Changes in Makefile

0fc8f6200d2313278fbf4539bbab74677c685531 - Merge drm/drm-fixes into drm-misc-fixes

Mon, 27 Apr 2026 10:26:49 +0200

Merge drm/drm-fixes into drm-misc-fixesGetting fixes and updates from v7.1-rc1.Signed-off-by: Thomas Zimmermann List of files: /linux/tools/testing/selftests/filesystems/move_mount/Makefile

7c8a4671dc3247a26a702e5f5996e9f453d7070d - Merge tag 'vfs-7.1-rc1.mount.v2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs

Wed, 15 Apr 2026 04:59:25 +0200

Merge tag 'vfs-7.1-rc1.mount.v2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfsPull vfs mount updates from Christian Brauner: - Add FSMOUNT_NAMESPACE flag to fsmount() that creates a new mount namespace with the newly created filesystem attached to a copy of the real rootfs. This returns a namespace file descriptor instead of an O_PATH mount fd, similar to how OPEN_TREE_NAMESPACE works for open_tree(). This allows creating a new filesystem and immediately placing it in a new mount namespace in a single operation, which is useful for container runtimes and other namespace-based isolation mechanisms. This accompanies OPEN_TREE_NAMESPACE and avoids a needless detour via OPEN_TREE_NAMESPACE to get the same effect. Will be especially useful when you mount an actual filesystem to be used as the container rootfs. - Currently, creating a new mount namespace always copies the entire mount tree from the caller's namespace. For containers and sandboxes that intend to build their mount table from scratch this is wasteful: they inherit a potentially large mount tree only to immediately tear it down. This series adds support for creating a mount namespace that contains only a clone of the root mount, with none of the child mounts. Two new flags are introduced: - CLONE_EMPTY_MNTNS (0x400000000) for clone3(), using the 64-bit flag space - UNSHARE_EMPTY_MNTNS (0x00100000) for unshare() Both flags imply CLONE_NEWNS. The resulting namespace contains a single nullfs root mount with an immutable empty directory. The intended workflow is to then mount a real filesystem (e.g., tmpfs) over the root and build the mount table from there. - Allow MOVE_MOUNT_BENEATH to target the caller's rootfs, allowing to switch out the rootfs without pivot_root(2). The traditional approach to switching the rootfs involves pivot_root(2) or a chroot_fs_refs()-based mechanism that atomically updates fs->root for all tasks sharing the same fs_struct. This has consequences for fork(), unshare(CLONE_FS), and setns(). This series instead decomposes root-switching into individually atomic, locally-scoped steps: fd_tree = open_tree(-EBADF, "/newroot", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC); fchdir(fd_tree); move_mount(fd_tree, "", AT_FDCWD, "/", MOVE_MOUNT_BENEATH | MOVE_MOUNT_F_EMPTY_PATH); chroot("."); umount2(".", MNT_DETACH); Since each step only modifies the caller's own state, the fork/unshare/setns races are eliminated by design. A key step to making this possible is to remove the locked mount restriction. Originally MOVE_MOUNT_BENEATH doesn't support mounting beneath a mount that is locked. The locked mount protects the underlying mount from being revealed. This is a core mechanism of unshare(CLONE_NEWUSER | CLONE_NEWNS). The mounts in the new mount namespace become locked. That effectively makes the new mount table useless as the caller cannot ever get rid of any of the mounts no matter how useless they are. We can lift this restriction though. We simply transfer the locked property from the top mount to the mount beneath. This works because what we care about is to protect the underlying mount aka the parent. The mount mounted between the parent and the top mount takes over the job of protecting the parent mount from the top mount mount. This leaves us free to remove the locked property from the top mount which can consequently be unmounted: unshare(CLONE_NEWUSER | CLONE_NEWNS) and we inherit a clone of procfs on /proc then currently we cannot unmount it as: umount -l /proc will fail with EINVAL because the procfs mount is locked. After this series we can now do: mount --beneath -t tmpfs tmpfs /proc umount -l /proc after which a tmpfs mount has been placed beneath the procfs mount. The tmpfs mount has become locked and the procfs mount has become unlocked. This means you can safely modify an inherited mount table after unprivileged namespace creation. Afterwards we simply make it possible to move a mount beneath the rootfs allowing to upgrade the rootfs. Removing the locked restriction makes this very useful for containers created with unshare(CLONE_NEWUSER | CLONE_NEWNS) to reshuffle an inherited mount table safely and MOVE_MOUNT_BENEATH makes it possible to switch out the rootfs instead of using the costly pivot_root(2).* tag 'vfs-7.1-rc1.mount.v2' of git://git.kernel.org/pub/scm/linux/kernel/git/vfs/vfs: selftests/namespaces: remove unused utils.h include from listns_efault_test selftests/fsmount_ns: add missing TARGETS and fix cap test selftests/empty_mntns: fix wrong CLONE_EMPTY_MNTNS hex value in comment selftests/empty_mntns: fix statmount_alloc() signature mismatch selftests/statmount: remove duplicate wait_for_pid() mount: always duplicate mount selftests/filesystems: add MOVE_MOUNT_BENEATH rootfs tests move_mount: allow MOVE_MOUNT_BENEATH on the rootfs move_mount: transfer MNT_LOCKED selftests/filesystems: add clone3 tests for empty mount namespaces selftests/filesystems: add tests for empty mount namespaces namespace: allow creating empty mount namespaces selftests: add FSMOUNT_NAMESPACE tests selftests/statmount: add statmount_alloc() helper tools: update mount.h header mount: add FSMOUNT_NAMESPACE mount: simplify __do_loopback() mount: start iterating from start of rbtree List of files: /linux/tools/testing/selftests/filesystems/move_mount/Makefile

43dcce3f2a6209898f31d1ef99e0a4a1335ebb67 - Merge patch series "move_mount: expand MOVE_MOUNT_BENEATH"

Mon, 02 Mar 2026 10:53:15 +0100

Merge patch series "move_mount: expand MOVE_MOUNT_BENEATH"Christian Brauner says:I'm too tired now to keep refining this but I think it's in good enoughshape for review.Allow MOVE_MOUNT_BENEATH to target the caller's rootfs, allowing toswitch out the rootfs without pivot_root(2).The traditional approach to switching the rootfs involves pivot_root(2)or a chroot_fs_refs()-based mechanism that atomically updates fs->rootfor all tasks sharing the same fs_struct. This has consequences forfork(), unshare(CLONE_FS), and setns().This series instead decomposes root-switching into individually atomic,locally-scoped steps: fd_tree = open_tree(-EBADF, "/newroot", OPEN_TREE_CLONE | OPEN_TREE_CLOEXEC); fchdir(fd_tree); move_mount(fd_tree, "", AT_FDCWD, "/", MOVE_MOUNT_BENEATH | MOVE_MOUNT_F_EMPTY_PATH); chroot("."); umount2(".", MNT_DETACH);Since each step only modifies the caller's own state, thefork/unshare/setns races are eliminated by design.A key step to making this possible is to remove the locked mountrestriction. Originally MOVE_MOUNT_BENEATH doesn't support mountingbeneath a mount that is locked. The locked mount protects the underlyingmount from being revealed. This is a core mechanism ofunshare(CLONE_NEWUSER | CLONE_NEWNS). The mounts in the new mountnamespace become locked. That effectively makes the new mount tableuseless as the caller cannot ever get rid of any of the mounts no matterhow useless they are.We can lift this restriction though. We simply transfer the lockedproperty from the top mount to the mount beneath. This works becausewhat we care about is to protect the underlying mount aka the parent.The mount mounted between the parent and the top mount takes over thejob of protecting the parent mount from the top mount mount. This leavesus free to remove the locked property from the top mount which canconsequently be unmounted: unshare(CLONE_NEWUSER | CLONE_NEWNS)and we inherit a clone of procfs on /proc then currently we cannotunmount it as: umount -l /procwill fail with EINVAL because the procfs mount is locked.After this series we can now do: mount --beneath -t tmpfs tmpfs /proc umount -l /procafter which a tmpfs mount has been placed beneath the procfs mount. Thetmpfs mount has become locked and the procfs mount has become unlocked.This means you can safely modify an inherited mount table afterunprivileged namespace creation.Afterwards we simply make it possible to move a mount beneath therootfs allowing to upgrade the rootfs.Removing the locked restriction makes this very useful for containerscreated with unshare(CLONE_NEWUSER | CLONE_NEWNS) to reshuffle aninherited mount table safely and MOVE_MOUNT_BENEATH makes it possible toswitch out the rootfs instead of using the costly pivot_root(2).* patches from https://patch.msgid.link/20260224-work-mount-beneath-rootfs-v1-0-8c58bf08488f@kernel.org: selftests/filesystems: add MOVE_MOUNT_BENEATH rootfs tests move_mount: allow MOVE_MOUNT_BENEATH on the rootfs move_mount: transfer MNT_LOCKEDLink: https://patch.msgid.link/20260224-work-mount-beneath-rootfs-v1-0-8c58bf08488f@kernel.orgSigned-off-by: Christian Brauner List of files: /linux/tools/testing/selftests/filesystems/move_mount/Makefile

bb5c17bc863d1ac9ee0d51d300d5399d632fe69f - selftests/filesystems: add MOVE_MOUNT_BENEATH rootfs tests

Tue, 24 Feb 2026 01:40:28 +0100

selftests/filesystems: add MOVE_MOUNT_BENEATH rootfs testsAdd tests for mounting beneath the rootfs using MOVE_MOUNT_BENEATH:- beneath_rootfs_success: mount beneath /, fchdir, chroot, umount2 MNT_DETACH -- verify root changed- beneath_rootfs_old_root_stacked: after mount-beneath, verify old root parent is clone via statmount- beneath_rootfs_in_chroot_fail: chroot into subdir of same mount, mount-beneath fails (dentry != mnt_root)- beneath_rootfs_in_chroot_success: chroot into separate tmpfs mount, mount-beneath succeeds- beneath_rootfs_locked_transfer: in user+mount ns: mount-beneath rootfs succeeds, MNT_LOCKED transfers, old root unmountable- beneath_rootfs_locked_containment: in user+mount ns: after full root-switch workflow, new root is MNT_LOCKED (containment preserved)- beneath_non_rootfs_locked_transfer: mounts created before unshare(CLONE_NEWUSER | CLONE_NEWNS) become locked; mount-beneath transfers MNT_LOCKED, displaced mount can be unmounted- beneath_non_rootfs_locked_containment: same setup, verify new mount is MNT_LOCKED (containment preserved)Link: https://patch.msgid.link/20260224-work-mount-beneath-rootfs-v1-3-8c58bf08488f@kernel.orgSigned-off-by: Christian Brauner List of files: /linux/tools/testing/selftests/filesystems/move_mount/Makefile