Multiple tapdisk2 processes may use the same parent disk images (later used to

detect sharable memory pages). This patch establishes unique id for each disk
image opened by tapdisk2, and stores it in shared memory region, thus making it
available to the remaining tapdisk2s.

Signed-off-by: Grzegorz Milos <Grzegorz.Milos@citrix.com>

1 files changed, 83 insertions, 2 deletions

diff --git a/tools/memshr/shm.c b/tools/memshr/shm.c
index 6489f61466..dcbea1e223 100644
--- a/tools/memshr/shm.c
+++ b/tools/memshr/shm.c
@@ -92,10 +92,11 @@ shared_memshr_info_t * shm_shared_info_open(int unlink)
 {
     shared_memshr_info_t *shared_info;
     pthread_mutexattr_t  lock_attr;
+    int nr_pages, i;
 
-    assert(sizeof(shared_memshr_info_t) < XC_PAGE_SIZE);
+    nr_pages = (sizeof(shared_memshr_info_t) >> XC_PAGE_SHIFT) + 1;
     if(shm_area_open(MEMSHR_INFO_SHM_FILE, 
-                     XC_PAGE_SIZE,
+                     nr_pages * XC_PAGE_SIZE,
                      unlink, 
                      &(shm_info.shared_info_area)) < 0)
     {
@@ -115,6 +116,12 @@ shared_memshr_info_t * shm_shared_info_open(int unlink)
             DPRINTF("Failed to init shared info lock.\n");
             return NULL;
         }
+        strcpy(shared_info->vbd_images[0].file, "list-head");
+        for(i=1; i<MAX_NR_VBD_IMAGES; i++)
+        {
+            shared_info->vbd_images[i].next = i; 
+            shared_info->vbd_images[i].prev = i; 
+        }
         shared_info->magic = MEMSHR_INFO_MAGIC;
     } 
     else
@@ -180,3 +187,77 @@ struct blockshr_hash * shm_blockshr_hash_open(int unlink)
     return h;
 } 
 
+uint16_t shm_vbd_image_get(char* file, vbd_image_info_t *vbd_imgs)
+{
+    vbd_image_info_t *img, *next_img;
+    int i, img_id;
+
+    /* Try to find the file in the existing list first */ 
+    img = vbd_imgs;
+    while(img->next != 0)
+    {
+        img = vbd_imgs + img->next;
+        if(strncmp(img->file, file, MAX_NAME_LEN) == 0)
+        {
+            img->ref_cnt++;
+            return (uint16_t)(img - vbd_imgs); 
+        }
+    }
+    
+    /* Couldn't find an existing entry. We need to add one. Find empty slot */ 
+    for(i=1; i<MAX_NR_VBD_IMAGES; i++)
+    {
+        img = vbd_imgs + i;
+        if((img->next == i) && (img->prev == i))
+            break;
+    }
+    /* No entries left! */
+    if(i == MAX_NR_VBD_IMAGES)
+    {
+        DPRINTF("No space in vbds table.\n");
+        return 0;
+    }
+    if(strlen(file) > MAX_NAME_LEN)
+    {
+        DPRINTF("Filename: %s too long (>%d).\n", file, MAX_NAME_LEN);
+        return 0; 
+    }
+    /* Init the entry */
+    img_id = (img - vbd_imgs);
+    next_img = vbd_imgs + vbd_imgs[0].next;
+    strcpy(img->file, file);
+    img->ref_cnt = 1;
+    img->next = vbd_imgs[0].next;
+    img->prev = 0;
+    next_img->prev = img_id;
+    vbd_imgs[0].next = img_id;
+
+    return img_id;
+}
+
+
+void shm_vbd_image_put(uint16_t memshr_id, vbd_image_info_t *vbd_imgs)
+{
+    vbd_image_info_t *img, *next_img, *prev_img;
+    
+    img = vbd_imgs + memshr_id;
+    if(img->ref_cnt == 0)
+    {
+        DPRINTF("Incorrect image put.\n");
+        return;
+    }
+
+    img->ref_cnt--; 
+
+    /* Remove from list if ref_cnt is zero */
+    if(img->ref_cnt == 0)
+    {
+        next_img = vbd_imgs + img->next;
+        prev_img = vbd_imgs + img->prev;
+        prev_img->next = img->next;
+        next_img->prev = img->prev;
+        img->next = img->prev = (img - vbd_imgs);
+        memset(img->file, 0, MAX_NAME_LEN);
+    }
+}
+