erofs: Add support for FS_IOC_GETFSLABEL

Add support for reading to the erofs volume label from the
FS_IOC_GETFSLABEL ioctls.

Signed-off-by: Bo Liu (OpenAnolis) <liubo03@inspur.com>
Reviewed-by: Gao Xiang <hsiangkao@linux.alibaba.com>
Reviewed-by: Chao Yu <chao@kernel.org>
Reviewed-by: Hongbo Li <lihongbo22@huawei.com>
Signed-off-by: Gao Xiang <hsiangkao@linux.alibaba.com>

fs/erofs/data.c

@@ -475,6 +475,10 @@ static loff_t erofs_file_llseek(struct file *file, loff_t offset, int whence)
 const struct file_operations erofs_file_fops = {
 	.llseek		= erofs_file_llseek,
 	.read_iter	= erofs_file_read_iter,
+	.unlocked_ioctl = erofs_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl   = erofs_compat_ioctl,
+#endif
 	.mmap_prepare	= erofs_file_mmap_prepare,
 	.get_unmapped_area = thp_get_unmapped_area,
 	.splice_read	= filemap_splice_read,

fs/erofs/dir.c

@@ -123,4 +123,8 @@ const struct file_operations erofs_dir_fops = {
 	.llseek		= generic_file_llseek,
 	.read		= generic_read_dir,
 	.iterate_shared	= erofs_readdir,
+	.unlocked_ioctl = erofs_ioctl,
+#ifdef CONFIG_COMPAT
+	.compat_ioctl   = erofs_compat_ioctl,
+#endif
 };

fs/erofs/inode.c

@@ -5,6 +5,7 @@
  * Copyright (C) 2021, Alibaba Cloud
  */
 #include "xattr.h"
+#include <linux/compat.h>
 #include <trace/events/erofs.h>
 
 static int erofs_fill_symlink(struct inode *inode, void *kaddr,
@@ -213,9 +214,6 @@ static int erofs_fill_inode(struct inode *inode)
 	switch (inode->i_mode & S_IFMT) {
 	case S_IFREG:
 		inode->i_op = &erofs_generic_iops;
-		if (erofs_inode_is_data_compressed(vi->datalayout))
-			inode->i_fop = &generic_ro_fops;
-		else
 		inode->i_fop = &erofs_file_fops;
 		break;
 	case S_IFDIR:
@@ -341,6 +339,40 @@ int erofs_getattr(struct mnt_idmap *idmap, const struct path *path,
 	return 0;
 }
 
+static int erofs_ioctl_get_volume_label(struct inode *inode, void __user *arg)
+{
+	struct erofs_sb_info *sbi = EROFS_I_SB(inode);
+	int ret;
+
+	if (!sbi->volume_name)
+		ret = clear_user(arg, 1);
+	else
+		ret = copy_to_user(arg, sbi->volume_name,
+				   strlen(sbi->volume_name));
+	return ret ? -EFAULT : 0;
+}
+
+long erofs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
+{
+	struct inode *inode = file_inode(filp);
+	void __user *argp = (void __user *)arg;
+
+	switch (cmd) {
+	case FS_IOC_GETFSLABEL:
+		return erofs_ioctl_get_volume_label(inode, argp);
+	default:
+		return -ENOTTY;
+	}
+}
+
+#ifdef CONFIG_COMPAT
+long erofs_compat_ioctl(struct file *filp, unsigned int cmd,
+			unsigned long arg)
+{
+	return erofs_ioctl(filp, cmd, (unsigned long)compat_ptr(arg));
+}
+#endif
+
 const struct inode_operations erofs_generic_iops = {
 	.getattr = erofs_getattr,
 	.listxattr = erofs_listxattr,

fs/erofs/internal.h

@@ -153,6 +153,7 @@ struct erofs_sb_info {
 	/* used for statfs, f_files - f_favail */
 	u64 inos;
 
+	char *volume_name;
 	u32 feature_compat;
 	u32 feature_incompat;
 
@@ -536,6 +537,10 @@ static inline struct bio *erofs_fscache_bio_alloc(struct erofs_map_dev *mdev) {
 static inline void erofs_fscache_submit_bio(struct bio *bio) {}
 #endif
 
+long erofs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg);
+long erofs_compat_ioctl(struct file *filp, unsigned int cmd,
+			unsigned long arg);
+
 #define EFSCORRUPTED    EUCLEAN         /* Filesystem is corrupted */
 
 #endif	/* __EROFS_INTERNAL_H */

fs/erofs/super.c

@@ -343,6 +343,13 @@ static int erofs_read_superblock(struct super_block *sb)
 	sbi->fixed_nsec = le32_to_cpu(dsb->fixed_nsec);
 	super_set_uuid(sb, (void *)dsb->uuid, sizeof(dsb->uuid));
 
+	if (dsb->volume_name[0]) {
+		sbi->volume_name = kstrndup(dsb->volume_name,
+					    sizeof(dsb->volume_name), GFP_KERNEL);
+		if (!sbi->volume_name)
+			return -ENOMEM;
+	}
+
 	/* parse on-disk compression configurations */
 	ret = z_erofs_parse_cfgs(sb, dsb);
 	if (ret < 0)
@@ -822,6 +829,7 @@ static void erofs_sb_free(struct erofs_sb_info *sbi)
 	kfree(sbi->domain_id);
 	if (sbi->dif0.file)
 		fput(sbi->dif0.file);
+	kfree(sbi->volume_name);
 	kfree(sbi);
 }