cgroup_clear_directroy is called by cgroup_d_remove_dir and cgroup_remount.
when we call cgroup_remount to remount the cgroup,the subsystem may be unlinked from cgroupfs_root->subsys_list in rebind_subsystem,this subsystem's files will not be removed in cgroup_clear_directroy. And the system will panic when we try to access these files. this patch fix it. Signed-off-by: Gao feng <[email protected]> --- kernel/cgroup.c | 86 ++++++++++++++++++++++++++++++++++-------------------- 1 files changed, 54 insertions(+), 32 deletions(-) diff --git a/kernel/cgroup.c b/kernel/cgroup.c index e5233b7..90429d5 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -982,10 +982,14 @@ 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; + int i; - for_each_subsys(cgrp->root, ss) { + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { struct cftype_set *set; + struct cgroup_subsys *ss = subsys[i]; + + if (ss == NULL) + continue; if (!test_bit(ss->subsys_id, &subsys_mask)) continue; list_for_each_entry(set, &ss->cftsets, node) @@ -1160,6 +1164,40 @@ static int cgroup_show_options(struct seq_file *seq, struct dentry *dentry) return 0; } +static int cgroup_get_module_refcounts(unsigned long subsys_mask) +{ + int i; + bool module_pin_failed = false; + + for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { + unsigned long bit = 1UL << i; + + if (!(bit & subsys_mask)) + continue; + if (!try_module_get(subsys[i]->module)) { + module_pin_failed = true; + break; + } + } + if (module_pin_failed) { + /* + * oops, one of the modules was going away. this means that we + * raced with a module_delete call, and to the user this is + * essentially a "subsystem doesn't exist" case. + */ + for (i--; i >= 0; i--) { + /* drop refcounts only on the ones we took */ + unsigned long bit = 1UL << i; + + if (!(bit & subsys_mask)) + continue; + module_put(subsys[i]->module); + } + return -ENOENT; + } + return 0; +} + struct cgroup_sb_opts { unsigned long subsys_mask; unsigned long flags; @@ -1185,7 +1223,6 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) bool all_ss = false, one_ss = false; unsigned long mask = (unsigned long)-1; int i; - bool module_pin_failed = false; BUG_ON(!mutex_is_locked(&cgroup_mutex)); @@ -1324,34 +1361,8 @@ static int parse_cgroupfs_options(char *data, struct cgroup_sb_opts *opts) * take duplicate reference counts on a subsystem that's already used, * but rebind_subsystems handles this case. */ - for (i = 0; i < CGROUP_SUBSYS_COUNT; i++) { - unsigned long bit = 1UL << i; - if (!(bit & opts->subsys_mask)) - continue; - if (!try_module_get(subsys[i]->module)) { - module_pin_failed = true; - break; - } - } - if (module_pin_failed) { - /* - * oops, one of the modules was going away. this means that we - * raced with a module_delete call, and to the user this is - * essentially a "subsystem doesn't exist" case. - */ - for (i--; i >= 0; i--) { - /* drop refcounts only on the ones we took */ - unsigned long bit = 1UL << i; - - if (!(bit & opts->subsys_mask)) - continue; - module_put(subsys[i]->module); - } - return -ENOENT; - } - - return 0; + return cgroup_get_module_refcounts(opts->subsys_mask); } static void drop_parsed_module_refcounts(unsigned long subsys_mask) @@ -1392,23 +1403,34 @@ static int cgroup_remount(struct super_block *sb, int *flags, char *data) removed_mask = root->subsys_mask & ~opts.subsys_mask; /* Don't allow flags or name to change at remount */ + ret = -EINVAL; if (opts.flags != root->flags || (opts.name && strcmp(opts.name, root->name))) { - ret = -EINVAL; drop_parsed_module_refcounts(opts.subsys_mask); goto out_unlock; } - ret = rebind_subsystems(root, opts.subsys_mask); + /* + * Add the reference of these removed subsystem,we + * need use subsystems to remove their cgroup files. + */ + ret = cgroup_get_module_refcounts(removed_mask); if (ret) { drop_parsed_module_refcounts(opts.subsys_mask); goto out_unlock; } + ret = rebind_subsystems(root, opts.subsys_mask); + if (ret) { + drop_parsed_module_refcounts(opts.subsys_mask | removed_mask); + goto out_unlock; + } + /* clear out any existing files and repopulate subsystem files */ cgroup_clear_directory(cgrp->dentry, false, removed_mask); /* re-populate subsystem files */ cgroup_populate_dir(cgrp, false, added_mask); + drop_parsed_module_refcounts(removed_mask); if (opts.release_agent) strcpy(root->release_agent_path, opts.release_agent); -- 1.7.7.6 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
