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MEDIUM: buffer: add a new buf_wanted dummy buffer to report failed allocations

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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.
This commit is contained in:
Willy Tarreau 2014-11-24 11:55:08 +01:00
parent 2a4b54359b
commit f2f7d6b27b
3 changed files with 22 additions and 12 deletions
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22
include/common/buffer.h
View File

@ -41,6 +41,7 @@ struct buffer {
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 @@ static inline void b_reset(struct buffer *buf)
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) */

8
src/buffer.c
View File

@ -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()

4
src/proto_http.c
View File

@ -6516,7 +6516,7 @@ int http_response_forward_body(struct session *s, struct channel *res, int an_bi
{
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 @@ int http_response_forward_body(struct session *s, struct channel *res, int an_bi
* 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 */