linux-kernel - [PATCH v4 2/2] fs: fat: add ioctl method in fat filesystem driver

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Message-Id: <20171225112020.2267-3-chen.chenchacha@foxmail.com>
Date:   Mon, 25 Dec 2017 19:20:20 +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 v4 2/2] fs: fat: add ioctl method in fat filesystem driver

Signed-off-by: ChenGuanqiao <chen.chenchacha@...mail.com>
---
 fs/fat/file.c | 133 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 133 insertions(+)

diff --git a/fs/fat/file.c b/fs/fat/file.c
index 4724cc9ad650..238c8e298930 100644
--- a/fs/fat/file.c
+++ b/fs/fat/file.c
@@ -15,11 +15,23 @@
 #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_volume_label(const char *label)
+{
+	int i;
+
+	for (i=0; i<11; ++i) {
+		if (islower(label[i]))
+			return -EINVAL;
+	}
+	return 0;
+}
+
 static int fat_ioctl_get_attributes(struct inode *inode, u32 __user *user_attr)
 {
	u32 attr;
@@ -121,10 +133,127 @@ 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;
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	if (sbi->fat_bits == 32)
+		bh = sb_bread(sb, sbi->data_start);
+	else
+		bh = sb_bread(sb, sbi->dir_start);
+
+	if (bh == NULL) {
+		fat_msg(sb, KERN_ERR, "unable to read root directory");
+		err = -EIO;
+		goto out;
+	}
+
+	de = (struct msdos_dir_entry *)bh->b_data;
+	if (copy_to_user(vol_label, de->name, MSDOS_NAME))
+		err = -EFAULT;
+
+	brelse(bh);
+
+out:
+	return err;
+}
+
+static int fat_ioctl_set_volume_label(struct file *file,
+				      u8 __user *vol_label)
+{
+	int err = 0;
+	u8 label[11];
+	struct buffer_head *bh;
+	struct fat_boot_sector *b;
+	struct msdos_dir_entry *de;
+	struct inode *inode = file_inode(file);
+	struct super_block *sb = inode->i_sb;
+	struct msdos_sb_info *sbi = MSDOS_SB(sb);
+
+	if (copy_from_user(label, vol_label, sizeof(label))) {
+		err = -EFAULT;
+		goto out;
+	}
+
+	if (fat_check_volume_label(label)) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	err = mnt_want_write_file(file);
+	if (err)
+		goto out;
+
+	/* Update sector's vol_label */
+	bh = sb_bread(sb, 0);
+	if (bh == NULL) {
+		fat_msg(sb, KERN_ERR,
+			"unable to read boot sector to write volume label");
+		err = -EIO;
+		goto out_drop_file;
+	}
+
+	b = (struct fat_boot_sector *)bh->b_data;
+
+	lock_buffer(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(bh);
+	unlock_buffer(bh);
+	err = sync_dirty_buffer(bh);
+	brelse(bh);
+	if (err)
+		goto out_drop_file;
+
+	/* updates root directory's vol_label */
+	if (sbi->fat_bits == 32)
+		bh = sb_bread(sb, sbi->data_start);
+	else
+		bh = sb_bread(sb, sbi->dir_start);
+
+	if (bh == NULL) {
+		fat_msg(sb, KERN_ERR,
+			"unable to read root directory to write volume label");
+		err = -EIO;
+		goto out_drop_file;
+	}
+
+	de = (struct msdos_dir_entry *)bh->b_data;
+	if (!(de->attr & ATTR_VOLUME)) {
+		err = -EFAULT;
+		goto out_drop_file;
+	}
+
+	lock_buffer(bh);
+	memcpy(de->name, label, sizeof(de->name));
+	mark_buffer_dirty(bh);
+	unlock_buffer(bh);
+	err = sync_dirty_buffer(bh);
+	brelse(bh);
+	if (err)
+		goto out_drop_file;
+
+	memcpy(sbi->vol_label, label, sizeof(sbi->vol_label));
+
+out_drop_file:
+	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 +262,10 @@ 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