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cgroup: remove cgroup_pid_fry() and friends 

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 @@ after:
* sorted by task pointer. As pidlists can be fairly large, allocating one * 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 * per open file is dangerous, so cgroup had to implement shared pool of
* pidlists keyed by cgroup and namespace. * 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) static int cmppid(const void *a, const void *b)
{ {
return *(pid_t *)a - *(pid_t *)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, static struct cgroup_pidlist *cgroup_pidlist_find(struct cgroup *cgrp,
enum cgroup_filetype type) 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); css_task_iter_end(&it);
length = n; length = n;
/* now sort & (if procs) strip out duplicates */ /* now sort & (if procs) strip out duplicates */
if (cgroup_on_dfl(cgrp)) sort(array, length, sizeof(pid_t), cmppid, NULL);
sort(array, length, sizeof(pid_t), fried_cmppid, NULL);
else
sort(array, length, sizeof(pid_t), cmppid, NULL);
if (type == CGROUP_FILE_PROCS) if (type == CGROUP_FILE_PROCS)
length = pidlist_uniq(array, length); length = pidlist_uniq(array, length);
@ -4876,10 +4843,10 @@ static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
while (index < end) { while (index < end) {
int mid = (index + end) / 2; int mid = (index + end) / 2;
if (cgroup_pid_fry(cgrp, l->list[mid]) == pid) { if (l->list[mid] == pid) {
index = mid; index = mid;
break; break;
} else if (cgroup_pid_fry(cgrp, l->list[mid]) <= pid) } else if (l->list[mid] <= pid)
index = mid + 1; index = mid + 1;
else else
end = mid; end = mid;
@ -4890,7 +4857,7 @@ static void *cgroup_pidlist_start(struct seq_file *s, loff_t *pos)
return NULL; return NULL;
/* Update the abstract position to be the actual pid that we found */ /* Update the abstract position to be the actual pid that we found */
iter = l->list + index; iter = l->list + index;
*pos = cgroup_pid_fry(cgrp, *iter); *pos = *iter;
return iter; return iter;
} }
@ -4919,7 +4886,7 @@ static void *cgroup_pidlist_next(struct seq_file *s, void *v, loff_t *pos)
if (p >= end) { if (p >= end) {
return NULL; return NULL;
} else { } else {
*pos = cgroup_pid_fry(seq_css(s)->cgroup, *p); *pos = *p;
return p; return p;
} }
} }