Re: Don't prevent removal of devices that break raid reqs

[Alexandre Oliva <oliva@xxxxxxxxxxxxxxxxx>]

On Nov 11, 2011, Chris Mason <chris.mason@xxxxxxxxxx> wrote:

> On Thu, Nov 10, 2011 at 05:32:48PM -0200, Alexandre Oliva wrote:
>> Instead of preventing the removal of devices that would render existing
>> raid10 or raid1 impossible, warn but go ahead with it; the rebalancing
>> code is smart enough to use different block group types.

> We'll need a --force or some kind.  There are definitely cases users
> have wanted to do this but it is rarely a good idea ;)

Even if it's just metadata that will turn from raid1 to dup, as in the
revised patch below?

>From 276b1af70556bf5bdbaa1f81cb630d6c83962323 Mon Sep 17 00:00:00 2001
From: Alexandre Oliva <lxoliva@xxxxxxxxx>
Date: Tue, 8 Nov 2011 12:33:11 -0200
Subject: [PATCH 1/8] Btrfs: enable removal of second disk with raid1 metadata

Enable removal of a second disk even if that requires conversion of
metadata from raid1 to dup, but not when data would lose replication.

Signed-off-by: Alexandre Oliva <oliva@xxxxxxxxxxxxxxxxx>
---
 fs/btrfs/volumes.c |    6 +++++-
 1 files changed, 5 insertions(+), 1 deletions(-)

diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c
index c37433d..7b348c2 100644
--- a/fs/btrfs/volumes.c
+++ b/fs/btrfs/volumes.c
@@ -1290,12 +1290,16 @@ int btrfs_rm_device(struct btrfs_root *root, char *device_path)
 		goto out;
 	}
 
-	if ((all_avail & BTRFS_BLOCK_GROUP_RAID1) &&
+	if ((root->fs_info->avail_data_alloc_bits & BTRFS_BLOCK_GROUP_RAID1) &&
 	    root->fs_info->fs_devices->num_devices <= 2) {
 		printk(KERN_ERR "btrfs: unable to go below two "
 		       "devices on raid1\n");
 		ret = -EINVAL;
 		goto out;
+	} else if ((all_avail & BTRFS_BLOCK_GROUP_RAID1) &&
+		   root->fs_info->fs_devices->num_devices <= 2) {
+		printk(KERN_ERR "btrfs: going below two devices "
+		       "will switch metadata from raid1 to dup\n");
 	}
 
 	if (strcmp(device_path, "missing") == 0) {
-- 
1.7.4.4


-- 
Alexandre Oliva, freedom fighter    http://FSFLA.org/~lxoliva/
You must be the change you wish to see in the world. -- Gandhi
Be Free! -- http://FSFLA.org/   FSF Latin America board member
Free Software Evangelist      Red Hat Brazil Compiler Engineer