[Xen-devel] [RFC PATCH 36/60] hyper_dmabuf: error handling when share_pages fails

[Dongwon Kim <dongwon.kim@xxxxxxxxx>]

From: Mateusz Polrola <mateuszx.potrola@xxxxxxxxx>

When error occurs while sharing pages, all pages already shared
needs to be un-shared and proper error code has to be returned.

Signed-off-by: Dongwon Kim <dongwon.kim@xxxxxxxxx>
---
 drivers/xen/hyper_dmabuf/hyper_dmabuf_ioctl.c      |  6 ++-
 .../xen/hyper_dmabuf/xen/hyper_dmabuf_xen_shm.c    | 50 ++++++++++++++++++++++
 2 files changed, 55 insertions(+), 1 deletion(-)

diff --git a/drivers/xen/hyper_dmabuf/hyper_dmabuf_ioctl.c 
b/drivers/xen/hyper_dmabuf/hyper_dmabuf_ioctl.c
index f1581d5..375b664 100644
--- a/drivers/xen/hyper_dmabuf/hyper_dmabuf_ioctl.c
+++ b/drivers/xen/hyper_dmabuf/hyper_dmabuf_ioctl.c
@@ -31,7 +31,7 @@
 #include <linux/module.h>
 #include <linux/slab.h>
 #include <linux/miscdevice.h>
-#include <linux/uaccess.h>
+#include <asm/uaccess.h>
 #include <linux/dma-buf.h>
 #include <linux/delay.h>
 #include <linux/list.h>
@@ -242,6 +242,10 @@ static int hyper_dmabuf_export_remote(struct file *filp, 
void *data)
        operands[6] = page_info->last_len;
        operands[7] = ops->share_pages (page_info->pages, 
export_remote_attr->remote_domain,
                                        page_info->nents, &sgt_info->refs_info);
+       if (operands[7] < 0) {
+               dev_err(hyper_dmabuf_private.device, "pages sharing failed\n");
+               goto fail_map_req;
+       }
 
        /* driver/application specific private info, max 4x4 bytes */
        operands[8] = export_remote_attr->private[0];
diff --git a/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_shm.c 
b/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_shm.c
index 1416a69..908eda8 100644
--- a/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_shm.c
+++ b/drivers/xen/hyper_dmabuf/xen/hyper_dmabuf_xen_shm.c
@@ -109,6 +109,16 @@ int hyper_dmabuf_xen_share_pages(struct page **pages, int 
domid, int nents,
                lvl2_table[i] = gnttab_grant_foreign_access(domid,
                                                            
pfn_to_mfn(page_to_pfn(pages[i])),
                                                            true /* read-only 
from remote domain */);
+               if (lvl2_table[i] == -ENOSPC) {
+                       dev_err(hyper_dmabuf_private.device, "No more space 
left in grant table\n");
+
+                       /* Unshare all already shared pages for lvl2 */
+                       while(i--) {
+                               gnttab_end_foreign_access_ref(lvl2_table[i], 0);
+                               gnttab_free_grant_reference(lvl2_table[i]);
+                       }
+                       goto err_cleanup;
+               }
        }
 
        /* Share 2nd level addressing pages in readonly mode*/
@@ -116,6 +126,23 @@ int hyper_dmabuf_xen_share_pages(struct page **pages, int 
domid, int nents,
                lvl3_table[i] = gnttab_grant_foreign_access(domid,
                                                            
virt_to_mfn((unsigned long)lvl2_table+i*PAGE_SIZE ),
                                                            true);
+               if (lvl3_table[i] == -ENOSPC) {
+                       dev_err(hyper_dmabuf_private.device, "No more space 
left in grant table\n");
+
+                       /* Unshare all already shared pages for lvl3 */
+                       while(i--) {
+                               gnttab_end_foreign_access_ref(lvl3_table[i], 1);
+                               gnttab_free_grant_reference(lvl3_table[i]);
+                       }
+
+                       /* Unshare all pages for lvl2 */
+                       while(nents--) {
+                               
gnttab_end_foreign_access_ref(lvl2_table[nents], 0);
+                               gnttab_free_grant_reference(lvl2_table[nents]);
+                       }
+
+                       goto err_cleanup;
+               }
        }
 
        /* Share lvl3_table in readonly mode*/
@@ -123,6 +150,23 @@ int hyper_dmabuf_xen_share_pages(struct page **pages, int 
domid, int nents,
                                                virt_to_mfn((unsigned 
long)lvl3_table),
                                                true);
 
+       if (lvl3_gref == -ENOSPC) {
+               dev_err(hyper_dmabuf_private.device, "No more space left in 
grant table\n");
+
+               /* Unshare all pages for lvl3 */
+               while(i--) {
+                       gnttab_end_foreign_access_ref(lvl3_table[i], 1);
+                       gnttab_free_grant_reference(lvl3_table[i]);
+               }
+
+               /* Unshare all pages for lvl2 */
+               while(nents--) {
+                       gnttab_end_foreign_access_ref(lvl2_table[nents], 0);
+                       gnttab_free_grant_reference(lvl2_table[nents]);
+               }
+
+               goto err_cleanup;
+       }
 
        /* Store lvl3_table page to be freed later */
        sh_pages_info->lvl3_table = lvl3_table;
@@ -136,6 +180,12 @@ int hyper_dmabuf_xen_share_pages(struct page **pages, int 
domid, int nents,
 
        dev_dbg(hyper_dmabuf_private.device, "%s exit\n", __func__);
        return lvl3_gref;
+
+err_cleanup:
+       free_pages((unsigned long)lvl2_table, n_lvl2_grefs);
+       free_pages((unsigned long)lvl3_table, 1);
+
+       return -ENOSPC;
 }
 
 int hyper_dmabuf_xen_unshare_pages(void **refs_info, int nents) {
-- 
2.7.4


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