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Message-ID: <CAFj3OHUQzShbmdCKYhWMum=hqM5XqK-_wcDyUajnZ1XWFGX1Xg@mail.gmail.com>
Date: Wed, 18 Jan 2012 15:23:45 +0800
From: Sha <handai.szj@...il.com>
To: Li Zefan <lizf@...fujitsu.com>
Cc: LKML <linux-kernel@...r.kernel.org>,
Cgroups <cgroups@...r.kernel.org>, Tejun Heo <tj@...nel.org>,
Lennart Poettering <mzxreary@...inter.de>,
Kay Sievers <kay.sievers@...y.org>
Subject: Re: [PATCH 1/2] cgroup: revise how we re-populate root directory
Hi Zefan,
On Mon, Jan 16, 2012 at 4:06 PM, Li Zefan <lizf@...fujitsu.com> wrote:
> When remounting cgroupfs with some subsystems added to it and some
> removed, cgroup will remove all the files in root directory and then
> re-popluate it.
>
> What I'm doing here is, only remove files which belong to subsystems that
> are to be unbound, and only create files for newly-added subsystems.
> The purpose is to have all other files untouched.
>
> This is a preparation for cgroup xattr support.
>
> Signed-off-by: Li Zefan <lizf@...fujitsu.com>
> ---
> include/linux/cgroup.h | 11 +++---
> kernel/cgroup.c | 92 +++++++++++++++++++++++++++++++----------------
> 2 files changed, 67 insertions(+), 36 deletions(-)
>
> diff --git a/include/linux/cgroup.h b/include/linux/cgroup.h
> index e9b6021..13db9e8 100644
> --- a/include/linux/cgroup.h
> +++ b/include/linux/cgroup.h
> @@ -327,6 +327,9 @@ struct cftype {
> */
> size_t max_write_len;
>
> + /* The subsystem this cgroup file belongs to */
> + struct cgroup_subsys *subsys;
> +
> int (*open)(struct inode *inode, struct file *file);
> ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
> struct file *file,
> @@ -419,16 +422,14 @@ struct cgroup_scanner {
> * called by subsystems from within a populate() method
> */
> int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
> - const struct cftype *cft);
> + struct cftype *cft);
>
> /*
> * Add a set of new files to the given cgroup directory. Should
> * only be called by subsystems from within a populate() method
> */
> -int cgroup_add_files(struct cgroup *cgrp,
> - struct cgroup_subsys *subsys,
> - const struct cftype cft[],
> - int count);
> +int cgroup_add_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
> + struct cftype cft[], int count);
>
> int cgroup_is_removed(const struct cgroup *cgrp);
>
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index a5d3b53..c4ed6fe 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -781,6 +781,8 @@ 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_repopulate_dir(struct cgroup *cgrp, unsigned long added_bits,
> + unsigned long removed_bits);
> static const struct inode_operations cgroup_dir_inode_operations;
> static const struct file_operations proc_cgroupstats_operations;
>
> @@ -882,34 +884,44 @@ static void remove_dir(struct dentry *d)
> dput(parent);
> }
>
> -static void cgroup_clear_directory(struct dentry *dentry)
> +static void cgroup_clear_directory(struct dentry *dentry, bool remove_all,
> + unsigned long removed_bits)
> {
> - struct list_head *node;
> + LIST_HEAD(head);
> + struct dentry *d, *node;
>
> BUG_ON(!mutex_is_locked(&dentry->d_inode->i_mutex));
> +
> spin_lock(&dentry->d_lock);
> - node = dentry->d_subdirs.next;
> - while (node != &dentry->d_subdirs) {
> - struct dentry *d = list_entry(node, struct dentry, d_u.d_child);
> + list_for_each_entry_safe(d, node, &dentry->d_subdirs, d_u.d_child) {
> + struct cftype *cft = d->d_fsdata;
> +
> + if (!remove_all && cft->subsys &&
> + !test_bit(cft->subsys->subsys_id, &removed_bits))
> + continue;
>
> spin_lock_nested(&d->d_lock, DENTRY_D_LOCK_NESTED);
> - list_del_init(node);
> + list_move(&d->d_u.d_child, &head);
> if (d->d_inode) {
> /* This should never be called on a cgroup
> * directory with child cgroups */
> BUG_ON(d->d_inode->i_mode & S_IFDIR);
> dget_dlock(d);
> - spin_unlock(&d->d_lock);
> - spin_unlock(&dentry->d_lock);
> + }
> + spin_unlock(&d->d_lock);
> + }
> + spin_unlock(&dentry->d_lock);
> +
> + list_for_each_entry_safe(d, node, &head, d_u.d_child) {
> + spin_lock(&d->d_lock);
> + list_del_init(&d->d_u.d_child);
> + spin_unlock(&d->d_lock);
> + if (d->d_inode) {
> d_delete(d);
> simple_unlink(dentry->d_inode, d);
> dput(d);
> - spin_lock(&dentry->d_lock);
> - } else
> - spin_unlock(&d->d_lock);
> - node = dentry->d_subdirs.next;
> + }
> }
> - spin_unlock(&dentry->d_lock);
> }
>
> /*
> @@ -919,7 +931,7 @@ static void cgroup_d_remove_dir(struct dentry *dentry)
> {
> struct dentry *parent;
>
> - cgroup_clear_directory(dentry);
> + cgroup_clear_directory(dentry, true, 0);
>
> parent = dentry->d_parent;
> spin_lock(&parent->d_lock);
> @@ -1284,6 +1296,7 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
> 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);
> @@ -1294,6 +1307,9 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
> if (ret)
> goto out_unlock;
>
> + added_bits = opts.subsys_bits & ~root->subsys_bits;
> + removed_bits = root->subsys_bits & ~opts.subsys_bits;
> +
Should it be the following？：
added_bits = opts.subsys_bits & ~root->actual_subsys_bits;
removed_bits = root->actual_subsys_bits & ~opts.subsys_bits;
Thanks,
Sha
> /* Don't allow flags or name to change at remount */
> if (opts.flags != root->flags ||
> (opts.name && strcmp(opts.name, root->name))) {
> @@ -1308,8 +1324,8 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
> goto out_unlock;
> }
>
> - /* (re)populate subsystem files */
> - cgroup_populate_dir(cgrp);
> + /* re-populate subsystem files */
> + cgroup_repopulate_dir(cgrp, added_bits, removed_bits);
>
> if (opts.release_agent)
> strcpy(root->release_agent_path, opts.release_agent);
> @@ -2710,16 +2726,17 @@ static umode_t cgroup_file_mode(const struct cftype *cft)
> return mode;
> }
>
> -int cgroup_add_file(struct cgroup *cgrp,
> - struct cgroup_subsys *subsys,
> - const struct cftype *cft)
> +int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
> + struct cftype *cft)
> {
> struct dentry *dir = cgrp->dentry;
> struct dentry *dentry;
> int error;
> umode_t mode;
> -
> char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
> +
> + cft->subsys = subsys;
> +
> if (subsys && !test_bit(ROOT_NOPREFIX, &cgrp->root->flags)) {
> strcpy(name, subsys->name);
> strcat(name, ".");
> @@ -2740,10 +2757,8 @@ int cgroup_add_file(struct cgroup *cgrp,
> }
> EXPORT_SYMBOL_GPL(cgroup_add_file);
>
> -int cgroup_add_files(struct cgroup *cgrp,
> - struct cgroup_subsys *subsys,
> - const struct cftype cft[],
> - int count)
> +int cgroup_add_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
> + struct cftype cft[], int count)
> {
> int i, err;
> for (i = 0; i < count; i++) {
> @@ -3703,26 +3718,27 @@ static struct cftype cft_release_agent = {
> .max_write_len = PATH_MAX,
> };
>
> -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;
>
> - /* First clear out any existing files */
> - cgroup_clear_directory(cgrp->dentry);
> -
> err = cgroup_add_files(cgrp, NULL, files, ARRAY_SIZE(files));
> if (err < 0)
> return err;
>
> if (cgrp == cgrp->top_cgroup) {
> - if ((err = cgroup_add_file(cgrp, NULL, &cft_release_agent)) < 0)
> + err = cgroup_add_file(cgrp, NULL, &cft_release_agent);
> + if (err < 0)
> return err;
> }
>
> for_each_subsys(cgrp->root, ss) {
> - if (ss->populate && (err = ss->populate(ss, cgrp)) < 0)
> - return err;
> + if (test_bit(ss->subsys_id, &added_bits) && ss->populate) {
> + err = ss->populate(ss, cgrp);
> + if (err < 0)
> + return err;
> + }
> }
> /* This cgroup is ready now */
> for_each_subsys(cgrp->root, ss) {
> @@ -3739,6 +3755,20 @@ static int cgroup_populate_dir(struct cgroup *cgrp)
> return 0;
> }
>
> +static int cgroup_populate_dir(struct cgroup *cgrp)
> +{
> + return __cgroup_populate_dir(cgrp, cgrp->root->subsys_bits);
> +}
> +
> +static int cgroup_repopulate_dir(struct cgroup *cgrp, unsigned long added_bits,
> + unsigned long removed_bits)
> +{
> + /* First clear out files */
> + cgroup_clear_directory(cgrp->dentry, false, removed_bits);
> +
> + return __cgroup_populate_dir(cgrp, added_bits);
> +}
> +
> static void init_cgroup_css(struct cgroup_subsys_state *css,
> struct cgroup_subsys *ss,
> struct cgroup *cgrp)
> --
> 1.7.3.1
> --
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