linux-ext4 - Re: [PATCH 2/2] test: mke2fs must not create fs with reszie_inode and meta

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Message-ID: <20180814145015.d4ou27ac5nkzml5f@localhost.localdomain>
Date:   Tue, 14 Aug 2018 16:50:15 +0200
From:   Lukas Czerner <lczerner@...hat.com>
To:     "Theodore Y. Ts'o" <tytso@....edu>
Cc:     linux-ext4@...r.kernel.org
Subject: Re: [PATCH 2/2] test: mke2fs must not create fs with reszie_inode
 and meta_bg

On Tue, Aug 14, 2018 at 10:20:27AM -0400, Theodore Y. Ts'o wrote:
> On Mon, Aug 13, 2018 at 03:17:06PM +0200, Lukas Czerner wrote:
> > Test that mke2fs does not allow to create file system with both
> > resize_inode and meta_bg features enabled.
> > 
> 
> > diff --git a/tests/m_resize_inode_meta_bg/script b/tests/m_resize_inode_meta_bg/script
> > new file mode 100644
> > index 00000000..41ffb32a
> > --- /dev/null
> > +++ b/tests/m_resize_inode_meta_bg/script
> > @@ -0,0 +1,7 @@
> > +DESCRIPTION="resize_inode and meta_bg enabled"
> > +FS_SIZE=15360
> > +MKE2FS_DEVICE_SECTSIZE=4096
> > +export MKE2FS_DEVICE_SECTSIZE
> > +MKE2FS_OPTS="-T ext4 -g256 -O 64bit"
> > +. $cmd_dir/run_mke2fs
> > +unset MKE2FS_DEVICE_SECTSIZE
> 
> This doesn't look right --- in order to trigger the bug the file
> system size has to be exactly 2**32, right?  And if so, then we need
> to add:

No it does not have to be that big. it's just that the ratio of
(s_reserved_gdt_blocks + desc_blocks) to s_blocks_per_group must be
bigger than 3:4 to trigger it.

So if we artificially limit the blocks per group (using -g) to the right
size then we can do this on smaller file systems. I did not really tried
to figure out the minimum size we can hit it I just wanted the fs to be
small enough in this case it's 60MB I think.

And indeed if you run it with 42e77d5db53e3ec09b5dc507169d15de219799e3.
reverted it will fail.

-Lukas

> 
> if [ $(uname -s) = "Darwin" ]; then
>        # creates a really big filesystem
>        echo "$test_name: $DESCRIPTION: skipped for HFS+ (no sparse files)"
>        return 0
> fi
> 
> right?
> 
> Hmm, Andreas, these checks were mostly for you IIRC.  APFS *does*
> support sparse files, so I wonder if we should be using an autoconf
> test to see if the system supports sparse files, and using this to set
> a variable in test_config (which would have to be generated from
> test_config.in)?  I don't plan to do anything like this since I don't
> have a development MacOS system, but if you do run High Sierra, maybe
> you could look in this?
> 
> 						- Ted