itself, so
+	 * we set 1 here to be fast
+	 */
+	sb->s_time_gran = 1;
 	mutex_init(&sbi->nfs_build_inode_lock);
 	ratelimit_state_init(&sbi->ratelimit, DEFAULT_RATELIMIT_INTERVAL,
 			     DEFAULT_RATELIMIT_BURST);
@@ -1698,6 +1704,12 @@
 	sbi->free_clus_valid = 0;
 	sbi->prev_free = FAT_START_ENT;
 	sb->s_maxbytes = 0xffffffff;
+	fat_time_fat2unix(sbi, &ts, 0, cpu_to_le16(FAT_DATE_MIN), 0);
+	sb->s_time_min = ts.tv_sec;
+
+	fat_time_fat2unix(sbi, &ts, cpu_to_le16(FAT_TIME_MAX),
+			  cpu_to_le16(FAT_DATE_MAX), 0);
+	sb->s_time_max = ts.tv_sec;
 
 	if (!sbi->fat_length && bpb.fat32_length) {
 		struct fat_boot_fsinfo *fsinfo;
@@ -1738,7 +1750,7 @@
 	}
 
 	/* interpret volume ID as a little endian 32 bit integer */
-	if (sbi->fat_bits == 32)
+	if (is_fat32(sbi))
 		sbi->vol_id = bpb.fat32_vol_id;
 	else /* fat 16 or 12 */
 		sbi->vol_id = bpb.fat16_vol_id;
@@ -1764,11 +1776,11 @@
 
 	total_clusters = (total_sectors - sbi->data_start) / sbi->sec_per_clus;
 
-	if (sbi->fat_bits != 32)
+	if (!is_fat32(sbi))
 		sbi->fat_bits = (total_clusters > MAX_FAT12) ? 16 : 12;
 
 	/* some OSes set FAT_STATE_DIRTY and clean it on unmount. */
-	if (sbi->fat_bits == 32)
+	if (is_fat32(sbi))
 		sbi->dirty = bpb.fat32_state & FAT_STATE_DIRTY;
 	else /* fat 16 or 12 */
 		sbi->dirty = bpb.fat16_state & FAT_STATE_DIRTY;
@@ -1776,7 +1788,7 @@
 	/* check that FAT table does not overflow */
 	fat_clusters = calc_fat_clusters(sb);
 	total_clusters = min(total_clusters, fat_clusters - FAT_START_ENT);
-	if (total_clusters > MAX_FAT(sb)) {
+	if (total_clusters > max_fat(sb)) {
 		if (!silent)
 			fat_msg(sb, KERN_ERR, "count of clusters too big (%u)",
 			       total_clusters);
@@ -1798,11 +1810,15 @@
 	fat_ent_access_init(sb);
 
 	/*
-	 * The low byte of FAT's first entry must have same value with
-	 * media-field.  But in real world, too many devices is
-	 * writing wrong value.  So, removed that validity check.
+	 * The low byte of the first FAT entry must have the same value as
+	 * the media field of the boot sector. But in real world, too many
+	 * devices are writing wrong values. So, removed that validity check.
 	 *
-	 * if (FAT_FIRST_ENT(sb, media) != first)
+	 * The removed check compared the first FAT entry to a value dependent
+	 * on the media field like this:
+	 * == (0x0F00 | media), for FAT12
+	 * == (0XFF00 | media), for FAT16
+	 * == (0x0FFFFF | media), for FAT32
 	 */
 
 	error = -EINVAL;
diff --git a/fs/fat/misc.c b/fs/fat/misc.c
index 573836d..1e08bd5 100644
--- a/fs/fat/misc.c
+++ b/fs/fat/misc.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/fs/fat/misc.c
  *
@@ -7,6 +8,7 @@
  */
 
 #include "fat.h"
+#include <linux/iversion.h>
 
 /*
  * fat_fs_error reports a file system problem that might indicate fa data
@@ -63,7 +65,7 @@
 	struct buffer_head *bh;
 	struct fat_boot_fsinfo *fsinfo;
 
-	if (sbi->fat_bits != 32)
+	if (!is_fat32(sbi))
 		return 0;
 
 	bh = sb_bread(sb, sbi->fsinfo_sector);
@@ -185,6 +187,13 @@
 	0,   0,  31,  59,  90, 120, 151, 181, 212, 243, 273, 304, 334, 0, 0, 0,
 };
 
+static inline int fat_tz_offset(struct msdos_sb_info *sbi)
+{
+	return (sbi->options.tz_set ?
+	       -sbi->options.time_offset :
+	       sys_tz.tz_minuteswest) * SECS_PER_MIN;
+}
+
 /* Convert a FAT time/date pair to a UNIX date (seconds since 1 1 70). */
 void fat_time_fat2unix(struct msdos_sb_info *sbi, struct timespec64 *ts,
 		       __le16 __time, __le16 __date, u8 time_cs)
@@ -210,10 +219,7 @@
 		   + days_in_year[month] + day
 		   + DAYS_DELTA) * SECS_PER_DAY;
 
-	if (!sbi->options.tz_set)
-		second += sys_tz.tz_minuteswest * SECS_PER_MIN;
-	else
-		second -= sbi->options.time_offset * SECS_PER_MIN;
+	second += fat_tz_offset(sbi);
 
 	if (time_cs) {
 		ts->tv_sec = second + (time_cs / 100);
@@ -229,9 +235,7 @@
 		       __le16 *time, __le16 *date, u8 *time_cs)
 {
 	struct tm tm;
-	time64_to_tm(ts->tv_sec,
-		   (sbi->options.tz_set ? sbi->options.time_offset :
-		   -sys_tz.tz_minuteswest) * SECS_PER_MIN, &tm);
+	time64_to_tm(ts->tv_sec, -fat_tz_offset(sbi), &tm);
 
 	/*  FAT can only support year between 1980 to 2107 */
 	if (tm.tm_year < 1980 - 1900) {
@@ -263,6 +267,80 @@
 }
 EXPORT_SYMBOL_GPL(fat_time_unix2fat);
 
+static inline struct timespec64 fat_timespec64_trunc_2secs(struct timespec64 ts)
+{
+	return (struct timespec64){ ts.tv_sec & ~1ULL, 0 };
+}
+/*
+ * truncate the various times with appropriate granularity:
+ *   root inode:
+ *     all times always 0
+ *   all other inodes:
+ *     mtime - 2 seconds
+ *     ctime
+ *       msdos - 2 seconds
+ *       vfat  - 10 milliseconds
+ *     atime - 24 hours (00:00:00 in local timezone)
+ */
+int fat_truncate_time(struct inode *inode, struct timespec64 *now, int flags)
+{
+	struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+	struct timespec64 ts;
+
+	if (inode->i_ino == MSDOS_ROOT_INO)
+		return 0;
+
+	if (now == NULL) {
+		now = &ts;
+		ts = current_time(inode);
+	}
+
+	if (flags & S_ATIME) {
+		/* to localtime */
+		time64_t seconds = now->tv_sec - fat_tz_offset(sbi);
+		s32 remainder;
+
+		div_s64_rem(seconds, SECS_PER_DAY, &remainder);
+		/* to day boundary, and back to unix time */
+		seconds = seconds + fat_tz_offset(sbi) - remainder;
+
+		inode->i_atime = (struct timespec64){ seconds, 0 };
+	}
+	if (flags & S_CTIME) {
+		if (sbi->options.isvfat)
+			inode->i_ctime = timespec64_trunc(*now, 10000000);
+		else
+			inode->i_ctime = fat_timespec64_trunc_2secs(*now);
+	}
+	if (flags & S_MTIME)
+		inode->i_mtime = fat_timespec64_trunc_2secs(*now);
+
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fat_truncate_time);
+
+int fat_update_time(struct inode *inode, struct timespec64 *now, int flags)
+{
+	int iflags = I_DIRTY_TIME;
+	bool dirty = false;
+
+	if (inode->i_ino == MSDOS_ROOT_INO)
+		return 0;
+
+	fat_truncate_time(inode, now, flags);
+	if (flags & S_VERSION)
+		dirty = inode_maybe_inc_iversion(inode, false);
+	if ((flags & (S_ATIME | S_CTIME | S_MTIME)) &&
+	    !(inode->i_sb->s_flags & SB_LAZYTIME))
+		dirty = true;
+
+	if (dirty)
+		iflags |= I_DIRTY_SYNC;
+	__mark_inode_dirty(inode, iflags);
+	return 0;
+}
+EXPORT_SYMBOL_GPL(fat_update_time);
+
 int fat_sync_bhs(struct buffer_head **bhs, int nr_bhs)
 {
 	int i, err = 0;
diff --git a/fs/fat/namei_msdos.c b/fs/fat/namei_msdos.c
index efb8c40..9d06288 100644
--- a/fs/fat/namei_msdos.c
+++ b/fs/fat/namei_msdos.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/fs/msdos/namei.c
  *
@@ -250,7 +251,7 @@
 	if (err)
 		return err;
 
-	dir->i_ctime = dir->i_mtime = *ts;
+	fat_truncate_time(dir, ts, S_CTIME|S_MTIME);
 	if (IS_DIRSYNC(dir))
 		(void)fat_sync_inode(dir);
 	else
@@ -294,7 +295,7 @@
 		err = PTR_ERR(inode);
 		goto out;
 	}
-	inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
+	fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
 	d_instantiate(dentry, inode);
@@ -327,7 +328,7 @@
 	drop_nlink(dir);
 
 	clear_nlink(inode);
-	inode->i_ctime = current_time(inode);
+	fat_truncate_time(inode, NULL, S_CTIME);
 	fat_detach(inode);
 out:
 	mutex_unlock(&MSDOS_SB(sb)->s_lock);
@@ -380,7 +381,7 @@
 		goto out;
 	}
 	set_nlink(inode, 2);
-	inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
+	fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
 	d_instantiate(dentry, inode);
@@ -413,7 +414,7 @@
 	if (err)
 		goto out;
 	clear_nlink(inode);
-	inode->i_ctime = current_time(inode);
+	fat_truncate_time(inode, NULL, S_CTIME);
 	fat_detach(inode);
 out:
 	mutex_unlock(&MSDOS_SB(sb)->s_lock);
@@ -478,7 +479,7 @@
 				mark_inode_dirty(old_inode);
 
 			inode_inc_iversion(old_dir);
-			old_dir->i_ctime = old_dir->i_mtime = current_time(old_dir);
+			fat_truncate_time(old_dir, NULL, S_CTIME|S_MTIME);
 			if (IS_DIRSYNC(old_dir))
 				(void)fat_sync_inode(old_dir);
 			else
@@ -538,7 +539,7 @@
 	if (err)
 		goto error_dotdot;
 	inode_inc_iversion(old_dir);
-	old_dir->i_ctime = old_dir->i_mtime = ts;
+	fat_truncate_time(old_dir, &ts, S_CTIME|S_MTIME);
 	if (IS_DIRSYNC(old_dir))
 		(void)fat_sync_inode(old_dir);
 	else
@@ -548,7 +549,7 @@
 		drop_nlink(new_inode);
 		if (is_dir)
 			drop_nlink(new_inode);
-		new_inode->i_ctime = ts;
+		fat_truncate_time(new_inode, &ts, S_CTIME);
 	}
 out:
 	brelse(sinfo.bh);
@@ -637,6 +638,7 @@
 	.rename		= msdos_rename,
 	.setattr	= fat_setattr,
 	.getattr	= fat_getattr,
+	.update_time	= fat_update_time,
 };
 
 static void setup(struct super_block *sb)
diff --git a/fs/fat/namei_vfat.c b/fs/fat/namei_vfat.c
index 82cd1e6..0cdd0fb 100644
--- a/fs/fat/namei_vfat.c
+++ b/fs/fat/namei_vfat.c
@@ -1,3 +1,4 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /*
  *  linux/fs/vfat/namei.c
  *
@@ -678,7 +679,7 @@
 		goto cleanup;
 
 	/* update timestamp */
-	dir->i_ctime = dir->i_mtime = dir->i_atime = *ts;
+	fat_truncate_time(dir, ts, S_CTIME|S_MTIME);
 	if (IS_DIRSYNC(dir))
 		(void)fat_sync_inode(dir);
 	else
@@ -779,7 +780,7 @@
 		goto out;
 	}
 	inode_inc_iversion(inode);
-	inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
+	fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
 	d_instantiate(dentry, inode);
@@ -810,7 +811,7 @@
 	drop_nlink(dir);
 
 	clear_nlink(inode);
-	inode->i_mtime = inode->i_atime = current_time(inode);
+	fat_truncate_time(inode, NULL, S_ATIME|S_MTIME);
 	fat_detach(inode);
 	vfat_d_version_set(dentry, inode_query_iversion(dir));
 out:
@@ -836,7 +837,7 @@
 	if (err)
 		goto out;
 	clear_nlink(inode);
-	inode->i_mtime = inode->i_atime = current_time(inode);
+	fat_truncate_time(inode, NULL, S_ATIME|S_MTIME);
 	fat_detach(inode);
 	vfat_d_version_set(dentry, inode_query_iversion(dir));
 out:
@@ -876,7 +877,7 @@
 	}
 	inode_inc_iversion(inode);
 	set_nlink(inode, 2);
-	inode->i_mtime = inode->i_atime = inode->i_ctime = ts;
+	fat_truncate_time(inode, &ts, S_ATIME|S_CTIME|S_MTIME);
 	/* timestamp is already written, so mark_inode_dirty() is unneeded. */
 
 	d_instantiate(dentry, inode);
@@ -969,7 +970,7 @@
 	if (err)
 		goto error_dotdot;
 	inode_inc_iversion(old_dir);
-	old_dir->i_ctime = old_dir->i_mtime = ts;
+	fat_truncate_time(old_dir, &ts, S_CTIME|S_MTIME);
 	if (IS_DIRSYNC(old_dir))
 		(void)fat_sync_inode(old_dir);
 	else
@@ -979,7 +980,7 @@
 		drop_nlink(new_inode);
 		if (is_dir)
 			drop_nlink(new_inode);
-		new_inode->i_ctime = ts;
+		fat_truncate_time(new_inode, &ts, S_CTIME);
 	}
 out:
 	brelse(sinfo.bh);
@@ -1032,6 +1033,7 @@
 	.rename		= vfat_rename,
 	.setattr	= fat_setattr,
 	.getattr	= fat_getattr,
+	.update_time	= fat_update_time,
 };
 
 static void setup(struct super_block *sb)
diff --git a/fs/fat/nfs.c b/fs/fat/nfs.c
index eb19265..af19137 100644
--- a/fs/fat/nfs.c
+++ b/fs/fat/nfs.c
@@ -1,14 +1,5 @@
+// SPDX-License-Identifier: GPL-2.0-only
 /* fs/fat/nfs.c
- *
- * This software is licensed under the terms of the GNU General Public
- * License version 2, as published by the Free Software Foundation, and
- * may be copied, distributed, and modified under those terms.
- *
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
- *
  */
 
 #include <linux/exportfs.h>