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cgroup: take options parsing into ->parse_monolithic()
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Store the results in cgroup_fs_context.  There's a nasty twist caused
by the enabling/disabling subsystems - we can't do the checks sensitive
to that until cgroup_mutex gets grabbed.  Frankly, these checks are
complete bullshit (e.g. all,none combination is accepted if all subsystems
are disabled; so's cpusets,none and all,cpusets when cpusets is disabled,
etc.), but touching that would be a userland-visible behaviour change ;-/

So we do parsing in ->parse_monolithic() and have the consistency checks
done in check_cgroupfs_options(), with the latter called (on already parsed
options) from cgroup1_get_tree() and cgroup1_reconfigure().

Freeing the strdup'ed strings is done from fs_context destructor, which
somewhat simplifies the life for cgroup1_{get_tree,reconfigure}().

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
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Al Viro committed Feb 28, 2019
1 parent 7feeef5 commit f5dfb53
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Showing 3 changed files with 104 additions and 116 deletions.
23 changes: 11 additions & 12 deletions kernel/cgroup/cgroup-internal.h
View file
Expand Up @@ -41,7 +41,15 @@ extern void __init enable_debug_cgroup(void);
* The cgroup filesystem superblock creation/mount context.
*/
struct cgroup_fs_context {
char *data;
unsigned int flags; /* CGRP_ROOT_* flags */

/* cgroup1 bits */
bool cpuset_clone_children;
bool none; /* User explicitly requested empty subsystem */
bool all_ss; /* Seen 'all' option */
u16 subsys_mask; /* Selected subsystems */
char *name; /* Hierarchy name */
char *release_agent; /* Path for release notifications */
};

static inline struct cgroup_fs_context *cgroup_fc2context(struct fs_context *fc)
Expand Down Expand Up @@ -130,16 +138,6 @@ struct cgroup_mgctx {
#define DEFINE_CGROUP_MGCTX(name) \
struct cgroup_mgctx name = CGROUP_MGCTX_INIT(name)

struct cgroup_sb_opts {
u16 subsys_mask;
unsigned int flags;
char *release_agent;
bool cpuset_clone_children;
char *name;
/* User explicitly requested empty subsystem */
bool none;
};

extern struct mutex cgroup_mutex;
extern spinlock_t css_set_lock;
extern struct cgroup_subsys *cgroup_subsys[];
Expand Down Expand Up @@ -210,7 +208,7 @@ int cgroup_path_ns_locked(struct cgroup *cgrp, char *buf, size_t buflen,
struct cgroup_namespace *ns);

void cgroup_free_root(struct cgroup_root *root);
void init_cgroup_root(struct cgroup_root *root, struct cgroup_sb_opts *opts);
void init_cgroup_root(struct cgroup_root *root, struct cgroup_fs_context *ctx);
int cgroup_setup_root(struct cgroup_root *root, u16 ss_mask);
int rebind_subsystems(struct cgroup_root *dst_root, u16 ss_mask);
struct dentry *cgroup_do_mount(struct file_system_type *fs_type, int flags,
Expand Down Expand Up @@ -266,6 +264,7 @@ void cgroup1_pidlist_destroy_all(struct cgroup *cgrp);
void cgroup1_release_agent(struct work_struct *work);
void cgroup1_check_for_release(struct cgroup *cgrp);
int cgroup1_get_tree(struct fs_context *fc);
int parse_cgroup1_options(char *data, struct cgroup_fs_context *ctx);
int cgroup1_reconfigure(struct fs_context *ctx);

#endif /* __CGROUP_INTERNAL_H */
143 changes: 67 additions & 76 deletions kernel/cgroup/cgroup-v1.c
View file
Expand Up @@ -906,61 +906,47 @@ static int cgroup1_show_options(struct seq_file *seq, struct kernfs_root *kf_roo
return 0;
}

static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
int parse_cgroup1_options(char *data, struct cgroup_fs_context *ctx)
{
char *token, *o = data;
bool all_ss = false, one_ss = false;
u16 mask = U16_MAX;
struct cgroup_subsys *ss;
int nr_opts = 0;
int i;

#ifdef CONFIG_CPUSETS
mask = ~((u16)1 << cpuset_cgrp_id);
#endif

memset(opts, 0, sizeof(*opts));

while ((token = strsep(&o, ",")) != NULL) {
nr_opts++;

if (!*token)
return -EINVAL;
if (!strcmp(token, "none")) {
/* Explicitly have no subsystems */
opts->none = true;
ctx->none = true;
continue;
}
if (!strcmp(token, "all")) {
/* Mutually exclusive option 'all' + subsystem name */
if (one_ss)
return -EINVAL;
all_ss = true;
ctx->all_ss = true;
continue;
}
if (!strcmp(token, "noprefix")) {
opts->flags |= CGRP_ROOT_NOPREFIX;
ctx->flags |= CGRP_ROOT_NOPREFIX;
continue;
}
if (!strcmp(token, "clone_children")) {
opts->cpuset_clone_children = true;
ctx->cpuset_clone_children = true;
continue;
}
if (!strcmp(token, "cpuset_v2_mode")) {
opts->flags |= CGRP_ROOT_CPUSET_V2_MODE;
ctx->flags |= CGRP_ROOT_CPUSET_V2_MODE;
continue;
}
if (!strcmp(token, "xattr")) {
opts->flags |= CGRP_ROOT_XATTR;
ctx->flags |= CGRP_ROOT_XATTR;
continue;
}
if (!strncmp(token, "release_agent=", 14)) {
/* Specifying two release agents is forbidden */
if (opts->release_agent)
if (ctx->release_agent)
return -EINVAL;
opts->release_agent =
ctx->release_agent =
kstrndup(token + 14, PATH_MAX - 1, GFP_KERNEL);
if (!opts->release_agent)
if (!ctx->release_agent)
return -ENOMEM;
continue;
}
Expand All @@ -983,12 +969,12 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
return -EINVAL;
}
/* Specifying two names is forbidden */
if (opts->name)
if (ctx->name)
return -EINVAL;
opts->name = kstrndup(name,
ctx->name = kstrndup(name,
MAX_CGROUP_ROOT_NAMELEN - 1,
GFP_KERNEL);
if (!opts->name)
if (!ctx->name)
return -ENOMEM;

continue;
Expand All @@ -997,50 +983,63 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts)
for_each_subsys(ss, i) {
if (strcmp(token, ss->legacy_name))
continue;
if (!cgroup_ssid_enabled(i))
continue;
if (cgroup1_ssid_disabled(i))
continue;

/* Mutually exclusive option 'all' + subsystem name */
if (all_ss)
return -EINVAL;
opts->subsys_mask |= (1 << i);
one_ss = true;

ctx->subsys_mask |= (1 << i);
break;
}
if (i == CGROUP_SUBSYS_COUNT)
return -ENOENT;
}
return 0;
}

static int check_cgroupfs_options(struct cgroup_fs_context *ctx)
{
u16 mask = U16_MAX;
u16 enabled = 0;
struct cgroup_subsys *ss;
int i;

#ifdef CONFIG_CPUSETS
mask = ~((u16)1 << cpuset_cgrp_id);
#endif
for_each_subsys(ss, i)
if (cgroup_ssid_enabled(i) && !cgroup1_ssid_disabled(i))
enabled |= 1 << i;

ctx->subsys_mask &= enabled;

/*
* If the 'all' option was specified select all the subsystems,
* otherwise if 'none', 'name=' and a subsystem name options were
* not specified, let's default to 'all'
* In absense of 'none', 'name=' or subsystem name options,
* let's default to 'all'.
*/
if (all_ss || (!one_ss && !opts->none && !opts->name))
for_each_subsys(ss, i)
if (cgroup_ssid_enabled(i) && !cgroup1_ssid_disabled(i))
opts->subsys_mask |= (1 << i);
if (!ctx->subsys_mask && !ctx->none && !ctx->name)
ctx->all_ss = true;

if (ctx->all_ss) {
/* Mutually exclusive option 'all' + subsystem name */
if (ctx->subsys_mask)
return -EINVAL;
/* 'all' => select all the subsystems */
ctx->subsys_mask = enabled;
}

/*
* We either have to specify by name or by subsystems. (So all
* empty hierarchies must have a name).
*/
if (!opts->subsys_mask && !opts->name)
if (!ctx->subsys_mask && !ctx->name)
return -EINVAL;

/*
* Option noprefix was introduced just for backward compatibility
* with the old cpuset, so we allow noprefix only if mounting just
* the cpuset subsystem.
*/
if ((opts->flags & CGRP_ROOT_NOPREFIX) && (opts->subsys_mask & mask))
if ((ctx->flags & CGRP_ROOT_NOPREFIX) && (ctx->subsys_mask & mask))
return -EINVAL;

/* Can't specify "none" and some subsystems */
if (opts->subsys_mask && opts->none)
if (ctx->subsys_mask && ctx->none)
return -EINVAL;

return 0;
Expand All @@ -1052,28 +1051,27 @@ int cgroup1_reconfigure(struct fs_context *fc)
struct kernfs_root *kf_root = kernfs_root_from_sb(fc->root->d_sb);
struct cgroup_root *root = cgroup_root_from_kf(kf_root);
int ret = 0;
struct cgroup_sb_opts opts;
u16 added_mask, removed_mask;

cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);

/* See what subsystems are wanted */
ret = parse_cgroupfs_options(ctx->data, &opts);
ret = check_cgroupfs_options(ctx);
if (ret)
goto out_unlock;

if (opts.subsys_mask != root->subsys_mask || opts.release_agent)
if (ctx->subsys_mask != root->subsys_mask || ctx->release_agent)
pr_warn("option changes via remount are deprecated (pid=%d comm=%s)\n",
task_tgid_nr(current), current->comm);

added_mask = opts.subsys_mask & ~root->subsys_mask;
removed_mask = root->subsys_mask & ~opts.subsys_mask;
added_mask = ctx->subsys_mask & ~root->subsys_mask;
removed_mask = root->subsys_mask & ~ctx->subsys_mask;

/* Don't allow flags or name to change at remount */
if ((opts.flags ^ root->flags) ||
(opts.name && strcmp(opts.name, root->name))) {
if ((ctx->flags ^ root->flags) ||
(ctx->name && strcmp(ctx->name, root->name))) {
pr_err("option or name mismatch, new: 0x%x \"%s\", old: 0x%x \"%s\"\n",
opts.flags, opts.name ?: "", root->flags, root->name);
ctx->flags, ctx->name ?: "", root->flags, root->name);
ret = -EINVAL;
goto out_unlock;
}
Expand All @@ -1090,17 +1088,15 @@ int cgroup1_reconfigure(struct fs_context *fc)

WARN_ON(rebind_subsystems(&cgrp_dfl_root, removed_mask));

if (opts.release_agent) {
if (ctx->release_agent) {
spin_lock(&release_agent_path_lock);
strcpy(root->release_agent_path, opts.release_agent);
strcpy(root->release_agent_path, ctx->release_agent);
spin_unlock(&release_agent_path_lock);
}

trace_cgroup_remount(root);

out_unlock:
kfree(opts.release_agent);
kfree(opts.name);
mutex_unlock(&cgroup_mutex);
return ret;
}
Expand All @@ -1117,7 +1113,6 @@ int cgroup1_get_tree(struct fs_context *fc)
{
struct cgroup_namespace *ns = current->nsproxy->cgroup_ns;
struct cgroup_fs_context *ctx = cgroup_fc2context(fc);
struct cgroup_sb_opts opts;
struct cgroup_root *root;
struct cgroup_subsys *ss;
struct dentry *dentry;
Expand All @@ -1130,7 +1125,7 @@ int cgroup1_get_tree(struct fs_context *fc)
cgroup_lock_and_drain_offline(&cgrp_dfl_root.cgrp);

/* First find the desired set of subsystems */
ret = parse_cgroupfs_options(ctx->data, &opts);
ret = check_cgroupfs_options(ctx);
if (ret)
goto out_unlock;

Expand All @@ -1142,7 +1137,7 @@ int cgroup1_get_tree(struct fs_context *fc)
* starting. Testing ref liveliness is good enough.
*/
for_each_subsys(ss, i) {
if (!(opts.subsys_mask & (1 << i)) ||
if (!(ctx->subsys_mask & (1 << i)) ||
ss->root == &cgrp_dfl_root)
continue;

Expand All @@ -1166,8 +1161,8 @@ int cgroup1_get_tree(struct fs_context *fc)
* name matches but sybsys_mask doesn't, we should fail.
* Remember whether name matched.
*/
if (opts.name) {
if (strcmp(opts.name, root->name))
if (ctx->name) {
if (strcmp(ctx->name, root->name))
continue;
name_match = true;
}
Expand All @@ -1176,15 +1171,15 @@ int cgroup1_get_tree(struct fs_context *fc)
* If we asked for subsystems (or explicitly for no
* subsystems) then they must match.
*/
if ((opts.subsys_mask || opts.none) &&
(opts.subsys_mask != root->subsys_mask)) {
if ((ctx->subsys_mask || ctx->none) &&
(ctx->subsys_mask != root->subsys_mask)) {
if (!name_match)
continue;
ret = -EBUSY;
goto out_unlock;
}

if (root->flags ^ opts.flags)
if (root->flags ^ ctx->flags)
pr_warn("new mount options do not match the existing superblock, will be ignored\n");

ret = 0;
Expand All @@ -1196,7 +1191,7 @@ int cgroup1_get_tree(struct fs_context *fc)
* specification is allowed for already existing hierarchies but we
* can't create new one without subsys specification.
*/
if (!opts.subsys_mask && !opts.none) {
if (!ctx->subsys_mask && !ctx->none) {
ret = -EINVAL;
goto out_unlock;
}
Expand All @@ -1213,24 +1208,20 @@ int cgroup1_get_tree(struct fs_context *fc)
goto out_unlock;
}

init_cgroup_root(root, &opts);
init_cgroup_root(root, ctx);

ret = cgroup_setup_root(root, opts.subsys_mask);
ret = cgroup_setup_root(root, ctx->subsys_mask);
if (ret)
cgroup_free_root(root);

out_unlock:
if (!ret && !percpu_ref_tryget_live(&root->cgrp.self.refcnt)) {
mutex_unlock(&cgroup_mutex);
msleep(10);
ret = restart_syscall();
goto out_free;
return restart_syscall();
}
mutex_unlock(&cgroup_mutex);
out_free:
kfree(opts.release_agent);
kfree(opts.name);

if (ret)
return ret;

Expand Down

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