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38aca3071c
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>
|
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|---|---|---|
| .. | ||
| cgroup-internal.h | ||
| cgroup-v1.c | ||
| cgroup.c | ||
| cpuset.c | ||
| debug.c | ||
| freezer.c | ||
| legacy_freezer.c | ||
| Makefile | ||
| namespace.c | ||
| pids.c | ||
| rdma.c | ||
| rstat.c | ||