On Tue, 2016-07-05 at 11:47 -0700, Omar Sandoval wrote:
> On Fri, Apr 08, 2016 at 08:51:03AM +0800, Ian Kent wrote:
> [snip]
> >
> > I think this is a better approach (beware, not even compile tested so it
> > almost certainly doesn't work properly) and I'm not even sure that
> > exposing __is_local_mountpoint() is ok from a VFS POV but something
> > needs to be done:
> >
> > autofs4 - make mountpoint checks namespace aware
> >
> > From: Ian Kent <ikent@xxxxxxxxxx>
> >
> > If an automount mount is clone(2)ed into a file system that is
> > propagation private, when it later expires the mount subsequent
> > calls to autofs ->d_automount() for in that dentry in that
> > namespace will return ELOOP until the mount is manually umounted.
> >
> > In the same way, if an autofs mount is triggered by automount(8)
> > within a container the dentry will be seen as mounted in the
> > root init namespace and calls to ->d_automount() in that namespace
> > will return ELOOP until the mount is umounted within the container.
> >
> > Also, have_submounts() can return an incorect result when a mount
> > exists in a namespace other than the one being checked.
> >
> > Signed-off-by: Ian Kent <ikent@xxxxxxxxxx>
> > Cc: Al Viro <viro@xxxxxxxxxxxxxxxxxx>
> > Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx>
> > ---
> > fs/autofs4/expire.c | 4 ++--
> > fs/autofs4/root.c | 14 +++++++-------
> > fs/dcache.c | 2 +-
> > fs/mount.h | 9 ---------
> > fs/namespace.c | 1 +
> > include/linux/mount.h | 9 +++++++++
> > 6 files changed, 20 insertions(+), 19 deletions(-)
> >
> > diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
> > index 9510d8d..23b9701 100644
> > --- a/fs/autofs4/expire.c
> > +++ b/fs/autofs4/expire.c
> > @@ -236,7 +236,7 @@ static int autofs4_tree_busy(struct vfsmount *mnt,
> > * count for the autofs dentry.
> > * If the fs is busy update the expiry counter.
> > */
> > - if (d_mountpoint(p)) {
> > + if (is_local_mountpoint(p)) {
> > if (autofs4_mount_busy(mnt, p)) {
> > top_ino->last_used = jiffies;
> > dput(p);
> > @@ -280,7 +280,7 @@ static struct dentry *autofs4_check_leaves(struct
> > vfsmount *mnt,
> > while ((p = get_next_positive_dentry(p, parent))) {
> > pr_debug("dentry %p %pd\n", p, p);
> >
> > - if (d_mountpoint(p)) {
> > + if (is_local_mountpoint(p)) {
> > /* Can we umount this guy */
> > if (autofs4_mount_busy(mnt, p))
> > continue;
> > diff --git a/fs/autofs4/root.c b/fs/autofs4/root.c
> > index 7ab9239..9ba487a 100644
> > --- a/fs/autofs4/root.c
> > +++ b/fs/autofs4/root.c
> > @@ -123,7 +123,7 @@ static int autofs4_dir_open(struct inode *inode, struct
> > file *file)
> > * it.
> > */
> > spin_lock(&sbi->lookup_lock);
> > - if (!d_mountpoint(dentry) && simple_empty(dentry)) {
> > + if (!is_local_mountpoint(dentry) && simple_empty(dentry)) {
> > spin_unlock(&sbi->lookup_lock);
> > return -ENOENT;
> > }
> > @@ -370,15 +370,15 @@ static struct vfsmount *autofs4_d_automount(struct
> > path *path)
> >
> > /*
> > * If the dentry is a symlink it's equivalent to a directory
> > - * having d_mountpoint() true, so there's no need to call back
> > - * to the daemon.
> > + * having is_local_mountpoint() true, so there's no need to
> > + * call back to the daemon.
> > */
> > if (d_really_is_positive(dentry) && d_is_symlink(dentry)) {
> > spin_unlock(&sbi->fs_lock);
> > goto done;
> > }
> >
> > - if (!d_mountpoint(dentry)) {
> > + if (!is_local_mountpoint(dentry)) {
> > /*
> > * It's possible that user space hasn't removed directories
> > * after umounting a rootless multi-mount, although it
> > @@ -431,7 +431,7 @@ static int autofs4_d_manage(struct dentry *dentry, bool
> > rcu_walk)
> >
> > /* The daemon never waits. */
> > if (autofs4_oz_mode(sbi)) {
> > - if (!d_mountpoint(dentry))
> > + if (!is_local_mountpoint(dentry))
> > return -EISDIR;
> > return 0;
> > }
> > @@ -460,7 +460,7 @@ static int autofs4_d_manage(struct dentry *dentry, bool
> > rcu_walk)
> >
> > if (ino->flags & (AUTOFS_INF_EXPIRING | AUTOFS_INF_NO_RCU))
> > return 0;
> > - if (d_mountpoint(dentry))
> > + if (is_local_mountpoint(dentry))
> > return 0;
> > inode = d_inode_rcu(dentry);
> > if (inode && S_ISLNK(inode->i_mode))
> > @@ -487,7 +487,7 @@ static int autofs4_d_manage(struct dentry *dentry, bool
> > rcu_walk)
> > * we can avoid needless calls ->d_automount() and avoid
> > * an incorrect ELOOP error return.
> > */
> > - if ((!d_mountpoint(dentry) && !simple_empty(dentry)) ||
> > + if ((!is_local_mountpoint(dentry) && !simple_empty(dentry))
> > ||
> > (d_really_is_positive(dentry) && d_is_symlink(dentry)))
> > status = -EISDIR;
> > }
> > diff --git a/fs/dcache.c b/fs/dcache.c
> > index 32ceae3..9c42dc9 100644
> > --- a/fs/dcache.c
> > +++ b/fs/dcache.c
> > @@ -1271,7 +1271,7 @@ rename_retry:
> > static enum d_walk_ret check_mount(void *data, struct dentry *dentry)
> > {
> > int *ret = data;
> > - if (d_mountpoint(dentry)) {
> > + if (is_local_mountpoint(dentry)) {
> > *ret = 1;
> > return D_WALK_QUIT;
> > }
> > diff --git a/fs/mount.h b/fs/mount.h
> > index 14db05d..c25e6e8 100644
> > --- a/fs/mount.h
> > +++ b/fs/mount.h
> > @@ -127,12 +127,3 @@ struct proc_mounts {
> > };
> >
> > extern const struct seq_operations mounts_op;
> > -
> > -extern bool __is_local_mountpoint(struct dentry *dentry);
> > -static inline bool is_local_mountpoint(struct dentry *dentry)
> > -{
> > - if (!d_mountpoint(dentry))
> > - return false;
> > -
> > - return __is_local_mountpoint(dentry);
> > -}
> > diff --git a/fs/namespace.c b/fs/namespace.c
> > index 4fb1691..9e1bc00 100644
> > --- a/fs/namespace.c
> > +++ b/fs/namespace.c
> > @@ -725,6 +725,7 @@ bool __is_local_mountpoint(struct dentry *dentry)
> > out:
> > return is_covered;
> > }
> > +EXPORT_SYMBOL(__is_local_mountpoint);
> >
> > static struct mountpoint *lookup_mountpoint(struct dentry *dentry)
> > {
> > diff --git a/include/linux/mount.h b/include/linux/mount.h
> > index f822c3c..7419c0c 100644
> > --- a/include/linux/mount.h
> > +++ b/include/linux/mount.h
> > @@ -15,6 +15,7 @@
> > #include <linux/spinlock.h>
> > #include <linux/seqlock.h>
> > #include <linux/atomic.h>
> > +#include <linux/dcache.h>
> >
> > struct super_block;
> > struct vfsmount;
> > @@ -95,4 +96,12 @@ extern void mark_mounts_for_expiry(struct list_head
> > *mounts);
> >
> > extern dev_t name_to_dev_t(const char *name);
> >
> > +extern bool __is_local_mountpoint(struct dentry *dentry);
> > +static inline bool is_local_mountpoint(struct dentry *dentry)
> > +{
> > + if (!d_mountpoint(dentry))
> > + return false;
> > +
> > + return __is_local_mountpoint(dentry);
> > +}
> > #endif /* _LINUX_MOUNT_H */
>
> Hi, Ian,
>
> Just wanted to check on the status of this fix. Is this still the
> approach you wanted to take/is there anything else you wanted to do with
> this?
The problem is that someone tested this back ported to an older kernel and
claimed it caused file system corruption.
That leaves me in a bad place indeed.
Ian
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