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From 9cc2c0f41c403a05989bc3ca2af650247d452f65 Mon Sep 17 00:00:00 2001
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From: "T.kabe" <kabe@>
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Date: Mon, 6 Mar 2017 15:18:55 +0900
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Subject: [PATCH 2/4] vfs: Keep a list of mounts on a mount point
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[upstream commit 0a5eb7c8189922e86a840972cd0b57e41de6f031]
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Author: Eric W. Biederman <ebiederman@twitter.com>
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Date: Sun Sep 22 19:37:01 2013 -0700
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vfs: Keep a list of mounts on a mount point
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To spot any possible problems call BUG if a mountpoint
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is put when it's list of mounts is not empty.
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AV: use hlist instead of list_head
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Reviewed-by: Miklos Szeredi <miklos@szeredi.hu>
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Signed-off-by: Eric W. Biederman <ebiederman@twitter.com>
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Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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---
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fs/mount.h | 2 ++
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fs/namespace.c | 6 ++++++
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2 files changed, 8 insertions(+)
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diff --git a/fs/mount.h b/fs/mount.h
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index b870800..92fecbe 100644
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--- a/fs/mount.h
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+++ b/fs/mount.h
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@@ -21,6 +21,7 @@ struct mnt_pcp {
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struct mountpoint {
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struct list_head m_hash;
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struct dentry *m_dentry;
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+ struct hlist_head m_list;
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int m_count;
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};
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@@ -47,6 +48,7 @@ struct mount {
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struct mount *mnt_master; /* slave is on master->mnt_slave_list */
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struct mnt_namespace *mnt_ns; /* containing namespace */
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struct mountpoint *mnt_mp; /* where is it mounted */
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+ struct hlist_node mnt_mp_list; /* list mounts with the same mountpoint */
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#ifdef CONFIG_FSNOTIFY
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struct hlist_head mnt_fsnotify_marks;
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__u32 mnt_fsnotify_mask;
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diff --git a/fs/namespace.c b/fs/namespace.c
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index 0053bfc..c238481 100644
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--- a/fs/namespace.c
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+++ b/fs/namespace.c
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@@ -197,6 +197,7 @@ static struct mount *alloc_vfsmnt(const char *name)
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INIT_LIST_HEAD(&mnt->mnt_share);
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INIT_LIST_HEAD(&mnt->mnt_slave_list);
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INIT_LIST_HEAD(&mnt->mnt_slave);
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+ INIT_HLIST_NODE(&mnt->mnt_mp_list);
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#ifdef CONFIG_FSNOTIFY
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INIT_HLIST_HEAD(&mnt->mnt_fsnotify_marks);
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#endif
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@@ -636,6 +637,7 @@ static struct mountpoint *new_mountpoint(struct dentry *dentry)
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mp->m_dentry = dentry;
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mp->m_count = 1;
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list_add(&mp->m_hash, chain);
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+ INIT_HLIST_HEAD(&mp->m_list);
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return mp;
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}
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@@ -643,6 +645,7 @@ static void put_mountpoint(struct mountpoint *mp)
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{
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if (!--mp->m_count) {
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struct dentry *dentry = mp->m_dentry;
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+ BUG_ON(!hlist_empty(&mp->m_list));
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spin_lock(&dentry->d_lock);
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dentry->d_flags &= ~DCACHE_MOUNTED;
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spin_unlock(&dentry->d_lock);
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@@ -689,6 +692,7 @@ static void detach_mnt(struct mount *mnt, struct path *old_path)
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mnt->mnt_mountpoint = mnt->mnt.mnt_root;
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list_del_init(&mnt->mnt_child);
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list_del_init(&mnt->mnt_hash);
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+ hlist_del_init(&mnt->mnt_mp_list);
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put_mountpoint(mnt->mnt_mp);
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mnt->mnt_mp = NULL;
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}
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@@ -705,6 +709,7 @@ void mnt_set_mountpoint(struct mount *mnt,
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child_mnt->mnt_mountpoint = dget(mp->m_dentry);
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child_mnt->mnt_parent = mnt;
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child_mnt->mnt_mp = mp;
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+ hlist_add_head(&child_mnt->mnt_mp_list, &mp->m_list);
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}
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/*
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@@ -1207,6 +1212,7 @@ void umount_tree(struct mount *mnt, int propagate)
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__touch_mnt_namespace(p->mnt_ns);
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p->mnt_ns = NULL;
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if (mnt_has_parent(p)) {
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+ hlist_del_init(&p->mnt_mp_list);
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p->mnt_parent->mnt_ghosts++;
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put_mountpoint(p->mnt_mp);
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p->mnt_mp = NULL;
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--
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1.8.3.1
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