Patch "dm thin: allocate the cell_sort_array dynamically" has been added to the 4.1-stable tree

This is a note to let you know that I've just added the patch titled

dm thin: allocate the cell_sort_array dynamically

to the 4.1-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
dm-thin-allocate-the-cell_sort_array-dynamically.patch
and it can be found in the queue-4.1 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Joe Thornber <[email protected]>
Date: Fri, 3 Jul 2015 10:22:42 +0100
Subject: dm thin: allocate the cell_sort_array dynamically

From: Joe Thornber <[email protected]>

commit a822c83e47d97cdef38c4352e1ef62d9f46cfe98 upstream.

Given the pool's cell_sort_array holds 8192 pointers it triggers an order 5 allocation via kmalloc. This order 5 allocation is prone to failure as system memory gets more fragmented over time.

Fix this by allocating the cell_sort_array using vmalloc.

---
 drivers/md/dm-thin.c |   13 ++++++++++++-
 1 file changed, 12 insertions(+), 1 deletion(-)

@@ -18,6 +18,7 @@
 #include <linux/init.h>
 #include <linux/module.h>
 #include <linux/slab.h>
+#include <linux/vmalloc.h>
 #include <linux/sort.h>
 #include <linux/rbtree.h>
 

@@ -260,7 +261,7 @@ struct pool {
 	process_mapping_fn process_prepared_mapping;
 	process_mapping_fn process_prepared_discard;
 
-	struct dm_bio_prison_cell *cell_sort_array[CELL_SORT_ARRAY_SIZE];
+	struct dm_bio_prison_cell **cell_sort_array;
 };
 
 static enum pool_mode get_pool_mode(struct pool *pool);

@@ -2499,6 +2500,7 @@ static void __pool_destroy(struct pool *
 {
 	__pool_table_remove(pool);
 
+	vfree(pool->cell_sort_array);
 	if (dm_pool_metadata_close(pool->pmd) < 0)
 		DMWARN("%s: dm_pool_metadata_close() failed.", __func__);
 

@@ -2611,6 +2613,13 @@ static struct pool *pool_create(struct m
 		goto bad_mapping_pool;
 	}
 
+	pool->cell_sort_array = vmalloc(sizeof(*pool->cell_sort_array) * CELL_SORT_ARRAY_SIZE);
+	if (!pool->cell_sort_array) {
+		*error = "Error allocating cell sort array";
+		err_p = ERR_PTR(-ENOMEM);
+		goto bad_sort_array;
+	}
+
 	pool->ref_count = 1;
 	pool->last_commit_jiffies = jiffies;
 	pool->pool_md = pool_md;

@@ -2619,6 +2628,8 @@ static struct pool *pool_create(struct m
 
 	return pool;
 
+bad_sort_array:
+	mempool_destroy(pool->mapping_pool);
 bad_mapping_pool:
 	dm_deferred_set_destroy(pool->all_io_ds);
 bad_all_io_ds:

Patches currently in stable-queue which might be from [email protected] are

queue-4.1/dm-btree-remove-fix-bug-in-redistribute3.patch queue-4.1/dm-btree-silence-lockdep-lock-inversion-in-dm_btree_del.patch queue-4.1/dm-cache-fix-race-when-issuing-a-policy_replace-operation.patch queue-4.1/dm-thin-allocate-the-cell_sort_array-dynamically.patch queue-4.1/dm-space-map-metadata-fix-occasional-leak-of-a-metadata-block-on-resize.patch