[Devel] [PATCH RHEL8 COMMIT] ovl: introduce new "uuid=off" option for inodes index feature
Konstantin Khorenko
khorenko at virtuozzo.com
Fri Aug 13 10:07:44 MSK 2021
The commit is pushed to "branch-rh8-4.18.0-305.3.1.vz8.7.x-ovz" and will appear at https://src.openvz.org/scm/ovz/vzkernel.git
after rh8-4.18.0-305.3.1.vz8.7.5
------>
commit 1982485145bcc4b038067c19bf0d4c6fdcb6f8d0
Author: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
Date: Fri Aug 13 10:07:44 2021 +0300
ovl: introduce new "uuid=off" option for inodes index feature
This replaces uuid with null in overlayfs file handles and thus relaxes
uuid checks for overlay index feature. It is only possible in case there is
only one filesystem for all the work/upper/lower directories and bare file
handles from this backing filesystem are unique. In other case when we have
multiple filesystems lets just fallback to "uuid=on" which is and
equivalent of how it worked before with all uuid checks.
This is needed when overlayfs is/was mounted in a container with index
enabled (e.g.: to be able to resolve inotify watch file handles on it to
paths in CRIU), and this container is copied and started alongside with the
original one. This way the "copy" container can't have the same uuid on the
superblock and mounting the overlayfs from it later would fail.
That is an example of the problem on top of loop+ext4:
dd if=/dev/zero of=loopbackfile.img bs=100M count=10
losetup -fP loopbackfile.img
losetup -a
#/dev/loop0: [64768]:35 (/loop-test/loopbackfile.img)
mkfs.ext4 loopbackfile.img
mkdir loop-mp
mount -o loop /dev/loop0 loop-mp
mkdir loop-mp/{lower,upper,work,merged}
mount -t overlay overlay -oindex=on,lowerdir=loop-mp/lower,\
upperdir=loop-mp/upper,workdir=loop-mp/work loop-mp/merged
umount loop-mp/merged
umount loop-mp
e2fsck -f /dev/loop0
tune2fs -U random /dev/loop0
mount -o loop /dev/loop0 loop-mp
mount -t overlay overlay -oindex=on,lowerdir=loop-mp/lower,\
upperdir=loop-mp/upper,workdir=loop-mp/work loop-mp/merged
#mount: /loop-test/loop-mp/merged:
#mount(2) system call failed: Stale file handle.
If you just change the uuid of the backing filesystem, overlay is not
mounting any more. In Virtuozzo we copy container disks (ploops) when
create the copy of container and we require fs uuid to be unique for a new
container.
Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
Reviewed-by: Amir Goldstein <amir73il at gmail.com>
Signed-off-by: Miklos Szeredi <mszeredi at redhat.com>
https://jira.sw.ru/browse/PSBM-123536
(cherry-picked from ms commit 5830fb6b54f7 ("ovl: introduce new
"uuid=off" option for inodes index feature"))
Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
====================
Patchset descrition:
ovl: replace "index=nouuid" with "uuid=off"
Mainstream base is a bit different so we need some more ovl_fs
propagation to functions. Also we still need some vz-specific hunks
which were not allowed to mainstream overlay, so add them as a separate
patch.
https://jira.sw.ru/browse/PSBM-123536
Signed-off-by: Pavel Tikhomirov <ptikhomirov at virtuozzo.com>
Pavel Tikhomirov (4):
Revert "ovl: introduce new "index=nouuid" option for inodes index
feature"
ovl: propagate ovl_fs to ovl_decode_real_fh and ovl_encode_real_fh
ovl: introduce new "uuid=off" option for inodes index feature
ovl: make uuid=off compatible with overlayfs created without it
---
Documentation/filesystems/overlayfs.rst | 5 +++++
fs/overlayfs/copy_up.c | 3 ++-
fs/overlayfs/namei.c | 4 +++-
fs/overlayfs/ovl_entry.h | 1 +
fs/overlayfs/super.c | 20 ++++++++++++++++++++
5 files changed, 31 insertions(+), 2 deletions(-)
diff --git a/Documentation/filesystems/overlayfs.rst b/Documentation/filesystems/overlayfs.rst
index 660dbaf0b9b8..067ece2d7d94 100644
--- a/Documentation/filesystems/overlayfs.rst
+++ b/Documentation/filesystems/overlayfs.rst
@@ -563,6 +563,11 @@ This verification may cause significant overhead in some cases.
Note: the mount options index=off,nfs_export=on are conflicting and will
result in an error.
+Note: the mount option uuid=off can be used to replace UUID of the underlying
+filesystem in file handles with null, and effectively disable UUID checks. This
+can be useful in case the underlying disk is copied and the UUID of this copy
+is changed. This is only applicable if all lower/upper/work directories are on
+the same filesystem, otherwise it will fallback to normal behaviour.
Testsuite
---------
diff --git a/fs/overlayfs/copy_up.c b/fs/overlayfs/copy_up.c
index 2cfb78473843..7f57bc627935 100644
--- a/fs/overlayfs/copy_up.c
+++ b/fs/overlayfs/copy_up.c
@@ -321,7 +321,8 @@ struct ovl_fh *ovl_encode_real_fh(struct ovl_fs *ofs, struct dentry *real,
if (is_upper)
fh->fb.flags |= OVL_FH_FLAG_PATH_UPPER;
fh->fb.len = sizeof(fh->fb) + buflen;
- fh->fb.uuid = *uuid;
+ if (ofs->config.uuid)
+ fh->fb.uuid = *uuid;
return fh;
diff --git a/fs/overlayfs/namei.c b/fs/overlayfs/namei.c
index fa22fc978307..141b9246f9ac 100644
--- a/fs/overlayfs/namei.c
+++ b/fs/overlayfs/namei.c
@@ -160,8 +160,10 @@ struct dentry *ovl_decode_real_fh(struct ovl_fs *ofs, struct ovl_fh *fh,
/*
* Make sure that the stored uuid matches the uuid of the lower
* layer where file handle will be decoded.
+ * In case of uuid=off option just make sure that stored uuid is null.
*/
- if (!uuid_equal(&fh->fb.uuid, &mnt->mnt_sb->s_uuid))
+ if (ofs->config.uuid ? !uuid_equal(&fh->fb.uuid, &mnt->mnt_sb->s_uuid) :
+ !uuid_is_null(&fh->fb.uuid))
return NULL;
bytes = (fh->fb.len - offsetof(struct ovl_fb, fid));
diff --git a/fs/overlayfs/ovl_entry.h b/fs/overlayfs/ovl_entry.h
index 0f3c34bd0b32..164c83256669 100644
--- a/fs/overlayfs/ovl_entry.h
+++ b/fs/overlayfs/ovl_entry.h
@@ -17,6 +17,7 @@ struct ovl_config {
bool redirect_follow;
const char *redirect_mode;
bool index;
+ bool uuid;
bool nfs_export;
int xino;
bool metacopy;
diff --git a/fs/overlayfs/super.c b/fs/overlayfs/super.c
index 6b3d4fa74a2b..feaa93132edc 100644
--- a/fs/overlayfs/super.c
+++ b/fs/overlayfs/super.c
@@ -388,6 +388,8 @@ static int ovl_show_options(struct seq_file *m, struct dentry *dentry)
seq_printf(m, ",redirect_dir=%s", ofs->config.redirect_mode);
if (ofs->config.index != ovl_index_def)
seq_printf(m, ",index=%s", ofs->config.index ? "on" : "off");
+ if (!ofs->config.uuid)
+ seq_puts(m, ",uuid=off");
if (ofs->config.nfs_export != ovl_nfs_export_def)
seq_printf(m, ",nfs_export=%s", ofs->config.nfs_export ?
"on" : "off");
@@ -437,6 +439,8 @@ enum {
OPT_REDIRECT_DIR,
OPT_INDEX_ON,
OPT_INDEX_OFF,
+ OPT_UUID_ON,
+ OPT_UUID_OFF,
OPT_NFS_EXPORT_ON,
OPT_NFS_EXPORT_OFF,
OPT_XINO_ON,
@@ -455,6 +459,8 @@ static const match_table_t ovl_tokens = {
{OPT_REDIRECT_DIR, "redirect_dir=%s"},
{OPT_INDEX_ON, "index=on"},
{OPT_INDEX_OFF, "index=off"},
+ {OPT_UUID_ON, "uuid=on"},
+ {OPT_UUID_OFF, "uuid=off"},
{OPT_NFS_EXPORT_ON, "nfs_export=on"},
{OPT_NFS_EXPORT_OFF, "nfs_export=off"},
{OPT_XINO_ON, "xino=on"},
@@ -574,6 +580,14 @@ static int ovl_parse_opt(char *opt, struct ovl_config *config)
index_opt = true;
break;
+ case OPT_UUID_ON:
+ config->uuid = true;
+ break;
+
+ case OPT_UUID_OFF:
+ config->uuid = false;
+ break;
+
case OPT_NFS_EXPORT_ON:
config->nfs_export = true;
nfs_export_opt = true;
@@ -1811,6 +1825,7 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
goto out_err;
ofs->config.index = ovl_index_def;
+ ofs->config.uuid = true;
ofs->config.nfs_export = ovl_nfs_export_def;
ofs->config.xino = ovl_xino_def();
ofs->config.metacopy = ovl_metacopy_def;
@@ -1870,6 +1885,11 @@ static int ovl_fill_super(struct super_block *sb, void *data, int silent)
if (!ofs->upper_mnt)
sb->s_flags |= SB_RDONLY;
+ if (!ofs->config.uuid && ofs->numfs > 1) {
+ pr_warn("The uuid=off requires a single fs for lower and upper, falling back to uuid=on.\n");
+ ofs->config.uuid = true;
+ }
+
if (!(ovl_force_readonly(ofs)) && ofs->config.index) {
err = ovl_get_indexdir(sb, ofs, oe, &ofs->upperpath);
if (err)
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