Re: [RFC PATCH 0/4] fs: introduce new writeback error tracking infrastructure and convert ext4 to use it

[NeilBrown <neilb@suse.com>]

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On Thu, Apr 06 2017, Matthew Wilcox wrote:

> On Thu, Apr 06, 2017 at 03:12:42PM +1000, NeilBrown wrote:
>> On Wed, Apr 05 2017, Matthew Wilcox wrote:
>> 
>> > On Thu, Apr 06, 2017 at 10:02:48AM +1000, NeilBrown wrote:
>> >> If you are concerned about space in 'struct address_space', just prune
>> >> some wastage.
>> >
>> > I'm trying to (via wlists).  still buggy though.
>> 
>> Cool.
>> (I wonder what a wlist is.... weighted list?)
>
> A homonym ;-)  Waitlists.  Yet Another Variation of a doubly linked list.
> This variation has only a single head pointer (like the hlist), allows
> O(1) deletion from any point in the list (but requires that you know the
> head of the list).  The tail of the list is pointed to by head->prev.
>
> http://git.infradead.org/users/willy/linux-dax.git/shortlog/refs/heads/wlist
>
> It also needs updating to the latest tree; WW locks got revamped.

So nothing points to the head, meaning you need both the node and the
head to delete something.  But the head is smaller.
I can see how that would be useful.
Thanks,
NeilBrown

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