path: root/packages/linux-kernel/patches/kernel/0002-inotify-support-for-stackable-filesystems.patch

From 77ce1f672326050d6b47dbab4f52f0bbcd553a37 Mon Sep 17 00:00:00 2001
From: Alex Harpin <development@landsofshadow.co.uk>
Date: Wed, 31 Dec 2014 10:33:38 +0000
Subject: [PATCH] VyOS: add inotify support for stackable filesystems
 (overlayfs)

As it stands at the moment, overlayfs doesn't have full support for
inotify, and as such anything that relies on inotify currently has
issues.  The simplest method of demonstrating this is to tail a file
(so tail -f /var/log/messages) and see that it doesn't follow changes
in that file.  This has been reported in a number of places, including
Bug #882147 in Ubuntu.  This patch is based on the version proposed by
Li Jianguo in response to this bug, adding support for inotify in
stackable filesystems.

This commit provides a complete fix for the workaround implemented
for bug #303, and will allow that commit to be reverted.

Bug #425 http://bugzilla.vyos.net/show_bug.cgi?id=425

(cherry picked from commit a93f1128bc83b5a6628da242e71c18ef05e81ea2)
---
 fs/notify/inotify/Kconfig        |   9 +++
 fs/notify/inotify/inotify_user.c | 110 ++++++++++++++++++++++++++++++-
 fs/overlayfs/super.c             |  24 ++++++-
 include/linux/inotify.h          |  28 ++++++++
 4 files changed, 168 insertions(+), 3 deletions(-)

diff --git a/fs/notify/inotify/Kconfig b/fs/notify/inotify/Kconfig
index 6736e47d94d8..84d9b31300c0 100644
--- a/fs/notify/inotify/Kconfig
+++ b/fs/notify/inotify/Kconfig
@@ -15,3 +15,12 @@ config INOTIFY_USER
 	  For more information, see <file:Documentation/filesystems/inotify.txt>
 
 	  If unsure, say Y.
+
+config INOTIFY_STACKFS
+	bool "Inotify support for stackable filesystem"
+	select INOTIFY_USER
+	default y
+	---help---
+	  Say Y here to enable inotify support for stackable filesystem.
+
+	  If unsure, say N.
diff --git a/fs/notify/inotify/inotify_user.c b/fs/notify/inotify/inotify_user.c
index 81ffc8629fc4..cacedffa6534 100644
--- a/fs/notify/inotify/inotify_user.c
+++ b/fs/notify/inotify/inotify_user.c
@@ -15,6 +15,7 @@
 
 #include <linux/file.h>
 #include <linux/fs.h> /* struct inode */
+#include <linux/mount.h>
 #include <linux/fsnotify_backend.h>
 #include <linux/idr.h>
 #include <linux/init.h> /* fs_initcall */
@@ -75,6 +76,92 @@ struct ctl_table inotify_table[] = {
 };
 #endif /* CONFIG_SYSCTL */
 
+#ifdef CONFIG_INOTIFY_STACKFS
+
+static DEFINE_RWLOCK(inotify_fs_lock);
+static LIST_HEAD(inotify_fs_list);
+
+static inline struct file_system_type* peek_fs_type(struct path *path)
+{
+	return path->mnt->mnt_sb->s_type;
+}
+
+static struct inotify_stackfs* inotify_get_stackfs(struct path *path)
+{
+	struct file_system_type *fs;
+	struct inotify_stackfs *fse, *ret = NULL;
+
+	fs = peek_fs_type(path);
+
+	read_lock(&inotify_fs_lock);
+	list_for_each_entry(fse, &inotify_fs_list, list) {
+		if (fse->fs_type == fs) {
+			ret = fse;
+			break;
+		}
+	}
+	read_unlock(&inotify_fs_lock);
+
+	return ret;
+}
+
+static inline void inotify_put_stackfs(struct inotify_stackfs *fs)
+{
+}
+
+int inotify_register_stackfs(struct inotify_stackfs *fs)
+{
+	int ret = 0;
+	struct inotify_stackfs *fse;
+
+	BUG_ON(IS_ERR_OR_NULL(fs->fs_type));
+	BUG_ON(IS_ERR_OR_NULL(fs->func));
+
+	INIT_LIST_HEAD(&fs->list);
+
+	write_lock(&inotify_fs_lock);
+	list_for_each_entry(fse, &inotify_fs_list, list) {
+		if (fse->fs_type == fs->fs_type) {
+			write_unlock(&inotify_fs_lock);
+			ret = -EBUSY;
+			goto out;
+		}
+	}
+	list_add_tail(&fs->list, &inotify_fs_list);
+	write_unlock(&inotify_fs_lock);
+
+out:
+	return ret;
+}
+EXPORT_SYMBOL_GPL(inotify_register_stackfs);
+
+void inotify_unregister_stackfs(struct inotify_stackfs *fs)
+{
+	struct inotify_stackfs *fse, *n;
+
+	write_lock(&inotify_fs_lock);
+	list_for_each_entry_safe(fse, n, &inotify_fs_list, list) {
+		if (fse == fs) {
+			list_del(&fse->list);
+			break;
+		}
+	}
+	write_unlock(&inotify_fs_lock);
+}
+EXPORT_SYMBOL_GPL(inotify_unregister_stackfs);
+
+#else
+static inline struct inotify_stackfs* inotify_get_stackfs(struct path *path)
+{
+	return NULL;
+}
+
+static inline void inotify_put_stackfs(struct inotify_stackfs *fs)
+{
+}
+
+#endif /* CONFIG_INOTIFY_STACKFS */
+
 static inline __u32 inotify_arg_to_mask(u32 arg)
 {
 	__u32 mask;
@@ -332,7 +419,7 @@ static const struct file_operations inotify_fops = {
 /*
  * find_inode - resolve a user-given path to a specific inode
  */
-static int inotify_find_inode(const char __user *dirname, struct path *path,
+static inline int __inotify_find_inode(const char __user *dirname, struct path *path,
 						unsigned int flags, __u64 mask)
 {
 	int error;
@@ -354,6 +441,27 @@ static int inotify_find_inode(const char __user *dirname, struct path *path,
 	return error;
 }
 
+static int inotify_find_inode(const char __user *dirname, struct path *path, unsigned flags, __u64 mask)
+{
+	int ret;
+	struct path tpath;
+	struct inotify_stackfs *fse;
+
+	ret = __inotify_find_inode(dirname, &tpath, flags, mask);
+	if (ret)
+		return ret;
+	fse = inotify_get_stackfs(&tpath);
+	if (fse == NULL) {
+		*path = tpath;
+		return 0;
+	}
+	ret = fse->func(path, &tpath);
+	inotify_put_stackfs(fse);
+	path_put(&tpath);
+
+	return ret;
+}
+
 static int inotify_add_to_idr(struct idr *idr, spinlock_t *idr_lock,
 			      struct inotify_inode_mark *i_mark)
 {
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index d6b724beb304..380ac598f2e4 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -15,6 +15,7 @@
 #include <linux/seq_file.h>
 #include <linux/posix_acl_xattr.h>
 #include <linux/exportfs.h>
+#include <linux/inotify.h>
 #include "overlayfs.h"
 
 MODULE_AUTHOR("Miklos Szeredi <miklos@szeredi.hu>");
@@ -1758,6 +1759,18 @@ static void ovl_inode_init_once(void *foo)
 	inode_init_once(&oi->vfs_inode);
 }
 
+static int ovl_inotify_path(struct path *dst, struct path *src)
+{
+	ovl_path_real(src->dentry, dst);
+	path_get(dst);
+	return 0;
+}
+
+static struct inotify_stackfs ovl_inotify = {
+	.fs_type	= &ovl_fs_type,
+	.func		= ovl_inotify_path,
+};
+
 static int __init ovl_init(void)
 {
 	int err;
@@ -1772,13 +1785,21 @@ static int __init ovl_init(void)
 
 	err = register_filesystem(&ovl_fs_type);
 	if (err)
-		kmem_cache_destroy(ovl_inode_cachep);
+		goto err;
+	err = inotify_register_stackfs(&ovl_inotify);
+	if (err)
+		goto err;
+	return err;
 
+err:
+	kmem_cache_destroy(ovl_inode_cachep);
+	unregister_filesystem(&ovl_fs_type);
 	return err;
 }
 
 static void __exit ovl_exit(void)
 {
+	inotify_unregister_stackfs(&ovl_inotify);
 	unregister_filesystem(&ovl_fs_type);
 
 	/*
@@ -1787,7 +1808,6 @@ static void __exit ovl_exit(void)
 	 */
 	rcu_barrier();
 	kmem_cache_destroy(ovl_inode_cachep);
-
 }
 
 module_init(ovl_init);
diff --git a/include/linux/inotify.h b/include/linux/inotify.h
index 6a24905f6e1e..4484f0760588 100644
--- a/include/linux/inotify.h
+++ b/include/linux/inotify.h
@@ -9,6 +9,8 @@
 
 #include <linux/sysctl.h>
 #include <uapi/linux/inotify.h>
+#include <linux/list.h>
+#include <linux/fs.h>
 
 extern struct ctl_table inotify_table[]; /* for sysctl */
 
@@ -20,4 +22,30 @@ extern struct ctl_table inotify_table[]; /* for sysctl */
 			  IN_DONT_FOLLOW | IN_EXCL_UNLINK | IN_MASK_ADD | \
 			  IN_MASK_CREATE | IN_ISDIR | IN_ONESHOT)
 
+typedef int (*inotify_path_proc)(struct path *dst, struct path *src);
+
+struct inotify_stackfs {
+	struct list_head	list;		/* entry in inotify_fs_list */
+	struct file_system_type	*fs_type;	/* registed file_system_type */
+	inotify_path_proc	func;		/* registed callback function */
+};
+
+#ifdef CONFIG_INOTIFY_STACKFS
+
+extern int inotify_register_stackfs(struct inotify_stackfs *fs);
+extern void inotify_unregister_stackfs(struct inotify_stackfs *fs);
+
+#else
+
+static inline int inotify_register_stackfs(struct inotify_stackfs *fs)
+{
+	return 0;
+}
+
+static inline void inotify_unregister_stackfs(struct inotify_stackfs *fs)
+{
+}
+
+#endif	/* CONFIG_INOTIFY_STACKFS */
+
 #endif	/* _LINUX_INOTIFY_H */
-- 
2.20.1