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Date: Mon, 19 Jan 2009 17:18:16 -0800
From: Paul Menage <menage@...gle.com>
To: Lai Jiangshan <laijs@...fujitsu.com>
Cc: Andrew Morton <akpm@...ux-foundation.org>, miaox@...fujitsu.com,
maxk@...lcomm.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] cgroup: convert open-coded mutex_lock(&cgroup_mutex)
calls into cgroup_lock() calls
On Sun, Jan 18, 2009 at 12:06 AM, Lai Jiangshan <laijs@...fujitsu.com> wrote:
>
> Convert open-coded mutex_lock(&cgroup_mutex) calls into cgroup_lock()
> calls and convert mutex_unlock(&cgroup_mutex) calls into cgroup_unlock()
> calls.
I don't really see a lot of value in this patch. I'd prefer to leave
cgroup.c as it is, and work towards removing the need for external
code to call cgroup_lock() at all.
Paul
>
> Signed-off-by: Lai Jiangshan <laijs@...fujitsu.com>
> Cc: Max Krasnyansky <maxk@...lcomm.com>
> Cc: Miao Xie <miaox@...fujitsu.com>
> ---
> diff --git a/kernel/cgroup.c b/kernel/cgroup.c
> index c298310..75a352b 100644
> --- a/kernel/cgroup.c
> +++ b/kernel/cgroup.c
> @@ -616,7 +688,7 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
> * agent */
> synchronize_rcu();
>
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
> /*
> * Release the subsystem state objects.
> */
> @@ -624,7 +696,7 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
> ss->destroy(ss, cgrp);
>
> cgrp->root->number_of_cgroups--;
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
>
> /*
> * Drop the active superblock reference that we took when we
> @@ -761,14 +833,14 @@ static int cgroup_show_options(struct seq_file *seq, struct vfsmount *vfs)
> struct cgroupfs_root *root = vfs->mnt_sb->s_fs_info;
> struct cgroup_subsys *ss;
>
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
> for_each_subsys(root, ss)
> seq_printf(seq, ",%s", ss->name);
> if (test_bit(ROOT_NOPREFIX, &root->flags))
> seq_puts(seq, ",noprefix");
> if (strlen(root->release_agent_path))
> seq_printf(seq, ",release_agent=%s", root->release_agent_path);
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> return 0;
> }
>
> @@ -843,7 +915,7 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
> struct cgroup_sb_opts opts;
>
> mutex_lock(&cgrp->dentry->d_inode->i_mutex);
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
>
> /* See what subsystems are wanted */
> ret = parse_cgroupfs_options(data, &opts);
> @@ -867,7 +939,7 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data)
> out_unlock:
> if (opts.release_agent)
> kfree(opts.release_agent);
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
> return ret;
> }
> @@ -1015,7 +1087,7 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
> inode = sb->s_root->d_inode;
>
> mutex_lock(&inode->i_mutex);
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
>
> /*
> * We're accessing css_set_count without locking
> @@ -1026,14 +1098,14 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
> */
> ret = allocate_cg_links(css_set_count, &tmp_cg_links);
> if (ret) {
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> mutex_unlock(&inode->i_mutex);
> goto drop_new_super;
> }
>
> ret = rebind_subsystems(root, root->subsys_bits);
> if (ret == -EBUSY) {
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> mutex_unlock(&inode->i_mutex);
> goto free_cg_links;
> }
> @@ -1068,7 +1140,7 @@ static int cgroup_get_sb(struct file_system_type *fs_type,
>
> cgroup_populate_dir(root_cgrp);
> mutex_unlock(&inode->i_mutex);
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> }
>
> return simple_set_mnt(mnt, sb);
> @@ -1094,7 +1166,7 @@ static void cgroup_kill_sb(struct super_block *sb) {
> BUG_ON(!list_empty(&cgrp->children));
> BUG_ON(!list_empty(&cgrp->sibling));
>
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
>
> /* Rebind all subsystems back to the default hierarchy */
> ret = rebind_subsystems(root, 0);
> @@ -1118,7 +1190,7 @@ static void cgroup_kill_sb(struct super_block *sb) {
> list_del(&root->root_list);
> root_count--;
>
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
>
> kfree(root);
> kill_litter_super(sb);
> @@ -2392,7 +2464,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
> * fs */
> atomic_inc(&sb->s_active);
>
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
>
> init_cgroup_housekeeping(cgrp);
>
> @@ -2427,7 +2499,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
> err = cgroup_populate_dir(cgrp);
> /* If err < 0, we have a half-filled directory - oh well ;) */
>
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> mutex_unlock(&cgrp->dentry->d_inode->i_mutex);
>
> return 0;
> @@ -2444,7 +2516,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry,
> ss->destroy(ss, cgrp);
> }
>
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
>
> /* Release the reference count that we took on the superblock */
> deactivate_super(sb);
> @@ -2550,16 +2622,16 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
>
> /* the vfs holds both inode->i_mutex already */
>
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
> if (atomic_read(&cgrp->count) != 0) {
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> return -EBUSY;
> }
> if (!list_empty(&cgrp->children)) {
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> return -EBUSY;
> }
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
>
> /*
> * Call pre_destroy handlers of subsys. Notify subsystems
> @@ -2567,13 +2639,13 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
> */
> cgroup_call_pre_destroy(cgrp);
>
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
> parent = cgrp->parent;
>
> if (atomic_read(&cgrp->count)
> || !list_empty(&cgrp->children)
> || !cgroup_clear_css_refs(cgrp)) {
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> return -EBUSY;
> }
>
> @@ -2598,7 +2670,7 @@ static int cgroup_rmdir(struct inode *unused_dir, struct dentry *dentry)
> set_bit(CGRP_RELEASABLE, &parent->flags);
> check_for_release(parent);
>
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> return 0;
> }
>
> @@ -2752,7 +2824,7 @@ static int proc_cgroup_show(struct seq_file *m, void *v)
>
> retval = 0;
>
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
>
> for_each_active_root(root) {
> struct cgroup_subsys *ss;
> @@ -2774,7 +2846,7 @@ static int proc_cgroup_show(struct seq_file *m, void *v)
> }
>
> out_unlock:
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> put_task_struct(tsk);
> out_free:
> kfree(buf);
> @@ -2801,14 +2873,14 @@ static int proc_cgroupstats_show(struct seq_file *m, void *v)
> int i;
>
> seq_puts(m, "#subsys_name\thierarchy\tnum_cgroups\tenabled\n");
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
> for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) {
> struct cgroup_subsys *ss = subsys[i];
> seq_printf(m, "%s\t%lu\t%d\t%d\n",
> ss->name, ss->root->subsys_bits,
> ss->root->number_of_cgroups, !ss->disabled);
> }
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> return 0;
> }
>
> @@ -2984,11 +3056,11 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
>
> /* First figure out what hierarchy and cgroup we're dealing
> * with, and pin them so we can drop cgroup_mutex */
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
> again:
> root = subsys->root;
> if (root == &rootnode) {
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> return 0;
> }
> task_lock(tsk);
> @@ -2998,14 +3070,14 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
> /* Pin the hierarchy */
> if (!atomic_inc_not_zero(&parent->root->sb->s_active)) {
> /* We race with the final deactivate_super() */
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> return 0;
> }
>
> /* Keep the cgroup alive */
> get_css_set(cg);
> task_unlock(tsk);
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
>
> /* Now do the VFS work to create a cgroup */
> inode = parent->dentry->d_inode;
> @@ -3036,7 +3108,7 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
> /* The cgroup now exists. Retake cgroup_mutex and check
> * that we're still in the same state that we thought we
> * were. */
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
> if ((root != subsys->root) ||
> (parent != task_cgroup(tsk, subsys->subsys_id))) {
> /* Aargh, we raced ... */
> @@ -3061,14 +3133,14 @@ int cgroup_clone(struct task_struct *tsk, struct cgroup_subsys *subsys,
>
> /* All seems fine. Finish by moving the task into the new cgroup */
> ret = cgroup_attach_task(child, tsk);
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
>
> out_release:
> mutex_unlock(&inode->i_mutex);
>
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
> put_css_set(cg);
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> deactivate_super(parent->root->sb);
> return ret;
> }
> @@ -3162,7 +3234,7 @@ void __css_put(struct cgroup_subsys_state *css)
> static void cgroup_release_agent(struct work_struct *work)
> {
> BUG_ON(work != &release_agent_work);
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
> spin_lock(&release_list_lock);
> while (!list_empty(&release_list)) {
> char *argv[3], *envp[3];
> @@ -3196,16 +3268,16 @@ static void cgroup_release_agent(struct work_struct *work)
> /* Drop the lock while we invoke the usermode helper,
> * since the exec could involve hitting disk and hence
> * be a slow process */
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> call_usermodehelper(argv[0], argv, envp, UMH_WAIT_EXEC);
> - mutex_lock(&cgroup_mutex);
> + cgroup_lock();
> continue_free:
> kfree(pathbuf);
> kfree(agentbuf);
> spin_lock(&release_list_lock);
> }
> spin_unlock(&release_list_lock);
> - mutex_unlock(&cgroup_mutex);
> + cgroup_unlock();
> }
>
> static int __init cgroup_disable(char *str)
>
>
>
>
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