fs: dlm: define max send buffer

This patch will set the maximum transmit buffer size for rcom messages
with "names" to 4096 bytes. It's a leftover change of
commit 4798cbbfbd00 ("fs: dlm: rework receive handling"). Fact is that we
cannot allocate a contiguous transmit buffer length above of 4096 bytes.
It seems at some places the upper layer protocol will calculate according
to dlm_config.ci_buffer_size the possible payload of a dlm recovery
message. As compiler setting we will use now the maximum possible
message which dlm can send out. Commit 4e192ee68e5af ("fs: dlm: disallow
buffer size below default") disallow a buffer setting smaller than the
4096 bytes and above 4096 bytes is definitely wrong because we will then
write out of buffer space as we cannot allocate a contiguous buffer above
4096 bytes. The ci_buffer_size is still there to define the possible
maximum receive buffer size of a recvmsg() which should be at least the
maximum possible dlm message size.

Signed-off-by: Alexander Aring <aahringo@redhat.com>
Signed-off-by: David Teigland <teigland@redhat.com>

1 files changed, 2 insertions, 0 deletions

diff --git a/fs/dlm/lowcomms.h b/fs/dlm/lowcomms.h
index 687b2894e469..0918f9376489 100644
--- a/fs/dlm/lowcomms.h
+++ b/fs/dlm/lowcomms.h
@@ -12,6 +12,8 @@
 #ifndef __LOWCOMMS_DOT_H__
 #define __LOWCOMMS_DOT_H__
 
+#define LOWCOMMS_MAX_TX_BUFFER_LEN	4096
+
 int dlm_lowcomms_start(void);
 void dlm_lowcomms_stop(void);
 void dlm_lowcomms_exit(void);