MEDIUM: buffer: add a new buf_wanted dummy buffer to report failed allocations
Doing so ensures that even when no memory is available, we leave the
channel in a sane condition. There's a special case in proto_http.c
regarding the compression, we simply pre-allocate the tmpbuf to point
to the dummy buffer. Not reusing &buf_empty for this allows the rest
of the code to differenciate an empty buffer that's not used from an
empty buffer that results from a failed allocation which has the same
semantics as a buffer full.
diff --git a/include/common/buffer.h b/include/common/buffer.h
index 5ea8fab..4e55285 100644
--- a/include/common/buffer.h
+++ b/include/common/buffer.h
@@ -41,6 +41,7 @@
extern struct pool_head *pool2_buffer;
extern struct buffer buf_empty;
+extern struct buffer buf_wanted;
int init_buffer();
int buffer_replace2(struct buffer *b, char *pos, char *end, const char *str, int len);
@@ -396,18 +397,23 @@
buf->p = buf->data;
}
-/* Allocates a buffer and replaces *buf with this buffer. No control is made
- * to check if *buf already pointed to another buffer. The allocated buffer
- * is returned, or NULL in case no memory is available.
+/* Allocates a buffer and replaces *buf with this buffer. If no memory is
+ * available, &buf_wanted is used instead. No control is made to check if *buf
+ * already pointed to another buffer. The allocated buffer is returned, or
+ * NULL in case no memory is available.
*/
static inline struct buffer *b_alloc(struct buffer **buf)
{
- *buf = pool_alloc_dirty(pool2_buffer);
- if (likely(*buf)) {
- (*buf)->size = pool2_buffer->size - sizeof(struct buffer);
- b_reset(*buf);
+ struct buffer *b;
+
+ *buf = &buf_wanted;
+ b = pool_alloc_dirty(pool2_buffer);
+ if (likely(b)) {
+ b->size = pool2_buffer->size - sizeof(struct buffer);
+ b_reset(b);
+ *buf = b;
}
- return *buf;
+ return b;
}
/* Releases buffer *buf (no check of emptiness) */
diff --git a/src/buffer.c b/src/buffer.c
index 7691026..d9301bf 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -22,10 +22,14 @@
struct pool_head *pool2_buffer;
-/* this buffer is used to have a valid pointer to an empty buffer in channels
- * which convey no more data.
+/* These buffers are used to always have a valid pointer to an empty buffer in
+ * channels. The first buffer is set once a buffer is empty. The second one is
+ * set when a buffer is desired but no more are available. It helps knowing
+ * what channel wants a buffer. They can reliably be exchanged, the split
+ * between the two is only an optimization.
*/
struct buffer buf_empty = { .p = buf_empty.data };
+struct buffer buf_wanted = { .p = buf_wanted.data };
/* perform minimal intializations, report 0 in case of error, 1 if OK. */
int init_buffer()
diff --git a/src/proto_http.c b/src/proto_http.c
index ee1a812..b4861ce 100644
--- a/src/proto_http.c
+++ b/src/proto_http.c
@@ -6516,7 +6516,7 @@
{
struct http_txn *txn = &s->txn;
struct http_msg *msg = &s->txn.rsp;
- static struct buffer *tmpbuf = NULL;
+ static struct buffer *tmpbuf = &buf_empty;
int compressing = 0;
int ret;
@@ -6570,7 +6570,7 @@
* output of compressed data, and in CRLF state to let the
* TRAILERS state finish the job of removing the trailing CRLF.
*/
- if (unlikely(tmpbuf == NULL)) {
+ if (unlikely(!tmpbuf->size)) {
/* this is the first time we need the compression buffer */
if (b_alloc(&tmpbuf) == NULL)
goto aborted_xfer; /* no memory */