Date:   Tue,  2 Jan 2018 14:42:29 +0800
From:   ChenGuanqiao <chen.chenchacha@...mail.com>
To:     hirofumi@...l.parknet.co.jp
Cc:     linux-kernel@...r.kernel.org,
        ChenGuanqiao <chen.chenchacha@...mail.com>
Subject: [PATCH v6 3/3] fs: fat: add ioctl method in fat filesystem driver

Signed-off-by: ChenGuanqiao <chen.chenchacha@...mail.com>
---
 fs/fat/file.c | 150 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 150 insertions(+)

diff --git a/fs/fat/file.c b/fs/fat/file.c
index 4724cc9ad650..829c91ef1ea0 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -15,11 +15,36 @@
 #include <linux/fsnotify.h>
 #include <linux/security.h>
 #include <linux/falloc.h>
+#include <linux/ctype.h>
 #include "fat.h"

 static long fat_fallocate(struct file *file, int mode,
			  loff_t offset, loff_t len);

+static int fat_check_d_characters(char *label, unsigned long len)
+{
+	int i;
+
+	for (i=0; i<len; ++i) {
+		switch (label[i]) {
+		case '0' ... '9':
+		case 'A' ... 'Z':
+		case '_':
+			continue;
+		case 0x20:
+			return 0;
+		default:
+			break;
+		}
+		break;
+	}
+
+	if (i == len)
+		return 0;
+	else
+		return -EINVAL;
+}
+
 static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
 {
	u32 attr;
@@ -121,10 +146,131 @@ static int fat_ioctl_get_volume_id(struct inode *inode, u32 __user *user_attr)
	return put_user(sbi->vol_id, user_attr);
 }

+static int fat_ioctl_get_volume_label(struct inode *inode,
+				      u8 __user *vol_label)
+{
+	int err = 0;
+	struct buffer_head *bh;
+	struct msdos_dir_entry *de;
+
+	inode_lock_shared(inode);
+	err = fat_scan_volume_label(inode, &bh, &de);
+	if (err)
+		goto out;
+
+	if (copy_to_user(vol_label, de->name, MSDOS_NAME))
+		err = -EFAULT;
+
+	brelse(bh);
+out:
+	inode_unlock_shared(inode);
+
+	return err;
+}
+
+static int fat_ioctl_set_volume_label(struct file *file,
+				      u8 __user *vol_label)
+{
+	int err = 0;
+	u8 label[MSDOS_NAME];
+	struct buffer_head *boot_bh;
+	struct buffer_head *vol_bh;
+	struct msdos_dir_entry *de;
+	struct fat_boot_sector *b;
+	struct inode *inode = file_inode(file);
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	if (inode->i_ino != MSDOS_ROOT_INO) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	if (copy_from_user(label, vol_label, sizeof(label))) {
+		err = -EFAULT;
+		goto out;
+	}
+
+	err = fat_check_d_characters(label, sizeof(label));
+	if (err)
+		goto out;
+
+	err = mnt_want_write_file(file);
+	if (err)
+		goto out;
+
+	down_write(&sb->s_umount);
+	inode_lock(inode);
+
+	/* Updates root directory's vol_label */
+	err = fat_scan_volume_label(inode, &vol_bh, &de);
+	if (err) {
+		/* Create volume label entry */
+		struct timespec ts;
+
+		mutex_lock(&sbi->s_lock);
+		ts = current_time(inode);
+		err = fat_add_volume_label_entry(inode, label, &ts);
+		mutex_unlock(&sbi->s_lock);
+
+		if (err)
+			goto out_vol_brelse;
+	} else {
+		/* Write to root directory */
+		lock_buffer(vol_bh);
+		memcpy(de->name, label, sizeof(de->name));
+		mark_buffer_dirty(vol_bh);
+		unlock_buffer(vol_bh);
+	}
+
+	/* Update sector's vol_label */
+	boot_bh = sb_bread(sb, 0);
+	if (boot_bh == NULL) {
+		fat_msg(sb, KERN_ERR,
+			"unable to read boot sector to write volume label");
+		err = -EIO;
+		goto out_boot_brelse;
+	}
+
+	b = (struct fat_boot_sector *)boot_bh->b_data;
+	lock_buffer(boot_bh);
+	if (sbi->fat_bits == 32)
+		memcpy(b->fat32.vol_label, label, sizeof(label));
+	else
+		memcpy(b->fat16.vol_label, label, sizeof(label));
+
+	mark_buffer_dirty(boot_bh);
+	unlock_buffer(boot_bh);
+
+	/* Synchronize the data together */
+	err = sync_dirty_buffer(boot_bh);
+	if (err)
+		goto out_boot_brelse;
+
+	err = sync_dirty_buffer(vol_bh);
+	if (err)
+		goto out_boot_brelse;
+
+	/* Flush sbi */
+	memcpy(sbi->vol_label, label, sizeof(sbi->vol_label));
+
+out_boot_brelse:
+	brelse(boot_bh);
+out_vol_brelse:
+	brelse(vol_bh);
+
+	inode_unlock(inode);
+	up_write(&sb->s_umount);
+	mnt_drop_write_file(file);
+out:
+	return err;
+}
+
 long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
	struct inode *inode = file_inode(filp);
	u32 __user *user_attr = (u32 __user *)arg;
+	u8 __user *user_vol_label = (u8 __user *)arg;

	switch (cmd) {
	case FAT_IOCTL_GET_ATTRIBUTES:
@@ -133,6 +279,10 @@ long fat_generic_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
		return fat_ioctl_set_attributes(filp, user_attr);
	case FAT_IOCTL_GET_VOLUME_ID:
		return fat_ioctl_get_volume_id(inode, user_attr);
+	case FAT_IOCTL_GET_VOLUME_LABEL:
+		return fat_ioctl_get_volume_label(inode, user_vol_label);
+	case FAT_IOCTL_SET_VOLUME_LABEL:
+		return fat_ioctl_set_volume_label(filp, user_vol_label);
	default:
		return -ENOTTY;	/* Inappropriate ioctl for device */
	}
--
2.11.0

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