Re: [PATCH 00/13] Fix the DAX-gup mistake

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 



On Thu, Sep 08, 2022 at 12:27:06PM -0700, Dan Williams wrote:
>    flag lets the fsdax core track when it has already dropped a page
>    reference, but still has use for things like memory-failure to
>    opportunistically use page->mapping on a 0-reference page.

This is not straightforward, as discussed before the page->mapping is
allowed to change while the refcount is zero, so there is no generic
way to safely obtain a pointer to the address space from a 0 reference
page.

You'd have to pass the 0 reference page into a new pgmap operation
which could obtain an appropriate internal lock to read page->mapping.

> > I'm not sure what it has to do with normal_page?
> 
> This thread is mainly about DAX slowly reinventing _mapcount that gets
> managed in all the right places for a normal_page. Longer term I think
> we either need to get back to the page-less DAX experiment and find a
> way to unwind some of this page usage creep, or cut over to finally
> making DAX-pages be normal pages and delete most of the special case
> handling in fs/dax.c. I am open to discussing the former, but I think
> the latter is more likely.

I think the latter is inevitable at this point..

Jason



[Index of Archives]     [Linux Ext4 Filesystem]     [Union Filesystem]     [Filesystem Testing]     [Ceph Users]     [Ecryptfs]     [NTFS 3]     [AutoFS]     [Kernel Newbies]     [Share Photos]     [Security]     [Netfilter]     [Bugtraq]     [Yosemite News]     [MIPS Linux]     [ARM Linux]     [Linux Security]     [Linux Cachefs]     [Reiser Filesystem]     [Linux RAID]     [NTFS 3]     [Samba]     [Device Mapper]     [CEPH Development]

  Powered by Linux