On Wed, Oct 19, 2011 at 02:38:49PM -0400, Steve Dickson wrote: > > > On 10/19/2011 01:36 PM, J. Bruce Fields wrote: > > On Wed, Oct 19, 2011 at 01:30:58PM -0400, Steve Dickson wrote: > >> > >> > >> On 10/19/2011 01:22 PM, Jeff Layton wrote: > >>> On Wed, 19 Oct 2011 13:10:19 -0400 > >>> Steve Dickson <SteveD@xxxxxxxxxx> wrote: > >>> > >>>> > >>>> > >>>> On 10/19/2011 12:36 PM, Jeff Layton wrote: > >>>>> On Wed, 19 Oct 2011 11:34:30 -0400 > >>>>> Steve Dickson <steved@xxxxxxxxxx> 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 <steved@xxxxxxxxxx> > >>>>>> --- > >>>>>> 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! > >>>> > >>> > >>> Ahh, then you have another problem here too then. Most likely it was > >>> crashing because it caught a SIGXFSZ. Writing out the mtab should not > >>> be affected by signals. > >> So calling fflush() generates a SIGXFSZ and call fsync() does not... > > > > fflush() must hit this because it's calling write() to write out the > > stream buffer.... > > > > But lock_mtab() should have set SIGXFSZ to be ignored; is that not > > happening? > This is the case. The following patch cause SIGXFSZ to be ignored. > > diff -up ./utils/mount/fstab.c.orig ./utils/mount/fstab.c > --- ./utils/mount/fstab.c.orig 2011-10-19 13:28:57.318132000 -0400 > +++ ./utils/mount/fstab.c 2011-10-19 14:02:07.715039000 -0400 > @@ -387,8 +387,9 @@ lock_mtab (void) { > sa.sa_flags = 0; > sigfillset (&sa.sa_mask); > > - while (sigismember (&sa.sa_mask, ++sig) != -1 > - && sig != SIGCHLD) { I'm very confused--the latest nfs-utils doesn't have this. Oh, I see: it was fixed by b3e190c4adfc9ec47567c968bd000d282d07b05e "mount: improve signal management when locking mtab". So if you're working with an older version then you probably want to backport that patch. --b. > + while (sigismember (&sa.sa_mask, ++sig) != -1) { > + if (sig == SIGCHLD) > + continue; > if (sig == SIGALRM) > sa.sa_handler = setlkw_timeout; > else > > Now all this does is cause mount to ignore the fact that > the write() during the fflush() fails, which causes the > following warning during the umount. > > [mntent]: warning: no final newline at the end of /etc/mtab > [mntent]: warning: no final newline at the end of /etc/mtab > [mntent]: warning: no final newline at the end of /etc/mtab > > I can live with those warnings.... > > steved. > > > > >> I really don't see what the problem is is call simply calling fsync() > >> which clearly works? > > > > We want to make sure the problem's really fixed. > > > > --b. -- To unsubscribe from this list: send the line "unsubscribe linux-nfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
