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authorDaniel Xu <dxu@dxuuu.xyz>2020-03-12 13:03:17 -0700
committerTejun Heo <tj@kernel.org>2020-03-16 15:53:47 -0400
commit38aca3071cebc90e6b07abd697cba5c9d7b37a94 (patch)
treed8a8f47eeaa770c2838e101f8231858b817eadd2 /kernel/cgroup
parent0c47383ba3bd10877956e41149d19644fba937d1 (diff)
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cgroupfs: Support user xattrs
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> Acked-by: Chris Down <chris@chrisdown.name> Reviewed-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Signed-off-by: Tejun Heo <tj@kernel.org>
Diffstat (limited to 'kernel/cgroup')
-rw-r--r--kernel/cgroup/cgroup.c3
1 files changed, 2 insertions, 1 deletions
diff --git a/kernel/cgroup/cgroup.c b/kernel/cgroup/cgroup.c
index 114dcbf8d4f4..33ff9ec4a523 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);