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authorErez Zadok <ezk@fsl.cs.sunysb.edu>2014-10-24 00:14:38 +0200
committerMiklos Szeredi <mszeredi@suse.cz>2014-10-24 00:14:38 +0200
commitf45827e84186af152492c6d0dcf4105b4a605f9b (patch)
treec202fa1dc66dec8c0cacd98d38492026a0359965 /fs
parentcc2596392af3b1404421aaef828a255303c46f93 (diff)
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: Erez Zadok <ezk@cs.sunysb.edu> Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Diffstat (limited to 'fs')
-rw-r--r--fs/overlayfs/super.c76
1 files changed, 48 insertions, 28 deletions
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index aaf562b9f937..7dcc24e84417 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -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;
}