From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: linux-nfs-owner@vger.kernel.org Received: from mx1.redhat.com ([209.132.183.28]:13197 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755659Ab1JSRKV (ORCPT ); Wed, 19 Oct 2011 13:10:21 -0400 Message-ID: <4E9F047B.5000600@RedHat.com> Date: Wed, 19 Oct 2011 13:10:19 -0400 From: Steve Dickson MIME-Version: 1.0 To: Jeff Layton CC: Linux NFS Mailing list Subject: Re: [PATCH 1/1] mount.nfs: mtab corruption when RLIMIT_FSIZE causes a partial write References: <1319038470-17750-1-git-send-email-steved@redhat.com> <20111019123626.7a80dfad@corrin.poochiereds.net> In-Reply-To: <20111019123626.7a80dfad@corrin.poochiereds.net> Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-nfs-owner@vger.kernel.org List-ID: On 10/19/2011 12:36 PM, Jeff Layton wrote: > On Wed, 19 Oct 2011 11:34:30 -0400 > Steve Dickson wrote: > >> This patch is a following on to commit 7a802337. Using the >> tool in https://bugzilla.redhat.com/show_bug.cgi?id=695916 >> caused the fflush() and fclose() to fail in turn causing >> corruption in the mtab. >> >> The failures were in the internals of both calls. Switch those >> calls with the actual system calls eliminated the failures. >> >> Signed-off-by: Steve Dickson >> --- >> support/nfs/nfs_mntent.c | 4 ++-- >> 1 files changed, 2 insertions(+), 2 deletions(-) >> >> diff --git a/support/nfs/nfs_mntent.c b/support/nfs/nfs_mntent.c >> index a2118a2..b80f270 100644 >> --- a/support/nfs/nfs_mntent.c >> +++ b/support/nfs/nfs_mntent.c >> @@ -117,7 +117,7 @@ void >> nfs_endmntent (mntFILE *mfp) { >> if (mfp) { >> if (mfp->mntent_fp) >> - fclose(mfp->mntent_fp); >> + close(fileno(mfp->mntent_fp)); >> if (mfp->mntent_file) >> free(mfp->mntent_file); >> free(mfp); >> @@ -147,7 +147,7 @@ nfs_addmntent (mntFILE *mfp, struct mntent *mnt) { >> free(m3); >> free(m4); >> if (res >= 0) { >> - res = fflush(mfp->mntent_fp); >> + res = fsync(fileno(mfp->mntent_fp)); > > fsync doesn't imply an fflush. With this, I think you may end up > without everything being committed to disk if part or all of it is > still in the file stream buffer. You probably want to do an fflush() > and then an fsync here. The problem was with the fflush() call. The call was causing the mount to drop core in turn causing mtab corruption. Changing that call to a fsync() worked just fine... no corruption... every time! steved. > >> if (res < 0) >> /* Avoid leaving a corrupt mtab file */ >> ftruncate(fileno(mfp->mntent_fp), length); > >