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Groups > linux.kernel > #1483510
| From | ebiederm@xmission.com (Eric W. Biederman) |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware |
| Date | 2016-09-14 19:50 +0200 |
| Message-ID | <shmtP-3OB-7@gated-at.bofh.it> (permalink) |
| References | <shbI5-5Bm-3@gated-at.bofh.it> <shbI5-5Bm-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Ian Kent <raven@themaw.net> writes:
> If an automount mount is clone(2)ed into a file system that is
> propagation private, when it later expires in the originating
> namespace subsequent calls to autofs ->d_automount() for that
> dentry in the original namespace will return ELOOP until the
> mount is manually umounted in the cloned namespace.
>
> In the same way, if an autofs mount is triggered by automount(8)
> running 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.
Overall this appears to be a fairly reasonable set of changes. It does
increase the expense when an actual mount point is encountered, but if
these are the desired some increase in cost when a dentry is a
mountpoint is unavoidable.
May I ask the motiviation for this set of changes? Reading through the
changes I don't grasp why we want to change the behavior of autofs.
What problem is being solved? What are the benefits?
Eric
> Signed-off-by: Ian Kent <raven@themaw.net>
> Cc: Al Viro <viro@ZenIV.linux.org.uk>
> Cc: Eric W. Biederman <ebiederm@xmission.com>
> Cc: Omar Sandoval <osandov@osandov.com>
> ---
> fs/autofs4/dev-ioctl.c | 2 +-
> fs/autofs4/expire.c | 4 ++--
> fs/autofs4/root.c | 30 +++++++++++++++---------------
> fs/autofs4/waitq.c | 2 +-
> 4 files changed, 19 insertions(+), 19 deletions(-)
>
> diff --git a/fs/autofs4/dev-ioctl.c b/fs/autofs4/dev-ioctl.c
> index c7fcc74..0024e25 100644
> --- a/fs/autofs4/dev-ioctl.c
> +++ b/fs/autofs4/dev-ioctl.c
> @@ -564,7 +564,7 @@ static int autofs_dev_ioctl_ismountpoint(struct file *fp,
>
> devid = new_encode_dev(dev);
>
> - err = have_submounts(path.dentry);
> + err = have_local_submounts(path.dentry);
>
> if (follow_down_one(&path))
> magic = path.dentry->d_sb->s_magic;
> diff --git a/fs/autofs4/expire.c b/fs/autofs4/expire.c
> index d8e6d42..7cc34ef 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 fa84bb8..4150ad6 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;
> }
> @@ -370,28 +370,28 @@ 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
> - * should. For v5 have_submounts() is sufficient to handle
> - * this because the leaves of the directory tree under the
> - * mount never trigger mounts themselves (they have an autofs
> - * trigger mount mounted on them). But v4 pseudo direct mounts
> - * do need the leaves to trigger mounts. In this case we
> - * have no choice but to use the list_empty() check and
> - * require user space behave.
> + * should. For v5 have_local_submounts() is sufficient to
> + * handle this because the leaves of the directory tree under
> + * the mount never trigger mounts themselves (they have an
> + * autofs trigger mount mounted on them). But v4 pseudo
> + * direct mounts do need the leaves to trigger mounts. In
> + * this case we have no choice but to use the list_empty()
> + * check and require user space behave.
> */
> if (sbi->version > 4) {
> - if (have_submounts(dentry)) {
> + if (have_local_submounts(dentry)) {
> spin_unlock(&sbi->fs_lock);
> goto done;
> }
> @@ -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_WANT_EXPIRE)
> 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/autofs4/waitq.c b/fs/autofs4/waitq.c
> index 431fd7e..911f4d5 100644
> --- a/fs/autofs4/waitq.c
> +++ b/fs/autofs4/waitq.c
> @@ -333,7 +333,7 @@ static int validate_request(struct autofs_wait_queue **wait,
> dentry = new;
> }
> }
> - if (have_submounts(dentry))
> + if (have_local_submounts(dentry))
> valid = 0;
>
> if (new)
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[PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-14 08:20 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware ebiederm@xmission.com (Eric W. Biederman) - 2016-09-14 19:50 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-15 02:10 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Omar Sandoval <osandov@osandov.com> - 2016-09-15 02:40 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware ebiederm@xmission.com (Eric W. Biederman) - 2016-09-15 04:30 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-15 06:20 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-15 10:30 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware ebiederm@xmission.com (Eric W. Biederman) - 2016-09-16 03:10 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-16 05:00 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-19 03:00 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware ebiederm@xmission.com (Eric W. Biederman) - 2016-09-20 18:30 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-15 03:10 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Omar Sandoval <osandov@osandov.com> - 2016-09-16 23:20 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Mateusz Guzik <mguzik@redhat.com> - 2016-09-17 22:20 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-19 03:40 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware ebiederm@xmission.com (Eric W. Biederman) - 2016-09-20 19:10 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-21 00:50 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-21 01:10 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-22 03:40 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware ebiederm@xmission.com (Eric W. Biederman) - 2016-09-22 18:00 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-23 03:00 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware ebiederm@xmission.com (Eric W. Biederman) - 2016-09-23 04:00 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-23 06:30 +0200
Re: [PATCH 3/4] autofs - make mountpoint checks namespace aware Ian Kent <raven@themaw.net> - 2016-09-23 14:10 +0200
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