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.
Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn@xxxxxxxxxxxxx>
---
fs/overlayfs/Kconfig | 26 ++++++++++++++++++++++++++
fs/overlayfs/overlayfs.h | 2 ++
fs/overlayfs/super.c | 15 +++++++++++++++
fs/overlayfs/util.c | 21 +++++++++++++++++++++
4 files changed, 64 insertions(+)
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index c24988527ef3..2797869c8d16 100644
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -154,4 +154,30 @@ 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.
\ No newline at end of file
diff --git a/fs/overlayfs/overlayfs.h b/fs/overlayfs/overlayfs.h
index 8722ed556e11..980fe06d15b5 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -305,6 +305,8 @@ ssize_t ovl_getxattr(struct dentry *dentry, char *name, char **value,
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 a449b6bb4b20..ee2ed125341c 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -57,6 +57,10 @@ static bool ovl_dyn_path_opts = IS_ENABLED(CONFIG_OVERLAY_FS_DYNAMIC_RESOLVE_PAT
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;
@@ -362,6 +366,17 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
seq_show_option(m, "workdir", ofs->config.workdir);
}
}
+
+ if (ovl_mnt_id_path_opts) {
+ print_mnt_ids_option(m, "lowerdir_mnt_id", ofs->lowerpaths, ofs->numlayer);
+ /*
+ * 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 36bb98c14d35..85106b2ed00a 100644
--- a/fs/overlayfs/util.c
+++ b/fs/overlayfs/util.c
@@ -14,6 +14,7 @@
#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)
@@ -941,3 +942,23 @@ 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);
+ }
+}
--
2.17.1
