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Subject[PATCH 02/13] vfs: keep list of mounts for each superblock
Date
From: Miklos Szeredi <mszeredi@suse.cz>

Keep track of vfsmounts belonging to a superblock. List is protected
by vfsmount_lock.

Signed-off-by: Miklos Szeredi <mszeredi@suse.cz>
Tested-by: Toshiyuki Okajima <toshi.okajima@jp.fujitsu.com>
---
fs/namespace.c | 10 ++++++++++
fs/super.c | 2 ++
include/linux/fs.h | 1 +
include/linux/mount.h | 1 +
4 files changed, 14 insertions(+), 0 deletions(-)
diff --git a/fs/namespace.c b/fs/namespace.c
index b4febb2..ccbec4e 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -696,6 +696,11 @@ vfs_kern_mount(struct file_system_type *type, int flags, const char *name, void
mnt->mnt_sb = root->d_sb;
mnt->mnt_mountpoint = mnt->mnt_root;
mnt->mnt_parent = mnt;
+
+ br_write_lock(vfsmount_lock);
+ list_add_tail(&mnt->mnt_instance, &mnt->mnt_sb->s_mounts);
+ br_write_unlock(vfsmount_lock);
+
return mnt;
}
EXPORT_SYMBOL_GPL(vfs_kern_mount);
@@ -745,6 +750,10 @@ static struct vfsmount *clone_mnt(struct vfsmount *old, struct dentry *root,
if (!list_empty(&old->mnt_expire))
list_add(&mnt->mnt_expire, &old->mnt_expire);
}
+
+ br_write_lock(vfsmount_lock);
+ list_add_tail(&mnt->mnt_instance, &mnt->mnt_sb->s_mounts);
+ br_write_unlock(vfsmount_lock);
}
return mnt;

@@ -805,6 +814,7 @@ put_again:
acct_auto_close_mnt(mnt);
goto put_again;
}
+ list_del(&mnt->mnt_instance);
br_write_unlock(vfsmount_lock);
mntfree(mnt);
}
diff --git a/fs/super.c b/fs/super.c
index 14948d6..a021ca2 100644
--- a/fs/super.c
+++ b/fs/super.c
@@ -142,6 +142,7 @@ static struct super_block *alloc_super(struct file_system_type *type)
INIT_LIST_HEAD(&s->s_dentry_lru);
INIT_LIST_HEAD(&s->s_inode_lru);
spin_lock_init(&s->s_inode_lru_lock);
+ INIT_LIST_HEAD(&s->s_mounts);
init_rwsem(&s->s_umount);
mutex_init(&s->s_lock);
lockdep_set_class(&s->s_umount, &type->s_umount_key);
@@ -200,6 +201,7 @@ static inline void destroy_super(struct super_block *s)
free_percpu(s->s_files);
#endif
security_sb_free(s);
+ WARN_ON(!list_empty(&s->s_mounts));
kfree(s->s_subtype);
kfree(s->s_options);
kfree(s);
diff --git a/include/linux/fs.h b/include/linux/fs.h
index ba98668..6eb9a30 100644
--- a/include/linux/fs.h
+++ b/include/linux/fs.h
@@ -1412,6 +1412,7 @@ struct super_block {
#else
struct list_head s_files;
#endif
+ struct list_head s_mounts; /* list of mounts */
/* s_dentry_lru, s_nr_dentry_unused protected by dcache.c lru locks */
struct list_head s_dentry_lru; /* unused dentry lru */
int s_nr_dentry_unused; /* # of dentry on lru */
diff --git a/include/linux/mount.h b/include/linux/mount.h
index 33fe53d..f88c726 100644
--- a/include/linux/mount.h
+++ b/include/linux/mount.h
@@ -67,6 +67,7 @@ struct vfsmount {
#endif
struct list_head mnt_mounts; /* list of children, anchored here */
struct list_head mnt_child; /* and going through their mnt_child */
+ struct list_head mnt_instance; /* mount instance on sb->s_mounts */
int mnt_flags;
/* 4 bytes hole on 64bits arches without fsnotify */
#ifdef CONFIG_FSNOTIFY
--
1.7.3.4


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