Commit 166d3863 authored Jul 10, 2022 by Demi Marie Obenour Committed by Juergen Gross Jul 11, 2022

xen/gntdev: Ignore failure to unmap INVALID_GRANT_HANDLE



The error paths of gntdev_mmap() can call unmap_grant_pages() even
though not all of the pages have been successfully mapped.  This will
trigger the WARN_ON()s in __unmap_grant_pages_done().  The number of
warnings can be very large; I have observed thousands of lines of
warnings in the systemd journal.

Avoid this problem by only warning on unmapping failure if the handle
being unmapped is not INVALID_GRANT_HANDLE.  The handle field of any
page that was not successfully mapped will be INVALID_GRANT_HANDLE, so
this catches all cases where unmapping can legitimately fail.

Fixes: dbe97cff ("xen/gntdev: Avoid blocking in unmap_grant_pages()")
Cc: stable@vger.kernel.org
Suggested-by: Juergen Gross <jgross@suse.com>
Signed-off-by: Demi Marie Obenour <demi@invisiblethingslab.com>
Reviewed-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@epam.com>
Reviewed-by: Juergen Gross <jgross@suse.com>
Link: https://lore.kernel.org/r/20220710230522.1563-1-demi@invisiblethingslab.com


Signed-off-by: Juergen Gross <jgross@suse.com>

parent dbe97cff

drivers/xen/gntdev.c

+4 −2

Original line number	Diff line number	Diff line
		@@ -396,13 +396,15 @@ static void __unmap_grant_pages_done(int result,
		unsigned int offset = data->unmap_ops - map->unmap_ops;

		for (i = 0; i < data->count; i++) {
		WARN_ON(map->unmap_ops[offset+i].status);
		WARN_ON(map->unmap_ops[offset + i].status != GNTST_okay &&
		map->unmap_ops[offset + i].handle != INVALID_GRANT_HANDLE);
		pr_debug("unmap handle=%d st=%d\n",
		map->unmap_ops[offset+i].handle,
		map->unmap_ops[offset+i].status);
		map->unmap_ops[offset+i].handle = INVALID_GRANT_HANDLE;
		if (use_ptemod) {
		WARN_ON(map->kunmap_ops[offset+i].status);
		WARN_ON(map->kunmap_ops[offset + i].status != GNTST_okay &&
		map->kunmap_ops[offset + i].handle != INVALID_GRANT_HANDLE);
		pr_debug("kunmap handle=%u st=%d\n",
		map->kunmap_ops[offset+i].handle,
		map->kunmap_ops[offset+i].status);