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UBUNTU: ubuntu: overlayfs -- overlayfs: implement show_options

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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.

Signed-off-by: Erez Zadok <ezk@cs.sunysb.edu>
Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Signed-off-by: Andy Whitcroft <apw@canonical.com>
This commit is contained in:
Erez Zadok
2011-05-23 20:59:20 -04:00
committed by Tim Gardner
parent b05bc8ad6a
commit 547b86cbfd
1 changed files with 45 additions and 22 deletions
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67
fs/overlayfs/super.c
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@@ -18,6 +18,7 @@
#include <linux/cred.h>
#include <linux/sched.h>
#include <linux/statfs.h>
#include <linux/seq_file.h>
#include "overlayfs.h"
MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
@@ -26,12 +27,21 @@ MODULE_LICENSE("GPL");
#define OVERLAYFS_SUPER_MAGIC 0x794c764f
struct ovl_config {
char *lowerdir;
char *upperdir;
};
/* private information held for overlayfs's superblock */
struct ovl_fs {
struct vfsmount *upper_mnt;
struct vfsmount *lower_mnt;
long lower_namelen;
/* pathnames of lower and upper dirs, for show_options */
struct ovl_config config;
};
/* private information held for every overlayfs dentry */
struct ovl_entry {
/*
* Keep "double reference" on upper dentries, so that
@@ -388,6 +398,8 @@ 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);
}
@@ -436,15 +448,27 @@ 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);
return 0;
}
static const struct super_operations ovl_super_operations = {
.put_super = ovl_put_super,
.remount_fs = ovl_remount_fs,
.statfs = ovl_statfs,
};
struct ovl_config {
char *lowerdir;
char *upperdir;
.show_options = ovl_show_options,
};
enum {
@@ -504,34 +528,33 @@ 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)
goto out;
err = -EINVAL;
if (!config.upperdir || !config.lowerdir) {
printk(KERN_ERR "overlayfs: missing upperdir or lowerdir\n");
goto out_free_config;
}
err = -ENOMEM;
ufs = kmalloc(sizeof(struct ovl_fs), GFP_KERNEL);
if (!ufs)
goto out;
err = ovl_parse_opt((char *) data, &ufs->config);
if (err)
goto out_free_ufs;
err = -EINVAL;
if (!ufs->config.upperdir || !ufs->config.lowerdir) {
printk(KERN_ERR "overlayfs: missing upperdir or lowerdir\n");
goto out_free_config;
}
oe = ovl_alloc_entry();
if (oe == NULL)
goto out_free_ufs;
goto out_free_config;
err = kern_path(config.upperdir, LOOKUP_FOLLOW, &upperpath);
err = kern_path(ufs->config.upperdir, LOOKUP_FOLLOW, &upperpath);
if (err)
goto out_free_oe;
err = kern_path(config.lowerdir, LOOKUP_FOLLOW, &lowerpath);
err = kern_path(ufs->config.lowerdir, LOOKUP_FOLLOW, &lowerpath);
if (err)
goto out_put_upperpath;
@@ -615,11 +638,11 @@ out_put_upperpath:
path_put(&upperpath);
out_free_oe:
kfree(oe);
out_free_config:
kfree(ufs->config.lowerdir);
kfree(ufs->config.upperdir);
out_free_ufs:
kfree(ufs);
out_free_config:
kfree(config.lowerdir);
kfree(config.upperdir);
out:
return err;
}