Commit 71cbad7e authored by hujianyang's avatar hujianyang Committed by Miklos Szeredi
Browse files

ovl: upper fs should not be R/O 



After importing multi-lower layer support, users could mount a r/o
partition as the left most lowerdir instead of using it as upperdir.
And a r/o upperdir may cause an error like

	overlayfs: failed to create directory ./workdir/work

during mount.

This patch check the *s_flags* of upper fs and return an error if
it is a r/o partition. The checking of *upper_mnt->mnt_sb->s_flags*
can be removed now.

This patch also remove

	/* FIXME: workdir is not needed for a R/O mount */

from ovl_fill_super() because:

1) for upper fs r/o case
Setting a r/o partition as upper is prevented, no need to care about
workdir in this case.

2) for "mount overlay -o ro" with a r/w upper fs case
Users could remount overlayfs to r/w in this case, so workdir should
not be omitted.

Signed-off-by: default avatarhujianyang <hujianyang@huawei.com>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent 6be4506e

fs/overlayfs/super.c

+19 −5
Original line number Diff line number Diff line
@@ -529,8 +529,7 @@ static int ovl_remount(struct super_block *sb, int *flags, char *data) 
{

	struct ovl_fs *ufs = sb->s_fs_info;



	if (!(*flags & MS_RDONLY) &&

	    (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY)))

	if (!(*flags & MS_RDONLY) && !ufs->upper_mnt)

		return -EROFS;



	return 0;
@@ -619,6 +618,15 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config) 
			return -EINVAL;

		}

	}



	/* Workdir is useless in non-upper mount */

	if (!config->upperdir && config->workdir) {

		pr_info("overlayfs: option \"workdir=%s\" is useless in a non-upper mount, ignore\n",

			config->workdir);

		kfree(config->workdir);

		config->workdir = NULL;

	}



	return 0;

}
@@ -838,7 +846,6 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 


	sb->s_stack_depth = 0;

	if (ufs->config.upperdir) {

		/* FIXME: workdir is not needed for a R/O mount */

		if (!ufs->config.workdir) {

			pr_err("overlayfs: missing 'workdir'\n");

			goto out_free_config;
@@ -848,6 +855,13 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
		if (err)

			goto out_free_config;



		/* Upper fs should not be r/o */

		if (upperpath.mnt->mnt_sb->s_flags & MS_RDONLY) {

			pr_err("overlayfs: upper fs is r/o, try multi-lower layers mount\n");

			err = -EINVAL;

			goto out_put_upperpath;

		}



		err = ovl_mount_dir(ufs->config.workdir, &workpath);

		if (err)

			goto out_put_upperpath;
@@ -939,8 +953,8 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
		ufs->numlower++;

	}



	/* If the upper fs is r/o or nonexistent, we mark overlayfs r/o too */

	if (!ufs->upper_mnt || (ufs->upper_mnt->mnt_sb->s_flags & MS_RDONLY))

	/* If the upper fs is nonexistent, we mark overlayfs r/o too */

	if (!ufs->upper_mnt)

		sb->s_flags |= MS_RDONLY;



	sb->s_d_op = &ovl_dentry_operations;

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