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>

4 files changed, 124 insertions, 6 deletions

diff --git a/tools/memshr/interface.c b/tools/memshr/interface.c
index 2c2f45423b..ad14bbf2a0 100644
--- a/tools/memshr/interface.c
+++ b/tools/memshr/interface.c
@@ -106,3 +106,23 @@ void memshr_vbd_initialize(void)
     vbd_info.enabled = 1;
 }
 
+uint16_t memshr_vbd_image_get(char* file)
+{
+    uint16_t id;
+
+    if(pthread_mutex_lock(&SHARED_INFO->lock)) goto error_out;
+    id = shm_vbd_image_get(file, SHARED_INFO->vbd_images);
+    if(pthread_mutex_unlock(&SHARED_INFO->lock)) goto error_out;
+
+    return id;
+error_out:
+    return 0;    
+}
+
+void memshr_vbd_image_put(uint16_t memshr_id)
+{
+    if(pthread_mutex_lock(&SHARED_INFO->lock)) return;
+    shm_vbd_image_put(memshr_id, SHARED_INFO->vbd_images);
+    if(pthread_mutex_unlock(&SHARED_INFO->lock)) return;
+}
+
diff --git a/tools/memshr/memshr.h b/tools/memshr/memshr.h
index 351323715c..1292d494f5 100644
--- a/tools/memshr/memshr.h
+++ b/tools/memshr/memshr.h
@@ -26,5 +26,7 @@ typedef uint64_t xen_mfn_t;
 extern void memshr_set_domid(int domid);
 extern void memshr_daemon_initialize(void);
 extern void memshr_vbd_initialize(void);
+extern uint16_t memshr_vbd_image_get(char* file);
+extern void memshr_vbd_image_put(uint16_t memshr_id);
 
 #endif /* __MEMSHR_H__ */
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);
+    }
+}
+
diff --git a/tools/memshr/shm.h b/tools/memshr/shm.h
index 0f6f665c6d..0d849ff787 100644
--- a/tools/memshr/shm.h
+++ b/tools/memshr/shm.h
@@ -20,16 +20,31 @@
 #define __SHM_H__
 
 #include <pthread.h>
+#include <unistd.h>
 
+#define MAX_NAME_LEN  1000
+
+typedef struct vbd_image_info {
+    char     file[MAX_NAME_LEN];
+    int      ref_cnt;
+    uint16_t next;
+    uint16_t prev;
+} vbd_image_info_t;
+
+#define MAX_NR_VBD_IMAGES   4096
+ 
 typedef struct shared_memshr_info {
-    unsigned long   magic;
-    pthread_mutex_t lock;
-    int             fgprtshr_hash_inited;
-    int             blockshr_hash_inited;
+    unsigned long    magic;
+    pthread_mutex_t  lock;
+    int              fgprtshr_hash_inited;
+    int              blockshr_hash_inited;
+    vbd_image_info_t vbd_images[MAX_NR_VBD_IMAGES];
 } shared_memshr_info_t;
 
 shared_memshr_info_t * shm_shared_info_open(int unlink);
 struct fgprtshr_hash * shm_fgprtshr_hash_open(int unlink);
 struct blockshr_hash * shm_blockshr_hash_open(int unlink);
+uint16_t shm_vbd_image_get(char* file, vbd_image_info_t *vbd_imgs);
+void     shm_vbd_image_put(uint16_t memshr_id, vbd_image_info_t *vbd_imgs);
 
 #endif /* __SHM_H__ */