[Openais] [PATCH 1/2] flight recorder: switch from int to bytes for requested allocation

[Fabio M. Di Nitto]

The flight recoder buffer size as specified in LOGSYS_DECLARE_SYSTEM
or _logsys_rec_init was expressed in number of ints. A developer asking
to allocate 512K would get a 2M allocation on a machine with sizeof(int) = 4.

This is confusing and the patch addresses it:

- rename rec_size to fltsize for external API (no type change),
  because rec_size is used many times internally for other reasons
  and it can be confusing.

- rename size to fltsize in _logsys_rec_init.

- document what we allocate and why.

- swap comments around to match the code.

- introduce a simple macro to perform rounding (stolen from linux-2.6.git).

Signed-off-by: Fabio M. Di Nitto <fdinitto at redhat.com>
---
:100644 100644 90efdf8... 904e631... M	exec/logsys.c
:100644 100644 b34b327... 19e5dae... M	include/corosync/engine/logsys.h
:100644 100644 e19836e... 6017f10... M	man/logsys_overview.8
 exec/logsys.c                    |   31 ++++++++++++++++++++++++++-----
 include/corosync/engine/logsys.h |    4 ++--
 man/logsys_overview.8            |    5 +++--
 3 files changed, 31 insertions(+), 9 deletions(-)

diff --git a/exec/logsys.c b/exec/logsys.c
index 90efdf8..904e631 100644
--- a/exec/logsys.c
+++ b/exec/logsys.c
@@ -66,6 +66,8 @@
 
 #define MIN(x,y) ((x) < (y) ? (x) : (y))
 
+#define roundup(x, y) ((((x) + ((y) - 1)) / (y)) * (y))
+
 /*
  * syslog prioritynames, facility names to value mapping
  * Some C libraries build this in to their headers, but it is non-portable
@@ -1044,17 +1046,36 @@ int _logsys_wthread_create (void)
 	return (0);
 }
 
-int _logsys_rec_init (unsigned int size)
+int _logsys_rec_init (unsigned int fltsize)
 {
 	/*
-	 * First record starts at zero
-	 * Last record ends at zero
+	 * we need to allocate:
+	 * - requested size +
+	 *   2 extra unsigned ints for HEAD/TAIL tracking
+	 *
+	 * then round it up to the next PAGESIZE
 	 */
-	flt_data = malloc ((size + 2) * sizeof (unsigned int));
+	size_t flt_real_size;
+
+	flt_real_size = roundup(
+			(fltsize + (2 * sizeof (unsigned int))),
+			sysconf(_SC_PAGESIZE));
+
+	flt_data = malloc (flt_real_size);
 	if (flt_data == NULL) {
 		return (-1);
 	}
-	flt_data_size = size;
+
+	/*
+	 * flt_data_size tracks data by ints and not bytes/chars.
+	 */
+
+	flt_data_size = (flt_real_size / sizeof (unsigned int));
+
+	/*
+	 * First record starts at zero
+	 * Last record ends at zero
+	 */
 	flt_data[FDHEAD_INDEX] = 0;
 	flt_data[FDTAIL_INDEX] = 0;
 
diff --git a/include/corosync/engine/logsys.h b/include/corosync/engine/logsys.h
index b34b327..19e5dae 100644
--- a/include/corosync/engine/logsys.h
+++ b/include/corosync/engine/logsys.h
@@ -305,7 +305,7 @@ extern void *logsys_rec_end;
 #define LOGSYS_REC_END (&logsys_rec_end)
 
 #define LOGSYS_DECLARE_SYSTEM(name,mode,debug,file,file_priority,	\
-		syslog_facility,syslog_priority,format,rec_size)	\
+		syslog_facility,syslog_priority,format,fltsize)		\
 __attribute__ ((constructor))						\
 static void logsys_system_init (void)					\
 {									\
@@ -322,7 +322,7 @@ static void logsys_system_init (void)					\
 		exit (-1);						\
 	}								\
 									\
-	if (_logsys_rec_init (rec_size) < 0) {				\
+	if (_logsys_rec_init (fltsize) < 0) {				\
 		fprintf (stderr,					\
 			"Unable to initialize log flight recorder.\n");	\
 		exit (-1);						\
diff --git a/man/logsys_overview.8 b/man/logsys_overview.8
index e19836e..6017f10 100644
--- a/man/logsys_overview.8
+++ b/man/logsys_overview.8
@@ -62,7 +62,7 @@ require it and enables full logging capabilities before any application code is
 executed.
 
 #define LOGSYS_DECLARE_SYSTEM (name, mode, debug, file, file_priority,
-syslog_facility, syslog_priority, format, rec_size)
+syslog_facility, syslog_priority, format, fltsize)
 
 The name parameter is the name of the application or system.
 
@@ -99,7 +99,8 @@ syslog.
 The format parameter allows to set custom output format.
 Set to NULL to use built-in default.
 
-The rec_size parameter specifies the flight recorder buffer size.
+The fltsize parameter specifies the flight recorder buffer size in bytes. The requested value
+is increased by the size of 2 unsigned ints and rounded to the next PAGE_SIZE.
 
 An example declaration would be:
 
-- 
1.5.4.3