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From 27034e7c64b00a1f2467afb5ebb1d5b9b1a06ce1 Mon Sep 17 00:00:00 2001
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From: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
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Date: Wed, 11 Jul 2018 13:43:33 +0300
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Subject: [PATCH] mount: fix regression where open_mountpoint failed on
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readonly fs
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If we fail to create temporary directory for doing a clean mount we can
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make mount clean reusing the code which enters new mountns to umount
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overmounts. As when last process exits mntns all mounts are implicitly
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cleaned from children, see in kernel source - sys_exit->do_exit
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->exit_task_namespaces->switch_task_namespaces->free_nsproxy
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->put_mnt_ns->umount_tree->drop_collected_mounts->umount_tree:
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/* Hide the mounts from mnt_mounts */
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list_for_each_entry(p, &tmp_list, mnt_list) {
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list_del_init(&p->mnt_child);
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}
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Fixes commit b6cfb1ce2948 ("mount: make open_mountpoint handle overmouts
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properly")
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https://github.com/checkpoint-restore/criu/issues/520
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Signed-off-by: Pavel Tikhomirov <ptikhomirov@virtuozzo.com>
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Acked-by: Adrian Reber <areber@redhat.com>
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Signed-off-by: Andrei Vagin <avagin@virtuozzo.com>
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---
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criu/mount.c | 28 ++++++++++++++++++++--------
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1 file changed, 20 insertions(+), 8 deletions(-)
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diff --git a/criu/mount.c b/criu/mount.c
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index b56164e953..9cc8f6e940 100644
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--- a/criu/mount.c
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+++ b/criu/mount.c
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@@ -1325,10 +1325,18 @@ int ns_open_mountpoint(void *arg)
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if (umount_overmounts(mi))
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goto err;
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- /* Save fd which we opened for parent due to CLONE_FILES flag */
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- *fd = get_clean_fd(mi);
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- if (*fd < 0)
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+ /*
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+ * Save fd which we opened for parent due to CLONE_FILES flag
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+ *
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+ * Mount can still have children in it, but we don't need to clean it
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+ * explicitly as when last process exits mntns all mounts in it are
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+ * cleaned from their children, and we are exactly the last process.
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+ */
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+ *fd = open(mi->mountpoint, O_DIRECTORY|O_RDONLY);
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+ if (*fd < 0) {
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+ pr_perror("Unable to open %s", mi->mountpoint);
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goto err;
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+ }
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return 0;
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err:
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@@ -1367,18 +1375,22 @@ int open_mountpoint(struct mount_info *pm)
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if (!mnt_is_overmounted(pm)) {
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pr_info("\tmount has children %s\n", pm->mountpoint);
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-
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fd = get_clean_fd(pm);
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- if (fd < 0)
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- goto err;
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- } else {
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+ }
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+
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+ /*
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+ * Mount is overmounted or probably we can't create a temporary
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+ * direcotry for a cleaned mount
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+ */
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+ if (fd < 0) {
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int pid, status;
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struct clone_arg ca = {
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.mi = pm,
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.fd = &fd
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};
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- pr_info("\tmount is overmounted %s\n", pm->mountpoint);
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+ pr_info("\tmount is overmounted or has children %s\n",
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+ pm->mountpoint);
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/*
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* We are overmounted - not accessible in a regular way. We
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