[GIT PULL 17/18 for v7.3] vfs super
From: Christian Brauner
Date: Fri Aug 14 2026 - 09:15:07 EST
Hey Linus,
/* Summary */
- Make it possible to share a block device between multiple filesystems.
erofs can mount read-only blob devices shared between many
superblocks. Because we only tracked a single superblock a freeze,
thaw, removal or sync on such a device was never propagated to all the
superblocks using it, and there was no way to find them. So add an
efficient table to lookup all superblocks using a given block device.
- A bunch of pre-existing fixes fell out of this work. A block-device
freeze racing a btrfs device change could leave the whole filesystem
stuck frozen. A bdev_freeze() issued by "dmsetup suspend" or an LVM
snapshot resolves that holder to freeze the filesystem. and
bdev_thaw() resolves it again to thaw. A freeze landing while btrfs is
adding, removing or replacing a device freezes the filesystem. The
membership change then drops that link. So the matching thaw could no
longer find the superblock.
Forbid freezing a device for the duration of a membership change,
modelled on deny_write_access()/allow_write_access().
/* Testing */
No build failures or warnings were observed.
/* Conflicts */
Merge conflicts with mainline
=============================
[1]: https://lore.kernel.org/linux-next/ak4urgJRb-83KEUI@xxxxxxxxxxxxx
This conflicts with commit d943e68edc5cb ("selftests/filesystems:
test O_TMPFILE creation on idmapped mounts") in
tools/testing/selftests/filesystems/Makefile and
tools/testing/selftests/filesystems/.gitignore. Both that commit and
commit a21db4dcaf4ad ("selftests/filesystems: add ustat() coverage")
from this tree register a new selftest on the same two lines. The
conflict resolves by keeping both.
This tag additionally conflicts with two of the earlier tags in this
pull request series, so please merge it after them:
- with vfs-7.3-rc1.mount
- with vfs-7.3-rc1.misc
Both resolve by keeping both sides.
diff --cc fs/namespace.c
index 3c382c2bdeec,7cef6dae0854..1ecd96c918b3
--- a/fs/namespace.c
+++ b/fs/namespace.c
@@@ -6270,6 -6259,11 +6270,8 @@@ void __init mnt_init(void
HASH_ZERO,
&mp_hash_shift, &mp_hash_mask, 0, 0);
- if (!mount_hashtable || !mountpoint_hashtable)
- panic("Failed to allocate mount hash table\n");
-
+ super_dev_init();
+
kernfs_init();
err = sysfs_init();
diff --cc fs/super.c
index 2c52c321885f,a62af36f7aaf..05e443173038
--- a/fs/super.c
+++ b/fs/super.c
@@@ -24,7 -24,7 +24,8 @@@
#include <linux/export.h>
#include <linux/slab.h>
#include <linux/blkdev.h>
+#include <linux/memcontrol.h>
+ #include <linux/rhashtable.h>
#include <linux/mount.h>
#include <linux/security.h>
#include <linux/writeback.h> /* for the emergency remount stuff */
diff --cc tools/testing/selftests/filesystems/.gitignore
index a78f894157de,1bd53d54553c..9eb185fb2f9d
--- a/tools/testing/selftests/filesystems/.gitignore
+++ b/tools/testing/selftests/filesystems/.gitignore
@@@ -5,4 -5,4 +5,5 @@@ fclo
file_stressor
anon_inode_test
kernfs_test
+idmapped_tmpfile
+ ustat_test
diff --cc tools/testing/selftests/filesystems/Makefile
index a7ec2ba2dd83,bbdd40b167fa..03be337c1f35
--- a/tools/testing/selftests/filesystems/Makefile
+++ b/tools/testing/selftests/filesystems/Makefile
@@@ -1,8 -1,7 +1,8 @@@
# SPDX-License-Identifier: GPL-2.0
CFLAGS += $(KHDR_INCLUDES)
- TEST_GEN_PROGS := devpts_pts file_stressor anon_inode_test kernfs_test fclog
+ TEST_GEN_PROGS := devpts_pts file_stressor anon_inode_test kernfs_test fclog ustat_test
+TEST_GEN_PROGS += idmapped_tmpfile
TEST_GEN_PROGS_EXTENDED := dnotify_test
include ../lib.mk
Merge conflicts with other trees
================================
No known conflicts.
The following changes since commit dc59e4fea9d83f03bad6bddf3fa2e52491777482:
Linux 7.2-rc1 (2026-06-28 12:01:31 -0700)
are available in the Git repository at:
git@xxxxxxxxxxxxxxxxxxx:pub/scm/linux/kernel/git/vfs/vfs tags/vfs-7.3-rc1.super
for you to fetch changes up to 9ac8fd831252e52aa78399eaccc11a72f6c2af1a:
super: fix dying superblock warning messages (2026-08-12 09:20:35 +0200)
----------------------------------------------------------------
vfs-7.3-rc1.super
Please consider pulling these changes from the signed vfs-7.3-rc1.super tag.
Thanks!
Christian
----------------------------------------------------------------
Christian Brauner (24):
block: allow making a block device unfreezable
block: split bdev_yield_claim() out of bdev_fput()
btrfs: deny freezing a device while it is being removed
btrfs: deny freezing a device while it is being added
btrfs: deny freezing devices undergoing a replace
Merge patch series "block,btrfs: fix frozen-superblock strand on device add/remove/replace"
super: convert s_count to refcount_t s_passive
super: take lock after last reference count
fs, block: move blk_mode_t and fop_flags_t into <linux/types.h>
ext4: use anonymous devices for KUnit test superblocks
ocfs2: don't reset s_dev on dismount
fs: maintain a global device-to-superblock table
fs: add dedicated block device open helpers for filesystems
xfs: port to fs_bdev_file_open_by_path()
btrfs: open via dedicated fs bdev helpers
ext4: open via dedicated fs bdev helpers
fs: look up superblocks via the device table in fs_holder_ops
fs: tolerate per-superblock freeze errors on shared devices
erofs: open via dedicated fs bdev helpers
f2fs: open via dedicated fs bdev helpers
super: make fs_holder_ops private
fs: look up the superblock via the device table in user_get_super()
selftests/filesystems: add ustat() coverage
Merge patch series "fs: support freeze/thaw/mark_dead/sync with shared devices"
Karl Mehltretter (1):
super: fix dying superblock warning messages
Yun Zhou (1):
block: reject block device inodes with i_rdev == 0 in lookup_bdev()
block/bdev.c | 125 ++++-
fs/btrfs/dev-replace.c | 65 ++-
fs/btrfs/ioctl.c | 4 +-
fs/btrfs/volumes.c | 105 +++-
fs/btrfs/volumes.h | 6 +-
fs/cramfs/inode.c | 2 +-
fs/erofs/super.c | 35 +-
fs/ext4/extents-test.c | 9 +-
fs/ext4/mballoc-test.c | 9 +-
fs/ext4/super.c | 12 +-
fs/f2fs/super.c | 6 +-
fs/internal.h | 1 +
fs/namespace.c | 2 +
fs/ocfs2/super.c | 1 -
fs/romfs/super.c | 2 +-
fs/super.c | 624 ++++++++++++++++-------
fs/xfs/xfs_buf.c | 2 +-
fs/xfs/xfs_super.c | 10 +-
include/linux/blk_types.h | 2 +-
include/linux/blkdev.h | 12 +-
include/linux/fs.h | 2 -
include/linux/fs/super.h | 8 +
include/linux/fs/super_types.h | 4 +-
include/linux/types.h | 2 +
tools/testing/selftests/filesystems/.gitignore | 1 +
tools/testing/selftests/filesystems/Makefile | 2 +-
tools/testing/selftests/filesystems/ustat_test.c | 135 +++++
27 files changed, 882 insertions(+), 306 deletions(-)
create mode 100644 tools/testing/selftests/filesystems/ustat_test.c