xen-blkback: fix memory leaks

I've at least identified two possible memory leaks in blkback, both
related to the shutdown path of a VBD:

- blkback doesn't wait for any pending purge work to finish before
  cleaning the list of free_pages. The purge work will call
  put_free_pages and thus we might end up with pages being added to
  the free_pages list after we have emptied it. Fix this by making
  sure there's no pending purge work before exiting
  xen_blkif_schedule, and moving the free_page cleanup code to
  xen_blkif_free.
- blkback doesn't wait for pending requests to end before cleaning
  persistent grants and the list of free_pages. Again this can add
  pages to the free_pages list or persistent grants to the
  persistent_gnts red-black tree. Fixed by moving the persistent
  grants and free_pages cleanup code to xen_blkif_free.

Also, add some checks in xen_blkif_free to make sure we are cleaning
everything.

Signed-off-by: Roger Pau Monné <roger.pau@citrix.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Reviewed-by: David Vrabel <david.vrabel@citrix.com>
Cc: Boris Ostrovsky <boris.ostrovsky@oracle.com>
Tested-by: Matt Rushton <mrushton@amazon.com>
Reviewed-by: Matt Rushton <mrushton@amazon.com>
Cc: Matt Wilson <msw@amazon.com>
Cc: Ian Campbell <Ian.Campbell@citrix.com>
Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>

1 files changed, 1 insertions, 0 deletions

diff --git a/drivers/block/xen-blkback/common.h b/drivers/block/xen-blkback/common.h
index 8d8807563d99..f733d7627120 100644
--- a/drivers/block/xen-blkback/common.h
+++ b/drivers/block/xen-blkback/common.h
@@ -376,6 +376,7 @@ int xen_blkif_xenbus_init(void);
 irqreturn_t xen_blkif_be_int(int irq, void *dev_id);
 int xen_blkif_schedule(void *arg);
 int xen_blkif_purge_persistent(void *arg);
+void xen_blkbk_free_caches(struct xen_blkif *blkif);
 
 int xen_blkbk_flush_diskcache(struct xenbus_transaction xbt,
 			      struct backend_info *be, int state);