Re: [PATCH] VFS: Go through the LRU list of inode from head

[mc]

Quoting Jan Kara <jack@xxxxxxx>:

> On Thu 21-06-12 17:00:27, Cong Meng wrote:
> > Go through the LRU list of inode from head.
> >
> > (I'm not sure whether there is any trick here I doesn't get.  If yes,
> > any one could explain it)
>   Look at inode_lru_list_add(). It adds at the head of the list. So you
> should take from the tail to get the least recently used element...

I still have a quetion about the subsequent code and comment:

inode = list_entry(sb->s_inode_lru.prev, struct inode, i_lru);
/*
 * we are inverting the sb->s_inode_lru_lock/inode->i_lock here,
 * so use a trylock. If we fail to get the lock, just move the
 * inode to the back of the list so we don't spin on it.
 */
if (!spin_trylock(&inode->i_lock)) {
        list_move_tail(&inode->i_lru, &sb->s_inode_lru);
        continue;
}

Shouldn't the inode be moved to the head to avoid spin on it?
I note that list_move was replaced by list_move_tail purposely in a commit.


and below piece of code (at the bottom of prune_icache_sb()):

if (inode != list_entry(sb->s_inode_lru.next,
                        struct inode, i_lru))
        continue;       /* wrong inode or list_empty */

Should the inode be compared against to the tail of the list other  
than the head
after re-get the lru lock?

thanks.
cong.
> 								Honza
>
> > Signed-off-by: Cong Meng <mc@xxxxxxxxxxxxxxxxxx>
> > ---
> >  fs/inode.c |    2 +-
> >  1 files changed, 1 insertions(+), 1 deletions(-)
> >
> > diff --git a/fs/inode.c b/fs/inode.c
> > index 775cbab..aac8449 100644
> > --- a/fs/inode.c
> > +++ b/fs/inode.c
> > @@ -704,7 +704,7 @@ void prune_icache_sb(struct super_block *sb,  
> > int nr_to_scan)
> >  		if (list_empty(&sb->s_inode_lru))
> >  			break;
> >
> > -		inode = list_entry(sb->s_inode_lru.prev, struct inode, i_lru);
> > +		inode = list_entry(sb->s_inode_lru.next, struct inode, i_lru);
> >
> >  		/*
> >  		 * we are inverting the sb->s_inode_lru_lock/inode->i_lock here,
> > --
> > 1.7.5.4
> >
> > --
> > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in
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> --
> Jan Kara <jack@xxxxxxx>
> SUSE Labs, CR



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