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Message-ID:
<PUZPR04MB63164B9367EBABF81B381D318103A@PUZPR04MB6316.apcprd04.prod.outlook.com>
Date: Fri, 5 Sep 2025 11:25:14 +0000
From: "Yuezhang.Mo@...y.com" <Yuezhang.Mo@...y.com>
To: Ethan Ferguson <ethan.ferguson@...ier.com>,
"linkinjeon@...nel.org"
<linkinjeon@...nel.org>,
"sj1557.seo@...sung.com" <sj1557.seo@...sung.com>
CC: "cpgs@...sung.com" <cpgs@...sung.com>,
"linux-fsdevel@...r.kernel.org"
<linux-fsdevel@...r.kernel.org>,
"linux-kernel@...r.kernel.org"
<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v5 1/1] exfat: Add support for FS_IOC_{GET,SET}FSLABEL
> Add support for reading / writing to the exfat volume label from the
> FS_IOC_GETFSLABEL and FS_IOC_SETFSLABEL ioctls
>
> Signed-off-by: Ethan Ferguson <ethan.ferguson@...ier.com>
> ---
> fs/exfat/exfat_fs.h | 7 ++
> fs/exfat/exfat_raw.h | 6 ++
> fs/exfat/file.c | 80 +++++++++++++++++++++
> fs/exfat/namei.c | 2 +-
> fs/exfat/super.c | 165 +++++++++++++++++++++++++++++++++++++++++++
> 5 files changed, 259 insertions(+), 1 deletion(-)
>
> diff --git a/fs/exfat/exfat_fs.h b/fs/exfat/exfat_fs.h
> index f8ead4d47ef0..a11a086c9d09 100644
> --- a/fs/exfat/exfat_fs.h
> +++ b/fs/exfat/exfat_fs.h
> @@ -431,6 +431,10 @@ static inline loff_t exfat_ondisk_size(const struct inode *inode)
> /* super.c */
> int exfat_set_volume_dirty(struct super_block *sb);
> int exfat_clear_volume_dirty(struct super_block *sb);
> +int exfat_read_volume_label(struct super_block *sb,
> + struct exfat_uni_name *label_out);
> +int exfat_write_volume_label(struct super_block *sb,
> + struct exfat_uni_name *label);
>
> /* fatent.c */
> #define exfat_get_next_cluster(sb, pclu) exfat_ent_get(sb, *(pclu), pclu)
> @@ -477,6 +481,9 @@ int exfat_force_shutdown(struct super_block *sb, u32 flags);
> /* namei.c */
> extern const struct dentry_operations exfat_dentry_ops;
> extern const struct dentry_operations exfat_utf8_dentry_ops;
> +int exfat_find_empty_entry(struct inode *inode,
> + struct exfat_chain *p_dir, int num_entries,
> + struct exfat_entry_set_cache *es);
>
> /* cache.c */
> int exfat_cache_init(void);
> diff --git a/fs/exfat/exfat_raw.h b/fs/exfat/exfat_raw.h
> index 971a1ccd0e89..4082fa7b8c14 100644
> --- a/fs/exfat/exfat_raw.h
> +++ b/fs/exfat/exfat_raw.h
> @@ -80,6 +80,7 @@
> #define BOOTSEC_OLDBPB_LEN 53
>
> #define EXFAT_FILE_NAME_LEN 15
> +#define EXFAT_VOLUME_LABEL_LEN 11
>
> #define EXFAT_MIN_SECT_SIZE_BITS 9
> #define EXFAT_MAX_SECT_SIZE_BITS 12
> @@ -159,6 +160,11 @@ struct exfat_dentry {
> __le32 start_clu;
> __le64 size;
> } __packed upcase; /* up-case table directory entry */
> + struct {
> + __u8 char_count;
> + __le16 volume_label[EXFAT_VOLUME_LABEL_LEN];
> + __u8 reserved[8];
> + } __packed volume_label; /* volume label directory entry */
> struct {
> __u8 flags;
> __u8 vendor_guid[16];
> diff --git a/fs/exfat/file.c b/fs/exfat/file.c
> index 538d2b6ac2ec..c44928c02474 100644
> --- a/fs/exfat/file.c
> +++ b/fs/exfat/file.c
> @@ -486,6 +486,82 @@ static int exfat_ioctl_shutdown(struct super_block *sb, unsigned long arg)
> return exfat_force_shutdown(sb, flags);
> }
>
> +static int exfat_ioctl_get_volume_label(struct super_block *sb, unsigned long arg)
> +{
> + int ret;
> + char utf8[FSLABEL_MAX] = {0};
> + struct exfat_uni_name *uniname;
> +
> + uniname = kmalloc(sizeof(struct exfat_uni_name), GFP_KERNEL);
> + if (!uniname)
> + return -ENOMEM;
> +
> + ret = exfat_read_volume_label(sb, uniname);
> + if (ret < 0)
> + goto cleanup;
> +
> + ret = exfat_utf16_to_nls(sb, uniname, utf8, FSLABEL_MAX);
> + if (ret < 0)
> + goto cleanup;
> +
> + if (copy_to_user((char __user *)arg, utf8, FSLABEL_MAX)) {
> + ret = -EFAULT;
> + goto cleanup;
> + }
> +
> + ret = 0;
> +
> +cleanup:
> + kfree(uniname);
> + return ret;
> +}
> +
> +static int exfat_ioctl_set_volume_label(struct super_block *sb,
> + unsigned long arg)
> +{
> + int ret, lossy;
> + char utf8[FSLABEL_MAX];
> + struct exfat_uni_name *uniname;
> +
> + if (!capable(CAP_SYS_ADMIN))
> + return -EPERM;
> +
> + uniname = kmalloc(sizeof(struct exfat_uni_name), GFP_KERNEL);
> + if (!uniname)
> + return -ENOMEM;
> +
> + if (copy_from_user(utf8, (char __user *)arg, FSLABEL_MAX)) {
> + ret = -EFAULT;
> + goto cleanup;
> + }
> +
> + if (utf8[0]) {
> + ret = exfat_nls_to_utf16(sb, utf8, strnlen(utf8, FSLABEL_MAX),
> + uniname, &lossy);
> + if (ret < 0) {
> + goto cleanup;
> + } else if (lossy & NLS_NAME_LOSSY) {
> + ret = -EINVAL;
> + goto cleanup;
> + }
> + } else {
> + uniname->name[0] = 0x0000;
> + uniname->name_len = 0;
> + }
> +
> + if (uniname->name_len > EXFAT_VOLUME_LABEL_LEN) {
> + exfat_info(sb, "Volume label length too long, truncating");
> + uniname->name_len = EXFAT_VOLUME_LABEL_LEN;
> + uniname->name[EXFAT_VOLUME_LABEL_LEN] = 0x0000;
> + }
> +
> + ret = exfat_write_volume_label(sb, uniname);
> +
> +cleanup:
> + kfree(uniname);
> + return ret;
> +}
> +
> long exfat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> {
> struct inode *inode = file_inode(filp);
> @@ -500,6 +576,10 @@ long exfat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
> 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;
> }
> diff --git a/fs/exfat/namei.c b/fs/exfat/namei.c
> index f5f1c4e8a29f..eaa781d6263c 100644
> --- a/fs/exfat/namei.c
> +++ b/fs/exfat/namei.c
> @@ -300,7 +300,7 @@ static int exfat_check_max_dentries(struct inode *inode)
> * the directory entry index in p_dir is returned on succeeds
> * -error code is returned on failure
> */
> -static int exfat_find_empty_entry(struct inode *inode,
> +int exfat_find_empty_entry(struct inode *inode,
> struct exfat_chain *p_dir, int num_entries,
> struct exfat_entry_set_cache *es)
> {
> diff --git a/fs/exfat/super.c b/fs/exfat/super.c
> index 8926e63f5bb7..0374e41b48a5 100644
> --- a/fs/exfat/super.c
> +++ b/fs/exfat/super.c
> @@ -573,6 +573,171 @@ static int exfat_verify_boot_region(struct super_block *sb)
> return 0;
> }
>
> +static int exfat_get_volume_label_ptrs(struct super_block *sb,
> + struct buffer_head **out_bh,
> + struct exfat_dentry **out_dentry,
> + bool create)
> +{
> + int i, ret;
> + unsigned int type;
> + struct exfat_sb_info *sbi = EXFAT_SB(sb);
> + struct inode *root_inode = sb->s_root->d_inode;
> + struct exfat_inode_info *ei = EXFAT_I(root_inode);
> + struct exfat_entry_set_cache es;
> + struct exfat_chain clu;
> + struct exfat_dentry *ep, *overwrite_ep = NULL;
> + struct buffer_head *bh, *overwrite_bh = NULL;
> +
> + clu.dir = sbi->root_dir;
> + clu.flags = ALLOC_FAT_CHAIN;
> +
> + while (clu.dir != EXFAT_EOF_CLUSTER) {
> + for (i = 0; i < sbi->dentries_per_clu; i++) {
> + ep = exfat_get_dentry(sb, &clu, i, &bh);
> +
> + if (!ep) {
> + ret = -EIO;
> + goto error;
> + }
> +
> + type = exfat_get_entry_type(ep);
> + if ((type == TYPE_DELETED || type == TYPE_UNUSED)
> + && !overwrite_ep && create) {
> + overwrite_ep = ep;
> + overwrite_bh = bh;
> + continue;
> + }
> +
> + if (type == TYPE_VOLUME) {
> + *out_bh = bh;
> + *out_dentry = ep;
> +
> + brelse(overwrite_bh);
> + return 0;
> + }
> +
> + brelse(bh);
> + }
> +
> + if (exfat_get_next_cluster(sb, &(clu.dir))) {
> + ret = -EIO;
> + goto error;
> + }
> + }
> +
> + if (!create) {
> + ret = -ENOENT;
> + goto error;
> + }
> +
> +
> + if (overwrite_ep) {
> + ep = overwrite_ep;
> + bh = overwrite_bh;
> + goto overwrite;
> + }
> +
> + ret = exfat_find_empty_entry(root_inode, &clu, 1, &es);
> + if (ret < 0)
> + goto error;
> +
> + ei->hint_femp.eidx = 0;
> + ei->hint_femp.count = sbi->dentries_per_clu;
> + ei->hint_femp.cur = clu;
> +
> + ep = exfat_get_dentry_cached(&es, 0);
> + bh = es.bh[EXFAT_B_TO_BLK(es.start_off, sb)];
> + /* increment use counter so exfat_put_dentry_set doesn't free */
> + get_bh(bh);
> + ret = exfat_put_dentry_set(&es, false);
> + if (ret < 0) {
> + bforget(bh);
> + goto error;
> + }
> + ei->hint_femp.eidx++;
> + ei->hint_femp.count--;
> +
> +overwrite:
> +
> + memset(ep, 0, sizeof(struct exfat_dentry));
> + ep->type = EXFAT_VOLUME;
> + *out_bh = bh;
> + *out_dentry = ep;
> + return 0;
> +
> +error:
> + *out_bh = NULL;
> + *out_dentry = NULL;
> + return ret;
> +}
exfat_get_volume_label_ptrs() involves finding and allocating volume
label dentry, which makes the logic complicated.
I suggest defining a function that only find volume label dentry,
likes exfat_find_volume_label_dentry().
exfat_find_volume_label_dentry()
{
while (clu.dir != EXFAT_EOF_CLUSTER) {
for (i = 0; i < sbi->dentries_per_clu; i++, dentry++) {
if (type == TYPE_DELETED || type == TYPE_UNUSED) {
if (hint_femp.eidx == EXFAT_HINT_NONE) {
set hint_femp
}
if (type == TYPE_UNUSED) {
not found
}
}
if (type == TYPE_VOLUME) {
found
}
}
}
/* no empty entry, hint that empty entry is in the new cluster */
if (hint_femp.eidx == EXFAT_HINT_NON) {
set hint_femp
}
EXFAT_I(root_inode)->hint_femp = hint_femp;
}
> +
> +int exfat_read_volume_label(struct super_block *sb, struct exfat_uni_name *label_out)
> +{
> + int ret, i;
> + struct exfat_sb_info *sbi = EXFAT_SB(sb);
> + struct buffer_head *bh = NULL;
> + struct exfat_dentry *ep = NULL;
> +
> + mutex_lock(&sbi->s_lock);
> +
> + ret = exfat_get_volume_label_ptrs(sb, &bh, &ep, false);
> + // ENOENT signifies that a volume label dentry doesn't exist
> + // We will treat this as an empty volume label and not fail.
Use /**/ for all comments.
> + if (ret == -ENOENT) {
> + label_out->name[0] = 0x0000;
> + label_out->name_len = 0;
> + ret = 0;
> + } else if (ret < 0) {
> + goto cleanup;
> + } else {
> + for (i = 0; i < EXFAT_VOLUME_LABEL_LEN; i++)
> + label_out->name[i] = le16_to_cpu(ep->dentry.volume_label.volume_label[i]);
> + label_out->name_len = ep->dentry.volume_label.char_count;
> + }
> +
> +cleanup:
> + mutex_unlock(&sbi->s_lock);
> + brelse(bh);
> + return ret;
> +}
> +
> +int exfat_write_volume_label(struct super_block *sb,
> + struct exfat_uni_name *label)
> +{
> + int ret, i;
> + struct exfat_sb_info *sbi = EXFAT_SB(sb);
> + struct buffer_head *bh = NULL;
> + struct exfat_dentry *ep = NULL;
> +
> + if (label->name_len > EXFAT_VOLUME_LABEL_LEN)
> + return -EINVAL;
> +
> + mutex_lock(&sbi->s_lock);
> +
> + ret = exfat_get_volume_label_ptrs(sb, &bh, &ep, true);
> + if (ret < 0)
> + goto cleanup;
> +
> + for (i = 0; i < label->name_len; i++)
> + ep->dentry.volume_label.volume_label[i] =
> + cpu_to_le16(label->name[i]);
> + // Fill the rest of the str with 0x0000
> + for (; i < EXFAT_VOLUME_LABEL_LEN; i++)
> + ep->dentry.volume_label.volume_label[i] = 0x0000;
> +
> + ep->dentry.volume_label.char_count = label->name_len;
> +
> +cleanup:
> + mutex_unlock(&sbi->s_lock);
> +
> + if (bh) {
> + exfat_update_bh(bh, IS_DIRSYNC(sb->s_root->d_inode));
> + brelse(bh);
> + }
> +
> + return ret;
> +}
If there is no volume label directory entry, no volume label
dentry needs to be allocated when clearing the volume label.
exfat_write_volume_label()
{
exfat_find_volume_label_dentry();
if (not found) {
if (label->name_len == 0)
/* return with nothing to do */
exfat_find_empty_entry()
}
/* set or clear volume label */
}
In exfat, exfat_{read, write}_volume_label() are directory operations,
so it would be better to move them to dir.c.
> +
> /* mount the file system volume */
> static int __exfat_fill_super(struct super_block *sb,
> struct exfat_chain *root_clu)
> --
> 2.34.1
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