linux-kernel - [patch] mm, mempool: do not allow atomic resizing

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Date:	Sat, 7 Mar 2015 19:19:11 -0800 (PST)
From:	David Rientjes <rientjes@...gle.com>
To:	Andrew Morton <akpm@...ux-foundation.org>
cc:	Steffen Maier <maier@...ux.vnet.ibm.com>,
	Martin Schwidefsky <schwidefsky@...ibm.com>,
	Heiko Carstens <heiko.carstens@...ibm.com>,
	Steve French <sfrench@...ba.org>, linux-kernel@...r.kernel.org,
	linux-cifs@...r.kernel.org, linux-s390@...r.kernel.org
Subject: [patch] mm, mempool: do not allow atomic resizing

Allocating a large number of elements in atomic context could quickly
deplete memory reserves, so just disallow atomic resizing entirely.

Nothing currently uses mempool_resize() with anything other than
GFP_KERNEL, so convert existing callers to drop the gfp_mask.

Signed-off-by: David Rientjes <rientjes@...gle.com>
---
 drivers/s390/scsi/zfcp_erp.c | 4 ++--
 fs/cifs/connect.c            | 6 ++----
 include/linux/mempool.h      | 2 +-
 mm/mempool.c                 | 9 +++++----
 4 files changed, 10 insertions(+), 11 deletions(-)

diff --git a/drivers/s390/scsi/zfcp_erp.c b/drivers/s390/scsi/zfcp_erp.c
--- a/drivers/s390/scsi/zfcp_erp.c
+++ b/drivers/s390/scsi/zfcp_erp.c
@@ -738,11 +738,11 @@ static int zfcp_erp_adapter_strategy_open_fsf(struct zfcp_erp_action *act)
 		return ZFCP_ERP_FAILED;
 
 	if (mempool_resize(act->adapter->pool.sr_data,
-			   act->adapter->stat_read_buf_num, GFP_KERNEL))
+			   act->adapter->stat_read_buf_num))
 		return ZFCP_ERP_FAILED;
 
 	if (mempool_resize(act->adapter->pool.status_read_req,
-			   act->adapter->stat_read_buf_num, GFP_KERNEL))
+			   act->adapter->stat_read_buf_num))
 		return ZFCP_ERP_FAILED;
 
 	atomic_set(&act->adapter->stat_miss, act->adapter->stat_read_buf_num);
diff --git a/fs/cifs/connect.c b/fs/cifs/connect.c
--- a/fs/cifs/connect.c
+++ b/fs/cifs/connect.c
@@ -773,8 +773,7 @@ static void clean_demultiplex_info(struct TCP_Server_Info *server)
 
 	length = atomic_dec_return(&tcpSesAllocCount);
 	if (length > 0)
-		mempool_resize(cifs_req_poolp, length + cifs_min_rcv,
-				GFP_KERNEL);
+		mempool_resize(cifs_req_poolp, length + cifs_min_rcv);
 }
 
 static int
@@ -848,8 +847,7 @@ cifs_demultiplex_thread(void *p)
 
 	length = atomic_inc_return(&tcpSesAllocCount);
 	if (length > 1)
-		mempool_resize(cifs_req_poolp, length + cifs_min_rcv,
-				GFP_KERNEL);
+		mempool_resize(cifs_req_poolp, length + cifs_min_rcv);
 
 	set_freezable();
 	while (server->tcpStatus != CifsExiting) {
diff --git a/include/linux/mempool.h b/include/linux/mempool.h
--- a/include/linux/mempool.h
+++ b/include/linux/mempool.h
@@ -29,7 +29,7 @@ extern mempool_t *mempool_create_node(int min_nr, mempool_alloc_t *alloc_fn,
 			mempool_free_t *free_fn, void *pool_data,
 			gfp_t gfp_mask, int nid);
 
-extern int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask);
+extern int mempool_resize(mempool_t *pool, int new_min_nr);
 extern void mempool_destroy(mempool_t *pool);
 extern void * mempool_alloc(mempool_t *pool, gfp_t gfp_mask);
 extern void mempool_free(void *element, mempool_t *pool);
diff --git a/mm/mempool.c b/mm/mempool.c
--- a/mm/mempool.c
+++ b/mm/mempool.c
@@ -113,23 +113,24 @@ EXPORT_SYMBOL(mempool_create_node);
  *              mempool_create().
  * @new_min_nr: the new minimum number of elements guaranteed to be
  *              allocated for this pool.
- * @gfp_mask:   the usual allocation bitmask.
  *
  * This function shrinks/grows the pool. In the case of growing,
  * it cannot be guaranteed that the pool will be grown to the new
  * size immediately, but new mempool_free() calls will refill it.
+ * This function may sleep.
  *
  * Note, the caller must guarantee that no mempool_destroy is called
  * while this function is running. mempool_alloc() & mempool_free()
  * might be called (eg. from IRQ contexts) while this function executes.
  */
-int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
+int mempool_resize(mempool_t *pool, int new_min_nr)
 {
 	void *element;
 	void **new_elements;
 	unsigned long flags;
 
 	BUG_ON(new_min_nr <= 0);
+	might_sleep();
 
 	spin_lock_irqsave(&pool->lock, flags);
 	if (new_min_nr <= pool->min_nr) {
@@ -145,7 +146,7 @@ int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
 	spin_unlock_irqrestore(&pool->lock, flags);
 
 	/* Grow the pool */
-	new_elements = kmalloc(new_min_nr * sizeof(*new_elements), gfp_mask);
+	new_elements = kmalloc(new_min_nr * sizeof(*new_elements), GFP_KERNEL);
 	if (!new_elements)
 		return -ENOMEM;
 
@@ -164,7 +165,7 @@ int mempool_resize(mempool_t *pool, int new_min_nr, gfp_t gfp_mask)
 
 	while (pool->curr_nr < pool->min_nr) {
 		spin_unlock_irqrestore(&pool->lock, flags);
-		element = pool->alloc(gfp_mask, pool->pool_data);
+		element = pool->alloc(GFP_KERNEL, pool->pool_data);
 		if (!element)
 			goto out;
 		spin_lock_irqsave(&pool->lock, flags);
--
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