Messages in this thread | | | Date | Fri, 14 Mar 2008 16:05:10 -0400 | Subject | Re: Oops in NFSv4 server in 2.6.23.17 | From | "J. Bruce Fields" <> |
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On Fri, Mar 14, 2008 at 08:53:03PM +0100, Lukas Hejtmanek wrote: > On Fri, Mar 14, 2008 at 03:33:50PM -0400, J. Bruce Fields wrote: > > OK, yes, I think so. Could you confirm whether this fixes it? > > I will test it on Monday as I cannot reboot the machine right now. > > Just a quick review - isn't the cache_get() call needed also on the line 185 in > the same file?
Right before the first nfsd_setuser_and_check_port()? I don't believe so.
The way it works is: the rqst_exp_find() calls bump the reference count on the export they return to us, as expected; so if we bail out after that line 185, the exp_put() at "out:" drops that reference, as it should, making fh_verify a no-op with respect to the reference count.
The only time we need a new reference is when we store that pointer in the filehandle, around line 233, as that's what creates a long-lived reference that will outlive the function.
The other cache_get() (in the "just rechecking" case) is there just to balance out the final exp_put() so every code path can share the same code at "out:".
I find that a little contorted. So I'll go ahead and submit this small patch to 2.6.25 and stable now (I have since managed to reproduce what I believe is your bug, though my symptoms were a little different), and then submit to 2.6.26 some cleanup which makes this more understandable, and brings fh_verify() a little closer to the kernel's aesthetic of small, minimally-indented functions.
That said, I'd definitely still appreciate your confirmation that this fixes your bug, so thanks for offering to retest that Monday.
--b.
> > > diff --git a/fs/nfsd/nfsfh.c b/fs/nfsd/nfsfh.c > > index 1eb771d..3e6b3f4 100644 > > --- a/fs/nfsd/nfsfh.c > > +++ b/fs/nfsd/nfsfh.c > > @@ -232,6 +232,7 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access) > > fhp->fh_dentry = dentry; > > fhp->fh_export = exp; > > nfsd_nr_verified++; > > + cache_get(&exp->h); > > } else { > > /* > > * just rechecking permissions > > @@ -241,6 +242,7 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access) > > dprintk("nfsd: fh_verify - just checking\n"); > > dentry = fhp->fh_dentry; > > exp = fhp->fh_export; > > + cache_get(&exp->h); > > /* > > * Set user creds for this exportpoint; necessary even > > * in the "just checking" case because this may be a > > @@ -252,8 +254,6 @@ fh_verify(struct svc_rqst *rqstp, struct svc_fh *fhp, int type, int access) > > if (error) > > goto out; > > } > > - cache_get(&exp->h); > > - > > > > error = nfsd_mode_check(rqstp, dentry->d_inode->i_mode, type); > > if (error) > > -- > Lukáš Hejtmánek -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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