Bug#500309: mdadm thinks disk is not large enough to be added, but it is (v1 superblock)

[Neil Brown]

On Saturday September 27, madduck at debian.org wrote:
> Package: mdadm
> Version: 2.6.7-3.1
> Severity: important
> Tags: upstream
> 
> md0 : active raid1 hda1[1]
>       64220 blocks super 1.0 [2/1] [_U]
> 
> wall:/# sfdisk -s /dev/hdc1
> 64228
> 
> wall:/# mdadm --add /dev/md0 /dev/hdc1
> mdadm: /dev/hdc1 not large enough to join array


This should be fixed by the following patch which I have just
committed as 

 http://neil.brown.name/git?p=mdadm;a=commitdiff;h=2a528478c75b6659188fc2ce0d9543124992fe6c


NeilBrown
---------------------------------------
From: NeilBrown <neilb at suse.de>
Date: Mon, 13 Oct 2008 05:15:16 +0000 (+1100)
Subject: Manage: allow adding device that is just large enough to v1.x array.
X-Git-Url: http://neil.brown.name/git?p=mdadm;a=commitdiff_plain;h=2a528478c75b6659188fc2ce0d9543124992fe6c

Manage: allow adding device that is just large enough to v1.x array.

When adding a device to an array, we check that it is large enough.

Currently the check makes sure there is also room for a reasonably
sized bitmap.  But if the array doesn't have a bitmap, then this test
might be too restrictive.
So when adding, only insist there is enough space for the current
bitmap.
When Creating, still require room for the standard sized bitmap.

This resolved Debian Bug 500309
---

diff --git a/Manage.c b/Manage.c
index 8297708..7b3fabe 100644
--- a/Manage.c
+++ b/Manage.c
@@ -349,14 +349,6 @@ int Manage_subdevs(char *devname, int fd,
 
 			if (array.not_persistent == 0) {
 
-				/* Make sure device is large enough */
-				if (tst->ss->avail_size(tst, ldsize/512) <
-				    array_size) {
-					fprintf(stderr, Name ": %s not large enough to join array\n",
-						dv->devname);
-					return 1;
-				}
-
 				/* need to find a sample superblock to copy, and
 				 * a spare slot to use
 				 */
@@ -386,6 +378,15 @@ int Manage_subdevs(char *devname, int fd,
 					fprintf(stderr, Name ": cannot find valid superblock in this array - HELP\n");
 					return 1;
 				}
+
+				/* Make sure device is large enough */
+				if (tst->ss->avail_size(tst, ldsize/512) <
+				    array_size) {
+					fprintf(stderr, Name ": %s not large enough to join array\n",
+						dv->devname);
+					return 1;
+				}
+
 				/* Possibly this device was recently part of the array
 				 * and was temporarily removed, and is now being re-added.
 				 * If so, we can simply re-add it.
diff --git a/bitmap.c b/bitmap.c
index fdf8884..b647939 100644
--- a/bitmap.c
+++ b/bitmap.c
@@ -115,6 +115,15 @@ unsigned long long bitmap_bits(unsigned long long array_size,
 	return (array_size * 512 + chunksize - 1) / chunksize;
 }
 
+unsigned long bitmap_sectors(struct bitmap_super_s *bsb)
+{
+	unsigned long long bits = bitmap_bits(__le64_to_cpu(bsb->sync_size),
+					      __le32_to_cpu(bsb->chunksize));
+	int bits_per_sector = 8*512;
+	return (bits + bits_per_sector - 1) / bits_per_sector;
+}
+
+
 bitmap_info_t *bitmap_fd_read(int fd, int brief)
 {
 	/* Note: fd might be open O_DIRECT, so we must be
diff --git a/mdadm.h b/mdadm.h
index 5c18d15..ce140e5 100644
--- a/mdadm.h
+++ b/mdadm.h
@@ -474,6 +474,7 @@ extern int CreateBitmap(char *filename, int force, char uuid[16],
 			int major);
 extern int ExamineBitmap(char *filename, int brief, struct supertype *st);
 extern int bitmap_update_uuid(int fd, int *uuid, int swap);
+extern unsigned long bitmap_sectors(struct bitmap_super_s *bsb);
 
 extern int md_get_version(int fd);
 extern int get_linux_version(void);
diff --git a/super1.c b/super1.c
index fe915f8..e1d0219 100644
--- a/super1.c
+++ b/super1.c
@@ -1214,10 +1214,21 @@ static struct supertype *match_metadata_desc1(char *arg)
  */
 static __u64 avail_size1(struct supertype *st, __u64 devsize)
 {
+	struct mdp_superblock_1 *super = st->sb;
 	if (devsize < 24)
 		return 0;
 
-	devsize -= choose_bm_space(devsize);
+	if (super == NULL)
+		/* creating:  allow suitable space for bitmap */
+		devsize -= choose_bm_space(devsize);
+#ifndef MDASSEMBLE
+	else if (__le32_to_cpu(super->feature_map)&MD_FEATURE_BITMAP_OFFSET) {
+		/* hot-add. allow for actual size of bitmap */
+		struct bitmap_super_s *bsb;
+		bsb = (struct bitmap_super_s *)(((char*)super)+1024);
+		devsize -= bitmap_sectors(bsb);
+	}
+#endif
 
 	switch(st->minor_version) {
 	case -1: /* no specified.  Now time to set default */