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cgroup: convert for_each_subsys_which() to do-while style 

for_each_subsys_which() allows iterating subsystems specified in a
subsystem bitmask; unfortunately, it requires the mask to be an
unsigned long l-value which can be inconvenient and makes it awkward
to use a smaller type for subsystem masks.

This patch converts for_each_subsy_which() to do-while style which
allows it to drop the l-value requirement.  The new iterator is named
do_each_subsys_mask() / while_each_subsys_mask().

Signed-off-by: Tejun Heo <tj@kernel.org>
Cc: Aleksa Sarai <cyphar@cyphar.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
This commit is contained in:
Tejun Heo 2016-02-22 22:25:46 -05:00
parent 8699b7762a
commit b4e0eeafba
1 changed files with 40 additions and 32 deletions
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72
kernel/cgroup.c
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@ -514,22 +514,28 @@ static int notify_on_release(const struct cgroup *cgrp)
(((ss) = cgroup_subsys[ssid]) || true); (ssid)++)
/**
* for_each_subsys_which - filter for_each_subsys with a bitmask
* do_each_subsys_mask - filter for_each_subsys with a bitmask
* @ss: the iteration cursor
* @ssid: the index of @ss, CGROUP_SUBSYS_COUNT after reaching the end
* @ss_maskp: a pointer to the bitmask
* @ss_mask: the bitmask
*
* The block will only run for cases where the ssid-th bit (1 << ssid) of
* mask is set to 1.
* @ss_mask is set.
*/
#define for_each_subsys_which(ss, ssid, ss_maskp) \
if (!CGROUP_SUBSYS_COUNT) /* to avoid spurious gcc warning */ \
#define do_each_subsys_mask(ss, ssid, ss_mask) do { \
unsigned long __ss_mask = (ss_mask); \
if (!CGROUP_SUBSYS_COUNT) { /* to avoid spurious gcc warning */ \
(ssid) = 0; \
else \
for_each_set_bit(ssid, ss_maskp, CGROUP_SUBSYS_COUNT) \
if (((ss) = cgroup_subsys[ssid]) && false) \
break; \
else
break; \
} \
for_each_set_bit(ssid, &__ss_mask, CGROUP_SUBSYS_COUNT) { \
(ss) = cgroup_subsys[ssid]; \
{
#define while_each_subsys_mask() \
} \
} \
} while (false)
/* iterate across the hierarchies */
#define for_each_root(root) \
@ -1284,8 +1290,9 @@ static unsigned long cgroup_calc_subtree_ss_mask(struct cgroup *cgrp,
while (true) {
unsigned long new_ss_mask = cur_ss_mask;
for_each_subsys_which(ss, ssid, &cur_ss_mask)
do_each_subsys_mask(ss, ssid, cur_ss_mask) {
new_ss_mask |= ss->depends_on;
} while_each_subsys_mask();
/*
* Mask out subsystems which aren't available. This can
@ -1469,7 +1476,7 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
lockdep_assert_held(&cgroup_mutex);
for_each_subsys_which(ss, ssid, &ss_mask) {
do_each_subsys_mask(ss, ssid, ss_mask) {
/* if @ss has non-root csses attached to it, can't move */
if (css_next_child(NULL, cgroup_css(&ss->root->cgrp, ss)))
return -EBUSY;
@ -1477,14 +1484,14 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
/* can't move between two non-dummy roots either */
if (ss->root != &cgrp_dfl_root && dst_root != &cgrp_dfl_root)
return -EBUSY;
}
} while_each_subsys_mask();
/* skip creating root files on dfl_root for inhibited subsystems */
tmp_ss_mask = ss_mask;
if (dst_root == &cgrp_dfl_root)
tmp_ss_mask &= ~cgrp_dfl_root_inhibit_ss_mask;
for_each_subsys_which(ss, ssid, &tmp_ss_mask) {
do_each_subsys_mask(ss, ssid, tmp_ss_mask) {
struct cgroup *scgrp = &ss->root->cgrp;
int tssid;
@ -1507,19 +1514,19 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
continue;
}
for_each_subsys_which(ss, tssid, &tmp_ss_mask) {
do_each_subsys_mask(ss, tssid, tmp_ss_mask) {
if (tssid == ssid)
break;
css_clear_dir(cgroup_css(scgrp, ss), dcgrp);
}
} while_each_subsys_mask();
return ret;
}
} while_each_subsys_mask();
/*
* Nothing can fail from this point on. Remove files for the
* removed subsystems and rebind each subsystem.
*/
for_each_subsys_which(ss, ssid, &ss_mask) {
do_each_subsys_mask(ss, ssid, ss_mask) {
struct cgroup_root *src_root = ss->root;
struct cgroup *scgrp = &src_root->cgrp;
struct cgroup_subsys_state *css = cgroup_css(scgrp, ss);
@ -1556,7 +1563,7 @@ static int rebind_subsystems(struct cgroup_root *dst_root,
if (ss->bind)
ss->bind(css);
}
} while_each_subsys_mask();
kernfs_activate(dcgrp->kn);
return 0;
@ -2838,12 +2845,12 @@ static void cgroup_print_ss_mask(struct seq_file *seq, unsigned long ss_mask)
bool printed = false;
int ssid;
for_each_subsys_which(ss, ssid, &ss_mask) {
do_each_subsys_mask(ss, ssid, ss_mask) {
if (printed)
seq_putc(seq, ' ');
seq_printf(seq, "%s", ss->name);
printed = true;
}
} while_each_subsys_mask();
if (printed)
seq_putc(seq, '\n');
}
@ -2956,11 +2963,9 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
*/
buf = strstrip(buf);
while ((tok = strsep(&buf, " "))) {
unsigned long tmp_ss_mask = ~cgrp_dfl_root_inhibit_ss_mask;
if (tok[0] == '\0')
continue;
for_each_subsys_which(ss, ssid, &tmp_ss_mask) {
do_each_subsys_mask(ss, ssid, ~cgrp_dfl_root_inhibit_ss_mask) {
if (!cgroup_ssid_enabled(ssid) ||
strcmp(tok + 1, ss->name))
continue;
@ -2975,7 +2980,7 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
return -EINVAL;
}
break;
}
} while_each_subsys_mask();
if (ssid == CGROUP_SUBSYS_COUNT)
return -EINVAL;
}
@ -3049,7 +3054,7 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
* still around. In such cases, wait till it's gone using
* offline_waitq.
*/
for_each_subsys_which(ss, ssid, &css_enable) {
do_each_subsys_mask(ss, ssid, css_enable) {
cgroup_for_each_live_child(child, cgrp) {
DEFINE_WAIT(wait);
@ -3066,7 +3071,7 @@ static ssize_t cgroup_subtree_control_write(struct kernfs_open_file *of,
return restart_syscall();
}
}
} while_each_subsys_mask();
cgrp->subtree_control = new_sc;
cgrp->subtree_ss_mask = new_ss;
@ -5509,11 +5514,11 @@ int cgroup_can_fork(struct task_struct *child)
struct cgroup_subsys *ss;
int i, j, ret;
for_each_subsys_which(ss, i, &have_canfork_callback) {
do_each_subsys_mask(ss, i, have_canfork_callback) {
ret = ss->can_fork(child);
if (ret)
goto out_revert;
}
} while_each_subsys_mask();
return 0;
@ -5598,8 +5603,9 @@ void cgroup_post_fork(struct task_struct *child)
* css_set; otherwise, @child might change state between ->fork()
* and addition to css_set.
*/
for_each_subsys_which(ss, i, &have_fork_callback)
do_each_subsys_mask(ss, i, have_fork_callback) {
ss->fork(child);
} while_each_subsys_mask();
}
/**
@ -5642,8 +5648,9 @@ void cgroup_exit(struct task_struct *tsk)
}
/* see cgroup_post_fork() for details */
for_each_subsys_which(ss, i, &have_exit_callback)
do_each_subsys_mask(ss, i, have_exit_callback) {
ss->exit(tsk);
} while_each_subsys_mask();
}
void cgroup_free(struct task_struct *task)
@ -5652,8 +5659,9 @@ void cgroup_free(struct task_struct *task)
struct cgroup_subsys *ss;
int ssid;
for_each_subsys_which(ss, ssid, &have_free_callback)
do_each_subsys_mask(ss, ssid, have_free_callback) {
ss->free(task);
} while_each_subsys_mask();
put_css_set(cset);
}