[PATCH] btrfs-progs: mkfs: set super_cache_generation to 0 if we're using free space tree

[PATCH] btrfs-progs: mkfs: set super_cache_generation to 0 if we're using free space tree

[Qu Wenruo]

[HICCUP]
There is a bug report that mkfs.btrfs -R free-space-tree still makes
kernel to try to cleanup the v1 space cache:

  # mkfs.btrfs -R free-space-tree -f /dev/test/scratch1
  # mount /dev/test/scratch1 /mnt/btrfs
  # dmesg | grep cleaning
  BTRFS info (device dm-6): cleaning free space cache v1

[CAUSE]
By default, mkfs.btrfs will set super cache generation to (u64)-1, which
will inform kernel that the v1 space cache is invalid, needs to
regenerate it.

But for free space cache tree, kernel will set super cache generation to
0, to indicate v1 space cache is not in use.

This means, even we enabled free space tree with all the RO compatible
bits and new tree, as long as super cache generation is not 0, kernel
still consider the fs has some invalid v1 space cache, and will try to
remove them.

[FIX]
This is not a big deal, but to make the "-R free-space-tree" to really
work as kernel, we also need to set super cache generation to 0.

Reported-by: Chris Murphy <lists@colorremedies.com>
Link: https://lore.kernel.org/linux-btrfs/CAJCQCtSvgzyOnxtrqQZZirSycEHp+g0eDH5c+Kw9mW=PgxuXmw@mail.gmail.com/
Signed-off-by: Qu Wenruo <wqu@suse.com>
---
 kernel-shared/free-space-tree.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/kernel-shared/free-space-tree.c b/kernel-shared/free-space-tree.c
index 2edc7fc716f5..7f589dfef950 100644
--- a/kernel-shared/free-space-tree.c
+++ b/kernel-shared/free-space-tree.c
@@ -1447,6 +1447,7 @@ int btrfs_create_free_space_tree(struct btrfs_fs_info *fs_info)
 
 	btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE);
 	btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
+	btrfs_set_super_cache_generation(fs_info->super_copy, 0);
 
 	ret = btrfs_commit_transaction(trans, tree_root);
 	if (ret)
-- 
2.32.0

Re: [PATCH] btrfs-progs: mkfs: set super_cache_generation to 0 if we're using free space tree

[Anand Jain]

On 31/07/2021 15:42, Qu Wenruo wrote:
> [HICCUP]
> There is a bug report that mkfs.btrfs -R free-space-tree still makes
> kernel to try to cleanup the v1 space cache:
> 
>    # mkfs.btrfs -R free-space-tree -f /dev/test/scratch1
>    # mount /dev/test/scratch1 /mnt/btrfs
>    # dmesg | grep cleaning
>    BTRFS info (device dm-6): cleaning free space cache v1
> 
> [CAUSE]
> By default, mkfs.btrfs will set super cache generation to (u64)-1, which
> will inform kernel that the v1 space cache is invalid, needs to
> regenerate it.
> 
> But for free space cache tree, kernel will set super cache generation to
> 0, to indicate v1 space cache is not in use.
> 
> This means, even we enabled free space tree with all the RO compatible
> bits and new tree, as long as super cache generation is not 0, kernel
> still consider the fs has some invalid v1 space cache, and will try to
> remove them.
> 
> [FIX]
> This is not a big deal, but to make the "-R free-space-tree" to really
> work as kernel, we also need to set super cache generation to 0.
> 
> Reported-by: Chris Murphy <lists@colorremedies.com>
> Link: https://lore.kernel.org/linux-btrfs/CAJCQCtSvgzyOnxtrqQZZirSycEHp+g0eDH5c+Kw9mW=PgxuXmw@mail.gmail.com/
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Looks good.

Reviewed-by: Anand Jain <anand.jain@oracle.com>


> ---
>   kernel-shared/free-space-tree.c | 1 +
>   1 file changed, 1 insertion(+)
> 
> diff --git a/kernel-shared/free-space-tree.c b/kernel-shared/free-space-tree.c
> index 2edc7fc716f5..7f589dfef950 100644
> --- a/kernel-shared/free-space-tree.c
> +++ b/kernel-shared/free-space-tree.c
> @@ -1447,6 +1447,7 @@ int btrfs_create_free_space_tree(struct btrfs_fs_info *fs_info)
>   
>   	btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE);
>   	btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
> +	btrfs_set_super_cache_generation(fs_info->super_copy, 0);
>   
>   	ret = btrfs_commit_transaction(trans, tree_root);
>   	if (ret)
> 

Re: [PATCH] btrfs-progs: mkfs: set super_cache_generation to 0 if we're using free space tree

[Nikolay Borisov]

On 31.07.21 г. 10:42, Qu Wenruo wrote:
> [HICCUP]
> There is a bug report that mkfs.btrfs -R free-space-tree still makes
> kernel to try to cleanup the v1 space cache:
> 
>   # mkfs.btrfs -R free-space-tree -f /dev/test/scratch1
>   # mount /dev/test/scratch1 /mnt/btrfs
>   # dmesg | grep cleaning
>   BTRFS info (device dm-6): cleaning free space cache v1
> 
> [CAUSE]
> By default, mkfs.btrfs will set super cache generation to (u64)-1, which
> will inform kernel that the v1 space cache is invalid, needs to
> regenerate it.
> 
> But for free space cache tree, kernel will set super cache generation to
> 0, to indicate v1 space cache is not in use.
> 
> This means, even we enabled free space tree with all the RO compatible
> bits and new tree, as long as super cache generation is not 0, kernel
> still consider the fs has some invalid v1 space cache, and will try to
> remove them.
> 
> [FIX]
> This is not a big deal, but to make the "-R free-space-tree" to really
> work as kernel, we also need to set super cache generation to 0.
> 
> Reported-by: Chris Murphy <lists@colorremedies.com>
> Link: https://lore.kernel.org/linux-btrfs/CAJCQCtSvgzyOnxtrqQZZirSycEHp+g0eDH5c+Kw9mW=PgxuXmw@mail.gmail.com/
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Reviewed-by: Nikolay Borisov <nborisov@suse.com>

> ---
>  kernel-shared/free-space-tree.c | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/kernel-shared/free-space-tree.c b/kernel-shared/free-space-tree.c
> index 2edc7fc716f5..7f589dfef950 100644
> --- a/kernel-shared/free-space-tree.c
> +++ b/kernel-shared/free-space-tree.c
> @@ -1447,6 +1447,7 @@ int btrfs_create_free_space_tree(struct btrfs_fs_info *fs_info)
>  
>  	btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE);
>  	btrfs_set_fs_compat_ro(fs_info, FREE_SPACE_TREE_VALID);
> +	btrfs_set_super_cache_generation(fs_info->super_copy, 0);
>  
>  	ret = btrfs_commit_transaction(trans, tree_root);
>  	if (ret)
> 

Re: [PATCH] btrfs-progs: mkfs: set super_cache_generation to 0 if we're using free space tree

[David Sterba]

On Sat, Jul 31, 2021 at 03:42:40PM +0800, Qu Wenruo wrote:
> [HICCUP]
> There is a bug report that mkfs.btrfs -R free-space-tree still makes
> kernel to try to cleanup the v1 space cache:
> 
>   # mkfs.btrfs -R free-space-tree -f /dev/test/scratch1
>   # mount /dev/test/scratch1 /mnt/btrfs
>   # dmesg | grep cleaning
>   BTRFS info (device dm-6): cleaning free space cache v1
> 
> [CAUSE]
> By default, mkfs.btrfs will set super cache generation to (u64)-1, which
> will inform kernel that the v1 space cache is invalid, needs to
> regenerate it.
> 
> But for free space cache tree, kernel will set super cache generation to
> 0, to indicate v1 space cache is not in use.
> 
> This means, even we enabled free space tree with all the RO compatible
> bits and new tree, as long as super cache generation is not 0, kernel
> still consider the fs has some invalid v1 space cache, and will try to
> remove them.
> 
> [FIX]
> This is not a big deal, but to make the "-R free-space-tree" to really
> work as kernel, we also need to set super cache generation to 0.
> 
> Reported-by: Chris Murphy <lists@colorremedies.com>
> Link: https://lore.kernel.org/linux-btrfs/CAJCQCtSvgzyOnxtrqQZZirSycEHp+g0eDH5c+Kw9mW=PgxuXmw@mail.gmail.com/
> Signed-off-by: Qu Wenruo <wqu@suse.com>

Added to devel, thanks.