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
