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Message-Id: <1400838223-30844-11-git-send-email-miklos@szeredi.hu>
Date: Fri, 23 May 2014 11:43:40 +0200
From: Miklos Szeredi <miklos@...redi.hu>
To: viro@...IV.linux.org.uk, torvalds@...ux-foundation.org
Cc: linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
hch@...radead.org, akpm@...ux-foundation.org, apw@...onical.com,
nbd@...nwrt.org, neilb@...e.de, jordipujolp@...il.com,
ezk@....cs.sunysb.edu, dhowells@...hat.com, sedat.dilek@...il.com,
hooanon05@...oo.co.jp, mszeredi@...e.cz,
Erez Zadok <ezk@...sunysb.edu>
Subject: [PATCH 10/13] overlayfs: implement show_options
From: Erez Zadok <ezk@....cs.sunysb.edu>
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@...sunysb.edu>
Signed-off-by: Miklos Szeredi <mszeredi@...e.cz>
---
fs/overlayfs/super.c | 76 +++++++++++++++++++++++++++++++++++-----------------
1 file changed, 51 insertions(+), 25 deletions(-)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 8b77f3f45579..fcbd92a14e69 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@...redi.hu>");
@@ -25,13 +26,23 @@ 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;
};
+/* private information held for every overlayfs dentry */
struct ovl_entry {
/*
* Keep "double reference" on upper dentries, so that
@@ -373,6 +384,9 @@ 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);
}
@@ -421,16 +435,28 @@ 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,
.remount_fs = ovl_remount_fs,
.statfs = ovl_statfs,
-};
-
-struct ovl_config {
- char *lowerdir;
- char *upperdir;
- char *workdir;
+ .show_options = ovl_show_options,
};
enum {
@@ -558,38 +584,38 @@ 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 = 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 (!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;
@@ -614,7 +640,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
err = vfs_statfs(&lowerpath, &statfs);
if (err) {
pr_err("overlayfs: statfs failed on lowerpath\n");
- goto out_put_lowerpath;
+ goto out_put_workpath;
}
ufs->lower_namelen = statfs.f_namelen;
@@ -636,7 +662,7 @@ 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;
}
@@ -702,12 +728,12 @@ out_put_upperpath:
path_put(&upperpath);
out_free_oe:
kfree(oe);
+out_free_config:
+ kfree(ufs->config.lowerdir);
+ kfree(ufs->config.upperdir);
+ kfree(ufs->config.workdir);
out_free_ufs:
kfree(ufs);
-out_free_config:
- kfree(config.lowerdir);
- kfree(config.upperdir);
- kfree(config.workdir);
out:
return err;
}
--
1.8.1.4
--
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