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Subject[PATCH 5/5] cgroup: remove cgroup_pid_fry() and friends
Date
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>
---
kernel/cgroup.c | 43 +++++--------------------------------------
1 file changed, 5 insertions(+), 38 deletions(-)

diff --git a/kernel/cgroup.c b/kernel/cgroup.c
index fd684bfd..b9e2d85 100644
--- a/kernel/cgroup.c
+++ b/kernel/cgroup.c
@@ -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;
}
}
--
2.9.3
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