Re: xfs-docs question

["Darrick J. Wong" <djwong@kernel.org>]

On Wed, Mar 24, 2021 at 09:34:58AM +0100, lukas@herbolt.com wrote:
> Hi,
> I came across chapter in XFS documentation "12.4.1 xfs_db AGI Example"
> quoting bellow:
> ---
> recs[1-85] = [startino,freecount,free]1:[96,0,0] 2:[160,0,0] 3:[224,0,0]
> 4:[288,0,0]
>                                       5:[352,0,0] 6:[416,0,0] 7:[480,0,0]
> 8:[544,0,0]
>                                       9:[608,0,0] 10:[672,0,0] 11:[736,0,0]
> 12:[800,0,0]
>                                       ...
>                                       85:[5792,9,0xff80000000000000]
> 
> Most of the inode chunks on this filesystem are totally full, since the free
> value is zero.
> This means that we ought to expect inode 160 to be linked somewhere in the
> directory structure.
> However, notice that 0xff80000000000000 in record 85 — this means that we
> would expect inode 5856
> to be free. Moving on to the free inode B+tree, we see that this is indeed
> the case:
> ---
> 
> As there are 9 inodes free in the last chunk of 64 inodes it gives me first
> free inode 5847 (5792+55),
> on the other hand inode 5856 is also free as it's last inode in the chunk.
> 
> My question is do I understand correctly that the first free inode in that
> AG is 5847?

Oops, yes, you are correct.  The first free inode is 5847, not 5856 as
stated in 12.4.1.

> Thanks, bellow possible patch.

It looks reasonable, but the patch needs to have a Signed-off-by tag
with your name and email (per kernel patch submission rules[1]) before
I can proceed with review.

[1] https://www.kernel.org/doc/html/latest/process/submitting-patches.html#sign-your-work-the-developer-s-certificate-of-origin

> ---
> diff --git a/design/XFS_Filesystem_Structure/allocation_groups.asciidoc
> b/design/XFS_Filesystem_Structure/allocation_groups.asciidoc
> index 992615d..cdc8545 100644
> --- a/design/XFS_Filesystem_Structure/allocation_groups.asciidoc
> +++ b/design/XFS_Filesystem_Structure/allocation_groups.asciidoc
> @@ -1099,7 +1099,7 @@ recs[1-85] = [startino,freecount,free]
>  Most of the inode chunks on this filesystem are totally full, since the
> +free+
>  value is zero.  This means that we ought to expect inode 160 to be linked
>  somewhere in the directory structure.  However, notice that
> 0xff80000000000000

This patch seems to have been line wrapped.  Would you mind resending it
with the DCO tag I mentioned above, and without wrapping?  Or as a text
attachment if that's the only option?

--D

> -in record 85 -- this means that we would expect inode 5856 to be free.
>  Moving
> +in record 85 -- this means that we would expect inode 5847 to be free.
>  Moving
>  on to the free inode B+tree, we see that this is indeed the case:
> ---
> 
> -- 
> Lukas Herbolt