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Subject[PATCH] trace_output: change struct trace_seq's size to PAGE_SIZE

It's not very good that we allocate pages with page_order > 1.
So we change struct trace_seq's size to PAGE_SIZE.
Where we allocate a struct trace_seq:

kernel/trace/trace.c:3720: s = kmalloc(sizeof(*s), GFP_KERNEL);
kernel/trace/trace_events.c:539: s = kmalloc(sizeof(*s), GFP_KERNEL);
kernel/trace/trace_events.c:580: s = kmalloc(sizeof(*s), GFP_KERNEL);
kernel/trace/trace_events.c:604: s = kmalloc(sizeof(*s), GFP_KERNEL);
kernel/trace/trace_events.c:660: s = kmalloc(sizeof(*s), GFP_KERNEL);
kernel/trace/trace_events.c:715: s = kmalloc(sizeof(*s), GFP_KERNEL);
kernel/trace/trace_ksym.c:230: s = kmalloc(sizeof(*s), GFP_KERNEL);

Signed-off-by: Lai Jiangshan <laijs@cn.fujitsu.com>
---
diff --git a/include/linux/trace_seq.h b/include/linux/trace_seq.h
index 09077f6..128d86a 100644
--- a/include/linux/trace_seq.h
+++ b/include/linux/trace_seq.h
@@ -7,13 +7,24 @@

/*
* Trace sequences are used to allow a function to call several other functions
- * to create a string of data to use (up to a max of PAGE_SIZE).
+ * to create a string of data to use (up to a max of TRACE_SEQ_BUFFER_SIZE).
*/

struct trace_seq {
- unsigned char buffer[PAGE_SIZE];
- unsigned int len;
- unsigned int readpos;
+ union {
+ struct {
+ unsigned int len;
+ unsigned int readpos;
+ unsigned char buffer[];
+ };
+ unsigned char __make_it_PAGE_SIZE[PAGE_SIZE];
+ };
+};
+
+#define TRACE_SEQ_BUFFER_SIZE (PAGE_SIZE - offsetof(struct trace_seq, buffer))
+
+struct __check_trace_seq_size {
+ int __check[-!!(sizeof(struct trace_seq) - PAGE_SIZE)];
};

static inline void
diff --git a/kernel/trace/trace_output.c b/kernel/trace/trace_output.c
index b6c12c6..578e347 100644
--- a/kernel/trace/trace_output.c
+++ b/kernel/trace/trace_output.c
@@ -25,7 +25,10 @@ static int next_event_type = __TRACE_LAST_TYPE + 1;

void trace_print_seq(struct seq_file *m, struct trace_seq *s)
{
- int len = s->len >= PAGE_SIZE ? PAGE_SIZE - 1 : s->len;
+ int len = s->len;
+
+ if (len >= TRACE_SEQ_BUFFER_SIZE)
+ len = TRACE_SEQ_BUFFER_SIZE - 1;

seq_write(m, s->buffer, len);

@@ -81,7 +84,7 @@ enum print_line_t trace_print_printk_msg_only(struct trace_iterator *iter)
int
trace_seq_printf(struct trace_seq *s, const char *fmt, ...)
{
- int len = (PAGE_SIZE - 1) - s->len;
+ int len = (TRACE_SEQ_BUFFER_SIZE - 1) - s->len;
va_list ap;
int ret;

@@ -116,7 +119,7 @@ EXPORT_SYMBOL_GPL(trace_seq_printf);
int
trace_seq_vprintf(struct trace_seq *s, const char *fmt, va_list args)
{
- int len = (PAGE_SIZE - 1) - s->len;
+ int len = (TRACE_SEQ_BUFFER_SIZE - 1) - s->len;
int ret;

if (!len)
@@ -136,7 +139,7 @@ EXPORT_SYMBOL_GPL(trace_seq_vprintf);

int trace_seq_bprintf(struct trace_seq *s, const char *fmt, const u32 *binary)
{
- int len = (PAGE_SIZE - 1) - s->len;
+ int len = (TRACE_SEQ_BUFFER_SIZE - 1) - s->len;
int ret;

if (!len)
@@ -167,7 +170,7 @@ int trace_seq_puts(struct trace_seq *s, const char *str)
{
int len = strlen(str);

- if (len > ((PAGE_SIZE - 1) - s->len))
+ if (len > ((TRACE_SEQ_BUFFER_SIZE - 1) - s->len))
return 0;

memcpy(s->buffer + s->len, str, len);
@@ -178,7 +181,7 @@ int trace_seq_puts(struct trace_seq *s, const char *str)

int trace_seq_putc(struct trace_seq *s, unsigned char c)
{
- if (s->len >= (PAGE_SIZE - 1))
+ if (s->len >= (TRACE_SEQ_BUFFER_SIZE - 1))
return 0;

s->buffer[s->len++] = c;
@@ -188,7 +191,7 @@ int trace_seq_putc(struct trace_seq *s, unsigned char c)

int trace_seq_putmem(struct trace_seq *s, const void *mem, size_t len)
{
- if (len > ((PAGE_SIZE - 1) - s->len))
+ if (len > ((TRACE_SEQ_BUFFER_SIZE - 1) - s->len))
return 0;

memcpy(s->buffer + s->len, mem, len);
@@ -220,7 +223,7 @@ void *trace_seq_reserve(struct trace_seq *s, size_t len)
{
void *ret;

- if (len > ((PAGE_SIZE - 1) - s->len))
+ if (len > ((TRACE_SEQ_BUFFER_SIZE - 1) - s->len))
return NULL;

ret = s->buffer + s->len;
@@ -233,9 +236,9 @@ int trace_seq_path(struct trace_seq *s, struct path *path)
{
unsigned char *p;

- if (s->len >= (PAGE_SIZE - 1))
+ if (s->len >= (TRACE_SEQ_BUFFER_SIZE - 1))
return 0;
- p = d_path(path, s->buffer + s->len, PAGE_SIZE - s->len);
+ p = d_path(path, s->buffer + s->len, TRACE_SEQ_BUFFER_SIZE - s->len);
if (!IS_ERR(p)) {
p = mangle_path(s->buffer + s->len, p, "\n");
if (p) {


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