From 13af07df9b7e49f1987cf36aa048dc6c49d0f93d Mon Sep 17 00:00:00 2001 From: Aristeu Rozanski Date: Thu, 23 Aug 2012 16:53:29 -0400 Subject: [PATCH] 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: Li Zefan Cc: Li Zefan Cc: Hugh Dickins Cc: Hillf Danton Cc: Lennart Poettering Signed-off-by: Li Zefan Signed-off-by: Aristeu Rozanski Signed-off-by: Tejun Heo --- kernel/cgroup.c | 61 ++++++++++++++++++++++++++++++++++++++----------- 1 file changed, 48 insertions(+), 13 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 79818507e444..875a7130647c 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -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; @@ -963,12 +964,29 @@ 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; - 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, &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); + } } /* @@ -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; - 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, &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); -- 2.34.1