| Message ID | 20200312200317.31736-5-dxu@dxuuu.xyz (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | Support user xattrs in cgroupfs | expand |
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c index 7a39dc882095..ae1d808c0b9b 100644 --- a/kernel/cgroup/cgroup.c +++ b/kernel/cgroup/cgroup.c @@ -1954,7 +1954,8 @@ int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask) root->kf_root = kernfs_create_root(kf_sops, KERNFS_ROOT_CREATE_DEACTIVATED | - KERNFS_ROOT_SUPPORT_EXPORTOP, + KERNFS_ROOT_SUPPORT_EXPORTOP | + KERNFS_ROOT_SUPPORT_USER_XATTR, root_cgrp); if (IS_ERR(root->kf_root)) { ret = PTR_ERR(root->kf_root);
This patch turns on xattr support for cgroupfs. This is useful for letting non-root owners of delegated subtrees attach metadata to cgroups. One use case is for subtree owners to tell a userspace out of memory killer to bias away from killing specific subtrees. Tests: [/sys/fs/cgroup]# for i in $(seq 0 130); \ do setfattr workload.slice -n user.name$i -v wow; done setfattr: workload.slice: No space left on device setfattr: workload.slice: No space left on device setfattr: workload.slice: No space left on device [/sys/fs/cgroup]# for i in $(seq 0 130); \ do setfattr workload.slice --remove user.name$i; done setfattr: workload.slice: No such attribute setfattr: workload.slice: No such attribute setfattr: workload.slice: No such attribute [/sys/fs/cgroup]# for i in $(seq 0 130); \ do setfattr workload.slice -n user.name$i -v wow; done setfattr: workload.slice: No space left on device setfattr: workload.slice: No space left on device setfattr: workload.slice: No space left on device `seq 0 130` is inclusive, and 131 - 128 = 3, which is the number of errors we expect to see. [/data]# cat testxattr.c #include <sys/types.h> #include <sys/xattr.h> #include <stdio.h> #include <stdlib.h> int main() { char name[256]; char *buf = malloc(64 << 10); if (!buf) { perror("malloc"); return 1; } for (int i = 0; i < 4; ++i) { snprintf(name, 256, "user.bigone%d", i); if (setxattr("/sys/fs/cgroup/system.slice", name, buf, 64 << 10, 0)) { printf("setxattr failed on iteration=%d\n", i); return 1; } } return 0; } [/data]# ./a.out setxattr failed on iteration=2 [/data]# ./a.out setxattr failed on iteration=0 [/sys/fs/cgroup]# setfattr -x user.bigone0 system.slice/ [/sys/fs/cgroup]# setfattr -x user.bigone1 system.slice/ [/data]# ./a.out setxattr failed on iteration=2 Signed-off-by: Daniel Xu <dxu@dxuuu.xyz> --- kernel/cgroup/cgroup.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)