[PATCH] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

[PATCH] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

[NeilBrown]

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Hi Trond/Anna,
 I'd like your thoughts on this patch.
 I have a customer whose NFS client occasionally gets into a state
 where it spins indefinitely sending WRITE (or OPEN) and getting an
 NFS4ERR_BAD_STATEID (or NFS4ERR_BAD_SEQID) error.  The  state manager
 doesn't try any recovery as the open owner is no longer in the rbtree -
 presumably due to an earlier NFS4ERR_BAD_SEQID.  I've seen at least one
   NFS: v4 server XXX returned a bad sequence-id error!
 in the logs.
 I don't know if this is a server problem or a client problem - client
 didn't have
  Commit: c7848f69ec4a ("NFSv4: OPEN must handle the NFS4ERR_IO return code correctly")
 which cause cause BAD_SEQID errors.
 However wherever the bug is we don't want the NFS client to spin like
 that.
 This patch removes the spinning when tested against a hacked NFS
 server which can be convinced to return BAD_SEQID and BAD_STATED for a
 given open owner.

 My main concern is: is there some other reason to remove the open owner
 from the rbtree other than to make sure it isn't used for new opens?

Thanks,
NeilBrown


When an NFS4ERR_BAD_SEQID is received the open-owner is removed from
the ->state_owners rbtree so that it will no longer be used.

If any stateids attached to this open-owner are still in use, and if a
request using one get an NFS4ERR_BAD_STATEID reply, this can for bad.

The state is marked as needing recovery and the nfs4_state_manager()
is scheduled to clean up.  nfs4_state_manager() finds states to be
recovered by walking the state_owners rbtree.  As the open-owner is
not in the rbtree, the bad state is not found so nfs4_state_manager()
completes having done nothing.  The request is then retried, with a
predicatable result (indefinite retries).

This patch changes NFS4ERR_BAD_SEQID handling to leave the open-owner
in the rbtree but mark it a 'stale'.  With this the indefinite retries
no longer happen.  Errors get to user-space instead if recovery
doesn't work.

Signed-off-by: NeilBrown <neilb@suse.com>
---
 fs/nfs/nfs4_fs.h   |  3 ++-
 fs/nfs/nfs4state.c | 18 +++++-------------
 2 files changed, 7 insertions(+), 14 deletions(-)

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 768456fa1b17..42244d1123f6 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -113,7 +113,8 @@ struct nfs4_state_owner {
 
 enum {
 	NFS_OWNER_RECLAIM_REBOOT,
-	NFS_OWNER_RECLAIM_NOGRACE
+	NFS_OWNER_RECLAIM_NOGRACE,
+	NFS_OWNER_STALE,
 };
 
 #define NFS_LOCK_NEW		0
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 9679f4749364..abacaf521d29 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -400,6 +400,8 @@ nfs4_find_state_owner_locked(struct nfs_server *server, struct rpc_cred *cred)
 			p = &parent->rb_left;
 		else if (cred > sp->so_cred)
 			p = &parent->rb_right;
+		else if (test_bit(NFS_OWNER_STALE, &sp->so_flags))
+			p = &parent->rb_left;
 		else {
 			if (!list_empty(&sp->so_lru))
 				list_del_init(&sp->so_lru);
@@ -427,6 +429,8 @@ nfs4_insert_state_owner_locked(struct nfs4_state_owner *new)
 			p = &parent->rb_left;
 		else if (new->so_cred > sp->so_cred)
 			p = &parent->rb_right;
+		else if (test_bit(NFS_OWNER_STALE, &sp->so_flags))
+			p = &parent->rb_left;
 		else {
 			if (!list_empty(&sp->so_lru))
 				list_del_init(&sp->so_lru);
@@ -499,19 +503,7 @@ nfs4_alloc_state_owner(struct nfs_server *server,
 static void
 nfs4_drop_state_owner(struct nfs4_state_owner *sp)
 {
-	struct rb_node *rb_node = &sp->so_server_node;
-
-	if (!RB_EMPTY_NODE(rb_node)) {
-		struct nfs_server *server = sp->so_server;
-		struct nfs_client *clp = server->nfs_client;
-
-		spin_lock(&clp->cl_lock);
-		if (!RB_EMPTY_NODE(rb_node)) {
-			rb_erase(rb_node, &server->state_owners);
-			RB_CLEAR_NODE(rb_node);
-		}
-		spin_unlock(&clp->cl_lock);
-	}
+	set_bit(NFS_OWNER_STALE, &sp->so_flags);
 }
 
 static void nfs4_free_state_owner(struct nfs4_state_owner *sp)
-- 
2.8.3


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Re: [PATCH] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

[NeilBrown]

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Hi again,
 I posted a version of this patch 4 months and got no reply, so
 thought it might be time to try again.
 This version includes a small change to handle the case when a
 delegation stateid gets a BAD_STATEID, in the context of the open-owner
 getting a BAD_SEQID.
 Obviously this whole issue can only happen if the server is buggy (or
 if the client is buggy, but I don't think it is), but it would be best
 to handle that case gracefully.  Currently it spins indefinitely.

Thanks,
NeilBrown

From: NeilBrown <neilb@suse.com>
Subject: [PATCH] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

When an NFS4ERR_BAD_SEQID is received the open-owner is removed from
the ->state_owners rbtree so that it will no longer be used.

If any stateids attached to this open-owner are still in use, and if a
request using one get an NFS4ERR_BAD_STATEID reply, this can for bad.

The state is marked as needing recovery and the nfs4_state_manager()
is scheduled to clean up.  nfs4_state_manager() finds states to be
recovered by walking the state_owners rbtree.  As the open-owner is
not in the rbtree, the bad state is not found so nfs4_state_manager()
completes having done nothing.  The request is then retried, with a
predicatable result (indefinite retries).

This patch changes NFS4ERR_BAD_SEQID handling to leave the open-owner
in the rbtree but mark it a 'stale'.  With this the indefinite retries
no longer happen.  Errors get to user-space instead if recovery
doesn't work.

If the stateid is for a delegation, the result is more complex.
nfs4_state_manager() tries to return the delegation but uses the
open-owner with the bad seqid to open files on the server, and this
fails with more BAD_SEQID errors.  To avoid this we update the
so_seqid.create_time of the bad open-owner so that it looks to the server
like a new open-owner and an OPEN_CONFIRM is requested.  This allows
the return of the delagation to complete.

Signed-off-by: NeilBrown <neilb@suse.com>
---
 fs/nfs/nfs4_fs.h   |  3 ++-
 fs/nfs/nfs4state.c | 22 +++++++++-------------
 2 files changed, 11 insertions(+), 14 deletions(-)

diff --git a/fs/nfs/nfs4_fs.h b/fs/nfs/nfs4_fs.h
index 3f0e459f2499..6be19814553f 100644
--- a/fs/nfs/nfs4_fs.h
+++ b/fs/nfs/nfs4_fs.h
@@ -113,7 +113,8 @@ struct nfs4_state_owner {
 
 enum {
 	NFS_OWNER_RECLAIM_REBOOT,
-	NFS_OWNER_RECLAIM_NOGRACE
+	NFS_OWNER_RECLAIM_NOGRACE,
+	NFS_OWNER_STALE,
 };
 
 #define NFS_LOCK_NEW		0
diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 74cc32490c7a..8ed2285fc527 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -397,6 +397,8 @@ nfs4_find_state_owner_locked(struct nfs_server *server, struct rpc_cred *cred)
 			p = &parent->rb_left;
 		else if (cred > sp->so_cred)
 			p = &parent->rb_right;
+		else if (test_bit(NFS_OWNER_STALE, &sp->so_flags))
+			p = &parent->rb_left;
 		else {
 			if (!list_empty(&sp->so_lru))
 				list_del_init(&sp->so_lru);
@@ -424,6 +426,8 @@ nfs4_insert_state_owner_locked(struct nfs4_state_owner *new)
 			p = &parent->rb_left;
 		else if (new->so_cred > sp->so_cred)
 			p = &parent->rb_right;
+		else if (test_bit(NFS_OWNER_STALE, &sp->so_flags))
+			p = &parent->rb_left;
 		else {
 			if (!list_empty(&sp->so_lru))
 				list_del_init(&sp->so_lru);
@@ -496,19 +500,11 @@ nfs4_alloc_state_owner(struct nfs_server *server,
 static void
 nfs4_drop_state_owner(struct nfs4_state_owner *sp)
 {
-	struct rb_node *rb_node = &sp->so_server_node;
-
-	if (!RB_EMPTY_NODE(rb_node)) {
-		struct nfs_server *server = sp->so_server;
-		struct nfs_client *clp = server->nfs_client;
-
-		spin_lock(&clp->cl_lock);
-		if (!RB_EMPTY_NODE(rb_node)) {
-			rb_erase(rb_node, &server->state_owners);
-			RB_CLEAR_NODE(rb_node);
-		}
-		spin_unlock(&clp->cl_lock);
-	}
+	set_bit(NFS_OWNER_STALE, &sp->so_flags);
+	/* Delegation recall might insist on using this open_owner
+	 * so reset it to force a new 'confirm' stage to be initiated.
+	 */
+	sp->so_seqid.create_time = ktime_get();
 }
 
 static void nfs4_free_state_owner(struct nfs4_state_owner *sp)
-- 
2.10.0


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Re: [PATCH] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

[Trond Myklebust]

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Re: [PATCH] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

[NeilBrown]

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On Sat, Oct 08 2016, Trond Myklebust wrote:

>> +	set_bit(NFS_OWNER_STALE, &sp->so_flags);
>> +	/* Delegation recall might insist on using this open_owner
>> +	 * so reset it to force a new 'confirm' stage to be initiated.
>> +	 */
>> +	sp->so_seqid.create_time = ktime_get();
>
> Hmm…. If you’re going to do this, then why mark the state_owner as stale at all? Why not just reset sp->so_seqid.flags and call nfs4_clear_open_state() to let the state recovery try to do what it can.

Good point ... I was too focused on how I got there and what I had
tested...

I cannot test this properly as I don't have a server that returned
BAD_SEQID, and I doubt I can convince the customer to test some new as
they have something that works, but I think this is correct.

Thanks,
NeilBrown

From: NeilBrown <neilb@suse.com>
Date: Fri, 3 Jun 2016 14:58:02 +1000
Subject: [PATCH] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

When an NFS4ERR_BAD_SEQID is received the open-owner is removed from
the ->state_owners rbtree so that it will no longer be used.

If any stateids attached to this open-owner are still in use, and if a
request using one gets an NFS4ERR_BAD_STATEID reply, this can for bad.

The state is marked as needing recovery and the nfs4_state_manager()
is scheduled to clean up.  nfs4_state_manager() finds states to be
recovered by walking the state_owners rbtree.  As the open-owner is
not in the rbtree, the bad state is not found so nfs4_state_manager()
completes having done nothing.  The request is then retried, with a
predicatable result (indefinite retries).

If the stateid is for a delegation, this open_owner will be used
to open files when the delegation is returned.  For that to work,
a new open-owner needs to be presented to the server.

This patch changes NFS4ERR_BAD_SEQID handling to leave the open-owner
in the rbtree but updates the 'create_time' so it looks like a new
open-owner.  With this the indefinite retries no longer happen.

Signed-off-by: NeilBrown <neilb@suse.com>
---
 fs/nfs/nfs4state.c | 17 ++++-------------
 1 file changed, 4 insertions(+), 13 deletions(-)

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index 74cc32490c7a..c4d721ed493d 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -496,19 +496,10 @@ nfs4_alloc_state_owner(struct nfs_server *server,
 static void
 nfs4_drop_state_owner(struct nfs4_state_owner *sp)
 {
-	struct rb_node *rb_node = &sp->so_server_node;
-
-	if (!RB_EMPTY_NODE(rb_node)) {
-		struct nfs_server *server = sp->so_server;
-		struct nfs_client *clp = server->nfs_client;
-
-		spin_lock(&clp->cl_lock);
-		if (!RB_EMPTY_NODE(rb_node)) {
-			rb_erase(rb_node, &server->state_owners);
-			RB_CLEAR_NODE(rb_node);
-		}
-		spin_unlock(&clp->cl_lock);
-	}
+	/* Delegation recall might insist on using this open_owner
+	 * so reset it to force a new 'confirm' stage to be initiated.
+	 */
+	sp->so_seqid.create_time = ktime_get();
 }
 
 static void nfs4_free_state_owner(struct nfs4_state_owner *sp)
-- 
2.10.0


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[PATCH resend] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

[NeilBrown]

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When an NFS4ERR_BAD_SEQID is received the open-owner is removed from
the ->state_owners rbtree so that it will no longer be used.

If any stateids attached to this open-owner are still in use, and if a
request using one gets an NFS4ERR_BAD_STATEID reply, this can for bad.

The state is marked as needing recovery and the nfs4_state_manager()
is scheduled to clean up.  nfs4_state_manager() finds states to be
recovered by walking the state_owners rbtree.  As the open-owner is
not in the rbtree, the bad state is not found so nfs4_state_manager()
completes having done nothing.  The request is then retried, with a
predicatable result (indefinite retries).

If the stateid is for a delegation, this open_owner will be used
to open files when the delegation is returned.  For that to work,
a new open-owner needs to be presented to the server.

This patch changes NFS4ERR_BAD_SEQID handling to leave the open-owner
in the rbtree but updates the 'create_time' so it looks like a new
open-owner.  With this the indefinite retries no longer happen.

Signed-off-by: NeilBrown <neilb@suse.com>
---

Hi Trond,
 It appears this one got lost too.
 I've added a comment as I thought an explanation was needed, and
 renamed the function from "drop" to "reset".

Thanks,
NeilBrown

 fs/nfs/nfs4state.c | 29 +++++++++++++----------------
 1 file changed, 13 insertions(+), 16 deletions(-)

diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
index cf869802ff23..1d152f4470cd 100644
--- a/fs/nfs/nfs4state.c
+++ b/fs/nfs/nfs4state.c
@@ -494,21 +494,18 @@ nfs4_alloc_state_owner(struct nfs_server *server,
 }
 
 static void
-nfs4_drop_state_owner(struct nfs4_state_owner *sp)
-{
-	struct rb_node *rb_node = &sp->so_server_node;
-
-	if (!RB_EMPTY_NODE(rb_node)) {
-		struct nfs_server *server = sp->so_server;
-		struct nfs_client *clp = server->nfs_client;
-
-		spin_lock(&clp->cl_lock);
-		if (!RB_EMPTY_NODE(rb_node)) {
-			rb_erase(rb_node, &server->state_owners);
-			RB_CLEAR_NODE(rb_node);
-		}
-		spin_unlock(&clp->cl_lock);
-	}
+nfs4_reset_state_owner(struct nfs4_state_owner *sp)
+{
+	/* This state_owner is no longer usable, but must
+	 * remain in place so that state recovery can find it
+	 * and the opens associated with it.
+	 * It may also be used for new 'open' request to
+	 * return a delegation to the server.
+	 * So update the 'create_time' so that it looks like
+	 * a new state_owner.  This will cause the server to
+	 * request an OPEN_CONFIRM to start a new sequence.
+	 */
+	sp->so_seqid.create_time = ktime_get();
 }
 
 static void nfs4_free_state_owner(struct nfs4_state_owner *sp)
@@ -1113,7 +1110,7 @@ void nfs_increment_open_seqid(int status, struct nfs_seqid *seqid)
 
 	sp = container_of(seqid->sequence, struct nfs4_state_owner, so_seqid);
 	if (status == -NFS4ERR_BAD_SEQID)
-		nfs4_drop_state_owner(sp);
+		nfs4_reset_state_owner(sp);
 	if (!nfs4_has_session(sp->so_server->nfs_client))
 		nfs_increment_seqid(status, seqid);
 }
-- 
2.11.0


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Re: [PATCH resend] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

[Olga Kornievskaia]

Since open_owner is no longer removed then the resources are not
freed. They will not be freed until unmount  (or reboot recovery).

There are (buggy) servers out there that might be forcing the client
to keep creating new open_owners. So if they are no longer released,
can't the client get into trouble here?

On Sun, Dec 18, 2016 at 7:48 PM, NeilBrown <neilb@suse.com> wrote:
>
> When an NFS4ERR_BAD_SEQID is received the open-owner is removed from
> the ->state_owners rbtree so that it will no longer be used.
>
> If any stateids attached to this open-owner are still in use, and if a
> request using one gets an NFS4ERR_BAD_STATEID reply, this can for bad.
>
> The state is marked as needing recovery and the nfs4_state_manager()
> is scheduled to clean up.  nfs4_state_manager() finds states to be
> recovered by walking the state_owners rbtree.  As the open-owner is
> not in the rbtree, the bad state is not found so nfs4_state_manager()
> completes having done nothing.  The request is then retried, with a
> predicatable result (indefinite retries).
>
> If the stateid is for a delegation, this open_owner will be used
> to open files when the delegation is returned.  For that to work,
> a new open-owner needs to be presented to the server.
>
> This patch changes NFS4ERR_BAD_SEQID handling to leave the open-owner
> in the rbtree but updates the 'create_time' so it looks like a new
> open-owner.  With this the indefinite retries no longer happen.
>
> Signed-off-by: NeilBrown <neilb@suse.com>
> ---
>
> Hi Trond,
>  It appears this one got lost too.
>  I've added a comment as I thought an explanation was needed, and
>  renamed the function from "drop" to "reset".
>
> Thanks,
> NeilBrown
>
>  fs/nfs/nfs4state.c | 29 +++++++++++++----------------
>  1 file changed, 13 insertions(+), 16 deletions(-)
>
> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
> index cf869802ff23..1d152f4470cd 100644
> --- a/fs/nfs/nfs4state.c
> +++ b/fs/nfs/nfs4state.c
> @@ -494,21 +494,18 @@ nfs4_alloc_state_owner(struct nfs_server *server,
>  }
>
>  static void
> -nfs4_drop_state_owner(struct nfs4_state_owner *sp)
> -{
> -       struct rb_node *rb_node = &sp->so_server_node;
> -
> -       if (!RB_EMPTY_NODE(rb_node)) {
> -               struct nfs_server *server = sp->so_server;
> -               struct nfs_client *clp = server->nfs_client;
> -
> -               spin_lock(&clp->cl_lock);
> -               if (!RB_EMPTY_NODE(rb_node)) {
> -                       rb_erase(rb_node, &server->state_owners);
> -                       RB_CLEAR_NODE(rb_node);
> -               }
> -               spin_unlock(&clp->cl_lock);
> -       }
> +nfs4_reset_state_owner(struct nfs4_state_owner *sp)
> +{
> +       /* This state_owner is no longer usable, but must
> +        * remain in place so that state recovery can find it
> +        * and the opens associated with it.
> +        * It may also be used for new 'open' request to
> +        * return a delegation to the server.
> +        * So update the 'create_time' so that it looks like
> +        * a new state_owner.  This will cause the server to
> +        * request an OPEN_CONFIRM to start a new sequence.
> +        */
> +       sp->so_seqid.create_time = ktime_get();
>  }
>
>  static void nfs4_free_state_owner(struct nfs4_state_owner *sp)
> @@ -1113,7 +1110,7 @@ void nfs_increment_open_seqid(int status, struct nfs_seqid *seqid)
>
>         sp = container_of(seqid->sequence, struct nfs4_state_owner, so_seqid);
>         if (status == -NFS4ERR_BAD_SEQID)
> -               nfs4_drop_state_owner(sp);
> +               nfs4_reset_state_owner(sp);
>         if (!nfs4_has_session(sp->so_server->nfs_client))
>                 nfs_increment_seqid(status, seqid);
>  }
> --
> 2.11.0
>

Re: [PATCH resend] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

[NeilBrown]

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On Mon, Mar 20 2017, Olga Kornievskaia wrote:

> Since open_owner is no longer removed then the resources are not
> freed. They will not be freed until unmount  (or reboot recovery).

I don't follow your reasoning.
When the last uses for a state owner is dropped by
nfs4_put_state_owner() (e.g. when the last open file using it is
closed), nfs4_put_state_owner() will add the state to
server->state_owners_lru.

nfs4_gc_state_owners() is called periodically (every time any file is
opened I think) and it will call nfs4_remove_state_owner_locked()
on any state which is sufficiently old enough (hasn't been used in
'lease-time'), and will then call nfs4_free_state_owner().
These two will release all resources.

Does that explanation fit with your understanding?

Thanks,
NeilBrown


>
> There are (buggy) servers out there that might be forcing the client
> to keep creating new open_owners. So if they are no longer released,
> can't the client get into trouble here?
>
> On Sun, Dec 18, 2016 at 7:48 PM, NeilBrown <neilb@suse.com> wrote:
>>
>> When an NFS4ERR_BAD_SEQID is received the open-owner is removed from
>> the ->state_owners rbtree so that it will no longer be used.
>>
>> If any stateids attached to this open-owner are still in use, and if a
>> request using one gets an NFS4ERR_BAD_STATEID reply, this can for bad.
>>
>> The state is marked as needing recovery and the nfs4_state_manager()
>> is scheduled to clean up.  nfs4_state_manager() finds states to be
>> recovered by walking the state_owners rbtree.  As the open-owner is
>> not in the rbtree, the bad state is not found so nfs4_state_manager()
>> completes having done nothing.  The request is then retried, with a
>> predicatable result (indefinite retries).
>>
>> If the stateid is for a delegation, this open_owner will be used
>> to open files when the delegation is returned.  For that to work,
>> a new open-owner needs to be presented to the server.
>>
>> This patch changes NFS4ERR_BAD_SEQID handling to leave the open-owner
>> in the rbtree but updates the 'create_time' so it looks like a new
>> open-owner.  With this the indefinite retries no longer happen.
>>
>> Signed-off-by: NeilBrown <neilb@suse.com>
>> ---
>>
>> Hi Trond,
>>  It appears this one got lost too.
>>  I've added a comment as I thought an explanation was needed, and
>>  renamed the function from "drop" to "reset".
>>
>> Thanks,
>> NeilBrown
>>
>>  fs/nfs/nfs4state.c | 29 +++++++++++++----------------
>>  1 file changed, 13 insertions(+), 16 deletions(-)
>>
>> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
>> index cf869802ff23..1d152f4470cd 100644
>> --- a/fs/nfs/nfs4state.c
>> +++ b/fs/nfs/nfs4state.c
>> @@ -494,21 +494,18 @@ nfs4_alloc_state_owner(struct nfs_server *server,
>>  }
>>
>>  static void
>> -nfs4_drop_state_owner(struct nfs4_state_owner *sp)
>> -{
>> -       struct rb_node *rb_node = &sp->so_server_node;
>> -
>> -       if (!RB_EMPTY_NODE(rb_node)) {
>> -               struct nfs_server *server = sp->so_server;
>> -               struct nfs_client *clp = server->nfs_client;
>> -
>> -               spin_lock(&clp->cl_lock);
>> -               if (!RB_EMPTY_NODE(rb_node)) {
>> -                       rb_erase(rb_node, &server->state_owners);
>> -                       RB_CLEAR_NODE(rb_node);
>> -               }
>> -               spin_unlock(&clp->cl_lock);
>> -       }
>> +nfs4_reset_state_owner(struct nfs4_state_owner *sp)
>> +{
>> +       /* This state_owner is no longer usable, but must
>> +        * remain in place so that state recovery can find it
>> +        * and the opens associated with it.
>> +        * It may also be used for new 'open' request to
>> +        * return a delegation to the server.
>> +        * So update the 'create_time' so that it looks like
>> +        * a new state_owner.  This will cause the server to
>> +        * request an OPEN_CONFIRM to start a new sequence.
>> +        */
>> +       sp->so_seqid.create_time = ktime_get();
>>  }
>>
>>  static void nfs4_free_state_owner(struct nfs4_state_owner *sp)
>> @@ -1113,7 +1110,7 @@ void nfs_increment_open_seqid(int status, struct nfs_seqid *seqid)
>>
>>         sp = container_of(seqid->sequence, struct nfs4_state_owner, so_seqid);
>>         if (status == -NFS4ERR_BAD_SEQID)
>> -               nfs4_drop_state_owner(sp);
>> +               nfs4_reset_state_owner(sp);
>>         if (!nfs4_has_session(sp->so_server->nfs_client))
>>                 nfs_increment_seqid(status, seqid);
>>  }
>> --
>> 2.11.0
>>

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Re: [PATCH resend] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

[Olga Kornievskaia]

On Mon, Mar 20, 2017 at 7:26 PM, NeilBrown <neilb@suse.com> wrote:
> On Mon, Mar 20 2017, Olga Kornievskaia wrote:
>
>> Since open_owner is no longer removed then the resources are not
>> freed. They will not be freed until unmount  (or reboot recovery).
>
> I don't follow your reasoning.
> When the last uses for a state owner is dropped by
> nfs4_put_state_owner() (e.g. when the last open file using it is
> closed), nfs4_put_state_owner() will add the state to
> server->state_owners_lru.
>
> nfs4_gc_state_owners() is called periodically (every time any file is
> opened I think) and it will call nfs4_remove_state_owner_locked()
> on any state which is sufficiently old enough (hasn't been used in
> 'lease-time'), and will then call nfs4_free_state_owner().
> These two will release all resources.
>
> Does that explanation fit with your understanding?

Thanks for the explanation. I was thinking about the rb-tree nodes.
The new open finds the same rb-tree node. I incorrectly thought that
it'd be generating a new node each time for the new open owner.

Thanks.

>
> Thanks,
> NeilBrown
>
>
>>
>> There are (buggy) servers out there that might be forcing the client
>> to keep creating new open_owners. So if they are no longer released,
>> can't the client get into trouble here?
>>
>> On Sun, Dec 18, 2016 at 7:48 PM, NeilBrown <neilb@suse.com> wrote:
>>>
>>> When an NFS4ERR_BAD_SEQID is received the open-owner is removed from
>>> the ->state_owners rbtree so that it will no longer be used.
>>>
>>> If any stateids attached to this open-owner are still in use, and if a
>>> request using one gets an NFS4ERR_BAD_STATEID reply, this can for bad.
>>>
>>> The state is marked as needing recovery and the nfs4_state_manager()
>>> is scheduled to clean up.  nfs4_state_manager() finds states to be
>>> recovered by walking the state_owners rbtree.  As the open-owner is
>>> not in the rbtree, the bad state is not found so nfs4_state_manager()
>>> completes having done nothing.  The request is then retried, with a
>>> predicatable result (indefinite retries).
>>>
>>> If the stateid is for a delegation, this open_owner will be used
>>> to open files when the delegation is returned.  For that to work,
>>> a new open-owner needs to be presented to the server.
>>>
>>> This patch changes NFS4ERR_BAD_SEQID handling to leave the open-owner
>>> in the rbtree but updates the 'create_time' so it looks like a new
>>> open-owner.  With this the indefinite retries no longer happen.
>>>
>>> Signed-off-by: NeilBrown <neilb@suse.com>
>>> ---
>>>
>>> Hi Trond,
>>>  It appears this one got lost too.
>>>  I've added a comment as I thought an explanation was needed, and
>>>  renamed the function from "drop" to "reset".
>>>
>>> Thanks,
>>> NeilBrown
>>>
>>>  fs/nfs/nfs4state.c | 29 +++++++++++++----------------
>>>  1 file changed, 13 insertions(+), 16 deletions(-)
>>>
>>> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
>>> index cf869802ff23..1d152f4470cd 100644
>>> --- a/fs/nfs/nfs4state.c
>>> +++ b/fs/nfs/nfs4state.c
>>> @@ -494,21 +494,18 @@ nfs4_alloc_state_owner(struct nfs_server *server,
>>>  }
>>>
>>>  static void
>>> -nfs4_drop_state_owner(struct nfs4_state_owner *sp)
>>> -{
>>> -       struct rb_node *rb_node = &sp->so_server_node;
>>> -
>>> -       if (!RB_EMPTY_NODE(rb_node)) {
>>> -               struct nfs_server *server = sp->so_server;
>>> -               struct nfs_client *clp = server->nfs_client;
>>> -
>>> -               spin_lock(&clp->cl_lock);
>>> -               if (!RB_EMPTY_NODE(rb_node)) {
>>> -                       rb_erase(rb_node, &server->state_owners);
>>> -                       RB_CLEAR_NODE(rb_node);
>>> -               }
>>> -               spin_unlock(&clp->cl_lock);
>>> -       }
>>> +nfs4_reset_state_owner(struct nfs4_state_owner *sp)
>>> +{
>>> +       /* This state_owner is no longer usable, but must
>>> +        * remain in place so that state recovery can find it
>>> +        * and the opens associated with it.
>>> +        * It may also be used for new 'open' request to
>>> +        * return a delegation to the server.
>>> +        * So update the 'create_time' so that it looks like
>>> +        * a new state_owner.  This will cause the server to
>>> +        * request an OPEN_CONFIRM to start a new sequence.
>>> +        */
>>> +       sp->so_seqid.create_time = ktime_get();
>>>  }
>>>
>>>  static void nfs4_free_state_owner(struct nfs4_state_owner *sp)
>>> @@ -1113,7 +1110,7 @@ void nfs_increment_open_seqid(int status, struct nfs_seqid *seqid)
>>>
>>>         sp = container_of(seqid->sequence, struct nfs4_state_owner, so_seqid);
>>>         if (status == -NFS4ERR_BAD_SEQID)
>>> -               nfs4_drop_state_owner(sp);
>>> +               nfs4_reset_state_owner(sp);
>>>         if (!nfs4_has_session(sp->so_server->nfs_client))
>>>                 nfs_increment_seqid(status, seqid);
>>>  }
>>> --
>>> 2.11.0
>>>

Re: [PATCH resend] NFS: Don't disconnect open-owner on NFS4ERR_BAD_SEQID

[Olga Kornievskaia]

On Tue, Mar 21, 2017 at 12:43 PM, Olga Kornievskaia <aglo@umich.edu> wrote:
> On Mon, Mar 20, 2017 at 7:26 PM, NeilBrown <neilb@suse.com> wrote:
>> On Mon, Mar 20 2017, Olga Kornievskaia wrote:
>>
>>> Since open_owner is no longer removed then the resources are not
>>> freed. They will not be freed until unmount  (or reboot recovery).
>>
>> I don't follow your reasoning.
>> When the last uses for a state owner is dropped by
>> nfs4_put_state_owner() (e.g. when the last open file using it is
>> closed), nfs4_put_state_owner() will add the state to
>> server->state_owners_lru.
>>
>> nfs4_gc_state_owners() is called periodically (every time any file is
>> opened I think) and it will call nfs4_remove_state_owner_locked()
>> on any state which is sufficiently old enough (hasn't been used in
>> 'lease-time'), and will then call nfs4_free_state_owner().
>> These two will release all resources.
>>
>> Does that explanation fit with your understanding?
>
> Thanks for the explanation. I was thinking about the rb-tree nodes.
> The new open finds the same rb-tree node. I incorrectly thought that
> it'd be generating a new node each time for the new open owner.

I have another question about this patch. With this patch, when the
new open owner is sent, it is sent with a seqid of what the old open
owner had. Is this intentional or accidental?

>
> Thanks.
>
>>
>> Thanks,
>> NeilBrown
>>
>>
>>>
>>> There are (buggy) servers out there that might be forcing the client
>>> to keep creating new open_owners. So if they are no longer released,
>>> can't the client get into trouble here?
>>>
>>> On Sun, Dec 18, 2016 at 7:48 PM, NeilBrown <neilb@suse.com> wrote:
>>>>
>>>> When an NFS4ERR_BAD_SEQID is received the open-owner is removed from
>>>> the ->state_owners rbtree so that it will no longer be used.
>>>>
>>>> If any stateids attached to this open-owner are still in use, and if a
>>>> request using one gets an NFS4ERR_BAD_STATEID reply, this can for bad.
>>>>
>>>> The state is marked as needing recovery and the nfs4_state_manager()
>>>> is scheduled to clean up.  nfs4_state_manager() finds states to be
>>>> recovered by walking the state_owners rbtree.  As the open-owner is
>>>> not in the rbtree, the bad state is not found so nfs4_state_manager()
>>>> completes having done nothing.  The request is then retried, with a
>>>> predicatable result (indefinite retries).
>>>>
>>>> If the stateid is for a delegation, this open_owner will be used
>>>> to open files when the delegation is returned.  For that to work,
>>>> a new open-owner needs to be presented to the server.
>>>>
>>>> This patch changes NFS4ERR_BAD_SEQID handling to leave the open-owner
>>>> in the rbtree but updates the 'create_time' so it looks like a new
>>>> open-owner.  With this the indefinite retries no longer happen.
>>>>
>>>> Signed-off-by: NeilBrown <neilb@suse.com>
>>>> ---
>>>>
>>>> Hi Trond,
>>>>  It appears this one got lost too.
>>>>  I've added a comment as I thought an explanation was needed, and
>>>>  renamed the function from "drop" to "reset".
>>>>
>>>> Thanks,
>>>> NeilBrown
>>>>
>>>>  fs/nfs/nfs4state.c | 29 +++++++++++++----------------
>>>>  1 file changed, 13 insertions(+), 16 deletions(-)
>>>>
>>>> diff --git a/fs/nfs/nfs4state.c b/fs/nfs/nfs4state.c
>>>> index cf869802ff23..1d152f4470cd 100644
>>>> --- a/fs/nfs/nfs4state.c
>>>> +++ b/fs/nfs/nfs4state.c
>>>> @@ -494,21 +494,18 @@ nfs4_alloc_state_owner(struct nfs_server *server,
>>>>  }
>>>>
>>>>  static void
>>>> -nfs4_drop_state_owner(struct nfs4_state_owner *sp)
>>>> -{
>>>> -       struct rb_node *rb_node = &sp->so_server_node;
>>>> -
>>>> -       if (!RB_EMPTY_NODE(rb_node)) {
>>>> -               struct nfs_server *server = sp->so_server;
>>>> -               struct nfs_client *clp = server->nfs_client;
>>>> -
>>>> -               spin_lock(&clp->cl_lock);
>>>> -               if (!RB_EMPTY_NODE(rb_node)) {
>>>> -                       rb_erase(rb_node, &server->state_owners);
>>>> -                       RB_CLEAR_NODE(rb_node);
>>>> -               }
>>>> -               spin_unlock(&clp->cl_lock);
>>>> -       }
>>>> +nfs4_reset_state_owner(struct nfs4_state_owner *sp)
>>>> +{
>>>> +       /* This state_owner is no longer usable, but must
>>>> +        * remain in place so that state recovery can find it
>>>> +        * and the opens associated with it.
>>>> +        * It may also be used for new 'open' request to
>>>> +        * return a delegation to the server.
>>>> +        * So update the 'create_time' so that it looks like
>>>> +        * a new state_owner.  This will cause the server to
>>>> +        * request an OPEN_CONFIRM to start a new sequence.
>>>> +        */
>>>> +       sp->so_seqid.create_time = ktime_get();
>>>>  }
>>>>
>>>>  static void nfs4_free_state_owner(struct nfs4_state_owner *sp)
>>>> @@ -1113,7 +1110,7 @@ void nfs_increment_open_seqid(int status, struct nfs_seqid *seqid)
>>>>
>>>>         sp = container_of(seqid->sequence, struct nfs4_state_owner, so_seqid);
>>>>         if (status == -NFS4ERR_BAD_SEQID)
>>>> -               nfs4_drop_state_owner(sp);
>>>> +               nfs4_reset_state_owner(sp);
>>>>         if (!nfs4_has_session(sp->so_server->nfs_client))
>>>>                 nfs_increment_seqid(status, seqid);
>>>>  }
>>>> --
>>>> 2.11.0
>>>>