nilfs2: add support for FS_IOC_GETFSLABEL

Implement support for FS_IOC_GETFSLABEL ioctl to read filesystem label.

Link: https://lkml.kernel.org/r/20240815074408.5550-4-konishi.ryusuke@gmail.com
Signed-off-by: Ryusuke Konishi <konishi.ryusuke@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/fs/nilfs2/ioctl.c b/fs/nilfs2/ioctl.c
index 8be471ce4f1950029e2f7479cd46f0369215b121..b5c6a50d6d5dc103b999077741693646461cb8b3 100644 (file)
--- a/fs/nilfs2/ioctl.c
+++ b/fs/nilfs2/ioctl.c
@@ -17,6 +17,7 @@
 #include <linux/mount.h>       /* mnt_want_write_file(), mnt_drop_write_file() */
 #include <linux/buffer_head.h>
 #include <linux/fileattr.h>
+#include <linux/string.h>
 #include "nilfs.h"
 #include "segment.h"
 #include "bmap.h"
@@ -1266,6 +1267,29 @@ out:
        return ret;
 }
 
+/**
+ * nilfs_ioctl_get_fslabel - get the volume name of the file system
+ * @sb:   super block instance
+ * @argp: pointer to userspace memory where the volume name should be stored
+ *
+ * Return: 0 on success, %-EFAULT if copying to userspace memory fails.
+ */
+static int nilfs_ioctl_get_fslabel(struct super_block *sb, void __user *argp)
+{
+       struct the_nilfs *nilfs = sb->s_fs_info;
+       char label[NILFS_MAX_VOLUME_NAME + 1];
+
+       BUILD_BUG_ON(NILFS_MAX_VOLUME_NAME >= FSLABEL_MAX);
+
+       down_read(&nilfs->ns_sem);
+       memtostr_pad(label, nilfs->ns_sbp[0]->s_volume_name);
+       up_read(&nilfs->ns_sem);
+
+       if (copy_to_user(argp, label, sizeof(label)))
+               return -EFAULT;
+       return 0;
+}
+
 long nilfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
 {
        struct inode *inode = file_inode(filp);
@@ -1308,6 +1332,8 @@ long nilfs_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
                return nilfs_ioctl_set_alloc_range(inode, argp);
        case FITRIM:
                return nilfs_ioctl_trim_fs(inode, argp);
+       case FS_IOC_GETFSLABEL:
+               return nilfs_ioctl_get_fslabel(inode->i_sb, argp);
        default:
                return -ENOTTY;
        }
@@ -1334,6 +1360,7 @@ long nilfs_compat_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
        case NILFS_IOCTL_RESIZE:
        case NILFS_IOCTL_SET_ALLOC_RANGE:
        case FITRIM:
+       case FS_IOC_GETFSLABEL:
                break;
        default:
                return -ENOIOCTLCMD;

diff --git a/fs/nilfs2/nilfs.h b/fs/nilfs2/nilfs.h
index 4017f78564405a09914b71341a1af42fcc692b61..3097490b6621d843ba273efd0258d70122293552 100644 (file)
--- a/fs/nilfs2/nilfs.h
+++ b/fs/nilfs2/nilfs.h
@@ -103,6 +103,18 @@ enum {
        NILFS_SB_COMMIT_ALL     /* Commit both super blocks */
 };
 
+/**
+ * define NILFS_MAX_VOLUME_NAME - maximum number of characters (bytes) in a
+ *                                file system volume name
+ *
+ * Defined by the size of the volume name field in the on-disk superblocks.
+ * This volume name does not include the terminating NULL byte if the string
+ * length matches the field size, so use (NILFS_MAX_VOLUME_NAME + 1) for the
+ * size of the buffer that requires a NULL byte termination.
+ */
+#define NILFS_MAX_VOLUME_NAME  \
+       sizeof_field(struct nilfs_super_block, s_volume_name)
+
 /*
  * Macros to check inode numbers
  */