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Date: Tue, 17 Jul 2012 17:29:27 -0400
From: Aristeu Rozanski <aris@...hat.com>
To: Tejun Heo <tj@...nel.org>
Cc: linux-kernel@...r.kernel.org, Li Zefan <lizefan@...wei.com>,
Hugh Dickins <hughd@...gle.com>,
Hillf Danton <dhillf@...il.com>
Subject: Re: [PATCH v3 2/3] cgroup: revise how we re-populate root directory
On Tue, Jul 17, 2012 at 11:38:51AM -0700, Tejun Heo wrote:
> Hello,
>
> Sorry about the delay.
no worries, thanks for doing this
> On Tue, Jul 10, 2012 at 03:27:22PM -0400, Aristeu Rozanski wrote:
> > Index: xattr/include/linux/cgroup.h
> > ===================================================================
> > --- xattr.orig/include/linux/cgroup.h 2012-07-03 15:43:43.404334484 -0400
> > +++ xattr/include/linux/cgroup.h 2012-07-10 13:17:32.285119770 -0400
> > @@ -306,6 +306,9 @@
> > */
> > size_t max_write_len;
> >
> > + /* The subsystem this cgroup file belongs to */
> > + struct cgroup_subsys *subsys;
>
> I couldn't find how this is used. How is it used?
ignore this, I forgot it there from a previous version of the patch
> Maybe @subsys_mask is better? Also, why is @remove_all a separate
> argument? Can't we define, say, CGRP_ALL_SUBSYS and pass it in as
> @subsys_mask?
(...)
> Ah, I see. We don't have a bit for the base files. I think it's a
> bit confusing that there are two params controlling subsys file
> removal. Maybe reserve a bit for NULL subsys or use
> @remove_base_files argument instead?
if we'd create one subsys id for base, a lot of code would have to be
changed in order to accomodate this. I think
remove_base_files/base_files will look better.
>
> > +static int cgroup_populate_dir(struct cgroup *cgrp)
> > +{
> > + int err;
> > +
> > + err = cgroup_addrm_files(cgrp, NULL, files, true);
> > + if (err < 0)
> > + return err;
> > +
> > + return __cgroup_populate_dir(cgrp, cgrp->root->subsys_bits);
> > +}
>
> I think it would be best to keep the clear and populate interface more
> or less symmetrical so that both have @subsys_mask (and maybe
> @base_files).
what about this version:
--- xattr.orig/kernel/cgroup.c 2012-07-03 15:43:43.404334484 -0400
+++ xattr/kernel/cgroup.c 2012-07-17 15:49:10.536825559 -0400
@@ -824,7 +824,8 @@
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);
static struct dentry *cgroup_lookup(struct inode *, struct dentry *, struct nameidata *);
static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry);
-static int cgroup_populate_dir(struct cgroup *cgrp);
+static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
+ unsigned long added_bits);
static const struct inode_operations cgroup_dir_inode_operations;
static const struct file_operations proc_cgroupstats_operations;
@@ -973,12 +974,23 @@
return -ENOENT;
}
-static void cgroup_clear_directory(struct dentry *dir)
+static void cgroup_clear_directory(struct dentry *dir, bool base_files,
+ unsigned long removed_bits)
{
struct cgroup *cgrp = __d_cgrp(dir);
+ struct cgroup_subsys *ss;
- while (!list_empty(&cgrp->files))
- cgroup_rm_file(cgrp, NULL);
+ for_each_subsys(cgrp->root, ss) {
+ struct cftype_set *set;
+ if (!test_bit(ss->subsys_id, &removed_bits))
+ continue;
+ list_for_each_entry(set, &ss->cftsets, node)
+ cgroup_rm_file(cgrp, set->cfts);
+ }
+ if (base_files) {
+ while (!list_empty(&cgrp->files))
+ cgroup_rm_file(cgrp, NULL);
+ }
}
/*
@@ -987,8 +999,9 @@
static void cgroup_d_remove_dir(struct dentry *dentry)
{
struct dentry *parent;
+ struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
- cgroup_clear_directory(dentry);
+ cgroup_clear_directory(dentry, true, root->subsys_bits);
parent = dentry->d_parent;
spin_lock(&parent->d_lock);
@@ -1353,6 +1366,7 @@
struct cgroupfs_root *root = sb->s_fs_info;
struct cgroup *cgrp = &root->top_cgroup;
struct cgroup_sb_opts opts;
+ unsigned long added_bits, removed_bits;
mutex_lock(&cgrp->dentry->d_inode->i_mutex);
mutex_lock(&cgroup_mutex);
@@ -1368,6 +1382,9 @@
pr_warning("cgroup: option changes via remount are deprecated (pid=%d comm=%s)\n",
task_tgid_nr(current), current->comm);
+ added_bits = opts.subsys_bits & ~root->subsys_bits;
+ removed_bits = root->subsys_bits & ~opts.subsys_bits;
+
/* Don't allow flags or name to change at remount */
if (opts.flags != root->flags ||
(opts.name && strcmp(opts.name, root->name))) {
@@ -1383,8 +1400,9 @@
}
/* clear out any existing files and repopulate subsystem files */
- cgroup_clear_directory(cgrp->dentry);
- cgroup_populate_dir(cgrp);
+ cgroup_clear_directory(cgrp->dentry, false, removed_bits);
+ /* re-populate subsystem files */
+ cgroup_populate_dir(cgrp, false, added_bits);
if (opts.release_agent)
strcpy(root->release_agent_path, opts.release_agent);
@@ -1684,7 +1702,7 @@
BUG_ON(root->number_of_cgroups != 1);
cred = override_creds(&init_cred);
- cgroup_populate_dir(root_cgrp);
+ cgroup_populate_dir(root_cgrp, true, root->subsys_bits);
revert_creds(cred);
mutex_unlock(&cgroup_root_mutex);
mutex_unlock(&cgroup_mutex);
@@ -3858,18 +3876,23 @@
{ } /* terminate */
};
-static int cgroup_populate_dir(struct cgroup *cgrp)
+static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,
+ unsigned long added_bits)
{
int err;
struct cgroup_subsys *ss;
- err = cgroup_addrm_files(cgrp, NULL, files, true);
- if (err < 0)
- return err;
+ if (base_files) {
+ err = cgroup_addrm_files(cgrp, NULL, files, true);
+ if (err < 0)
+ return err;
+ }
/* process cftsets of each subsystem */
for_each_subsys(cgrp->root, ss) {
struct cftype_set *set;
+ if (!test_bit(ss->subsys_id, &added_bits))
+ continue;
list_for_each_entry(set, &ss->cftsets, node)
cgroup_addrm_files(cgrp, ss, set->cfts, true);
@@ -4032,7 +4055,7 @@
list_add_tail(&cgrp->allcg_node, &root->allcg_list);
- err = cgroup_populate_dir(cgrp);
+ err = cgroup_populate_dir(cgrp, true, root->subsys_bits);
/* If err < 0, we have a half-filled directory - oh well ;) */
mutex_unlock(&cgroup_mutex);
--
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