Re: [PATCH 3/3] ext4: Fix estimate extent index blocks in ext4_ext_index_trans_blocks()

Hi!

On Fri 07-08-26 12:07:52, Ojaswin Mujoo wrote:
> On Wed, Aug 05, 2026 at 05:35:49PM +0200, Jan Kara wrote:
> > The estimate of the number of impacted extent tree index blocks could be
> > one-too-low. If we modify say 2 extents, already two leaf index blocks
> 
> Its minor but just to be sure, by two "leaf index blocks" do you mean
> the two leaf blocks that hold extents or the last index blocks which
> hold pointers to leaf blocks?

I meant two leaf blocks that hold extents.

								Honza

> 
> > could be impacted, not just one the current estimate counts with. Fix
> > the estimate.
> > 
> > Signed-off-by: Jan Kara <[email protected]>
> > ---
> >  fs/ext4/extents.c | 14 +++++++++++---
> >  1 file changed, 11 insertions(+), 3 deletions(-)
> > 
> > diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
> > index 44ab246a3176..713b2c098af5 100644
> > --- a/fs/ext4/extents.c
> > +++ b/fs/ext4/extents.c
> > @@ -2427,9 +2427,17 @@ int ext4_ext_index_trans_blocks(struct inode *inode, int extents)
> >  	 */
> >  	if (extents <= 1)
> >  		index = (EXT4_MAX_EXTENT_DEPTH * 2) + extents;
> > -	else
> > -		index = (EXT4_MAX_EXTENT_DEPTH * 3) +
> > -			DIV_ROUND_UP(extents, ext4_ext_space_block(inode, 0));
> > +	else {
> > +		int ext_max = ext4_ext_space_block(inode, 0);
> > +
> > +		index = EXT4_MAX_EXTENT_DEPTH * 3;
> > +		/*
> > +		 * Modified extents need not start at the beginning of the
> > +		 * leaf. Already two extents may need two leaf block
> > +		 * modifications...
> > +		 */
> > +		index += DIV_ROUND_UP(extents + ext_max - 1, ext_max);
> > +	}
> >  
> >  	return index;
> >  }
> > -- 
> > 2.51.0
> > 
-- 
Jan Kara <[email protected]>
SUSE Labs, CR