lkml.org 
[lkml]   [2017]   [Oct]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH v3 00/13] dax: fix dma vs truncate and remove 'page-less' support
On Thu, Oct 26, 2017 at 12:58:50PM +0200, Jan Kara wrote:
> But are we guaranteed page refs are short term? E.g. if someone creates
> v4l2 videobuf in MAP_SHARED mapping of a file on DAX filesystem, page refs
> can be rather long-term similarly as in RDMA case. Also freeing of blocks
> on page reference drop is another async entry point into the filesystem
> which could unpleasantly surprise us but I guess workqueues would solve
> that reasonably fine.

The point is that we need to prohibit long term elevated page counts
with DAX anyway - we can't just let people grab allocated blocks forever
while ignoring file system operations. For stage 1 we'll just need to
fail those, and in the long run they will have to use a mechanism
similar to FL_LAYOUT locks to deal with file system allocation changes.

\
 
 \ /
  Last update: 2017-10-28 20:16    [W:0.079 / U:0.432 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site