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Subject[PATCH 2/4] vfio: ccw: refactor and improve pfn_array_alloc_pin()
Date
This refactors pfn_array_alloc_pin() and also improves it by adding
defensive code in error handling so that calling pfn_array_unpin_free()
after error return won't lead to problem. This mains does:
1. Merge pfn_array_pin() into pfn_array_alloc_pin(), since there is no
other user of pfn_array_pin(). As a result, also remove kernel-doc
for pfn_array_pin() and add kernel-doc for pfn_array_alloc_pin().
2. For a vfio_pin_pages() failure, set pa->pa_nr to zero to indicate
zero pages were pinned.
3. Set pa->pa_iova_pfn to NULL right after it was freed.

Signed-off-by: Dong Jia Shi <bjsdjshi@linux.vnet.ibm.com>
---
drivers/s390/cio/vfio_ccw_cp.c | 84 ++++++++++++++++++------------------------
1 file changed, 36 insertions(+), 48 deletions(-)

diff --git a/drivers/s390/cio/vfio_ccw_cp.c b/drivers/s390/cio/vfio_ccw_cp.c
index 2be114db02f9..3abc9770910a 100644
--- a/drivers/s390/cio/vfio_ccw_cp.c
+++ b/drivers/s390/cio/vfio_ccw_cp.c
@@ -46,65 +46,32 @@ struct ccwchain {
};

/*
- * pfn_array_pin() - pin user pages in memory
+ * pfn_array_alloc_pin() - alloc memory for PFNs, then pin user pages in memory
* @pa: pfn_array on which to perform the operation
* @mdev: the mediated device to perform pin/unpin operations
+ * @iova: target guest physical address
+ * @len: number of bytes that should be pinned from @iova
*
- * Attempt to pin user pages in memory.
+ * Attempt to allocate memory for PFNs, and pin user pages in memory.
*
* Usage of pfn_array:
- * @pa->pa_iova starting guest physical I/O address. Assigned by caller.
+ * @pa->pa_iova starting guest physical I/O address. Assigned by callee.
* @pa->pa_iova_pfn array that stores PFNs of the pages need to pin. Allocated
- * by caller.
+ * by callee.
* @pa->pa_pfn array that receives PFNs of the pages pinned. Allocated by
- * caller.
- * @pa->pa_nr number of pages from @pa->pa_iova to pin. Assigned by
- * caller.
- * number of pages pinned. Assigned by callee.
+ * callee.
+ * @pa->pa_nr initiated as 0 by caller.
+ * number of pages pinned from @pa->pa_iova. Assigned by callee.
*
* Returns:
* Number of pages pinned on success.
- * If @pa->pa_nr is 0 or negative, returns 0.
+ * If @pa->pa_nr is not 0 initially, returns -EINVAL.
* If no pages were pinned, returns -errno.
*/
-static int pfn_array_pin(struct pfn_array *pa, struct device *mdev)
-{
- int i, ret;
-
- if (pa->pa_nr <= 0) {
- pa->pa_nr = 0;
- return 0;
- }
-
- pa->pa_iova_pfn[0] = pa->pa_iova >> PAGE_SHIFT;
- for (i = 1; i < pa->pa_nr; i++)
- pa->pa_iova_pfn[i] = pa->pa_iova_pfn[i - 1] + 1;
-
- ret = vfio_pin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr,
- IOMMU_READ | IOMMU_WRITE, pa->pa_pfn);
-
- if (ret > 0 && ret != pa->pa_nr) {
- vfio_unpin_pages(mdev, pa->pa_iova_pfn, ret);
- pa->pa_nr = 0;
- return 0;
- }
-
- return ret;
-}
-
-/* Unpin the pages before releasing the memory. */
-static void pfn_array_unpin_free(struct pfn_array *pa, struct device *mdev)
-{
- vfio_unpin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr);
- pa->pa_nr = 0;
- kfree(pa->pa_iova_pfn);
-}
-
-/* Alloc memory for PFNs, then pin pages with them. */
static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev,
u64 iova, unsigned int len)
{
- int ret = 0;
+ int i, ret = 0;

if (!len)
return 0;
@@ -126,18 +93,39 @@ static int pfn_array_alloc_pin(struct pfn_array *pa, struct device *mdev,
return -ENOMEM;
pa->pa_pfn = pa->pa_iova_pfn + pa->pa_nr;

- ret = pfn_array_pin(pa, mdev);
+ pa->pa_iova_pfn[0] = pa->pa_iova >> PAGE_SHIFT;
+ for (i = 1; i < pa->pa_nr; i++)
+ pa->pa_iova_pfn[i] = pa->pa_iova_pfn[i - 1] + 1;
+
+ ret = vfio_pin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr,
+ IOMMU_READ | IOMMU_WRITE, pa->pa_pfn);

- if (ret > 0)
- return ret;
- else if (!ret)
+ if (ret < 0) {
+ goto err_out;
+ } else if (ret > 0 && ret != pa->pa_nr) {
+ vfio_unpin_pages(mdev, pa->pa_iova_pfn, ret);
ret = -EINVAL;
+ goto err_out;
+ }
+
+ return ret;

+err_out:
+ pa->pa_nr = 0;
kfree(pa->pa_iova_pfn);
+ pa->pa_iova_pfn = NULL;

return ret;
}

+/* Unpin the pages before releasing the memory. */
+static void pfn_array_unpin_free(struct pfn_array *pa, struct device *mdev)
+{
+ vfio_unpin_pages(mdev, pa->pa_iova_pfn, pa->pa_nr);
+ pa->pa_nr = 0;
+ kfree(pa->pa_iova_pfn);
+}
+
static int pfn_array_table_init(struct pfn_array_table *pat, int nr)
{
pat->pat_pa = kcalloc(nr, sizeof(*pat->pat_pa), GFP_KERNEL);
--
2.13.5
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