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Commit 2fae9863 authored by Tejun Heo's avatar Tejun Heo
Browse files

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: default avatarTejun Heo <tj@kernel.org>
Acked-by: default avatarAcked-by: Zefan Li <lizefan@huawei.com>
parent b4b90a8e

kernel/cgroup.c

+5 −38
Original line number Diff line number Diff line
@@ -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)

{
@@ -4741,9 +4711,6 @@ 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);

	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;

	}

}