Commit f45827e8 authored by Erez Zadok's avatar Erez Zadok Committed by Miklos Szeredi
Browse files

overlayfs: implement show_options 



This is useful because of the stacking nature of overlayfs.  Users like to
find out (via /proc/mounts) which lower/upper directory were used at mount
time.

AV: even failing ovl_parse_opt() could've done some kstrdup()
AV: failure of ovl_alloc_entry() should end up with ENOMEM, not EINVAL

Signed-off-by: default avatarErez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: default avatarMiklos Szeredi <mszeredi@suse.cz>
parent cc259639

fs/overlayfs/super.c

+48 −28
Original line number Diff line number Diff line
@@ -17,6 +17,7 @@ 
#include <linux/module.h>

#include <linux/sched.h>

#include <linux/statfs.h>

#include <linux/seq_file.h>

#include "overlayfs.h"



MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
@@ -25,12 +26,20 @@ MODULE_LICENSE("GPL"); 


#define OVERLAYFS_SUPER_MAGIC 0x794c764f



struct ovl_config {

	char *lowerdir;

	char *upperdir;

	char *workdir;

};



/* private information held for overlayfs's superblock */

struct ovl_fs {

	struct vfsmount *upper_mnt;

	struct vfsmount *lower_mnt;

	struct dentry *workdir;

	long lower_namelen;

	/* pathnames of lower and upper dirs, for show_options */

	struct ovl_config config;

};



struct ovl_dir_cache;
@@ -384,6 +393,9 @@ static void ovl_put_super(struct super_block *sb) 
	mntput(ufs->upper_mnt);

	mntput(ufs->lower_mnt);



	kfree(ufs->config.lowerdir);

	kfree(ufs->config.upperdir);

	kfree(ufs->config.workdir);

	kfree(ufs);

}
@@ -413,15 +425,27 @@ static int ovl_statfs(struct dentry *dentry, struct kstatfs *buf) 
	return err;

}



/**

 * ovl_show_options

 *

 * Prints the mount options for a given superblock.

 * Returns zero; does not fail.

 */

static int ovl_show_options(struct seq_file *m, struct dentry *dentry)

{

	struct super_block *sb = dentry->d_sb;

	struct ovl_fs *ufs = sb->s_fs_info;



	seq_printf(m, ",lowerdir=%s", ufs->config.lowerdir);

	seq_printf(m, ",upperdir=%s", ufs->config.upperdir);

	seq_printf(m, ",workdir=%s", ufs->config.workdir);

	return 0;

}



static const struct super_operations ovl_super_operations = {

	.put_super	= ovl_put_super,

	.statfs		= ovl_statfs,

};



struct ovl_config {

	char *lowerdir;

	char *upperdir;

	char *workdir;

	.show_options	= ovl_show_options,

};



enum {
@@ -442,10 +466,6 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config) 
{

	char *p;



	config->upperdir = NULL;

	config->lowerdir = NULL;

	config->workdir = NULL;



	while ((p = strsep(&opt, ",")) != NULL) {

		int token;

		substring_t args[MAX_OPT_ARGS];
@@ -586,39 +606,40 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
	struct dentry *root_dentry;

	struct ovl_entry *oe;

	struct ovl_fs *ufs;

	struct ovl_config config;

	struct kstatfs statfs;

	int err;



	err = ovl_parse_opt((char *) data, &config);

	if (err)

	err = -ENOMEM;

	ufs = kzalloc(sizeof(struct ovl_fs), GFP_KERNEL);

	if (!ufs)

		goto out;



	err = ovl_parse_opt((char *) data, &ufs->config);

	if (err)

		goto out_free_config;



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

	err = -EINVAL;

	if (!config.upperdir || !config.lowerdir || !config.workdir) {

	if (!ufs->config.upperdir || !ufs->config.lowerdir ||

	    !ufs->config.workdir) {

		pr_err("overlayfs: missing upperdir or lowerdir or workdir\n");

		goto out_free_config;

	}



	err = -ENOMEM;

	ufs = kmalloc(sizeof(struct ovl_fs), GFP_KERNEL);

	if (!ufs)

		goto out_free_config;



	oe = ovl_alloc_entry();

	if (oe == NULL)

		goto out_free_ufs;

		goto out_free_config;



	err = ovl_mount_dir(config.upperdir, &upperpath);

	err = ovl_mount_dir(ufs->config.upperdir, &upperpath);

	if (err)

		goto out_free_oe;



	err = ovl_mount_dir(config.lowerdir, &lowerpath);

	err = ovl_mount_dir(ufs->config.lowerdir, &lowerpath);

	if (err)

		goto out_put_upperpath;



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

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

	if (err)

		goto out_put_lowerpath;
@@ -674,7 +695,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent) 
	err = PTR_ERR(ufs->workdir);

	if (IS_ERR(ufs->workdir)) {

		pr_err("overlayfs: failed to create directory %s/%s\n",

		       config.workdir, OVL_WORKDIR_NAME);

		       ufs->config.workdir, OVL_WORKDIR_NAME);

		goto out_put_lower_mnt;

	}
@@ -729,12 +750,11 @@ out_put_upperpath: 
	path_put(&upperpath);

out_free_oe:

	kfree(oe);

out_free_ufs:

	kfree(ufs);

out_free_config:

	kfree(config.lowerdir);

	kfree(config.upperdir);

	kfree(config.workdir);

	kfree(ufs->config.lowerdir);

	kfree(ufs->config.upperdir);

	kfree(ufs->config.workdir);

	kfree(ufs);

out:

	return err;

}

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