[Libguestfs] [nbdkit PATCH] plugins: Use static buffer for plugin_zeroes
No need to calloc/free a buffer every time NBD_CMD_WRITE_ZEROES has to
fall back to a .pread call. Just reserve the maximum buffer up front
in our bss.
Signed-off-by: Eric Blake <eblake(a)redhat.com>
---
I noticed that buf was a candidate for CLEANUP_FREE, but then further
noticed that we can avoid the calloc/free altogether if we don't mind
the bss being 64M larger.
server/plugins.c | 10 ++--------
1 file changed, 2 insertions(+), 8 deletions(-)
diff --git a/server/plugins.c b/server/plugins.c
index 947bb6d..acdfa1f 100644
--- a/server/plugins.c
+++ b/server/plugins.c
@@ -594,7 +594,7 @@ plugin_zero (struct backend *b, struct connection *conn,
uint32_t count, uint64_t offset, uint32_t flags, int *err)
{
struct backend_plugin *p = container_of (b, struct backend_plugin, backend);
- char *buf;
+ static const char buf[MAX_REQUEST_SIZE];
uint32_t limit;
int r = -1;
bool may_trim = flags & NBDKIT_FLAG_MAY_TRIM;
@@ -639,12 +639,7 @@ plugin_zero (struct backend *b, struct connection *conn,
assert (p->plugin.pwrite || p->plugin._pwrite_old);
flags &= ~NBDKIT_FLAG_MAY_TRIM;
threadlocal_set_error (0);
- limit = count < MAX_REQUEST_SIZE ? count : MAX_REQUEST_SIZE;
- buf = calloc (limit, 1);
- if (!buf) {
- *err = ENOMEM;
- return -1;
- }
+ limit = count < sizeof (buf) ? count : sizeof (buf);
while (count) {
r = plugin_pwrite (b, conn, buf, limit, offset, flags, err);
@@ -656,7 +651,6 @@ plugin_zero (struct backend *b, struct connection *conn,
}
*err = errno;
- free (buf);
errno = *err;
done:
--
2.20.1