dm kcopyd: reserve fewer pages

Reserve just the minimum of pages needed to process one job.

Because we allocate pages from page allocator, we don't need to reserve
a large number of pages.  The maximum job size is SUB_JOB_SIZE and we
calculate the number of reserved pages based on this.
Signed-off-by: Mikulas Patocka <mpatocka@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>

drivers/md/dm-kcopyd.c

@@ -30,6 +30,7 @@
 #define SUB_JOB_SIZE	128
 #define SPLIT_COUNT	8
 #define MIN_JOBS	8
+#define RESERVE_PAGES	(DIV_ROUND_UP(SUB_JOB_SIZE << SECTOR_SHIFT, PAGE_SIZE))
 
 /*-----------------------------------------------------------------
  * Each kcopyd client has its own little pool of preallocated
@@ -636,8 +637,7 @@ int kcopyd_cancel(struct kcopyd_job *job, int block)
 /*-----------------------------------------------------------------
  * Client setup
  *---------------------------------------------------------------*/
-int dm_kcopyd_client_create(unsigned min_pages,
-			    struct dm_kcopyd_client **result)
+int dm_kcopyd_client_create(struct dm_kcopyd_client **result)
 {
 	int r = -ENOMEM;
 	struct dm_kcopyd_client *kc;
@@ -663,7 +663,7 @@ int dm_kcopyd_client_create(unsigned min_pages,
 
 	kc->pages = NULL;
 	kc->nr_reserved_pages = kc->nr_free_pages = 0;
-	r = client_reserve_pages(kc, min_pages);
+	r = client_reserve_pages(kc, RESERVE_PAGES);
 	if (r)
 		goto bad_client_pages;
 

drivers/md/dm-raid1.c

@@ -22,7 +22,6 @@
 #define DM_MSG_PREFIX "raid1"
 
 #define MAX_RECOVERY 1	/* Maximum number of regions recovered in parallel. */
-#define DM_KCOPYD_PAGES 64
 
 #define DM_RAID1_HANDLE_ERRORS 0x01
 #define errors_handled(p)	((p)->features & DM_RAID1_HANDLE_ERRORS)
@@ -1116,7 +1115,7 @@ static int mirror_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		goto err_destroy_wq;
 	}
 
-	r = dm_kcopyd_client_create(DM_KCOPYD_PAGES, &ms->kcopyd_client);
+	r = dm_kcopyd_client_create(&ms->kcopyd_client);
 	if (r)
 		goto err_destroy_wq;
 

drivers/md/dm-snap.c

@@ -39,11 +39,6 @@ static const char dm_snapshot_merge_target_name[] = "snapshot-merge";
  */
 #define SNAPSHOT_COPY_PRIORITY 2
 
-/*
- * Reserve 1MB for each snapshot initially (with minimum of 1 page).
- */
-#define SNAPSHOT_PAGES (((1UL << 20) >> PAGE_SHIFT) ? : 1)
-
 /*
  * The size of the mempool used to track chunks in use.
  */
@@ -1116,7 +1111,7 @@ static int snapshot_ctr(struct dm_target *ti, unsigned int argc, char **argv)
 		goto bad_hash_tables;
 	}
 
-	r = dm_kcopyd_client_create(SNAPSHOT_PAGES, &s->kcopyd_client);
+	r = dm_kcopyd_client_create(&s->kcopyd_client);
 	if (r) {
 		ti->error = "Could not create kcopyd client";
 		goto bad_kcopyd;

include/linux/dm-kcopyd.h

@@ -25,8 +25,7 @@
  * To use kcopyd you must first create a dm_kcopyd_client object.
  */
 struct dm_kcopyd_client;
-int dm_kcopyd_client_create(unsigned num_pages,
-			    struct dm_kcopyd_client **result);
+int dm_kcopyd_client_create(struct dm_kcopyd_client **result);
 void dm_kcopyd_client_destroy(struct dm_kcopyd_client *kc);
 
 /*