[Devel] [PATCH RHEL7 COMMIT] overlayfs: add mnt_id paths options
Konstantin Khorenko
khorenko at virtuozzo.com
Thu Jun 11 19:05:38 MSK 2020
The commit is pushed to "branch-rh7-3.10.0-1127.10.1.vz7.162.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh7-3.10.0-1127.10.1.vz7.162.2
------>
commit c14b3044c39507ebd65e1f41c085d9920fa2a6e0
Author: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
Date: Thu Jun 4 11:34:35 2020 +0300
overlayfs: add mnt_id paths options
This patch adds config OVERLAY_FS_PATH_OPTIONS_MNT_ID
compile-time option, and "mnt_id_path_opts" runtime module option.
If enabled, user may see mnt_ids for lowerdir, upperdir paths
in mountinfo in separate lowerdir_mnt_id/upperdir_mnt_id options.
This patch is very helpful to checkpoint/restore functionality
of overlayfs mounts in case when we have overmounts on
lowerdir, workdir, upperdir paths.
https://jira.sw.ru/browse/PSBM-58614
Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
Reviewed-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
=====================
Patchset description:
overlayfs: C/R enhancements
This patchset aimed to make C/R of overlayfs mounts with CRIU possible.
We introduce two new overlayfs module options -- dyn_path_opts and
mnt_id_path_opts. If enabled this options allows to see real *full* paths
in lowerdir, workdir, upperdir options, and also mnt_ids for corresponding
paths.
This changes should not break anything because for showing mnt_ids we simply
introduce new show-time mount options. And for paths we simply *always*
provide *full paths* instead of relative path on mountinfo.
BEFORE
overlay on /var/lib/docker/overlay2/XYZ/merged type overlay (rw,relatime,
lowerdir=/var/lib/docker/overlay2/XYZ-init/diff:/var/lib/docker/overlay2/
ABC/diff,upperdir=/var/lib/docker/overlay2/XYZ/diff,workdir=/var/lib/docker
/overlay2/XYZ/work)
none on /sys type sysfs (rw,relatime)
AFTER
overlay on /var/lib/docker/overlay2/XYZ/merged type overlay (rw,relatime,
lowerdir=/var/lib/docker/overlay2/XYZ-init/diff:/var/lib/docker/overlay2/
ABC/diff,upperdir=/var/lib/docker/overlay2/XYZ/diff,workdir=/var/lib/docker
/overlay2/XYZ/work,lowerdir_mnt_id=175:175,upperdir_mnt_id=175)
none on /sys type sysfs (rw,relatime)
Alexander Mikhalitsyn (2):
overlayfs: add dynamic path resolving in mount options
overlayfs: add mnt_id paths options
---
fs/overlayfs/Kconfig | 26 ++++++++++++++++++++++++++
fs/overlayfs/overlayfs.h | 4 ++++
fs/overlayfs/super.c | 16 ++++++++++++++++
fs/overlayfs/util.c | 22 ++++++++++++++++++++++
4 files changed, 68 insertions(+)
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index 6a076014718db..32e8195a0cbef 100644
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -134,3 +134,29 @@ config OVERLAY_FS_DYNAMIC_RESOLVE_PATH_OPTIONS
For more information, see Documentation/filesystems/overlayfs.txt
If unsure, say N.
+
+config OVERLAY_FS_PATH_OPTIONS_MNT_ID
+ bool "Overlayfs: show mnt_id for all mount paths options"
+ default y
+ depends on OVERLAY_FS
+ help
+ This option helps checkpoint/restore of overlayfs mounts.
+ If N selected, old behavior is saved.
+
+ If this config option is enabled then in overlay filesystems mount
+ options you will be able to see additional parameters
+ lowerdir_mnt_id/upperdir_mnt_id with corresponding mnt_ids.
+
+ It's also possible to change this behavior on overlayfs module
+ loading or through sysfs (mnt_id_path_opts parameter).
+
+ Disable this to get a backward compatible with previous kernels
+ configuration, but in this case checkpoint/restore functionality
+ for overlayfs mounts may not fully work.
+
+ If backward compatibility is not an issue, then it is safe and
+ recommended to say Y here.
+
+ For more information, see Documentation/filesystems/overlayfs.txt
+
+ If unsure, say N.
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index f508cd2e93dbc..1b3a2c9d8a126 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -256,6 +256,10 @@ int ovl_lock_rename_workdir(struct dentry *workdir, struct dentry *upperdir);
void print_path_option(struct seq_file *m, const char *name, struct path *path);
void print_paths_option(struct seq_file *m, const char *name,
struct path *paths, unsigned int num);
+void print_mnt_id_option(struct seq_file *m, const char *name,
+ struct path *path);
+void print_mnt_ids_option(struct seq_file *m, const char *name,
+ struct path *paths, unsigned int num);
static inline bool ovl_is_impuredir(struct dentry *dentry)
{
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 374e243ca07a2..6a2611834480f 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -62,6 +62,10 @@ static bool ovl_dyn_path_opts =
module_param_named(dyn_path_opts, ovl_dyn_path_opts, bool, 0644);
MODULE_PARM_DESC(dyn_path_opts, "dyn_path_opts feature enabled");
+static bool ovl_mnt_id_path_opts = IS_ENABLED(OVERLAY_FS_PATH_OPTIONS_MNT_ID);
+module_param_named(mnt_id_path_opts, ovl_mnt_id_path_opts, bool, 0644);
+MODULE_PARM_DESC(mnt_id_path_opts, "mnt_id_path_opts feature enabled");
+
static void ovl_entry_stack_free(struct ovl_entry *oe)
{
unsigned int i;
@@ -394,6 +398,18 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
}
}
+ if (ovl_mnt_id_path_opts) {
+ print_mnt_ids_option(m, "lowerdir_mnt_id", ofs->lowerpaths,
+ ofs->numlower);
+ /*
+ * We don't need to show mnt_id for workdir because it
+ * on the same mount as upperdir.
+ */
+ if (ofs->config.upperdir)
+ print_mnt_id_option(m, "upperdir_mnt_id",
+ &ofs->upperpath);
+ }
+
if (ofs->config.default_permissions)
seq_puts(m, ",default_permissions");
if (strcmp(ofs->config.redirect_mode, ovl_redirect_mode_def()) != 0)
diff --git a/fs/overlayfs/util.c b/fs/overlayfs/util.c
index bb670ee99ff16..52a5116d4b6e6 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -18,6 +18,7 @@
#include <linux/namei.h>
#include <linux/ratelimit.h>
#include <linux/seq_file.h>
+#include "../mount.h"
#include "overlayfs.h"
int ovl_want_write(struct dentry *dentry)
@@ -699,3 +700,24 @@ void print_paths_option(struct seq_file *m, const char *name,
seq_path(m, &paths[i], ", \t\n\\");
}
}
+
+void print_mnt_id_option(struct seq_file *m, const char *name,
+ struct path *path)
+{
+ seq_show_option(m, name, "");
+ seq_printf(m, "%i", real_mount(path->mnt)->mnt_id);
+}
+
+void print_mnt_ids_option(struct seq_file *m, const char *name,
+ struct path *paths, unsigned int num)
+{
+ int i;
+
+ seq_show_option(m, name, "");
+
+ for (i = 0; i < num; i++) {
+ if (i)
+ seq_putc(m, ':');
+ seq_printf(m, "%i", real_mount(paths[i].mnt)->mnt_id);
+ }
+}
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