* [PATCH] xen-blkback: prevent premature module unload
@ 2019-12-10 14:53 ` Paul Durrant
0 siblings, 0 replies; 14+ messages in thread
From: Paul Durrant @ 2019-12-10 14:53 UTC (permalink / raw)
To: xen-devel, linux-block, linux-kernel
Cc: Paul Durrant, Konrad Rzeszutek Wilk, Roger Pau Monné, Jens Axboe
Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
cache. This cache is destoyed when xen-blkif is unloaded so it is
necessary to wait for the deferred free routine used for such objects to
complete. This necessity was missed in commit 14855954f636 "xen-blkback:
allow module to be cleanly unloaded". This patch fixes the problem by
taking/releasing extra module references in xen_blkif_alloc/free()
respectively.
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: Jens Axboe <axboe@kernel.dk>
---
drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index e8c5c54e1d26..59d576d27ca7 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -171,6 +171,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
blkif->domid = domid;
atomic_set(&blkif->refcnt, 1);
init_completion(&blkif->drain_complete);
+
+ /*
+ * Because freeing back to the cache may be deferred, it is not
+ * safe to unload the module (and hence destroy the cache) until
+ * this has completed. To prevent premature unloading, take an
+ * extra module reference here and release only when the object
+ * has been free back to the cache.
+ */
+ __module_get(THIS_MODULE);
INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
return blkif;
@@ -320,6 +329,7 @@ static void xen_blkif_free(struct xen_blkif *blkif)
/* Make sure everything is drained before shutting down */
kmem_cache_free(xen_blkif_cachep, blkif);
+ module_put(THIS_MODULE);
}
int __init xen_blkif_interface_init(void)
--
2.20.1
^ permalink raw reply related [flat|nested] 14+ messages in thread
* [Xen-devel] [PATCH] xen-blkback: prevent premature module unload
@ 2019-12-10 14:53 ` Paul Durrant
0 siblings, 0 replies; 14+ messages in thread
From: Paul Durrant @ 2019-12-10 14:53 UTC (permalink / raw)
To: xen-devel, linux-block, linux-kernel
Cc: Jens Axboe, Paul Durrant, Roger Pau Monné, Konrad Rzeszutek Wilk
Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
cache. This cache is destoyed when xen-blkif is unloaded so it is
necessary to wait for the deferred free routine used for such objects to
complete. This necessity was missed in commit 14855954f636 "xen-blkback:
allow module to be cleanly unloaded". This patch fixes the problem by
taking/releasing extra module references in xen_blkif_alloc/free()
respectively.
Signed-off-by: Paul Durrant <pdurrant@amazon.com>
---
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: "Roger Pau Monné" <roger.pau@citrix.com>
Cc: Jens Axboe <axboe@kernel.dk>
---
drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
index e8c5c54e1d26..59d576d27ca7 100644
--- a/drivers/block/xen-blkback/xenbus.c
+++ b/drivers/block/xen-blkback/xenbus.c
@@ -171,6 +171,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
blkif->domid = domid;
atomic_set(&blkif->refcnt, 1);
init_completion(&blkif->drain_complete);
+
+ /*
+ * Because freeing back to the cache may be deferred, it is not
+ * safe to unload the module (and hence destroy the cache) until
+ * this has completed. To prevent premature unloading, take an
+ * extra module reference here and release only when the object
+ * has been free back to the cache.
+ */
+ __module_get(THIS_MODULE);
INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
return blkif;
@@ -320,6 +329,7 @@ static void xen_blkif_free(struct xen_blkif *blkif)
/* Make sure everything is drained before shutting down */
kmem_cache_free(xen_blkif_cachep, blkif);
+ module_put(THIS_MODULE);
}
int __init xen_blkif_interface_init(void)
--
2.20.1
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply related [flat|nested] 14+ messages in thread
* Re: [PATCH] xen-blkback: prevent premature module unload
2019-12-10 14:53 ` [Xen-devel] " Paul Durrant
@ 2019-12-11 11:28 ` Roger Pau Monné
-1 siblings, 0 replies; 14+ messages in thread
From: Roger Pau Monné @ 2019-12-11 11:28 UTC (permalink / raw)
To: Paul Durrant
Cc: xen-devel, linux-block, linux-kernel, Konrad Rzeszutek Wilk, Jens Axboe
On Tue, Dec 10, 2019 at 02:53:05PM +0000, Paul Durrant wrote:
> Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
> cache. This cache is destoyed when xen-blkif is unloaded so it is
> necessary to wait for the deferred free routine used for such objects to
> complete. This necessity was missed in commit 14855954f636 "xen-blkback:
> allow module to be cleanly unloaded". This patch fixes the problem by
> taking/releasing extra module references in xen_blkif_alloc/free()
> respectively.
>
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
One nit below.
> ---
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: "Roger Pau Monné" <roger.pau@citrix.com>
> Cc: Jens Axboe <axboe@kernel.dk>
> ---
> drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
> index e8c5c54e1d26..59d576d27ca7 100644
> --- a/drivers/block/xen-blkback/xenbus.c
> +++ b/drivers/block/xen-blkback/xenbus.c
> @@ -171,6 +171,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
> blkif->domid = domid;
> atomic_set(&blkif->refcnt, 1);
> init_completion(&blkif->drain_complete);
> +
> + /*
> + * Because freeing back to the cache may be deferred, it is not
> + * safe to unload the module (and hence destroy the cache) until
> + * this has completed. To prevent premature unloading, take an
> + * extra module reference here and release only when the object
> + * has been free back to the cache.
^ freed
> + */
> + __module_get(THIS_MODULE);
> INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
>
> return blkif;
> @@ -320,6 +329,7 @@ static void xen_blkif_free(struct xen_blkif *blkif)
>
> /* Make sure everything is drained before shutting down */
> kmem_cache_free(xen_blkif_cachep, blkif);
> + module_put(THIS_MODULE);
> }
>
> int __init xen_blkif_interface_init(void)
> --
> 2.20.1
>
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [Xen-devel] [PATCH] xen-blkback: prevent premature module unload
@ 2019-12-11 11:28 ` Roger Pau Monné
0 siblings, 0 replies; 14+ messages in thread
From: Roger Pau Monné @ 2019-12-11 11:28 UTC (permalink / raw)
To: Paul Durrant
Cc: linux-block, xen-devel, Jens Axboe, linux-kernel, Konrad Rzeszutek Wilk
On Tue, Dec 10, 2019 at 02:53:05PM +0000, Paul Durrant wrote:
> Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
> cache. This cache is destoyed when xen-blkif is unloaded so it is
> necessary to wait for the deferred free routine used for such objects to
> complete. This necessity was missed in commit 14855954f636 "xen-blkback:
> allow module to be cleanly unloaded". This patch fixes the problem by
> taking/releasing extra module references in xen_blkif_alloc/free()
> respectively.
>
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
One nit below.
> ---
> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> Cc: "Roger Pau Monné" <roger.pau@citrix.com>
> Cc: Jens Axboe <axboe@kernel.dk>
> ---
> drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
> 1 file changed, 10 insertions(+)
>
> diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
> index e8c5c54e1d26..59d576d27ca7 100644
> --- a/drivers/block/xen-blkback/xenbus.c
> +++ b/drivers/block/xen-blkback/xenbus.c
> @@ -171,6 +171,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t domid)
> blkif->domid = domid;
> atomic_set(&blkif->refcnt, 1);
> init_completion(&blkif->drain_complete);
> +
> + /*
> + * Because freeing back to the cache may be deferred, it is not
> + * safe to unload the module (and hence destroy the cache) until
> + * this has completed. To prevent premature unloading, take an
> + * extra module reference here and release only when the object
> + * has been free back to the cache.
^ freed
> + */
> + __module_get(THIS_MODULE);
> INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
>
> return blkif;
> @@ -320,6 +329,7 @@ static void xen_blkif_free(struct xen_blkif *blkif)
>
> /* Make sure everything is drained before shutting down */
> kmem_cache_free(xen_blkif_cachep, blkif);
> + module_put(THIS_MODULE);
> }
>
> int __init xen_blkif_interface_init(void)
> --
> 2.20.1
>
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 14+ messages in thread
* RE: [PATCH] xen-blkback: prevent premature module unload
2019-12-11 11:28 ` [Xen-devel] " Roger Pau Monné
@ 2019-12-11 13:27 ` Durrant, Paul
-1 siblings, 0 replies; 14+ messages in thread
From: Durrant, Paul @ 2019-12-11 13:27 UTC (permalink / raw)
To: Roger Pau Monné
Cc: xen-devel, linux-block, linux-kernel, Konrad Rzeszutek Wilk, Jens Axboe
> -----Original Message-----
> From: Roger Pau Monné <roger.pau@citrix.com>
> Sent: 11 December 2019 11:29
> To: Durrant, Paul <pdurrant@amazon.com>
> Cc: xen-devel@lists.xenproject.org; linux-block@vger.kernel.org; linux-
> kernel@vger.kernel.org; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
> Jens Axboe <axboe@kernel.dk>
> Subject: Re: [PATCH] xen-blkback: prevent premature module unload
>
> On Tue, Dec 10, 2019 at 02:53:05PM +0000, Paul Durrant wrote:
> > Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
> > cache. This cache is destoyed when xen-blkif is unloaded so it is
> > necessary to wait for the deferred free routine used for such objects to
> > complete. This necessity was missed in commit 14855954f636 "xen-blkback:
> > allow module to be cleanly unloaded". This patch fixes the problem by
> > taking/releasing extra module references in xen_blkif_alloc/free()
> > respectively.
> >
> > Signed-off-by: Paul Durrant <pdurrant@amazon.com>
>
> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
>
> One nit below.
>
> > ---
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > Cc: "Roger Pau Monné" <roger.pau@citrix.com>
> > Cc: Jens Axboe <axboe@kernel.dk>
> > ---
> > drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-
> blkback/xenbus.c
> > index e8c5c54e1d26..59d576d27ca7 100644
> > --- a/drivers/block/xen-blkback/xenbus.c
> > +++ b/drivers/block/xen-blkback/xenbus.c
> > @@ -171,6 +171,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t
> domid)
> > blkif->domid = domid;
> > atomic_set(&blkif->refcnt, 1);
> > init_completion(&blkif->drain_complete);
> > +
> > + /*
> > + * Because freeing back to the cache may be deferred, it is not
> > + * safe to unload the module (and hence destroy the cache) until
> > + * this has completed. To prevent premature unloading, take an
> > + * extra module reference here and release only when the object
> > + * has been free back to the cache.
> ^ freed
Oh yes. Can this be done on commit, or would you like me to send a v2?
Paul
> > + */
> > + __module_get(THIS_MODULE);
> > INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
> >
> > return blkif;
> > @@ -320,6 +329,7 @@ static void xen_blkif_free(struct xen_blkif *blkif)
> >
> > /* Make sure everything is drained before shutting down */
> > kmem_cache_free(xen_blkif_cachep, blkif);
> > + module_put(THIS_MODULE);
> > }
> >
> > int __init xen_blkif_interface_init(void)
> > --
> > 2.20.1
> >
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [Xen-devel] [PATCH] xen-blkback: prevent premature module unload
@ 2019-12-11 13:27 ` Durrant, Paul
0 siblings, 0 replies; 14+ messages in thread
From: Durrant, Paul @ 2019-12-11 13:27 UTC (permalink / raw)
To: Roger Pau Monné
Cc: linux-block, xen-devel, Jens Axboe, linux-kernel, Konrad Rzeszutek Wilk
> -----Original Message-----
> From: Roger Pau Monné <roger.pau@citrix.com>
> Sent: 11 December 2019 11:29
> To: Durrant, Paul <pdurrant@amazon.com>
> Cc: xen-devel@lists.xenproject.org; linux-block@vger.kernel.org; linux-
> kernel@vger.kernel.org; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
> Jens Axboe <axboe@kernel.dk>
> Subject: Re: [PATCH] xen-blkback: prevent premature module unload
>
> On Tue, Dec 10, 2019 at 02:53:05PM +0000, Paul Durrant wrote:
> > Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
> > cache. This cache is destoyed when xen-blkif is unloaded so it is
> > necessary to wait for the deferred free routine used for such objects to
> > complete. This necessity was missed in commit 14855954f636 "xen-blkback:
> > allow module to be cleanly unloaded". This patch fixes the problem by
> > taking/releasing extra module references in xen_blkif_alloc/free()
> > respectively.
> >
> > Signed-off-by: Paul Durrant <pdurrant@amazon.com>
>
> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
>
> One nit below.
>
> > ---
> > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > Cc: "Roger Pau Monné" <roger.pau@citrix.com>
> > Cc: Jens Axboe <axboe@kernel.dk>
> > ---
> > drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
> > 1 file changed, 10 insertions(+)
> >
> > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-
> blkback/xenbus.c
> > index e8c5c54e1d26..59d576d27ca7 100644
> > --- a/drivers/block/xen-blkback/xenbus.c
> > +++ b/drivers/block/xen-blkback/xenbus.c
> > @@ -171,6 +171,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t
> domid)
> > blkif->domid = domid;
> > atomic_set(&blkif->refcnt, 1);
> > init_completion(&blkif->drain_complete);
> > +
> > + /*
> > + * Because freeing back to the cache may be deferred, it is not
> > + * safe to unload the module (and hence destroy the cache) until
> > + * this has completed. To prevent premature unloading, take an
> > + * extra module reference here and release only when the object
> > + * has been free back to the cache.
> ^ freed
Oh yes. Can this be done on commit, or would you like me to send a v2?
Paul
> > + */
> > + __module_get(THIS_MODULE);
> > INIT_WORK(&blkif->free_work, xen_blkif_deferred_free);
> >
> > return blkif;
> > @@ -320,6 +329,7 @@ static void xen_blkif_free(struct xen_blkif *blkif)
> >
> > /* Make sure everything is drained before shutting down */
> > kmem_cache_free(xen_blkif_cachep, blkif);
> > + module_put(THIS_MODULE);
> > }
> >
> > int __init xen_blkif_interface_init(void)
> > --
> > 2.20.1
> >
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] xen-blkback: prevent premature module unload
2019-12-11 13:27 ` [Xen-devel] " Durrant, Paul
@ 2019-12-11 13:55 ` Roger Pau Monné
-1 siblings, 0 replies; 14+ messages in thread
From: Roger Pau Monné @ 2019-12-11 13:55 UTC (permalink / raw)
To: Durrant, Paul, Juergen Gross
Cc: xen-devel, linux-block, linux-kernel, Konrad Rzeszutek Wilk, Jens Axboe
On Wed, Dec 11, 2019 at 01:27:42PM +0000, Durrant, Paul wrote:
> > -----Original Message-----
> > From: Roger Pau Monné <roger.pau@citrix.com>
> > Sent: 11 December 2019 11:29
> > To: Durrant, Paul <pdurrant@amazon.com>
> > Cc: xen-devel@lists.xenproject.org; linux-block@vger.kernel.org; linux-
> > kernel@vger.kernel.org; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
> > Jens Axboe <axboe@kernel.dk>
> > Subject: Re: [PATCH] xen-blkback: prevent premature module unload
> >
> > On Tue, Dec 10, 2019 at 02:53:05PM +0000, Paul Durrant wrote:
> > > Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
> > > cache. This cache is destoyed when xen-blkif is unloaded so it is
> > > necessary to wait for the deferred free routine used for such objects to
> > > complete. This necessity was missed in commit 14855954f636 "xen-blkback:
> > > allow module to be cleanly unloaded". This patch fixes the problem by
> > > taking/releasing extra module references in xen_blkif_alloc/free()
> > > respectively.
> > >
> > > Signed-off-by: Paul Durrant <pdurrant@amazon.com>
> >
> > Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
> >
> > One nit below.
> >
> > > ---
> > > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > > Cc: "Roger Pau Monné" <roger.pau@citrix.com>
> > > Cc: Jens Axboe <axboe@kernel.dk>
> > > ---
> > > drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
> > > 1 file changed, 10 insertions(+)
> > >
> > > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-
> > blkback/xenbus.c
> > > index e8c5c54e1d26..59d576d27ca7 100644
> > > --- a/drivers/block/xen-blkback/xenbus.c
> > > +++ b/drivers/block/xen-blkback/xenbus.c
> > > @@ -171,6 +171,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t
> > domid)
> > > blkif->domid = domid;
> > > atomic_set(&blkif->refcnt, 1);
> > > init_completion(&blkif->drain_complete);
> > > +
> > > + /*
> > > + * Because freeing back to the cache may be deferred, it is not
> > > + * safe to unload the module (and hence destroy the cache) until
> > > + * this has completed. To prevent premature unloading, take an
> > > + * extra module reference here and release only when the object
> > > + * has been free back to the cache.
> > ^ freed
>
> Oh yes. Can this be done on commit, or would you like me to send a v2?
Adjusting on commit would be fine for me, but it's up to Juergen since
he is the one that will pick this up. IIRC the module unload patches
didn't go through the block subsystem.
Thanks, Roger.
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [Xen-devel] [PATCH] xen-blkback: prevent premature module unload
@ 2019-12-11 13:55 ` Roger Pau Monné
0 siblings, 0 replies; 14+ messages in thread
From: Roger Pau Monné @ 2019-12-11 13:55 UTC (permalink / raw)
To: Durrant, Paul, Juergen Gross
Cc: linux-block, xen-devel, Jens Axboe, linux-kernel, Konrad Rzeszutek Wilk
On Wed, Dec 11, 2019 at 01:27:42PM +0000, Durrant, Paul wrote:
> > -----Original Message-----
> > From: Roger Pau Monné <roger.pau@citrix.com>
> > Sent: 11 December 2019 11:29
> > To: Durrant, Paul <pdurrant@amazon.com>
> > Cc: xen-devel@lists.xenproject.org; linux-block@vger.kernel.org; linux-
> > kernel@vger.kernel.org; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
> > Jens Axboe <axboe@kernel.dk>
> > Subject: Re: [PATCH] xen-blkback: prevent premature module unload
> >
> > On Tue, Dec 10, 2019 at 02:53:05PM +0000, Paul Durrant wrote:
> > > Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
> > > cache. This cache is destoyed when xen-blkif is unloaded so it is
> > > necessary to wait for the deferred free routine used for such objects to
> > > complete. This necessity was missed in commit 14855954f636 "xen-blkback:
> > > allow module to be cleanly unloaded". This patch fixes the problem by
> > > taking/releasing extra module references in xen_blkif_alloc/free()
> > > respectively.
> > >
> > > Signed-off-by: Paul Durrant <pdurrant@amazon.com>
> >
> > Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
> >
> > One nit below.
> >
> > > ---
> > > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > > Cc: "Roger Pau Monné" <roger.pau@citrix.com>
> > > Cc: Jens Axboe <axboe@kernel.dk>
> > > ---
> > > drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
> > > 1 file changed, 10 insertions(+)
> > >
> > > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-
> > blkback/xenbus.c
> > > index e8c5c54e1d26..59d576d27ca7 100644
> > > --- a/drivers/block/xen-blkback/xenbus.c
> > > +++ b/drivers/block/xen-blkback/xenbus.c
> > > @@ -171,6 +171,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t
> > domid)
> > > blkif->domid = domid;
> > > atomic_set(&blkif->refcnt, 1);
> > > init_completion(&blkif->drain_complete);
> > > +
> > > + /*
> > > + * Because freeing back to the cache may be deferred, it is not
> > > + * safe to unload the module (and hence destroy the cache) until
> > > + * this has completed. To prevent premature unloading, take an
> > > + * extra module reference here and release only when the object
> > > + * has been free back to the cache.
> > ^ freed
>
> Oh yes. Can this be done on commit, or would you like me to send a v2?
Adjusting on commit would be fine for me, but it's up to Juergen since
he is the one that will pick this up. IIRC the module unload patches
didn't go through the block subsystem.
Thanks, Roger.
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] xen-blkback: prevent premature module unload
2019-12-11 13:55 ` [Xen-devel] " Roger Pau Monné
@ 2019-12-11 13:56 ` Jürgen Groß
-1 siblings, 0 replies; 14+ messages in thread
From: Jürgen Groß @ 2019-12-11 13:56 UTC (permalink / raw)
To: Roger Pau Monné, Durrant, Paul
Cc: xen-devel, linux-block, linux-kernel, Konrad Rzeszutek Wilk, Jens Axboe
On 11.12.19 14:55, Roger Pau Monné wrote:
> On Wed, Dec 11, 2019 at 01:27:42PM +0000, Durrant, Paul wrote:
>>> -----Original Message-----
>>> From: Roger Pau Monné <roger.pau@citrix.com>
>>> Sent: 11 December 2019 11:29
>>> To: Durrant, Paul <pdurrant@amazon.com>
>>> Cc: xen-devel@lists.xenproject.org; linux-block@vger.kernel.org; linux-
>>> kernel@vger.kernel.org; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
>>> Jens Axboe <axboe@kernel.dk>
>>> Subject: Re: [PATCH] xen-blkback: prevent premature module unload
>>>
>>> On Tue, Dec 10, 2019 at 02:53:05PM +0000, Paul Durrant wrote:
>>>> Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
>>>> cache. This cache is destoyed when xen-blkif is unloaded so it is
>>>> necessary to wait for the deferred free routine used for such objects to
>>>> complete. This necessity was missed in commit 14855954f636 "xen-blkback:
>>>> allow module to be cleanly unloaded". This patch fixes the problem by
>>>> taking/releasing extra module references in xen_blkif_alloc/free()
>>>> respectively.
>>>>
>>>> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
>>>
>>> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
>>>
>>> One nit below.
>>>
>>>> ---
>>>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>>>> Cc: "Roger Pau Monné" <roger.pau@citrix.com>
>>>> Cc: Jens Axboe <axboe@kernel.dk>
>>>> ---
>>>> drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
>>>> 1 file changed, 10 insertions(+)
>>>>
>>>> diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-
>>> blkback/xenbus.c
>>>> index e8c5c54e1d26..59d576d27ca7 100644
>>>> --- a/drivers/block/xen-blkback/xenbus.c
>>>> +++ b/drivers/block/xen-blkback/xenbus.c
>>>> @@ -171,6 +171,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t
>>> domid)
>>>> blkif->domid = domid;
>>>> atomic_set(&blkif->refcnt, 1);
>>>> init_completion(&blkif->drain_complete);
>>>> +
>>>> + /*
>>>> + * Because freeing back to the cache may be deferred, it is not
>>>> + * safe to unload the module (and hence destroy the cache) until
>>>> + * this has completed. To prevent premature unloading, take an
>>>> + * extra module reference here and release only when the object
>>>> + * has been free back to the cache.
>>> ^ freed
>>
>> Oh yes. Can this be done on commit, or would you like me to send a v2?
>
> Adjusting on commit would be fine for me, but it's up to Juergen since
> he is the one that will pick this up. IIRC the module unload patches
> didn't go through the block subsystem.
Oh, right. Yes, will fix this when committing.
Juergen
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [Xen-devel] [PATCH] xen-blkback: prevent premature module unload
@ 2019-12-11 13:56 ` Jürgen Groß
0 siblings, 0 replies; 14+ messages in thread
From: Jürgen Groß @ 2019-12-11 13:56 UTC (permalink / raw)
To: Roger Pau Monné, Durrant, Paul
Cc: linux-block, xen-devel, Jens Axboe, linux-kernel, Konrad Rzeszutek Wilk
On 11.12.19 14:55, Roger Pau Monné wrote:
> On Wed, Dec 11, 2019 at 01:27:42PM +0000, Durrant, Paul wrote:
>>> -----Original Message-----
>>> From: Roger Pau Monné <roger.pau@citrix.com>
>>> Sent: 11 December 2019 11:29
>>> To: Durrant, Paul <pdurrant@amazon.com>
>>> Cc: xen-devel@lists.xenproject.org; linux-block@vger.kernel.org; linux-
>>> kernel@vger.kernel.org; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
>>> Jens Axboe <axboe@kernel.dk>
>>> Subject: Re: [PATCH] xen-blkback: prevent premature module unload
>>>
>>> On Tue, Dec 10, 2019 at 02:53:05PM +0000, Paul Durrant wrote:
>>>> Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
>>>> cache. This cache is destoyed when xen-blkif is unloaded so it is
>>>> necessary to wait for the deferred free routine used for such objects to
>>>> complete. This necessity was missed in commit 14855954f636 "xen-blkback:
>>>> allow module to be cleanly unloaded". This patch fixes the problem by
>>>> taking/releasing extra module references in xen_blkif_alloc/free()
>>>> respectively.
>>>>
>>>> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
>>>
>>> Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
>>>
>>> One nit below.
>>>
>>>> ---
>>>> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
>>>> Cc: "Roger Pau Monné" <roger.pau@citrix.com>
>>>> Cc: Jens Axboe <axboe@kernel.dk>
>>>> ---
>>>> drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
>>>> 1 file changed, 10 insertions(+)
>>>>
>>>> diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-
>>> blkback/xenbus.c
>>>> index e8c5c54e1d26..59d576d27ca7 100644
>>>> --- a/drivers/block/xen-blkback/xenbus.c
>>>> +++ b/drivers/block/xen-blkback/xenbus.c
>>>> @@ -171,6 +171,15 @@ static struct xen_blkif *xen_blkif_alloc(domid_t
>>> domid)
>>>> blkif->domid = domid;
>>>> atomic_set(&blkif->refcnt, 1);
>>>> init_completion(&blkif->drain_complete);
>>>> +
>>>> + /*
>>>> + * Because freeing back to the cache may be deferred, it is not
>>>> + * safe to unload the module (and hence destroy the cache) until
>>>> + * this has completed. To prevent premature unloading, take an
>>>> + * extra module reference here and release only when the object
>>>> + * has been free back to the cache.
>>> ^ freed
>>
>> Oh yes. Can this be done on commit, or would you like me to send a v2?
>
> Adjusting on commit would be fine for me, but it's up to Juergen since
> he is the one that will pick this up. IIRC the module unload patches
> didn't go through the block subsystem.
Oh, right. Yes, will fix this when committing.
Juergen
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 14+ messages in thread
* RE: [PATCH] xen-blkback: prevent premature module unload
2019-12-11 13:55 ` [Xen-devel] " Roger Pau Monné
@ 2019-12-11 13:57 ` Durrant, Paul
-1 siblings, 0 replies; 14+ messages in thread
From: Durrant, Paul @ 2019-12-11 13:57 UTC (permalink / raw)
To: Roger Pau Monné, Juergen Gross
Cc: xen-devel, linux-block, linux-kernel, Konrad Rzeszutek Wilk, Jens Axboe
> -----Original Message-----
> From: Roger Pau Monné <roger.pau@citrix.com>
> Sent: 11 December 2019 13:55
> To: Durrant, Paul <pdurrant@amazon.com>; Juergen Gross <jgross@suse.com>
> Cc: xen-devel@lists.xenproject.org; linux-block@vger.kernel.org; linux-
> kernel@vger.kernel.org; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
> Jens Axboe <axboe@kernel.dk>
> Subject: Re: [PATCH] xen-blkback: prevent premature module unload
>
> On Wed, Dec 11, 2019 at 01:27:42PM +0000, Durrant, Paul wrote:
> > > -----Original Message-----
> > > From: Roger Pau Monné <roger.pau@citrix.com>
> > > Sent: 11 December 2019 11:29
> > > To: Durrant, Paul <pdurrant@amazon.com>
> > > Cc: xen-devel@lists.xenproject.org; linux-block@vger.kernel.org;
> linux-
> > > kernel@vger.kernel.org; Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com>;
> > > Jens Axboe <axboe@kernel.dk>
> > > Subject: Re: [PATCH] xen-blkback: prevent premature module unload
> > >
> > > On Tue, Dec 10, 2019 at 02:53:05PM +0000, Paul Durrant wrote:
> > > > Objects allocated by xen_blkif_alloc come from the 'blkif_cache'
> kmem
> > > > cache. This cache is destoyed when xen-blkif is unloaded so it is
> > > > necessary to wait for the deferred free routine used for such
> objects to
> > > > complete. This necessity was missed in commit 14855954f636 "xen-
> blkback:
> > > > allow module to be cleanly unloaded". This patch fixes the problem
> by
> > > > taking/releasing extra module references in xen_blkif_alloc/free()
> > > > respectively.
> > > >
> > > > Signed-off-by: Paul Durrant <pdurrant@amazon.com>
> > >
> > > Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
> > >
> > > One nit below.
> > >
> > > > ---
> > > > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > > > Cc: "Roger Pau Monné" <roger.pau@citrix.com>
> > > > Cc: Jens Axboe <axboe@kernel.dk>
> > > > ---
> > > > drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
> > > > 1 file changed, 10 insertions(+)
> > > >
> > > > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-
> > > blkback/xenbus.c
> > > > index e8c5c54e1d26..59d576d27ca7 100644
> > > > --- a/drivers/block/xen-blkback/xenbus.c
> > > > +++ b/drivers/block/xen-blkback/xenbus.c
> > > > @@ -171,6 +171,15 @@ static struct xen_blkif
> *xen_blkif_alloc(domid_t
> > > domid)
> > > > blkif->domid = domid;
> > > > atomic_set(&blkif->refcnt, 1);
> > > > init_completion(&blkif->drain_complete);
> > > > +
> > > > + /*
> > > > + * Because freeing back to the cache may be deferred, it is
> not
> > > > + * safe to unload the module (and hence destroy the cache)
> until
> > > > + * this has completed. To prevent premature unloading, take an
> > > > + * extra module reference here and release only when the
> object
> > > > + * has been free back to the cache.
> > > ^ freed
> >
> > Oh yes. Can this be done on commit, or would you like me to send a v2?
>
> Adjusting on commit would be fine for me, but it's up to Juergen since
> he is the one that will pick this up. IIRC the module unload patches
> didn't go through the block subsystem.
True. I forgot manually add Juergen cc list.
Paul
>
> Thanks, Roger.
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [Xen-devel] [PATCH] xen-blkback: prevent premature module unload
@ 2019-12-11 13:57 ` Durrant, Paul
0 siblings, 0 replies; 14+ messages in thread
From: Durrant, Paul @ 2019-12-11 13:57 UTC (permalink / raw)
To: Roger Pau Monné, Juergen Gross
Cc: linux-block, xen-devel, Jens Axboe, linux-kernel, Konrad Rzeszutek Wilk
> -----Original Message-----
> From: Roger Pau Monné <roger.pau@citrix.com>
> Sent: 11 December 2019 13:55
> To: Durrant, Paul <pdurrant@amazon.com>; Juergen Gross <jgross@suse.com>
> Cc: xen-devel@lists.xenproject.org; linux-block@vger.kernel.org; linux-
> kernel@vger.kernel.org; Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>;
> Jens Axboe <axboe@kernel.dk>
> Subject: Re: [PATCH] xen-blkback: prevent premature module unload
>
> On Wed, Dec 11, 2019 at 01:27:42PM +0000, Durrant, Paul wrote:
> > > -----Original Message-----
> > > From: Roger Pau Monné <roger.pau@citrix.com>
> > > Sent: 11 December 2019 11:29
> > > To: Durrant, Paul <pdurrant@amazon.com>
> > > Cc: xen-devel@lists.xenproject.org; linux-block@vger.kernel.org;
> linux-
> > > kernel@vger.kernel.org; Konrad Rzeszutek Wilk
> <konrad.wilk@oracle.com>;
> > > Jens Axboe <axboe@kernel.dk>
> > > Subject: Re: [PATCH] xen-blkback: prevent premature module unload
> > >
> > > On Tue, Dec 10, 2019 at 02:53:05PM +0000, Paul Durrant wrote:
> > > > Objects allocated by xen_blkif_alloc come from the 'blkif_cache'
> kmem
> > > > cache. This cache is destoyed when xen-blkif is unloaded so it is
> > > > necessary to wait for the deferred free routine used for such
> objects to
> > > > complete. This necessity was missed in commit 14855954f636 "xen-
> blkback:
> > > > allow module to be cleanly unloaded". This patch fixes the problem
> by
> > > > taking/releasing extra module references in xen_blkif_alloc/free()
> > > > respectively.
> > > >
> > > > Signed-off-by: Paul Durrant <pdurrant@amazon.com>
> > >
> > > Reviewed-by: Roger Pau Monné <roger.pau@citrix.com>
> > >
> > > One nit below.
> > >
> > > > ---
> > > > Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
> > > > Cc: "Roger Pau Monné" <roger.pau@citrix.com>
> > > > Cc: Jens Axboe <axboe@kernel.dk>
> > > > ---
> > > > drivers/block/xen-blkback/xenbus.c | 10 ++++++++++
> > > > 1 file changed, 10 insertions(+)
> > > >
> > > > diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-
> > > blkback/xenbus.c
> > > > index e8c5c54e1d26..59d576d27ca7 100644
> > > > --- a/drivers/block/xen-blkback/xenbus.c
> > > > +++ b/drivers/block/xen-blkback/xenbus.c
> > > > @@ -171,6 +171,15 @@ static struct xen_blkif
> *xen_blkif_alloc(domid_t
> > > domid)
> > > > blkif->domid = domid;
> > > > atomic_set(&blkif->refcnt, 1);
> > > > init_completion(&blkif->drain_complete);
> > > > +
> > > > + /*
> > > > + * Because freeing back to the cache may be deferred, it is
> not
> > > > + * safe to unload the module (and hence destroy the cache)
> until
> > > > + * this has completed. To prevent premature unloading, take an
> > > > + * extra module reference here and release only when the
> object
> > > > + * has been free back to the cache.
> > > ^ freed
> >
> > Oh yes. Can this be done on commit, or would you like me to send a v2?
>
> Adjusting on commit would be fine for me, but it's up to Juergen since
> he is the one that will pick this up. IIRC the module unload patches
> didn't go through the block subsystem.
True. I forgot manually add Juergen cc list.
Paul
>
> Thanks, Roger.
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [PATCH] xen-blkback: prevent premature module unload
2019-12-10 14:53 ` [Xen-devel] " Paul Durrant
@ 2019-12-13 9:00 ` Jürgen Groß
-1 siblings, 0 replies; 14+ messages in thread
From: Jürgen Groß @ 2019-12-13 9:00 UTC (permalink / raw)
To: Paul Durrant, xen-devel, linux-block, linux-kernel
Cc: Konrad Rzeszutek Wilk, Roger Pau Monné, Jens Axboe
On 10.12.19 15:53, Paul Durrant wrote:
> Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
> cache. This cache is destoyed when xen-blkif is unloaded so it is
> necessary to wait for the deferred free routine used for such objects to
> complete. This necessity was missed in commit 14855954f636 "xen-blkback:
> allow module to be cleanly unloaded". This patch fixes the problem by
> taking/releasing extra module references in xen_blkif_alloc/free()
> respectively.
>
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Pushed to xen/tip.git for-linus-5.5b
Juergen
^ permalink raw reply [flat|nested] 14+ messages in thread
* Re: [Xen-devel] [PATCH] xen-blkback: prevent premature module unload
@ 2019-12-13 9:00 ` Jürgen Groß
0 siblings, 0 replies; 14+ messages in thread
From: Jürgen Groß @ 2019-12-13 9:00 UTC (permalink / raw)
To: Paul Durrant, xen-devel, linux-block, linux-kernel
Cc: Jens Axboe, Roger Pau Monné, Konrad Rzeszutek Wilk
On 10.12.19 15:53, Paul Durrant wrote:
> Objects allocated by xen_blkif_alloc come from the 'blkif_cache' kmem
> cache. This cache is destoyed when xen-blkif is unloaded so it is
> necessary to wait for the deferred free routine used for such objects to
> complete. This necessity was missed in commit 14855954f636 "xen-blkback:
> allow module to be cleanly unloaded". This patch fixes the problem by
> taking/releasing extra module references in xen_blkif_alloc/free()
> respectively.
>
> Signed-off-by: Paul Durrant <pdurrant@amazon.com>
Pushed to xen/tip.git for-linus-5.5b
Juergen
_______________________________________________
Xen-devel mailing list
Xen-devel@lists.xenproject.org
https://lists.xenproject.org/mailman/listinfo/xen-devel
^ permalink raw reply [flat|nested] 14+ messages in thread
end of thread, other threads:[~2019-12-13 9:01 UTC | newest]
Thread overview: 14+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2019-12-10 14:53 [PATCH] xen-blkback: prevent premature module unload Paul Durrant
2019-12-10 14:53 ` [Xen-devel] " Paul Durrant
2019-12-11 11:28 ` Roger Pau Monné
2019-12-11 11:28 ` [Xen-devel] " Roger Pau Monné
2019-12-11 13:27 ` Durrant, Paul
2019-12-11 13:27 ` [Xen-devel] " Durrant, Paul
2019-12-11 13:55 ` Roger Pau Monné
2019-12-11 13:55 ` [Xen-devel] " Roger Pau Monné
2019-12-11 13:56 ` Jürgen Groß
2019-12-11 13:56 ` [Xen-devel] " Jürgen Groß
2019-12-11 13:57 ` Durrant, Paul
2019-12-11 13:57 ` [Xen-devel] " Durrant, Paul
2019-12-13 9:00 ` Jürgen Groß
2019-12-13 9:00 ` [Xen-devel] " Jürgen Groß
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.