linux-ext4 - Re: [PATCH 2/5] ext2: code cleanup by calling ext2_group_last_block

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Date:   Thu, 07 Nov 2019 17:44:23 +0800
From:   Chengguang Xu <cgxu519@...ernel.net>
To:     "Jan Kara" <jack@...e.cz>
Cc:     "jack" <jack@...e.com>, "linux-ext4" <linux-ext4@...r.kernel.org>
Subject: Re: [PATCH 2/5] ext2: code cleanup by calling
 ext2_group_last_block_no()

 ---- 在 星期四, 2019-11-07 17:21:17 Jan Kara <jack@...e.cz> 撰写 ----
 > On Thu 07-11-19 10:54:43, Chengguang Xu wrote:
 > >  ---- 在 星期三, 2019-11-06 23:42:36 Jan Kara <jack@...e.cz> 撰写 ----
 > >  > On Mon 04-11-19 19:40:33, Chengguang Xu wrote:
 > >  > > Call common helper ext2_group_last_block_no() to
 > >  > > calculate group last block number.
 > >  > > 
 > >  > > Signed-off-by: Chengguang Xu <cgxu519@...ernel.net>
 > >  > 
 > >  > Thanks for the patch! I've applied it (as well as 1/5) and added attached
 > >  > simplification on top.
 > >  > 
 > > 
 > > In ext2_try_to_allocate()
 > > 
 > > +        if (my_rsv->_rsv_end < group_last_block)
 > > +            end = my_rsv->_rsv_end - group_first_block + 1;
 > > +        if (grp_goal < start || grp_goal > end)
 > > 
 > > Based on original code, shouldn't it be  if (grp_goal < start || grp_goal
 > > >=end) ?
 > 
 > Hum, that's a good point. The original code actually had an off-by-one bug
 > because 'end' is really the last block that can be used so grp_goal == end
 > still makes sense. And my cleanup fixed it. Now looking at the code in
 > ext2_try_to_allocate() we also have a similar bug in the loop allocating
 > blocks. There we can also go upto 'end' inclusive. Added a patch to fix
 > that. Thanks for pointing me to this!
 > 

Doesn't it depend on what starting number for grp_block inside block group?
if it starts from 0, is the end number block still available for allocation?

Thanks,
Chengguang