When glibc needs buffers for line buffering of input and output buffers, it

allocates these buffers in such way it adds memory page for each such buffer
and size of unlock memory check will mismatch by 1 or 2 pages.

This happens when we print or read lines without '\n' so these buffers are
used. To avoid this extra allocation, use setvbuf to set these bufffers ahead.

Signed-off-by: Zdenek Kabelac <zkabelac@redhat.com>
Reviewed-by: Milan Broz <mbroz@redhat.com>
Reviewed-by: Petr Rockai <prockai@redhat.com>

5 files changed, 35 insertions, 5 deletions

diff --git a/daemons/clvmd/lvm-functions.c b/daemons/clvmd/lvm-functions.c
index 166cd7f1..8e68ed98 100644
--- a/daemons/clvmd/lvm-functions.c
+++ b/daemons/clvmd/lvm-functions.c
@@ -919,7 +919,7 @@ int init_clvm(int using_gulm, char **argv)
 	init_syslog(LOG_DAEMON);
 	openlog("clvmd", LOG_PID, LOG_DAEMON);
 
-	if (!(cmd = create_toolcontext(1, NULL))) {
+	if (!(cmd = create_toolcontext(1, NULL, 0))) {
 		log_error("Failed to allocate command context");
 		return 0;
 	}
diff --git a/lib/commands/toolcontext.c b/lib/commands/toolcontext.c
index 9b3e27f4..918362ce 100644
--- a/lib/commands/toolcontext.c
+++ b/lib/commands/toolcontext.c
@@ -58,6 +58,8 @@
 #  include <malloc.h>
 #endif
 
+static const size_t linebuffer_size = 4096;
+
 static int _get_env_vars(struct cmd_context *cmd)
 {
 	const char *e;
@@ -1148,7 +1150,8 @@ static void _init_globals(struct cmd_context *cmd)
 
 /* Entry point */
 struct cmd_context *create_toolcontext(unsigned is_long_lived,
-				       const char *system_dir)
+				       const char *system_dir,
+				       unsigned set_buffering)
 {
 	struct cmd_context *cmd;
 
@@ -1183,6 +1186,22 @@ struct cmd_context *create_toolcontext(unsigned is_long_lived,
 	/* FIXME Make this configurable? */
 	reset_lvm_errno(1);
 
+	/* Set in/out stream buffering before glibc */
+	if (set_buffering) {
+		/* Allocate 2 buffers */
+		if (!(cmd->linebuffer = dm_malloc(2 * linebuffer_size))) {
+			log_error("Failed to allocate line buffer.");
+			goto out;
+		}
+		if ((setvbuf(stdin, cmd->linebuffer, _IOLBF, linebuffer_size) ||
+		     setvbuf(stdout, cmd->linebuffer + linebuffer_size,
+			     _IOLBF, linebuffer_size))) {
+			log_sys_error("setvbuf", "");
+			goto out;
+		}
+		/* Buffers are used for lines without '\n' */
+	}
+
 	/*
 	 * Environment variable LVM_SYSTEM_DIR overrides this below.
 	 */
@@ -1419,6 +1438,15 @@ void destroy_toolcontext(struct cmd_context *cmd)
 	_destroy_tag_configs(cmd);
 	if (cmd->libmem)
 		dm_pool_destroy(cmd->libmem);
+
+	if (cmd->linebuffer) {
+		/* Reset stream buffering to defaults */
+		setlinebuf(stdin);
+		fflush(stdout);
+		setlinebuf(stdout);
+		dm_free(cmd->linebuffer);
+	}
+
 	dm_free(cmd);
 
 	release_log_memory();
diff --git a/lib/commands/toolcontext.h b/lib/commands/toolcontext.h
index 4628c7c2..1c3368e6 100644
--- a/lib/commands/toolcontext.h
+++ b/lib/commands/toolcontext.h
@@ -66,6 +66,7 @@ struct cmd_context {
 	const char *kernel_vsn;
 
 	unsigned rand_seed;
+	char *linebuffer;
 	const char *cmd_line;
 	struct command *command;
 	char **argv;
@@ -109,7 +110,8 @@ struct cmd_context {
  * The environment variable LVM_SYSTEM_DIR always takes precedence.
  */
 struct cmd_context *create_toolcontext(unsigned is_long_lived,
-				       const char *system_dir);
+				       const char *system_dir,
+				       unsigned set_buffering);
 void destroy_toolcontext(struct cmd_context *cmd);
 int refresh_toolcontext(struct cmd_context *cmd);
 int refresh_filters(struct cmd_context *cmd);
diff --git a/liblvm/lvm_base.c b/liblvm/lvm_base.c
index 9e1a8ecd..f44b786c 100644
--- a/liblvm/lvm_base.c
+++ b/liblvm/lvm_base.c
@@ -34,7 +34,7 @@ lvm_t lvm_init(const char *system_dir)
 	/* create context */
 	/* FIXME: split create_toolcontext */
 	/* FIXME: make all globals configurable */
-	cmd = create_toolcontext(0, system_dir);
+	cmd = create_toolcontext(0, system_dir, 1);
 	if (!cmd)
 		return NULL;
 
diff --git a/tools/lvmcmdline.c b/tools/lvmcmdline.c
index 197cd143..3e13a27d 100644
--- a/tools/lvmcmdline.c
+++ b/tools/lvmcmdline.c
@@ -1282,7 +1282,7 @@ struct cmd_context *init_lvm(void)
 	if (!udev_init_library_context())
 		stack;
 
-	if (!(cmd = create_toolcontext(0, NULL)))
+	if (!(cmd = create_toolcontext(0, NULL, 1)))
 		return_NULL;
 
 	_cmdline.arg_props = &_arg_props[0];