Core Dump / panic sleeping thread

[Rick Macklem]

Konstantin Belousov wrote:
> On Wed, Mar 20, 2013 at 12:13:05PM +0100, Michael Landin Hostbaek
> wrote:
> >
> > On Mar 20, 2013, at 10:49 AM, Konstantin Belousov
> > <kostikbel at gmail.com> wrote:
> > >
> > > I do not like it. As I said in the previous response to Andrey,
> > > I think that moving the vnode_pager_setsize() after the unlock is
> > > better, since it reduces races with other thread seeing half-done
> > > attribute update or making attribute change simultaneously.
> >
> > OK - so should I wait for another patch - or?
> 
> I think the following is what I mean. As an additional note, why nfs
> client does not trim the buffers when server reported node size change
> ?
> 
> diff --git a/sys/fs/nfsclient/nfs_clport.c
> b/sys/fs/nfsclient/nfs_clport.c
> index a07a67f..4fe2e35 100644
> --- a/sys/fs/nfsclient/nfs_clport.c
> +++ b/sys/fs/nfsclient/nfs_clport.c
> @@ -361,6 +361,8 @@ nfscl_loadattrcache(struct vnode **vpp, struct
> nfsvattr *nap, void *nvaper,
> struct nfsnode *np;
> struct nfsmount *nmp;
> struct timespec mtime_save;
> + u_quad_t nsize;
> + int setnsize;
> 
> /*
> * If v_type == VNON it is a new node, so fill in the v_type,
> @@ -418,6 +420,7 @@ nfscl_loadattrcache(struct vnode **vpp, struct
> nfsvattr *nap, void *nvaper,
> } else
> vap->va_fsid = vp->v_mount->mnt_stat.f_fsid.val[0];
> np->n_attrstamp = time_second;
> + setnsize = 0;
> if (vap->va_size != np->n_size) {
> if (vap->va_type == VREG) {
> if (dontshrink && vap->va_size < np->n_size) {
> @@ -444,10 +447,13 @@ nfscl_loadattrcache(struct vnode **vpp, struct
> nfsvattr *nap, void *nvaper,
> np->n_size = vap->va_size;
> np->n_flag |= NSIZECHANGED;
> }
> - vnode_pager_setsize(vp, np->n_size);
> } else {
> np->n_size = vap->va_size;
> }
> + if (vap->va_type == VREG || vap->va_type == VDIR) {
> + setnsize = 1;
> + nsize = vap->va_size;
I might have used np->n_size here, since that is what is given
as the argument for the pre-patched version, but since
np->n_size should equal vap->va_size (it is set the same for
all cases in the code at this point), it doesn't really matter.

I have no idea what the implications of doing vnode_pager_setsize()
for VDIR is, but Kostik would be much more conversant that I on this,
so if he thinks it's ok, that's fine with me.

> + }
> }
> /*
> * The following checks are added to prevent a race between (say)
> @@ -480,6 +486,8 @@ nfscl_loadattrcache(struct vnode **vpp, struct
> nfsvattr *nap, void *nvaper,
> KDTRACE_NFS_ATTRCACHE_LOAD_DONE(vp, vap, 0);
> #endif
> NFSUNLOCKNODE(np);
> + if (setnsize)
> + vnode_pager_setsize(vp, nsize);
> return (0);
> }
Yes, I think Kostik's version of the patch is good. I had thought
of doing it that way, but want for the "minimal change" version.
I agree that avoiding unlocking/relocking the mutex is a good idea,
although I didn't see anything after the relock that I thought
might be an issue if something changed while unlocked.

Kostik, thanks for posting this version, rick
ps: Michael, I'd suggest you try this patch instead of mine.