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Old 01-22-2009, 05:52 PM
"J. Bruce Fields"
 
Default nfsd: only set file_lock.fl_lmops in nfsd4_lockt if a stateowner is found

On Wed, Jan 21, 2009 at 11:34:51AM -0500, Jeff Layton wrote:
> nfsd4_lockt does a search for a lockstateowner when building the lock
> struct to test. If one is found, it'll set fl_owner to it. Regardless of
> whether that happens, it'll also set fl_lmops.
>
> If a lockstateowner is not found, then we'll have fl_owner set to NULL
> and fl_lmops set pointing to nfsd_posix_mng_ops. Other parts of the
> NFSv4 server code assume that fl_owner will point to a valid
> nfs4_stateowner if fl_lmops is set this way.
>
> This behavior exposed a bug in DLM's GETLK implementation where it
> wasn't clearing out the fields in the file_lock before filling in
> conflicting lock info. While we were able to fix this in DLM, it
> still seems pointless and dangerous to set the fl_lmops this way
> when we have a NULL lockstateowner.
>
> Signed-off-by: Jeff Layton <jlayton@redhat.com>
> ---
> fs/nfsd/nfs4state.c | 6 ++++--
> 1 files changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 88db7d3..07d196a 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -2867,11 +2867,13 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
>
> lockt->lt_stateowner = find_lockstateowner_str(inode,
> &lockt->lt_clientid, &lockt->lt_owner);
> - if (lockt->lt_stateowner)
> + if (lockt->lt_stateowner) {
> file_lock.fl_owner = (fl_owner_t)lockt->lt_stateowner;
> + file_lock.fl_lmops = &nfsd_posix_mng_ops;

So I think we just shouldn't need this second assignment at all.

--b.

> + }
> +
> file_lock.fl_pid = current->tgid;
> file_lock.fl_flags = FL_POSIX;
> - file_lock.fl_lmops = &nfsd_posix_mng_ops;
>
> file_lock.fl_start = lockt->lt_offset;
> file_lock.fl_end = last_byte_offset(lockt->lt_offset, lockt->lt_length);
> --
> 1.5.5.6
>
> _______________________________________________
> NFSv4 mailing list
> NFSv4@linux-nfs.org
> http://linux-nfs.org/cgi-bin/mailman/listinfo/nfsv4
 
Old 01-22-2009, 06:12 PM
"J. Bruce Fields"
 
Default nfsd: only set file_lock.fl_lmops in nfsd4_lockt if a stateowner is found

On Thu, Jan 22, 2009 at 01:58:38PM -0500, Jeff Layton wrote:
> On Thu, 22 Jan 2009 13:52:32 -0500
> "J. Bruce Fields" <bfields@fieldses.org> wrote:
>
> > On Wed, Jan 21, 2009 at 11:34:51AM -0500, Jeff Layton wrote:
> > > nfsd4_lockt does a search for a lockstateowner when building the lock
> > > struct to test. If one is found, it'll set fl_owner to it. Regardless of
> > > whether that happens, it'll also set fl_lmops.
> > >
> > > If a lockstateowner is not found, then we'll have fl_owner set to NULL
> > > and fl_lmops set pointing to nfsd_posix_mng_ops. Other parts of the
> > > NFSv4 server code assume that fl_owner will point to a valid
> > > nfs4_stateowner if fl_lmops is set this way.
> > >
> > > This behavior exposed a bug in DLM's GETLK implementation where it
> > > wasn't clearing out the fields in the file_lock before filling in
> > > conflicting lock info. While we were able to fix this in DLM, it
> > > still seems pointless and dangerous to set the fl_lmops this way
> > > when we have a NULL lockstateowner.
> > >
> > > Signed-off-by: Jeff Layton <jlayton@redhat.com>
> > > ---
> > > fs/nfsd/nfs4state.c | 6 ++++--
> > > 1 files changed, 4 insertions(+), 2 deletions(-)
> > >
> > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > > index 88db7d3..07d196a 100644
> > > --- a/fs/nfsd/nfs4state.c
> > > +++ b/fs/nfsd/nfs4state.c
> > > @@ -2867,11 +2867,13 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> > >
> > > lockt->lt_stateowner = find_lockstateowner_str(inode,
> > > &lockt->lt_clientid, &lockt->lt_owner);
> > > - if (lockt->lt_stateowner)
> > > + if (lockt->lt_stateowner) {
> > > file_lock.fl_owner = (fl_owner_t)lockt->lt_stateowner;
> > > + file_lock.fl_lmops = &nfsd_posix_mng_ops;
> >
> > So I think we just shouldn't need this second assignment at all.
> >
> > --b.
> >
>
> Do we even need to worry about the lockstateowner at all then? If
> fl_lmops isn't set then I think the fl_owner will be basically ignored
> by nfs4_set_lock_denied anyway.

Yeah, I think nfs4_set_lock_denied should just set dummy values for now.

If we don't, then nfsd_test_lock is passing back a lock with a pointer
to a real reference-counted object, and I worry about what happens if
e.g. locks are being freed concurrently with our processing of the
conflicting lock here.

Our holding the nfs4_state_lock() here may be enough to prevent
problems, but it seems fragile.

And getting the conflicting lock completely right just isn't that high a
priority.

--b.
 
Old 01-22-2009, 06:15 PM
"J. Bruce Fields"
 
Default nfsd: only set file_lock.fl_lmops in nfsd4_lockt if a stateowner is found

On Thu, Jan 22, 2009 at 02:09:02PM -0500, Jeff Layton wrote:
> On Thu, 22 Jan 2009 13:59:30 -0500
> Jeff Layton <jlayton@redhat.com> wrote:
>
> > On Thu, 22 Jan 2009 13:52:32 -0500
> > "J. Bruce Fields" <bfields@fieldses.org> wrote:
> >
> > > On Wed, Jan 21, 2009 at 11:34:51AM -0500, Jeff Layton wrote:
> > > > nfsd4_lockt does a search for a lockstateowner when building the lock
> > > > struct to test. If one is found, it'll set fl_owner to it. Regardless of
> > > > whether that happens, it'll also set fl_lmops.
> > > >
> > > > If a lockstateowner is not found, then we'll have fl_owner set to NULL
> > > > and fl_lmops set pointing to nfsd_posix_mng_ops. Other parts of the
> > > > NFSv4 server code assume that fl_owner will point to a valid
> > > > nfs4_stateowner if fl_lmops is set this way.
> > > >
> > > > This behavior exposed a bug in DLM's GETLK implementation where it
> > > > wasn't clearing out the fields in the file_lock before filling in
> > > > conflicting lock info. While we were able to fix this in DLM, it
> > > > still seems pointless and dangerous to set the fl_lmops this way
> > > > when we have a NULL lockstateowner.
> > > >
> > > > Signed-off-by: Jeff Layton <jlayton@redhat.com>
> > > > ---
> > > > fs/nfsd/nfs4state.c | 6 ++++--
> > > > 1 files changed, 4 insertions(+), 2 deletions(-)
> > > >
> > > > diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> > > > index 88db7d3..07d196a 100644
> > > > --- a/fs/nfsd/nfs4state.c
> > > > +++ b/fs/nfsd/nfs4state.c
> > > > @@ -2867,11 +2867,13 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> > > >
> > > > lockt->lt_stateowner = find_lockstateowner_str(inode,
> > > > &lockt->lt_clientid, &lockt->lt_owner);
> > > > - if (lockt->lt_stateowner)
> > > > + if (lockt->lt_stateowner) {
> > > > file_lock.fl_owner = (fl_owner_t)lockt->lt_stateowner;
> > > > + file_lock.fl_lmops = &nfsd_posix_mng_ops;
> > >
> > > So I think we just shouldn't need this second assignment at all.
> > >
> > > --b.
> > >
> >
> > Do we even need to worry about the lockstateowner at all then? If
> > fl_lmops isn't set then I think the fl_owner will be basically ignored
> > by nfs4_set_lock_denied anyway.
> >
>
> Ahh, nm. I think we do need to set fl_owner so that posix_same_owner
> does the right thing. I'll just get rid of the fl_lmops setting and I
> think that'll be done.

Right, but that does mean set_lock_denied is never going to see fl_lmops
set and hence isn't really going to use the returned fl_owner. Which I
can live with.

--b.
 
Old 01-27-2009, 09:33 PM
"J. Bruce Fields"
 
Default nfsd: only set file_lock.fl_lmops in nfsd4_lockt if a stateowner is found

On Thu, Jan 22, 2009 at 02:16:04PM -0500, Jeff Layton wrote:
> nfsd4_lockt does a search for a lockstateowner when building the lock
> struct to test. If one is found, it'll set fl_owner to it. Regardless of
> whether that happens, it'll also set fl_lmops. Given that this lock is
> basically a "lightweight" lock that's just used for checking conflicts,
> setting fl_lmops is probably not appropriate for it.
>
> This behavior exposed a bug in DLM's GETLK implementation where it
> wasn't clearing out the fields in the file_lock before filling in
> conflicting lock info. While we were able to fix this in DLM, it
> still seems pointless and dangerous to set the fl_lmops this way
> when we may have a NULL lockstateowner.
>
> Signed-off-by: Jeff Layton <jlayton@redhat.com>

Thanks, applied.--b.

> ---
> fs/nfsd/nfs4state.c | 1 -
> 1 files changed, 0 insertions(+), 1 deletions(-)
>
> diff --git a/fs/nfsd/nfs4state.c b/fs/nfsd/nfs4state.c
> index 88db7d3..b6f60f4 100644
> --- a/fs/nfsd/nfs4state.c
> +++ b/fs/nfsd/nfs4state.c
> @@ -2871,7 +2871,6 @@ nfsd4_lockt(struct svc_rqst *rqstp, struct nfsd4_compound_state *cstate,
> file_lock.fl_owner = (fl_owner_t)lockt->lt_stateowner;
> file_lock.fl_pid = current->tgid;
> file_lock.fl_flags = FL_POSIX;
> - file_lock.fl_lmops = &nfsd_posix_mng_ops;
>
> file_lock.fl_start = lockt->lt_offset;
> file_lock.fl_end = last_byte_offset(lockt->lt_offset, lockt->lt_length);
> --
> 1.5.5.6
>
 

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