[Devel] [PATCH RHEL COMMIT] overlayfs: add mnt_id paths options
Konstantin Khorenko
khorenko at virtuozzo.com
Mon Oct 4 20:39:05 MSK 2021
The commit is pushed to "branch-rh9-5.14.vz9.1.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after ark-5.14
------>
commit 0f01030446b3afcecc8846eee744a5a3c5743d2a
Author: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
Date: Mon Oct 4 20:39:05 2021 +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>
=====================
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
=====================
Rebase to RHEL8.3 kernel-4.18.0-240.1.1.el8_3 note:
- original patch from vz8 kernel has been dropped (did not apply):
c38c281cbe49 ("overlayfs: add mnt_id paths options")
- a patchset developed for mainstream has been appliedi
(it's not accepted in ms yet):
https://lore.kernel.org/lkml/20200604161133.20949-1-alexander.mikhalitsyn@virtuozzo.com/
+++
fs/overlayfs: Fixed default value for parameter 'mnt_id_path_opts'
The value queries .config with IS_ENABLED macro but CONFIG_ prefix
is not provided.
mFixes: c38c281cbe49 ("overlayfs: add mnt_id paths options")
Signed-off-by: Valeriy.Vdovin <valeriy.vdovin at virtuozzo.com>
+++
fs/ovelayfs: Fix crash on overlayfs mount
Kdump kernel fails to load because of crash on mount of overlayfs:
BUG: unable to handle kernel NULL pointer dereference at 0000000000000060
....
Call Trace:
seq_path+0x64/0xb0
print_paths_option+0x79/0xa0
ovl_show_options+0x3a/0x320
show_mountinfo+0x1ee/0x290
seq_read+0x2f8/0x400
vfs_read+0x9d/0x150
ksys_read+0x4f/0xb0
do_syscall_64+0x5b/0x1a0
This is cause by OOB access of ofs->lowerpaths.
We transfer to print_paths_option() ofs->numlayer as size of ->lowerpaths
array, but it's not.
The correct number of lowerpaths elements is ->numlower in 'struct ovl_entry'.
So move lowerpaths there and use oe->numlower as array size.
mFixes: 17fc61697f73 ("overlayfs: add dynamic path resolving in mount options")
mFixes: 2191d729083d ("overlayfs: add mnt_id paths options")
https://jira.sw.ru/browse/PSBM-123508
Signed-off-by: Andrey Ryabinin <aryabinin at virtuozzo.com>
Reviewed-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
+++
fs/overlayfs: Fix crash on overlayfs mount
[ 261.403900] BUG: unable to handle kernel NULL pointer dereference at 0000000000000008
[ 261.412847] Call Trace:
[ 261.413463] seq_path+0x3c/0xa0
[ 261.414090] print_paths_option+0x8c/0xa0
[ 261.414736] ovl_show_options+0x41/0x320
[ 261.415378] show_mountinfo+0x1df/0x2b0
[ 261.416019] seq_read+0x26e/0x3d0
[ 261.416644] vfs_read+0x89/0x140
[ 261.417269] ksys_read+0x52/0xc0
[ 261.418918] do_syscall_64+0x5b/0x1e0
[ 261.419580] entry_SYSCALL_64_after_hwframe+0x65/0xca
[ 261.420256] RIP: 0033:0x7f20b59f28e4
The problem is that we take overlayfs lower layers info not
from root dentry. Non-root dentries can have less layers than
root dentry.
Crash reproducer:
mkdir {lower,upper,work,merged}
touch lower/lower
touch upper/upper
touch lowermnt
touch uppermnt
mount -t overlay overlay -o lowerdir=lower,upperdir=upper,workdir=work merged
mount --bind merged/upper uppermnt
mount --bind merged/lower lowermnt
mFixes: 4267859a0 ("fs/ovelayfs: Fix crash on overlayfs mount")
https://jira.sw.ru/browse/PSBM-129333
Signed-off-by: Alexander Mikhalitsyn <alexander.mikhalitsyn at virtuozzo.com>
(cherry picked from vz8 commit d001a4d7b50a13b2f459a307f4542e3beb1ed1fd)
Signed-off-by: Andrey Zhadchenko <andrey.zhadchenko at virtuozzo.com>
---
fs/overlayfs/Kconfig | 26 ++++++++++++++++++++++++++
fs/overlayfs/overlayfs.h | 3 +++
fs/overlayfs/super.c | 15 +++++++++++++++
fs/overlayfs/util.c | 21 +++++++++++++++++++++
4 files changed, 65 insertions(+)
diff --git a/fs/overlayfs/Kconfig b/fs/overlayfs/Kconfig
index be733bcd4c00..1ba9411d9a6a 100644
--- a/fs/overlayfs/Kconfig
+++ b/fs/overlayfs/Kconfig
@@ -155,3 +155,29 @@ 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 d30e097fcea5..b4a7d2f72186 100644
--- a/fs/overlayfs/overlayfs.h
+++ b/fs/overlayfs/overlayfs.h
@@ -355,6 +355,9 @@ static inline bool ovl_test_flag(unsigned long flag, struct inode *inode)
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 super_block *sb,
struct dentry *dentry)
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index fdb0d9a45104..065b7778e720 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(CONFIG_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;
@@ -382,6 +386,17 @@ 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", oe->lowerpaths, oe->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 29cf1947fd00..0dd8356e1145 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)
@@ -997,3 +998,23 @@ 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);
+ }
+}
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