mirror of https://gitee.com/openkylin/linux.git
cgroup: add xattr support
This is one of the items in the plumber's wish list. For use cases: >> What would the use case be for this? > > Attaching meta information to services, in an easily discoverable > way. For example, in systemd we create one cgroup for each service, and > could then store data like the main pid of the specific service as an > xattr on the cgroup itself. That way we'd have almost all service state > in the cgroupfs, which would make it possible to terminate systemd and > later restart it without losing any state information. But there's more: > for example, some very peculiar services cannot be terminated on > shutdown (i.e. fakeraid DM stuff) and it would be really nice if the > services in question could just mark that on their cgroup, by setting an > xattr. On the more desktopy side of things there are other > possibilities: for example there are plans defining what an application > is along the lines of a cgroup (i.e. an app being a collection of > processes). With xattrs one could then attach an icon or human readable > program name on the cgroup. > > The key idea is that this would allow attaching runtime meta information > to cgroups and everything they model (services, apps, vms), that doesn't > need any complex userspace infrastructure, has good access control > (i.e. because the file system enforces that anyway, and there's the > "trusted." xattr namespace), notifications (inotify), and can easily be > shared among applications. > > Lennart v7: - no changes v6: - remove user xattr namespace, only allow trusted and security v5: - check for capabilities before setting/removing xattrs v4: - no changes v3: - instead of config option, use mount option to enable xattr support Original-patch-by: Li Zefan <lizefan@huawei.com> Cc: Li Zefan <lizefan@huawei.com> Cc: Tejun Heo <tj@kernel.org> Cc: Hugh Dickins <hughd@google.com> Cc: Hillf Danton <dhillf@gmail.com> Cc: Lennart Poettering <lpoetter@redhat.com> Signed-off-by: Li Zefan <lizefan@huawei.com> Signed-off-by: Aristeu Rozanski <aris@redhat.com> Signed-off-by: Tejun Heo <tj@kernel.org>
This commit is contained in:
Aristeu Rozanski
Tejun Heo
parent
13af07df9b
commit
03b1cde6b2
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@ -17,6 +17,7 @@
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#include <linux/rwsem.h>
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#include <linux/idr.h>
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#include <linux/workqueue.h>
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#include <linux/xattr.h>
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#ifdef CONFIG_CGROUPS
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@ -216,6 +217,9 @@ struct cgroup {
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/* List of events which userspace want to receive */
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struct list_head event_list;
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spinlock_t event_list_lock;
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/* directory xattrs */
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struct simple_xattrs xattrs;
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};
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/*
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@ -309,6 +313,9 @@ struct cftype {
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/* CFTYPE_* flags */
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unsigned int flags;
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/* file xattrs */
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struct simple_xattrs xattrs;
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int (*open)(struct inode *inode, struct file *file);
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ssize_t (*read)(struct cgroup *cgrp, struct cftype *cft,
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struct file *file,
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@ -394,7 +401,7 @@ struct cftype {
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*/
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struct cftype_set {
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struct list_head node; /* chained at subsys->cftsets */
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const struct cftype *cfts;
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struct cftype *cfts;
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};
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struct cgroup_scanner {
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@ -406,8 +413,8 @@ struct cgroup_scanner {
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void *data;
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};
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int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts);
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int cgroup_rm_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts);
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int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
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int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts);
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int cgroup_is_removed(const struct cgroup *cgrp);
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100
kernel/cgroup.c
100
kernel/cgroup.c
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@ -276,7 +276,8 @@ inline int cgroup_is_removed(const struct cgroup *cgrp)
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/* bits in struct cgroupfs_root flags field */
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enum {
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ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
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ROOT_NOPREFIX, /* mounted subsystems have no named prefix */
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ROOT_XATTR, /* supports extended attributes */
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};
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static int cgroup_is_releasable(const struct cgroup *cgrp)
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@ -913,15 +914,19 @@ static void cgroup_diput(struct dentry *dentry, struct inode *inode)
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*/
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BUG_ON(!list_empty(&cgrp->pidlists));
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simple_xattrs_free(&cgrp->xattrs);
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kfree_rcu(cgrp, rcu_head);
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} else {
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struct cfent *cfe = __d_cfe(dentry);
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struct cgroup *cgrp = dentry->d_parent->d_fsdata;
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struct cftype *cft = cfe->type;
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WARN_ONCE(!list_empty(&cfe->node) &&
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cgrp != &cgrp->root->top_cgroup,
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"cfe still linked for %s\n", cfe->type->name);
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kfree(cfe);
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simple_xattrs_free(&cft->xattrs);
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}
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iput(inode);
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}
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@ -1140,6 +1145,8 @@ static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry)
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seq_printf(seq, ",%s", ss->name);
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if (test_bit(ROOT_NOPREFIX, &root->flags))
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seq_puts(seq, ",noprefix");
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if (test_bit(ROOT_XATTR, &root->flags))
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seq_puts(seq, ",xattr");
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if (strlen(root->release_agent_path))
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seq_printf(seq, ",release_agent=%s", root->release_agent_path);
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if (clone_children(&root->top_cgroup))
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@ -1208,6 +1215,10 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
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opts->clone_children = true;
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continue;
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}
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if (!strcmp(token, "xattr")) {
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set_bit(ROOT_XATTR, &opts->flags);
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continue;
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}
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if (!strncmp(token, "release_agent=", 14)) {
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/* Specifying two release agents is forbidden */
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if (opts->release_agent)
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@ -1425,6 +1436,7 @@ static void init_cgroup_housekeeping(struct cgroup *cgrp)
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mutex_init(&cgrp->pidlist_mutex);
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INIT_LIST_HEAD(&cgrp->event_list);
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spin_lock_init(&cgrp->event_list_lock);
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simple_xattrs_init(&cgrp->xattrs);
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}
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static void init_cgroup_root(struct cgroupfs_root *root)
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@ -1769,6 +1781,8 @@ static void cgroup_kill_sb(struct super_block *sb) {
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mutex_unlock(&cgroup_root_mutex);
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mutex_unlock(&cgroup_mutex);
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simple_xattrs_free(&cgrp->xattrs);
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kill_litter_super(sb);
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cgroup_drop_root(root);
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}
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@ -2575,6 +2589,64 @@ static int cgroup_rename(struct inode *old_dir, struct dentry *old_dentry,
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return simple_rename(old_dir, old_dentry, new_dir, new_dentry);
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}
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static struct simple_xattrs *__d_xattrs(struct dentry *dentry)
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{
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if (S_ISDIR(dentry->d_inode->i_mode))
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return &__d_cgrp(dentry)->xattrs;
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else
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return &__d_cft(dentry)->xattrs;
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}
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static inline int xattr_enabled(struct dentry *dentry)
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{
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struct cgroupfs_root *root = dentry->d_sb->s_fs_info;
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return test_bit(ROOT_XATTR, &root->flags);
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}
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static bool is_valid_xattr(const char *name)
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{
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if (!strncmp(name, XATTR_TRUSTED_PREFIX, XATTR_TRUSTED_PREFIX_LEN) ||
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!strncmp(name, XATTR_SECURITY_PREFIX, XATTR_SECURITY_PREFIX_LEN))
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return true;
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return false;
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}
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static int cgroup_setxattr(struct dentry *dentry, const char *name,
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const void *val, size_t size, int flags)
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{
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if (!xattr_enabled(dentry))
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return -EOPNOTSUPP;
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if (!is_valid_xattr(name))
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return -EINVAL;
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return simple_xattr_set(__d_xattrs(dentry), name, val, size, flags);
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}
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static int cgroup_removexattr(struct dentry *dentry, const char *name)
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{
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if (!xattr_enabled(dentry))
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return -EOPNOTSUPP;
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if (!is_valid_xattr(name))
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return -EINVAL;
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return simple_xattr_remove(__d_xattrs(dentry), name);
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}
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static ssize_t cgroup_getxattr(struct dentry *dentry, const char *name,
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void *buf, size_t size)
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{
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if (!xattr_enabled(dentry))
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return -EOPNOTSUPP;
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if (!is_valid_xattr(name))
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return -EINVAL;
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return simple_xattr_get(__d_xattrs(dentry), name, buf, size);
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}
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static ssize_t cgroup_listxattr(struct dentry *dentry, char *buf, size_t size)
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{
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if (!xattr_enabled(dentry))
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return -EOPNOTSUPP;
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return simple_xattr_list(__d_xattrs(dentry), buf, size);
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}
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static const struct file_operations cgroup_file_operations = {
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.read = cgroup_file_read,
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.write = cgroup_file_write,
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@ -2583,11 +2655,22 @@ static const struct file_operations cgroup_file_operations = {
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.release = cgroup_file_release,
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};
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static const struct inode_operations cgroup_file_inode_operations = {
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.setxattr = cgroup_setxattr,
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.getxattr = cgroup_getxattr,
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.listxattr = cgroup_listxattr,
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.removexattr = cgroup_removexattr,
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};
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static const struct inode_operations cgroup_dir_inode_operations = {
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.lookup = cgroup_lookup,
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.mkdir = cgroup_mkdir,
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.rmdir = cgroup_rmdir,
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.rename = cgroup_rename,
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.setxattr = cgroup_setxattr,
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.getxattr = cgroup_getxattr,
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.listxattr = cgroup_listxattr,
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.removexattr = cgroup_removexattr,
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};
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static struct dentry *cgroup_lookup(struct inode *dir, struct dentry *dentry, unsigned int flags)
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@ -2635,6 +2718,7 @@ static int cgroup_create_file(struct dentry *dentry, umode_t mode,
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} else if (S_ISREG(mode)) {
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inode->i_size = 0;
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inode->i_fop = &cgroup_file_operations;
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inode->i_op = &cgroup_file_inode_operations;
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}
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d_instantiate(dentry, inode);
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dget(dentry); /* Extra count - pin the dentry in core */
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@ -2695,7 +2779,7 @@ static umode_t cgroup_file_mode(const struct cftype *cft)
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}
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static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
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const struct cftype *cft)
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struct cftype *cft)
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{
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struct dentry *dir = cgrp->dentry;
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struct cgroup *parent = __d_cgrp(dir);
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@ -2705,6 +2789,8 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
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umode_t mode;
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char name[MAX_CGROUP_TYPE_NAMELEN + MAX_CFTYPE_NAME + 2] = { 0 };
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simple_xattrs_init(&cft->xattrs);
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/* does @cft->flags tell us to skip creation on @cgrp? */
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if ((cft->flags & CFTYPE_NOT_ON_ROOT) && !cgrp->parent)
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return 0;
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@ -2745,9 +2831,9 @@ static int cgroup_add_file(struct cgroup *cgrp, struct cgroup_subsys *subsys,
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}
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static int cgroup_addrm_files(struct cgroup *cgrp, struct cgroup_subsys *subsys,
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const struct cftype cfts[], bool is_add)
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struct cftype cfts[], bool is_add)
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{
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const struct cftype *cft;
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struct cftype *cft;
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int err, ret = 0;
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for (cft = cfts; cft->name[0] != '\0'; cft++) {
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@ -2781,7 +2867,7 @@ static void cgroup_cfts_prepare(void)
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}
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static void cgroup_cfts_commit(struct cgroup_subsys *ss,
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const struct cftype *cfts, bool is_add)
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struct cftype *cfts, bool is_add)
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__releases(&cgroup_mutex) __releases(&cgroup_cft_mutex)
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{
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LIST_HEAD(pending);
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@ -2832,7 +2918,7 @@ static void cgroup_cfts_commit(struct cgroup_subsys *ss,
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* function currently returns 0 as long as @cfts registration is successful
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* even if some file creation attempts on existing cgroups fail.
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*/
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int cgroup_add_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
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int cgroup_add_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
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{
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struct cftype_set *set;
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@ -2862,7 +2948,7 @@ EXPORT_SYMBOL_GPL(cgroup_add_cftypes);
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* Returns 0 on successful unregistration, -ENOENT if @cfts is not
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* registered with @ss.
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*/
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int cgroup_rm_cftypes(struct cgroup_subsys *ss, const struct cftype *cfts)
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int cgroup_rm_cftypes(struct cgroup_subsys *ss, struct cftype *cfts)
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{
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struct cftype_set *set;
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