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Message-ID: <20180601031829.GQ30522@ZenIV.linux.org.uk>
Date: Fri, 1 Jun 2018 04:18:29 +0100
From: Al Viro <viro@...IV.linux.org.uk>
To: David Howells <dhowells@...hat.com>
Cc: linux-fsdevel@...r.kernel.org, linux-afs@...ts.infradead.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH 20/32] vfs: Make close() unmount the attached mount if so
flagged [ver #8]
FWIW, this on top of your current branch (I'll fold and reorder) gets
your move_mount(2) test work, AFAICS:
diff --git a/fs/file_table.c b/fs/file_table.c
index 06e979e1347e..6dd9760b3ddc 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -200,9 +200,6 @@ static void __fput(struct file *file)
eventpoll_release(file);
locks_remove_file(file);
- if (unlikely(file->f_mode & FMODE_NEED_UNMOUNT))
- drop_collected_mounts(mnt);
-
ima_file_free(file);
if (unlikely(file->f_flags & FASYNC)) {
if (file->f_op->fasync)
@@ -228,7 +225,10 @@ static void __fput(struct file *file)
file->f_inode = NULL;
file_free(file);
dput(dentry);
- mntput(mnt);
+ if (unlikely(file->f_mode & FMODE_NEED_UNMOUNT))
+ umount_on_fput(mnt);
+ else
+ mntput(mnt);
}
static LLIST_HEAD(delayed_fput_list);
diff --git a/fs/internal.h b/fs/internal.h
index 6d0538af32d9..7ec629916f6d 100644
--- a/fs/internal.h
+++ b/fs/internal.h
@@ -75,7 +75,7 @@ extern struct vfsmount *lookup_mnt(const struct path *);
extern int finish_automount(struct vfsmount *, struct path *);
extern int sb_prepare_remount_readonly(struct super_block *);
-extern int copy_mount_for_o_path(struct path *, struct path *, bool);
+extern int copy_mount_for_o_path(struct path *, bool);
extern void __init mnt_init(void);
@@ -86,6 +86,8 @@ extern void __mnt_drop_write(struct vfsmount *);
extern void __mnt_drop_write_file(struct file *);
extern void mnt_drop_write_file_path(struct file *);
+extern void umount_on_fput(struct vfsmount *);
+
/*
* fs_struct.c
*/
diff --git a/fs/namei.c b/fs/namei.c
index 7430e000c1d2..b1c451b6b508 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -3454,28 +3454,20 @@ static int do_tmpfile(struct nameidata *nd, unsigned flags,
static int do_o_path(struct nameidata *nd, unsigned flags, struct file *file)
{
- struct path path, tmp;
- int error;
-
- error = path_lookupat(nd, flags, &path);
+ struct path path;
+ int error = path_lookupat(nd, flags, &path);
if (error)
return error;
if (file->f_flags & O_CLONE_MOUNT) {
- error = copy_mount_for_o_path(
- &path, &tmp, !(file->f_flags & O_NON_RECURSIVE));
- path_put(&path);
+ error = copy_mount_for_o_path(&path,
+ !(file->f_flags & O_NON_RECURSIVE));
if (error < 0)
return error;
- path = tmp;
}
audit_inode(nd->name, path.dentry, 0);
error = vfs_open(&path, file, current_cred());
- if (error < 0 &&
- (flags & O_CLONE_MOUNT) &&
- !(file->f_mode & FMODE_NEED_UNMOUNT))
- __detach_mounts(path.dentry);
path_put(&path);
return error;
}
diff --git a/fs/namespace.c b/fs/namespace.c
index dd9cf81c2aea..74c68a23d088 100644
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@ -1793,7 +1793,7 @@ struct vfsmount *collect_mounts(const struct path *path)
return &tree->mnt;
}
-void drop_collected_mounts(struct vfsmount *mnt)
+void umount_on_fput(struct vfsmount *mnt)
{
namespace_lock();
lock_mount_hash();
@@ -1803,6 +1803,15 @@ void drop_collected_mounts(struct vfsmount *mnt)
namespace_unlock();
}
+void drop_collected_mounts(struct vfsmount *mnt)
+{
+ namespace_lock();
+ lock_mount_hash();
+ umount_tree(real_mount(mnt), UMOUNT_SYNC);
+ unlock_mount_hash();
+ namespace_unlock();
+}
+
/**
* clone_private_mount - create a private clone of a path
*
@@ -2153,6 +2162,30 @@ static bool has_locked_children(struct mount *mnt, struct dentry *dentry)
return false;
}
+static struct mount *__do_loopback(struct path *old_path, int recurse)
+{
+ struct mount *mnt = ERR_PTR(-EINVAL), *old = real_mount(old_path->mnt);
+
+ if (IS_MNT_UNBINDABLE(old))
+ return mnt;
+
+ if (!check_mnt(old) && old_path->dentry->d_op != &ns_dentry_operations)
+ return mnt;
+
+ if (!recurse && has_locked_children(old, old_path->dentry))
+ return mnt;
+
+ if (recurse)
+ mnt = copy_tree(old, old_path->dentry, CL_COPY_MNT_NS_FILE);
+ else
+ mnt = clone_mnt(old, old_path->dentry, 0);
+
+ if (!IS_ERR(mnt))
+ mnt->mnt.mnt_flags &= ~MNT_LOCKED;
+
+ return mnt;
+}
+
/*
* do loopback mount.
*/
@@ -2160,7 +2193,7 @@ static int do_loopback(struct path *path, const char *old_name,
int recurse)
{
struct path old_path;
- struct mount *mnt = NULL, *old, *parent;
+ struct mount *mnt = NULL, *parent;
struct mountpoint *mp;
int err;
if (!old_name || !*old_name)
@@ -2174,38 +2207,21 @@ static int do_loopback(struct path *path, const char *old_name,
goto out;
mp = lock_mount(path);
- err = PTR_ERR(mp);
- if (IS_ERR(mp))
+ if (IS_ERR(mp)) {
+ err = PTR_ERR(mp);
goto out;
+ }
- old = real_mount(old_path.mnt);
parent = real_mount(path->mnt);
-
- err = -EINVAL;
- if (IS_MNT_UNBINDABLE(old))
- goto out2;
-
if (!check_mnt(parent))
goto out2;
- if (!check_mnt(old) && old_path.dentry->d_op != &ns_dentry_operations)
- goto out2;
-
- if (!recurse && has_locked_children(old, old_path.dentry))
- goto out2;
-
- if (recurse)
- mnt = copy_tree(old, old_path.dentry, CL_COPY_MNT_NS_FILE);
- else
- mnt = clone_mnt(old, old_path.dentry, 0);
-
+ mnt = __do_loopback(&old_path, recurse);
if (IS_ERR(mnt)) {
err = PTR_ERR(mnt);
goto out2;
}
- mnt->mnt.mnt_flags &= ~MNT_LOCKED;
-
err = graft_tree(mnt, parent, mp);
if (err) {
lock_mount_hash();
@@ -2223,44 +2239,16 @@ static int do_loopback(struct path *path, const char *old_name,
* Copy the mount or mount subtree at the specified path for
* open(O_PATH|O_CLONE_MOUNT).
*/
-int copy_mount_for_o_path(struct path *from, struct path *to, bool recurse)
+int copy_mount_for_o_path(struct path *path, bool recurse)
{
- struct mountpoint *mp;
- struct mount *mnt = NULL, *f = real_mount(from->mnt);
- int ret;
-
- mp = lock_mount(from);
- if (IS_ERR(mp))
- return PTR_ERR(mp);
-
- ret = -EINVAL;
- if (IS_MNT_UNBINDABLE(f))
- goto out_unlock;
-
- if (!check_mnt(f) && from->dentry->d_op != &ns_dentry_operations)
- goto out_unlock;
-
- if (!recurse && has_locked_children(f, from->dentry))
- goto out_unlock;
-
- if (recurse)
- mnt = copy_tree(f, from->dentry, CL_COPY_MNT_NS_FILE);
- else
- mnt = clone_mnt(f, from->dentry, 0);
+ struct mount *mnt = __do_loopback(path, recurse);
if (IS_ERR(mnt)) {
- ret = PTR_ERR(mnt);
- goto out_unlock;
+ path_put(path);
+ return PTR_ERR(mnt);
}
-
- mnt->mnt.mnt_flags &= ~MNT_LOCKED;
-
- to->mnt = &mnt->mnt;
- to->dentry = dget(from->dentry);
- ret = 0;
-
-out_unlock:
- unlock_mount(mp);
- return ret;
+ mntput(path->mnt);
+ path->mnt = &mnt->mnt;
+ return 0;
}
static int change_mount_flags(struct vfsmount *mnt, int ms_flags)
@@ -2398,11 +2386,12 @@ static inline int tree_contains_unbindable(struct mount *mnt)
static int do_move_mount(struct path *old_path, struct path *new_path)
{
- struct path parent_path;
+ struct path parent_path = {.mnt = NULL, .dentry = NULL};
struct mount *p;
struct mount *old;
struct mountpoint *mp;
int err;
+ bool attached;
mp = lock_mount(new_path);
err = PTR_ERR(mp);
@@ -2420,10 +2409,11 @@ static int do_move_mount(struct path *old_path, struct path *new_path)
if (old->mnt_ns && !check_mnt(old))
goto out1;
+ attached = mnt_has_parent(old);
/* We need to allow open(O_PATH|O_CLONE_MOUNT) or fsmount() followed by
* move_mount(), but mustn't allow "/" to be moved.
*/
- if (old->mnt_ns && !mnt_has_parent(old))
+ if (old->mnt_ns && !attached)
goto out1;
if (old->mnt.mnt_flags & MNT_LOCKED)
@@ -2438,7 +2428,7 @@ static int do_move_mount(struct path *old_path, struct path *new_path)
/*
* Don't move a mount residing in a shared parent.
*/
- if (IS_MNT_SHARED(old->mnt_parent))
+ if (attached && IS_MNT_SHARED(old->mnt_parent))
goto out1;
/*
* Don't move a mount tree containing unbindable mounts to a destination
@@ -2452,7 +2442,7 @@ static int do_move_mount(struct path *old_path, struct path *new_path)
goto out1;
err = attach_recursive_mnt(old, real_mount(new_path->mnt), mp,
- &parent_path);
+ attached ? &parent_path : NULL);
if (err)
goto out1;
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