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cgroup: remove cgroup_pid_fry() and friends

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cgroup_pid_fry() was added to mangle cgroup.procs pid listing order on
v2 to make it clear that the output is not sorted.  Now that v2 now
uses a separate "cgroup.procs" read method, this is no longer used.
Remove it.

Signed-off-by: Tejun Heo <tj@kernel.org>
Acked-by: Acked-by: Zefan Li <lizefan@huawei.com>
This commit is contained in:
Tejun Heo 2016-12-27 14:49:05 -05:00
parent b4b90a8e86
commit 2fae986343
1 changed files with 5 additions and 38 deletions
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43
kernel/cgroup.c
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@ -4618,42 +4618,12 @@ static int pidlist_uniq(pid_t *list, int length)
* sorted by task pointer. As pidlists can be fairly large, allocating one
* per open file is dangerous, so cgroup had to implement shared pool of
* pidlists keyed by cgroup and namespace.
*
* All this extra complexity was caused by the original implementation
* committing to an entirely unnecessary property. In the long term, we
* want to do away with it. Explicitly scramble sort order if on the
* default hierarchy so that no such expectation exists in the new
* interface.
*
* Scrambling is done by swapping every two consecutive bits, which is
* non-identity one-to-one mapping which disturbs sort order sufficiently.
*/
static pid_t pid_fry(pid_t pid)
{
unsigned a = pid & 0x55555555;
unsigned b = pid & 0xAAAAAAAA;
return (a << 1) | (b >> 1);
}
static pid_t cgroup_pid_fry(struct cgroup *cgrp, pid_t pid)
{
if (cgroup_on_dfl(cgrp))
return pid_fry(pid);
else
return pid;
}
static int cmppid(const void *a, const void *b)
{
return *(pid_t *)a - *(pid_t *)b;
}
static int fried_cmppid(const void *a, const void *b)
{
return pid_fry(*(pid_t *)a) - pid_fry(*(pid_t *)b);
}
static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
enum cgroup_filetype type)
{
@ -4741,10 +4711,7 @@ static int pidlist_array_load(struct cgroup *cgrp, enum cgroup_filetype type,
css_task_iter_end(&it);
length = n;
/* now sort & (if procs) strip out duplicates */
if (cgroup_on_dfl(cgrp))
sort(array, length, sizeof(pid_t), fried_cmppid, NULL);
else
sort(array, length, sizeof(pid_t), cmppid, NULL);
sort(array, length, sizeof(pid_t), cmppid, NULL);
if (type == CGROUP_FILE_PROCS)
length = pidlist_uniq(array, length);
@ -4876,10 +4843,10 @@ static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
while (index < end) {
int mid = (index + end) / 2;
if (cgroup_pid_fry(cgrp, l->list[mid]) == pid) {
if (l->list[mid] == pid) {
index = mid;
break;
} else if (cgroup_pid_fry(cgrp, l->list[mid]) <= pid)
} else if (l->list[mid] <= pid)
index = mid + 1;
else
end = mid;
@ -4890,7 +4857,7 @@ static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
return NULL;
/* Update the abstract position to be the actual pid that we found */
iter = l->list + index;
*pos = cgroup_pid_fry(cgrp, *iter);
*pos = *iter;
return iter;
}
@ -4919,7 +4886,7 @@ static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
if (p >= end) {
return NULL;
} else {
*pos = cgroup_pid_fry(seq_css(s)->cgroup, *p);
*pos = *p;
return p;
}
}