On Thu, 2019-04-25 at 11:02 -0700, Linus Torvalds wrote: > On Thu, Apr 25, 2019 at 10:48 AM Ilya Dryomov <idryomov@xxxxxxxxx> wrote: > > dentry name handling fixes from Jeff and a memory leak fix from Zheng. > > Both are old issues, marked for stable. > > Hmm. You probably should have talked to Al about the dentry name > issue, because he'd most likely have pointed you towards our helper > function for exactly this thing: > > struct name_snapshot stable; > > take_dentry_name_snapshot(&stable, dentry); > ... use stable.name .. > release_dentry_name_snapshot(&stable); > > which doesn't need any extra memory allocation outside of some fairly > limited stack allocation for the 'name_snapshot' itself, because it > knows about the dentry name rules, and > > - for inline names, it copies it under the d_lock into the fixed > DNAME_INLINE_LEN-sized buffer > > - for out-of-line names, it knows that the name allocation is stable > and ref-counted, and just increments the refcount and uses the > existing name pointer. > > now, maybe you need to always do that name allocation anyway (looking > at the diff it looks like you often do that for other cases), so maybe > the name snapshot capability isn't all that useful for you and the > above wouldn't have helped, but I suspect you might not even have > realized that there was an option like this. > > I've pulled this, but maybe Jeff wants to look at whether that > snapshotting model could have helped. > > Linus Thanks for the info! I think it would have. I took a quick look at the dcache code to see if we had something like that before I did this, but I guess I didn't look closely enough. Those routines do look nicer than my hand-rolled version. I'll look at spinning up a patch to switch that over in the near future. Thanks, -- Jeff Layton <jlayton@xxxxxxxxxx>
