From: Paul Durrant <pdurrant@amazon.com> To: <xen-devel@lists.xenproject.org>, <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org> Cc: "Paul Durrant" <pdurrant@amazon.com>, "Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com>, "Roger Pau Monné" <roger.pau@citrix.com>, "Jens Axboe" <axboe@kernel.dk> Subject: [PATCH] xen-blkback: prevent premature module unload Date: Tue, 10 Dec 2019 14:53:05 +0000 [thread overview] Message-ID: <20191210145305.6605-1-pdurrant@amazon.com> (raw) 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
WARNING: multiple messages have this Message-ID (diff)
From: Paul Durrant <pdurrant@amazon.com> To: <xen-devel@lists.xenproject.org>, <linux-block@vger.kernel.org>, <linux-kernel@vger.kernel.org> Cc: "Jens Axboe" <axboe@kernel.dk>, "Paul Durrant" <pdurrant@amazon.com>, "Roger Pau Monné" <roger.pau@citrix.com>, "Konrad Rzeszutek Wilk" <konrad.wilk@oracle.com> Subject: [Xen-devel] [PATCH] xen-blkback: prevent premature module unload Date: Tue, 10 Dec 2019 14:53:05 +0000 [thread overview] Message-ID: <20191210145305.6605-1-pdurrant@amazon.com> (raw) 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
next reply other threads:[~2019-12-10 14:53 UTC|newest] Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-12-10 14:53 Paul Durrant [this message] 2019-12-10 14:53 ` [Xen-devel] [PATCH] xen-blkback: prevent premature module unload 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
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