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Message-ID: <20220318123058.348938b1@gandalf.local.home> Date: Fri, 18 Mar 2022 12:30:58 -0400 From: Steven Rostedt <rostedt@...dmis.org> To: Sven Schnelle <svens@...ux.ibm.com> Cc: Ritesh Harjani <riteshh@...ux.ibm.com>, linux-ext4@...r.kernel.org, Jan Kara <jack@...e.cz>, "Theodore Ts'o" <tytso@....edu>, Harshad Shirwadkar <harshadshirwadkar@...il.com>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, stable@...nel.org Subject: Re: [PATCHv3 02/10] ext4: Fix ext4_fc_stats trace point On Thu, 17 Mar 2022 14:39:38 -0400 Steven Rostedt <rostedt@...dmis.org> wrote: > [ here I wanted to add a patch, but I haven't figured out the best way to > fix it yet. ] Care to try this patch? -- Steve diff --git a/kernel/trace/trace_events.c b/kernel/trace/trace_events.c index 7b558c72f595..e11e167b7809 100644 --- a/kernel/trace/trace_events.c +++ b/kernel/trace/trace_events.c @@ -40,6 +40,14 @@ static LIST_HEAD(ftrace_generic_fields); static LIST_HEAD(ftrace_common_fields); static bool eventdir_initialized; +static LIST_HEAD(module_strings); + +struct module_string { + struct list_head next; + struct module *module; + char *str; +}; + #define GFP_TRACE (GFP_KERNEL | __GFP_ZERO) static struct kmem_cache *field_cachep; @@ -2643,14 +2651,40 @@ static void update_event_printk(struct trace_event_call *call, } } +static void add_str_to_module(struct module *module, char *str) +{ + struct module_string *modstr; + + modstr = kmalloc(sizeof(*modstr), GFP_KERNEL); + + /* + * If we failed to allocate memory here, then we'll just + * let the str memory leak when the module is removed. + * If this fails to allocate, there's worse problems than + * a leaked string on module removal. + */ + if (WARN_ON_ONCE(!modstr)) + return; + + modstr->module = module; + modstr->str = str; + + list_add(&modstr->next, &module_strings); +} + static void update_event_fields(struct trace_event_call *call, struct trace_eval_map *map) { struct ftrace_event_field *field; struct list_head *head; char *ptr; + char *str; int len = strlen(map->eval_string); + /* Dynamic events should never have field maps */ + if (WARN_ON_ONCE(call->flags & TRACE_EVENT_FL_DYNAMIC)) + return; + head = trace_get_fields(call); list_for_each_entry(field, head, link) { ptr = strchr(field->type, '['); @@ -2664,9 +2698,26 @@ static void update_event_fields(struct trace_event_call *call, if (strncmp(map->eval_string, ptr, len) != 0) continue; + str = kstrdup(field->type, GFP_KERNEL); + if (WARN_ON_ONCE(!str)) + return; + ptr = str + (ptr - field->type); ptr = eval_replace(ptr, map, len); /* enum/sizeof string smaller than value */ - WARN_ON_ONCE(!ptr); + if (WARN_ON_ONCE(!ptr)) { + kfree(str); + continue; + } + + /* + * If the event is part of a module, then we need to free the string + * when the module is removed. Otherwise, it will stay allocated + * until a reboot. + */ + if (call->module) + add_str_to_module(call->module, str); + + field->type = str; } } @@ -2893,6 +2944,7 @@ static void trace_module_add_events(struct module *mod) static void trace_module_remove_events(struct module *mod) { struct trace_event_call *call, *p; + struct module_string *modstr, *m; down_write(&trace_event_sem); list_for_each_entry_safe(call, p, &ftrace_events, list) { @@ -2901,6 +2953,14 @@ static void trace_module_remove_events(struct module *mod) if (call->module == mod) __trace_remove_event_call(call); } + /* Check for any strings allocade for this module */ + list_for_each_entry_safe(modstr, m, &module_strings, next) { + if (modstr->module != mod) + continue; + list_del(&modstr->next); + kfree(modstr->str); + kfree(modstr); + } up_write(&trace_event_sem); /*
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