[Xen-devel] [PATCH v3 1/2] xmalloc: remove struct xmem_pool init_region

[Paul Durrant <paul.durrant@citrix.com>]

This patch dispenses with the init_region. It's simply not necessary
(pools will still happily grow and shrink on demand in its absence) and the
code can be shortended by removing it. It also avoids the sole evaluation
of ADD_REGION without holding the pool lock (which is unsafe).

NOTE: The if statement that is removed from xmem_pool_destroy() has actually
      been bogus since commit 6009f4dd "Transcendent memory ("tmem") for
      Xen." when the allocation of the init_region was moved out of
      xmem_pool_create().

Signed-off-by: Paul Durrant <paul.durrant@citrix.com>
Suggested-by: Jan Beulich <jbeulich@suse.com>
Reviewed-by: Jan Beulich <jbeulich@suse.com>
---
Cc: Andrew Cooper <andrew.cooper3@citrix.com>
Cc: George Dunlap <George.Dunlap@eu.citrix.com>
Cc: Ian Jackson <ian.jackson@eu.citrix.com>
Cc: Jan Beulich <jbeulich@suse.com>
Cc: Julien Grall <julien.grall@arm.com>
Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>
Cc: Tim Deegan <tim@xen.org>
Cc: Wei Liu <wl@xen.org>

v2:
 - remove init_region instead of fixing the locking
---
 xen/common/xmalloc_tlsf.c | 34 ++++------------------------------
 xen/include/xen/xmalloc.h |  2 --
 2 files changed, 4 insertions(+), 32 deletions(-)

diff --git a/xen/common/xmalloc_tlsf.c b/xen/common/xmalloc_tlsf.c
index f585388dfa..e4e476a27c 100644
--- a/xen/common/xmalloc_tlsf.c
+++ b/xen/common/xmalloc_tlsf.c
@@ -101,7 +101,6 @@ struct xmem_pool {
 
     spinlock_t lock;
 
-    unsigned long init_size;
     unsigned long max_size;
     unsigned long grow_size;
 
@@ -115,7 +114,6 @@ struct xmem_pool {
 
     struct list_head list;
 
-    void *init_region;
     char name[MAX_POOL_NAME_LEN];
 };
 
@@ -287,14 +285,13 @@ struct xmem_pool *xmem_pool_create(
     const char *name,
     xmem_pool_get_memory get_mem,
     xmem_pool_put_memory put_mem,
-    unsigned long init_size,
     unsigned long max_size,
     unsigned long grow_size)
 {
     struct xmem_pool *pool;
     int pool_bytes, pool_order;
 
-    BUG_ON(max_size && (max_size < init_size));
+    BUG_ON(max_size && (max_size < grow_size));
 
     pool_bytes = ROUNDUP_SIZE(sizeof(*pool));
     pool_order = get_order_from_bytes(pool_bytes);
@@ -305,23 +302,18 @@ struct xmem_pool *xmem_pool_create(
     memset(pool, 0, pool_bytes);
 
     /* Round to next page boundary */
-    init_size = ROUNDUP_PAGE(init_size);
     max_size = ROUNDUP_PAGE(max_size);
     grow_size = ROUNDUP_PAGE(grow_size);
 
     /* pool global overhead not included in used size */
     pool->used_size = 0;
 
-    pool->init_size = init_size;
     pool->max_size = max_size;
     pool->grow_size = grow_size;
     pool->get_mem = get_mem;
     pool->put_mem = put_mem;
     strlcpy(pool->name, name, sizeof(pool->name));
 
-    /* always obtain init_region lazily now to ensure it is get_mem'd
-     * in the same "context" as all other regions */
-
     spin_lock_init(&pool->lock);
 
     spin_lock(&pool_list_lock);
@@ -340,7 +332,6 @@ unsigned long xmem_pool_get_total_size(struct xmem_pool *pool)
 {
     unsigned long total;
     total = ROUNDUP_SIZE(sizeof(*pool))
-        + pool->init_size
         + (pool->num_regions - 1) * pool->grow_size;
     return total;
 }
@@ -352,13 +343,6 @@ void xmem_pool_destroy(struct xmem_pool *pool)
     if ( pool == NULL )
         return;
 
-    /* User is destroying without ever allocating from this pool */
-    if ( xmem_pool_get_used_size(pool) == BHDR_OVERHEAD )
-    {
-        ASSERT(!pool->init_region);
-        pool->used_size -= BHDR_OVERHEAD;
-    }
-
     /* Check for memory leaks in this pool */
     if ( xmem_pool_get_used_size(pool) )
         printk("memory leak in pool: %s (%p). "
@@ -380,14 +364,6 @@ void *xmem_pool_alloc(unsigned long size, struct xmem_pool *pool)
     int fl, sl;
     unsigned long tmp_size;
 
-    if ( pool->init_region == NULL )
-    {
-        if ( (region = pool->get_mem(pool->init_size)) == NULL )
-            goto out;
-        ADD_REGION(region, pool->init_size, pool);
-        pool->init_region = region;
-    }
-
     size = (size < MIN_BLOCK_SIZE) ? MIN_BLOCK_SIZE : ROUNDUP_SIZE(size);
     /* Rounding up the requested size and calculating fl and sl */
 
@@ -401,8 +377,7 @@ void *xmem_pool_alloc(unsigned long size, struct xmem_pool *pool)
         /* Not found */
         if ( size > (pool->grow_size - 2 * BHDR_OVERHEAD) )
             goto out_locked;
-        if ( pool->max_size && (pool->init_size +
-                                pool->num_regions * pool->grow_size
+        if ( pool->max_size && (pool->num_regions * pool->grow_size
                                 > pool->max_size) )
             goto out_locked;
         spin_unlock(&pool->lock);
@@ -551,9 +526,8 @@ static void *xmalloc_whole_pages(unsigned long size, unsigned long align)
 
 static void tlsf_init(void)
 {
-    xenpool = xmem_pool_create(
-        "xmalloc", xmalloc_pool_get, xmalloc_pool_put,
-        PAGE_SIZE, 0, PAGE_SIZE);
+    xenpool = xmem_pool_create("xmalloc", xmalloc_pool_get,
+                               xmalloc_pool_put, 0, PAGE_SIZE);
     BUG_ON(!xenpool);
 }
 
diff --git a/xen/include/xen/xmalloc.h b/xen/include/xen/xmalloc.h
index b486fe4b06..f075d2da91 100644
--- a/xen/include/xen/xmalloc.h
+++ b/xen/include/xen/xmalloc.h
@@ -84,7 +84,6 @@ typedef void (xmem_pool_put_memory)(void *ptr);
  * @name: name of the pool
  * @get_mem: callback function used to expand pool
  * @put_mem: callback function used to shrink pool
- * @init_size: inital pool size (in bytes)
  * @max_size: maximum pool size (in bytes) - set this as 0 for no limit
  * @grow_size: amount of memory (in bytes) added to pool whenever required
  *
@@ -94,7 +93,6 @@ struct xmem_pool *xmem_pool_create(
     const char *name,
     xmem_pool_get_memory get_mem,
     xmem_pool_put_memory put_mem,
-    unsigned long init_size,
     unsigned long max_size,
     unsigned long grow_size);
 
-- 
2.20.1.2.gb21ebb671


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