linux-ext4 - Re: [PATCH 3/4] ext4: fix init_itable=n to work as expected for n=0

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Date:	Fri, 20 May 2011 11:21:12 +0200 (CEST)
From:	Lukas Czerner <lczerner@...hat.com>
To:	Eric Sandeen <sandeen@...hat.com>
cc:	Lukas Czerner <lczerner@...hat.com>, linux-ext4@...r.kernel.org,
	tytso@....edu
Subject: Re: [PATCH 3/4] ext4: fix init_itable=n to work as expected for
 n=0

On Thu, 19 May 2011, Eric Sandeen wrote:

> On 5/9/11 10:57 AM, Lukas Czerner wrote:
> > For some reason, when we set mount option init_itable=0 it behaves as
> > we would set init_itable=20 which is not right at all. Basically when we
> > set it to zero we are saying to lazyinit thread not to wait between
> > zeroing the inode table (except of cond_resched()) so this commit fixes
> > that and removes the unnecessary condition. The 'n' should be also
> > properly used on remount.
> > 
> > When the n is not set at all, it means that the default miltiplier
> > EXT4_DEF_LI_WAIT_MULT is set instead.
> > 
> > Signed-off-by: Lukas Czerner <lczerner@...hat.com>
> > Reported-by: Eric Sandeen <sandeen@...hat.com>
> 
> This is why last-minute maintainer changes that bypass the list can be dangerous ;)
> (This code wasn't in Lukas' last version on the list...)
> 
> nitpick: Documentation/fs/ext4.txt should probably be updated to clarify
> that the "=n" value is optional and defaults to 20...

Will do.

> 
> nitpick2: Is there any reason to set the default in parse_options() since it's
> already set in ext4_fill_super just prior?
> 
> i.e. would something like:
> 
>                 case Opt_init_inode_table:
>                         set_opt(sb, INIT_INODE_TABLE);
>                         if (args[0].from) {
>                                 if (match_int(&args[0], &option))
>                                         return 0;
> 	                        if (option < 0)
> 					return 0;
> 				sbi->s_li_wait_mult = option;
>                         }
>                         break;
> 
> suffice?
Yes, it did not notice that.

Thanks!
-Lukas

> 
> -Eric
> 
> > ---
> >  fs/ext4/super.c |   21 +++++++++++++++------
> >  1 files changed, 15 insertions(+), 6 deletions(-)
> > 
> > diff --git a/fs/ext4/super.c b/fs/ext4/super.c
> > index 6ccf0e2..c379af6 100644
> > --- a/fs/ext4/super.c
> > +++ b/fs/ext4/super.c
> > @@ -2690,11 +2690,8 @@ static int ext4_run_li_request(struct ext4_li_request *elr)
> >  		ret = ext4_init_inode_table(sb, group,
> >  					    elr->lr_timeout ? 0 : 1);
> >  		if (elr->lr_timeout == 0) {
> > -			timeout = jiffies - timeout;
> > -			if (elr->lr_sbi->s_li_wait_mult)
> > -				timeout *= elr->lr_sbi->s_li_wait_mult;
> > -			else
> > -				timeout *= 20;
> > +			timeout = (jiffies - timeout) *
> > +				  elr->lr_sbi->s_li_wait_mult;
> >  			elr->lr_timeout = timeout;
> >  		}
> >  		elr->lr_next_sched = jiffies + elr->lr_timeout;
> > @@ -2931,8 +2928,14 @@ static int ext4_register_li_request(struct super_block *sb,
> >  	ext4_group_t ngroups = EXT4_SB(sb)->s_groups_count;
> >  	int ret = 0;
> >  
> > -	if (sbi->s_li_request != NULL)
> > +	if (sbi->s_li_request != NULL) {
> > +		/*
> > +		 * Reset timeout so it can be computed again, because
> > +		 * s_li_wait_mult might have changed.
> > +		 */
> > +		sbi->s_li_request->lr_timeout = 0;
> >  		return 0;
> > +	}
> >  
> >  	if (first_not_zeroed == ngroups ||
> >  	    (sb->s_flags & MS_RDONLY) ||
> > @@ -3137,6 +3140,12 @@ static int ext4_fill_super(struct super_block *sb, void *data, int silent)
> >  	    ((def_mount_opts & EXT4_DEFM_NODELALLOC) == 0))
> >  		set_opt(sb, DELALLOC);
> >  
> > +	/*
> > +	 * set default s_li_wait_mult for lazyinit, for the case there is
> > +	 * no mount option specified.
> > +	 */
> > +	sbi->s_li_wait_mult = EXT4_DEF_LI_WAIT_MULT;
> 
> >  	if (!parse_options((char *) sbi->s_es->s_mount_opts, sb,
> >  			   &journal_devnum, &journal_ioprio, NULL, 0)) {
> >  		ext4_msg(sb, KERN_WARNING,
> 
> 

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