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Commit d240e067 authored by Ryusuke Konishi's avatar Ryusuke Konishi
Browse files

nilfs2: disallow remount of snapshot from/to a regular mount 



Snapshots and regular ro/rw mounts are essentially-different within
the meaning whether the checkpoint is static or not and is marked with
a snapshot flag or not.

The current implemenation, however, allows to remount a snapshot to a
regular rw-mount if the checkpoint number equals the latest one.

This transition is actually impossible since changing a checkpoint to
a snapshot makes another checkpoint, thus the condition is never
satisfied.

This fixes the weird state of affairs, and specifically separates
snapshots and regular rw/ro-mounts.

Signed-off-by: default avatarRyusuke Konishi <konishi.ryusuke@lab.ntt.co.jp>
parent cdce214e

fs/nilfs2/super.c

+23 −34
Original line number Diff line number Diff line
@@ -754,9 +754,7 @@ nilfs_fill_super(struct super_block *sb, void *data, int silent, 
				goto failed_sbi;

			}

			cno = sbi->s_snapshot_cno;

		} else

			/* Read-only mount */

			sbi->s_snapshot_cno = cno;

		}

	}



	err = nilfs_attach_checkpoint(sbi, cno);
@@ -825,7 +823,7 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data) 
	struct the_nilfs *nilfs = sbi->s_nilfs;

	unsigned long old_sb_flags;

	struct nilfs_mount_options old_opts;

	int err;

	int was_snapshot, err;



	lock_kernel();
@@ -833,6 +831,7 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data) 
	old_sb_flags = sb->s_flags;

	old_opts.mount_opt = sbi->s_mount_opt;

	old_opts.snapshot_cno = sbi->s_snapshot_cno;

	was_snapshot = nilfs_test_opt(sbi, SNAPSHOT);



	if (!parse_options(data, sb)) {

		err = -EINVAL;
@@ -840,20 +839,32 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data) 
	}

	sb->s_flags = (sb->s_flags & ~MS_POSIXACL);



	if ((*flags & MS_RDONLY) &&

	    sbi->s_snapshot_cno != old_opts.snapshot_cno) {

		printk(KERN_WARNING "NILFS (device %s): couldn't "

	err = -EINVAL;

	if (was_snapshot) {

		if (!(*flags & MS_RDONLY)) {

			printk(KERN_ERR "NILFS (device %s): cannot remount "

			       "snapshot read/write.\n",

			       sb->s_id);

			goto restore_opts;

		} else if (sbi->s_snapshot_cno != old_opts.snapshot_cno) {

			printk(KERN_ERR "NILFS (device %s): cannot "

			       "remount to a different snapshot.\n",

			       sb->s_id);

		err = -EINVAL;

			goto restore_opts;

		}

	} else {

		if (nilfs_test_opt(sbi, SNAPSHOT)) {

			printk(KERN_ERR "NILFS (device %s): cannot change "

			       "a regular mount to a snapshot.\n",

			       sb->s_id);

			goto restore_opts;

		}

	}



	if (!nilfs_valid_fs(nilfs)) {

		printk(KERN_WARNING "NILFS (device %s): couldn't "

		       "remount because the filesystem is in an "

		       "incomplete recovery state.\n", sb->s_id);

		err = -EINVAL;

		goto restore_opts;

	}
@@ -864,9 +875,6 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data) 
		nilfs_detach_segment_constructor(sbi);

		sb->s_flags |= MS_RDONLY;



		sbi->s_snapshot_cno = nilfs_last_cno(nilfs);

		/* nilfs_set_opt(sbi, SNAPSHOT); */



		/*

		 * Remounting a valid RW partition RDONLY, so set

		 * the RDONLY flag and then mark the partition as valid again.
@@ -885,24 +893,7 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data) 
		 * store the current valid flag.  (It may have been changed

		 * by fsck since we originally mounted the partition.)

		 */

		if (nilfs->ns_current && nilfs->ns_current != sbi) {

			printk(KERN_WARNING "NILFS (device %s): couldn't "

			       "remount because an RW-mount exists.\n",

			       sb->s_id);

			err = -EBUSY;

			goto restore_opts;

		}

		if (sbi->s_snapshot_cno != nilfs_last_cno(nilfs)) {

			printk(KERN_WARNING "NILFS (device %s): couldn't "

			       "remount because the current RO-mount is not "

			       "the latest one.\n",

			       sb->s_id);

			err = -EINVAL;

			goto restore_opts;

		}

		sb->s_flags &= ~MS_RDONLY;

		nilfs_clear_opt(sbi, SNAPSHOT);

		sbi->s_snapshot_cno = 0;



		err = nilfs_attach_segment_constructor(sbi);

		if (err)
@@ -911,8 +902,6 @@ static int nilfs_remount(struct super_block *sb, int *flags, char *data) 
		down_write(&nilfs->ns_sem);

		nilfs_setup_super(sbi);

		up_write(&nilfs->ns_sem);



		nilfs->ns_current = sbi;

	}

 out:

	up_write(&nilfs->ns_super_sem);