[RFC PATCH 07/17] seq_buf: Add seq_buf_can_fit() helper function

From: Wang Long
Date: Thu May 14 2015 - 07:39:42 EST


From: "Steven Rostedt (Red Hat)" <rostedt@xxxxxxxxxxx>

commit 9b77215382b42ef9c5b34293ad3a95332e5b71ef upsteam.

Add a seq_buf_can_fit() helper function that removes the possible mistakes
of comparing the seq_buf length plus added data compared to the size of
the buffer.

Link: http://lkml.kernel.org/r/20141118164025.GL23958@xxxxxxxxxxxxxxx

Reviewed-by: Petr Mladek <pmladek@xxxxxxx>
[wanglong: backport to 3.10 stable]
Signed-off-by: Wang Long <long.wanglong@xxxxxxxxxx>
Signed-off-by: Steven Rostedt <rostedt@xxxxxxxxxxx>
---
kernel/trace/seq_buf.c | 23 ++++++++++++++++++-----
1 file changed, 18 insertions(+), 5 deletions(-)

diff --git a/kernel/trace/seq_buf.c b/kernel/trace/seq_buf.c
index ce17f65..6fc9d02 100644
--- a/kernel/trace/seq_buf.c
+++ b/kernel/trace/seq_buf.c
@@ -17,6 +17,19 @@
#include <linux/seq_buf.h>

/**
+ * seq_buf_can_fit - can the new data fit in the current buffer?
+ * @s: the seq_buf descriptor
+ * @len: The length to see if it can fit in the current buffer
+ *
+ * Returns true if there's enough unused space in the seq_buf buffer
+ * to fit the amount of new data according to @len.
+ */
+static bool seq_buf_can_fit(struct seq_buf *s, size_t len)
+{
+ return s->len + len < s->size;
+}
+
+/**
* seq_buf_print_seq - move the contents of seq_buf into a seq_file
* @m: the seq_file descriptor that is the destination
* @s: the seq_buf descriptor that is the source.
@@ -48,7 +61,7 @@ int seq_buf_vprintf(struct seq_buf *s, const char *fmt, va_list args)

if (s->len < s->size) {
len = vsnprintf(s->buffer + s->len, s->size - s->len, fmt, args);
- if (s->len + len < s->size) {
+ if (seq_buf_can_fit(s, len)) {
s->len += len;
return 0;
}
@@ -137,7 +150,7 @@ int seq_buf_bprintf(struct seq_buf *s, const char *fmt, const u32 *binary)

if (s->len < s->size) {
ret = bstr_printf(s->buffer + s->len, len, fmt, binary);
- if (s->len + ret < s->size) {
+ if (seq_buf_can_fit(s, ret)) {
s->len += ret;
return 0;
}
@@ -161,7 +174,7 @@ int seq_buf_puts(struct seq_buf *s, const char *str)

WARN_ON(s->size == 0);

- if (s->len + len < s->size) {
+ if (seq_buf_can_fit(s, len)) {
memcpy(s->buffer + s->len, str, len);
s->len += len;
return 0;
@@ -183,7 +196,7 @@ int seq_buf_putc(struct seq_buf *s, unsigned char c)
{
WARN_ON(s->size == 0);

- if (s->len + 1 < s->size) {
+ if (seq_buf_can_fit(s, 1)) {
s->buffer[s->len++] = c;
return 0;
}
@@ -207,7 +220,7 @@ int seq_buf_putmem(struct seq_buf *s, const void *mem, unsigned int len)
{
WARN_ON(s->size == 0);

- if (s->len + len < s->size) {
+ if (seq_buf_can_fit(s, len)) {
memcpy(s->buffer + s->len, mem, len);
s->len += len;
return 0;
--
1.8.3.4

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