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Date: Tue, 10 Jul 2012 15:27:22 -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
Hi Tejun,
On Mon, Jul 09, 2012 at 10:28:31AM -0700, Tejun Heo wrote:
> On Mon, Jul 09, 2012 at 10:22:20AM -0700, Tejun Heo wrote:
> > > Changing subsys_bits via remount is being deprecated. No need to
> > > worry about this.
> >
> > Also, why does this matter? The xattrs are kept in cgrp anyway. Why
> > does keeping dentry/inode around make difference?
>
> Ah, okay, the file xattrs are kept in cfe which goes away on file
> deletion. :)
>
> While changing subsys via remount is going away, I think removing
> files selectively is still nice to have (even for single hierarchy).
> I wish it were implemented differently tho. As cgroup_rm_file()
> already has @cft argument, wouldn't it be better to e.g. add @subsys
> arg to cgroup_clear_directory() and let that walk subsys->cftsets
> instead?
something like this? (will resubmit if you're ok with this version)
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;
+
/* CFTYPE_* flags */
unsigned int flags;
Index: xattr/kernel/cgroup.c
===================================================================
--- xattr.orig/kernel/cgroup.c 2012-07-03 15:43:43.404334484 -0400
+++ xattr/kernel/cgroup.c 2012-07-10 13:28:18.424657727 -0400
@@ -825,6 +825,7 @@
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_repopulate_dir(struct cgroup *cgrp, 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 remove_all,
+ 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 (!remove_all && !test_bit(ss->subsys_id, &removed_bits))
+ continue;
+ list_for_each_entry(set, &ss->cftsets, node)
+ cgroup_rm_file(cgrp, set->cfts);
+ }
+ if (remove_all) {
+ while (!list_empty(&cgrp->files))
+ cgroup_rm_file(cgrp, NULL);
+ }
}
/*
@@ -988,7 +1000,7 @@
{
struct dentry *parent;
- cgroup_clear_directory(dentry);
+ cgroup_clear_directory(dentry, true, 0);
parent = dentry->d_parent;
spin_lock(&parent->d_lock);
@@ -1353,6 +1365,7 @@
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 +1381,9 @@
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 +1399,9 @@
}
/* 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_repopulate_dir(cgrp, added_bits);
if (opts.release_agent)
strcpy(root->release_agent_path, opts.release_agent);
@@ -2696,6 +2713,8 @@
umode_t mode;
char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
+ cft->subsys = subsys;
+
/* does @cft->flags tell us to skip creation on @cgrp? */
if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
return 0;
@@ -3858,18 +3877,16 @@
{ } /* terminate */
};
-static int cgroup_populate_dir(struct cgroup *cgrp)
+static int __cgroup_populate_dir(struct cgroup *cgrp, unsigned long added_bits)
{
int err;
struct cgroup_subsys *ss;
- 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);
@@ -3890,6 +3907,22 @@
return 0;
}
+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);
+}
+
+static int cgroup_repopulate_dir(struct cgroup *cgrp, unsigned long added_bits)
+{
+ return __cgroup_populate_dir(cgrp, added_bits);
+}
+
static void css_dput_fn(struct work_struct *work)
{
struct cgroup_subsys_state *css =
--
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