lkml.org 
[lkml]   [2020]   [Apr]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [PATCH V9 09/11] fs: Introduce DCACHE_DONTCACHE
On Wed, Apr 22, 2020 at 03:34:07AM +0100, Al Viro wrote:
> On Tue, Apr 21, 2020 at 01:25:19PM -0700, Darrick J. Wong wrote:
>
> > > DCACHE_DONTCACHE indicates a dentry should not be cached on final
> > > dput().
> > >
> > > Also add a helper function to mark DCACHE_DONTCACHE on all dentries
> > > pointing to a specific inode when that inode is being set I_DONTCACHE.
> > >
> > > This facilitates dropping dentry references to inodes sooner which
> > > require eviction to swap S_DAX mode.
>
> Explain, please. Questions:
>
> 1) does that ever happen to directories?

Directories never get S_DAX set. So the eviction only needs to happen on
inodes. But that can't happen without dentries also dropping their references.

> 2) how much trouble do we get if such inode is *NOT* evicted for, say, several
> days?

No trouble at all. Users understand that changing the FS_XFLAG_DAX setting
does _not_ immediately result in S_DAX changing.

It is intended that applications requiring a change of mode would flip the
FS_XFLAG_DAX close the file and wait for the eviction (or force it through a
drop cache if they have permission).

Ira

\
 
 \ /
  Last update: 2020-04-22 05:46    [W:0.522 / U:0.052 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site