linux-ext4 - Re: [RFC 2/6] ext4: Implement ext4_group_block

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Date:   Fri, 4 Feb 2022 15:38:44 +0530
From:   Ritesh Harjani <riteshh@...ux.ibm.com>
To:     Jan Kara <jack@...e.cz>
Cc:     linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
        "Theodore Ts'o" <tytso@....edu>,
        Harshad Shirwadkar <harshadshirwadkar@...il.com>
Subject: Re: [RFC 2/6] ext4: Implement ext4_group_block_valid() as common
 function

On 22/02/01 12:34PM, Jan Kara wrote:
> On Mon 31-01-22 20:46:51, Ritesh Harjani wrote:
> > This patch implements ext4_group_block_valid() check functionality,
> > and refactors all the callers to use this common function instead.
> >
> > Signed-off-by: Ritesh Harjani <riteshh@...ux.ibm.com>
> ...
>
> > diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
> > index 8d23108cf9d7..60d32d3d8dc4 100644
> > --- a/fs/ext4/mballoc.c
> > +++ b/fs/ext4/mballoc.c
> > @@ -6001,13 +6001,7 @@ void ext4_free_blocks(handle_t *handle, struct inode *inode,
> >  		goto error_return;
> >  	}
> >
> > -	if (in_range(ext4_block_bitmap(sb, gdp), block, count) ||
> > -	    in_range(ext4_inode_bitmap(sb, gdp), block, count) ||
> > -	    in_range(block, ext4_inode_table(sb, gdp),
> > -		     sbi->s_itb_per_group) ||
> > -	    in_range(block + count - 1, ext4_inode_table(sb, gdp),
> > -		     sbi->s_itb_per_group)) {
> > -
> > +	if (!ext4_group_block_valid(sb, block_group, block, count)) {
> >  		ext4_error(sb, "Freeing blocks in system zone - "
> >  			   "Block = %llu, count = %lu", block, count);
> >  		/* err = 0. ext4_std_error should be a no op */
>
> When doing this, why not rather directly use ext4_inode_block_valid() here?

This is because while freeing these blocks we have their's corresponding block
group too. So there is little point in checking FS Metadata of all block groups
v/s FS Metadata of just this block group, no?

Also, I am not sure if we changing this to check against system-zone's blocks
(which has FS Metadata blocks from all block groups), can add any additional
penalty?

-riteshh

>
> > @@ -6194,11 +6188,7 @@ int ext4_group_add_blocks(handle_t *handle, struct super_block *sb,
> >  		goto error_return;
> >  	}
> >
> > -	if (in_range(ext4_block_bitmap(sb, desc), block, count) ||
> > -	    in_range(ext4_inode_bitmap(sb, desc), block, count) ||
> > -	    in_range(block, ext4_inode_table(sb, desc), sbi->s_itb_per_group) ||
> > -	    in_range(block + count - 1, ext4_inode_table(sb, desc),
> > -		     sbi->s_itb_per_group)) {
> > +	if (!ext4_group_block_valid(sb, block_group, block, count)) {
> >  		ext4_error(sb, "Adding blocks in system zones - "
> >  			   "Block = %llu, count = %lu",
> >  			   block, count);
>
> And here I'd rather refactor ext4_inode_block_valid() a bit to provide a
> more generic helper not requiring an inode and use it here...
>
> 								Honza
> --
> Jan Kara <jack@...e.com>
> SUSE Labs, CR