NeilBrown: mapfile: just have one place to store the mapfile

[Martin F. Krafft]

Module: mdadm
Branch: master
Commit: 9e751dc7a08389b72011be6099710fdadc722b2d
URL:    http://git.debian.org/?p=pkg-mdadm/mdadm.git;a=commit;h=9e751dc7a08389b72011be6099710fdadc722b2d

Author: NeilBrown <neilb at suse.de>
Date:   Fri Aug  6 14:54:10 2010 +1000

mapfile: just have one place to store the mapfile

Having multiple possible locations and guessing where best to put the
file is too messy, confusing and makes locking problematic.

So just keep it in /dev/.mdadm/map.  It is a horrible place but it is
really all we have.  System integrators can change this easily at
build time.

Signed-off-by: NeilBrown <neilb at suse.de>

---

 mapfile.c |   84 +++++++++++++++++++++++++++---------------------------------
 1 files changed, 38 insertions(+), 46 deletions(-)

diff --git a/mapfile.c b/mapfile.c
index cc222d2..f334822 100644
--- a/mapfile.c
+++ b/mapfile.c
@@ -1,8 +1,8 @@
 /*
- * mapfile - manage /var/run/mdadm/map. Part of:
+ * mapfile - keep track of uuid <-> array mapping. Part of:
  * mdadm - manage Linux "md" devices aka RAID arrays.
  *
- * Copyright (C) 2006-2009 Neil Brown <neilb at suse.de>
+ * Copyright (C) 2006-2010 Neil Brown <neilb at suse.de>
  *
  *
  *    This program is free software; you can redistribute it and/or modify
@@ -28,7 +28,7 @@
  *           Australia
  */
 
-/* /var/run/mdadm/map is used to track arrays being created in --incremental
+/* The mapfile is used to track arrays being created in --incremental
  * mode.  It particularly allows lookup from UUID to array device, but
  * also allows the array device name to be easily found.
  *
@@ -38,54 +38,49 @@
  *  UUID       -  uuid of the array
  *  path       -  path where device created: /dev/md/home
  *
- * The preferred location for the map file is /var/run/mdadm/map.
- * However /var/run may not exist or be writable in early boot.  And if
- * no-one has created /var/run/mdadm, we still want to survive.
- * So possible locations are:
- *   /var/run/mdadm/map  /dev/.mdadm/map(changable at compile time).
- * We read from the first one that exists and write to the first
- * one that we can.
+ * The best place for the mapfile wold be /var/run/mdadm/map.  However
+ * it is needed during initramfs early-boot, and /var/run doesn't exist there
+ * and certainly doesn't persist through to normal boot.
+ * So we store it in /dev/.mdadm/map but allow this to be changed at
+ * compile time. via MAP_DIR and MAP_FILE
+ *
  */
 #include	"mdadm.h"
 #include	<sys/file.h>
 #include	<ctype.h>
 
+#ifndef MAP_DIR
+#define MAP_DIR "/dev/.mdadm"
+#define MAP_FILE "map"
+#endif
+
 #define MAP_READ 0
 #define MAP_NEW 1
 #define MAP_LOCK 2
 #define MAP_DIRNAME 3
 #define mapnames(dir, base) { \
-			dir "/" base,				\
-			dir "/" base ".new",			\
-			dir "/" base ".lock",			\
-			dir }
-
-#define MAP_DIRS 2
-char *mapname[MAP_DIRS][4] = {
-	mapnames("/var/run/mdadm", "map"),
-	mapnames(MAP_DIR, MAP_FILE),
+
+char *mapname[4] = {
+	MAP_DIR "/" MAP_FILE,
+	MAP_DIR "/" MAP_FILE ".new",
+	MAP_DIR "/" MAP_FILE ".lock",
+	MAP_DIR
 };
 
 int mapmode[3] = { O_RDONLY, O_RDWR|O_CREAT, O_RDWR|O_CREAT|O_TRUNC };
 char *mapsmode[3] = { "r", "w", "w"};
 
-FILE *open_map(int modenum, int *choice)
+FILE *open_map(int modenum)
 {
-	int i;
-
-	for (i = 0 ; i <= MAP_DIRS ; i++) {
-		int fd;
-		if ((mapmode[modenum] & O_CREAT))
-			/* Attempt to create directory, don't worry about
-			 * failure.
-			 */
-			(void)mkdir(mapname[i][MAP_DIRNAME], 0755);
-		fd = open(mapname[i][modenum], mapmode[modenum], 0600);
-		if (fd >= 0) {
-			*choice = i;
-			return fdopen(fd, mapsmode[modenum]);
-		}
-	}
+	int fd;
+	if ((mapmode[modenum] & O_CREAT))
+		/* Attempt to create directory, don't worry about
+		 * failure.
+		 */
+		(void)mkdir(mapname[MAP_DIRNAME], 0755);
+	fd = open(mapname[modenum], mapmode[modenum], 0600);
+	if (fd >= 0)
+		return fdopen(fd, mapsmode[modenum]);
 	return NULL;
 }
 
@@ -93,9 +88,8 @@ int map_write(struct map_ent *mel)
 {
 	FILE *f;
 	int err;
-	int which;
 
-	f = open_map(MAP_NEW, &which);
+	f = open_map(MAP_NEW);
 
 	if (!f)
 		return 0;
@@ -115,21 +109,20 @@ int map_write(struct map_ent *mel)
 	err = ferror(f);
 	fclose(f);
 	if (err) {
-		unlink(mapname[which][1]);
+		unlink(mapname[1]);
 		return 0;
 	}
-	return rename(mapname[which][1],
-		      mapname[which][0]) == 0;
+	return rename(mapname[1],
+		      mapname[0]) == 0;
 }
 
 
 static FILE *lf = NULL;
-static int lwhich = 0;
 int map_lock(struct map_ent **melp)
 {
 	while (lf == NULL) {
 		struct stat buf;
-		lf = open_map(MAP_LOCK, &lwhich);
+		lf = open_map(MAP_LOCK);
 		if (lf == NULL)
 			return -1;
 		if (flock(fileno(lf), LOCK_EX) != 0) {
@@ -160,7 +153,7 @@ void map_unlock(struct map_ent **melp)
 		 * as only the owner of the lock may
 		 * unlink the file
 		 */
-		unlink(mapname[lwhich][2]);
+		unlink(mapname[2]);
 		fclose(lf);
 	}
 	lf = NULL;
@@ -188,14 +181,13 @@ void map_read(struct map_ent **melp)
 	int devnum, uuid[4];
 	char metadata[30];
 	char nam[4];
-	int which;
 
 	*melp = NULL;
 
-	f = open_map(MAP_READ, &which);
+	f = open_map(MAP_READ);
 	if (!f) {
 		RebuildMap();
-		f = open_map(MAP_READ, &which);
+		f = open_map(MAP_READ);
 	}
 	if (!f)
 		return;