Commit 13af07df authored by Aristeu Rozanski's avatar Aristeu Rozanski Committed by Tejun Heo
Browse files

cgroup: revise how we re-populate root directory 



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 unbinded, 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.

v7:
- checkpatch warnings fixed
v6:
- no changes
v5:
- no changes
v4:
- refactored cgroup_clear_directory() to not use cgroup_rm_file()
- instead of going thru the list of files, get the file list using the
  subsystems
- use 'subsys_mask' instead of {added,removed}_bits and made
  cgroup_populate_dir() to match the parameters with cgroup_clear_directory()
v3:
- refresh patches after recent refactoring

Original-patch-by: default avatarLi Zefan <lizefan@huawei.com>
Cc: Li Zefan <lizefan@huawei.com>
Cc: Hugh Dickins <hughd@google.com>
Cc: Hillf Danton <dhillf@gmail.com>
Cc: Lennart Poettering <lpoetter@redhat.com>
Signed-off-by: default avatarLi Zefan <lizefan@huawei.com>
Signed-off-by: default avatarAristeu Rozanski <aris@redhat.com>
Signed-off-by: default avatarTejun Heo <tj@kernel.org>
parent 38f38657

kernel/cgroup.c

+48 −13
Original line number Diff line number Diff line
@@ -824,7 +824,8 @@ EXPORT_SYMBOL_GPL(cgroup_unlock); 
static int cgroup_mkdir(struct inode *dir, struct dentry *dentry, umode_t mode);

static struct dentry *cgroup_lookup(struct inode *, struct dentry *, unsigned int);

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 subsys_mask);

static const struct inode_operations cgroup_dir_inode_operations;

static const struct file_operations proc_cgroupstats_operations;
@@ -963,13 +964,30 @@ static int cgroup_rm_file(struct cgroup *cgrp, const struct cftype *cft) 
	return -ENOENT;

}



static void cgroup_clear_directory(struct dentry *dir)

/**

 * cgroup_clear_directory - selective removal of base and subsystem files

 * @dir: directory containing the files

 * @base_files: true if the base files should be removed

 * @subsys_mask: mask of the subsystem ids whose files should be removed

 */

static void cgroup_clear_directory(struct dentry *dir, bool base_files,

				   unsigned long subsys_mask)

{

	struct cgroup *cgrp = __d_cgrp(dir);

	struct cgroup_subsys *ss;



	for_each_subsys(cgrp->root, ss) {

		struct cftype_set *set;

		if (!test_bit(ss->subsys_id, &subsys_mask))

			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);

	}

}



/*

 * NOTE : the dentry must have been dget()'ed
@@ -977,8 +995,9 @@ static void cgroup_clear_directory(struct dentry *dir) 
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);
@@ -1339,6 +1358,7 @@ 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);
@@ -1354,6 +1374,9 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data) 
		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))) {
@@ -1369,8 +1392,9 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data) 
	}



	/* 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);
@@ -1669,7 +1693,7 @@ static struct dentry *cgroup_mount(struct file_system_type *fs_type, 
		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);
@@ -3843,18 +3867,29 @@ static struct cftype files[] = { 
	{ }	/* terminate */

};



static int cgroup_populate_dir(struct cgroup *cgrp)

/**

 * cgroup_populate_dir - selectively creation of files in a directory

 * @cgrp: target cgroup

 * @base_files: true if the base files should be added

 * @subsys_mask: mask of the subsystem ids whose files should be added

 */

static int cgroup_populate_dir(struct cgroup *cgrp, bool base_files,

			       unsigned long subsys_mask)

{

	int err;

	struct cgroup_subsys *ss;



	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, &subsys_mask))

			continue;



		list_for_each_entry(set, &ss->cftsets, node)

			cgroup_addrm_files(cgrp, ss, set->cfts, true);
@@ -3988,7 +4023,7 @@ static long cgroup_create(struct cgroup *parent, struct dentry *dentry, 


	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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