6.6-stable review patch. If anyone has any objections, please let me know.
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From: Steven Rostedt (Google) rostedt@goodmis.org
[ Upstream commit 0b18c852cc6fb8284ac0ab97e3e840974a6a8a64 ]
The saved_cmdlines have three arrays for mapping PIDs to COMMs:
- map_pid_to_cmdline[] - map_cmdline_to_pid[] - saved_cmdlines
The map_pid_to_cmdline[] is PID_MAX_DEFAULT in size and holds the index into the other arrays. The map_cmdline_to_pid[] is a mapping back to the full pid as it can be larger than PID_MAX_DEFAULT. And the saved_cmdlines[] just holds the COMMs associated to the pids.
Currently the map_pid_to_cmdline[] and saved_cmdlines[] are allocated together (in reality the saved_cmdlines is just in the memory of the rounding of the allocation of the structure as it is always allocated in powers of two). The map_cmdline_to_pid[] array is allocated separately.
Since the rounding to a power of two is rather large (it allows for 8000 elements in saved_cmdlines), also include the map_cmdline_to_pid[] array. (This drops it to 6000 by default, which is still plenty for most use cases). This saves even more memory as the map_cmdline_to_pid[] array doesn't need to be allocated.
Link: https://lore.kernel.org/linux-trace-kernel/20240212174011.068211d9@gandalf.l... Link: https://lore.kernel.org/linux-trace-kernel/20240220140703.182330529@goodmis....
Cc: Mark Rutland mark.rutland@arm.com Cc: Mathieu Desnoyers mathieu.desnoyers@efficios.com Cc: Andrew Morton akpm@linux-foundation.org Cc: Tim Chen tim.c.chen@linux.intel.com Cc: Vincent Donnefort vdonnefort@google.com Cc: Sven Schnelle svens@linux.ibm.com Cc: Mete Durlu meted@linux.ibm.com Fixes: 44dc5c41b5b1 ("tracing: Fix wasted memory in saved_cmdlines logic") Acked-by: Masami Hiramatsu (Google) mhiramat@kernel.org Signed-off-by: Steven Rostedt (Google) rostedt@goodmis.org Signed-off-by: Sasha Levin sashal@kernel.org --- kernel/trace/trace.c | 18 ++++++++---------- 1 file changed, 8 insertions(+), 10 deletions(-)
diff --git a/kernel/trace/trace.c b/kernel/trace/trace.c index be878005e3449..4f93d57cc0299 100644 --- a/kernel/trace/trace.c +++ b/kernel/trace/trace.c @@ -2316,6 +2316,10 @@ struct saved_cmdlines_buffer { }; static struct saved_cmdlines_buffer *savedcmd;
+/* Holds the size of a cmdline and pid element */ +#define SAVED_CMDLINE_MAP_ELEMENT_SIZE(s) \ + (TASK_COMM_LEN + sizeof((s)->map_cmdline_to_pid[0])) + static inline char *get_saved_cmdlines(int idx) { return &savedcmd->saved_cmdlines[idx * TASK_COMM_LEN]; @@ -2330,7 +2334,6 @@ static void free_saved_cmdlines_buffer(struct saved_cmdlines_buffer *s) { int order = get_order(sizeof(*s) + s->cmdline_num * TASK_COMM_LEN);
- kfree(s->map_cmdline_to_pid); kmemleak_free(s); free_pages((unsigned long)s, order); } @@ -2343,7 +2346,7 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val) int order;
/* Figure out how much is needed to hold the given number of cmdlines */ - orig_size = sizeof(*s) + val * TASK_COMM_LEN; + orig_size = sizeof(*s) + val * SAVED_CMDLINE_MAP_ELEMENT_SIZE(s); order = get_order(orig_size); size = 1 << (order + PAGE_SHIFT); page = alloc_pages(GFP_KERNEL, order); @@ -2355,16 +2358,11 @@ static struct saved_cmdlines_buffer *allocate_cmdlines_buffer(unsigned int val) memset(s, 0, sizeof(*s));
/* Round up to actual allocation */ - val = (size - sizeof(*s)) / TASK_COMM_LEN; + val = (size - sizeof(*s)) / SAVED_CMDLINE_MAP_ELEMENT_SIZE(s); s->cmdline_num = val;
- s->map_cmdline_to_pid = kmalloc_array(val, - sizeof(*s->map_cmdline_to_pid), - GFP_KERNEL); - if (!s->map_cmdline_to_pid) { - free_saved_cmdlines_buffer(s); - return NULL; - } + /* Place map_cmdline_to_pid array right after saved_cmdlines */ + s->map_cmdline_to_pid = (unsigned *)&s->saved_cmdlines[val * TASK_COMM_LEN];
s->cmdline_idx = 0; memset(&s->map_pid_to_cmdline, NO_CMDLINE_MAP,