dm: allocate struct mapped_device with kvzalloc (856eb091) · Commits · 戴 / test

The structure srcu_struct can be very big, its size is proportional to the value CONFIG_NR_CPUS. The Fedora kernel has CONFIG_NR_CPUS 8192, the field io_barrier in the struct mapped_device has 84kB in the debugging kernel and 50kB in the non-debugging kernel. The large size may result in failure of the function kzalloc_node. In order to avoid the allocation failure, we use the function kvzalloc_node, this function falls back to vmalloc if a large contiguous chunk of memory is not available. This patch also moves the field io_barrier to the last position of struct mapped_device - the reason is that on many processor architectures, short memory offsets result in smaller code than long memory offsets - on x86-64 it reduces code size by 320 bytes. Note to stable kernel maintainers - the kernels 4.11 and older don't have the function kvzalloc_node, you can use the function vzalloc_node instead. Signed-off-by:

Mikulas Patocka <mpatocka@redhat.com> Cc: stable@vger.kernel.org Signed-off-by:

Mike Snitzer <snitzer@redhat.com>

drivers/md/dm-core.h

+2 −1

Original line number	Diff line number	Diff line
		@@ -29,7 +29,6 @@ struct dm_kobject_holder {
		* DM targets must _not_ deference a mapped_device to directly access its members!
		*/
		struct mapped_device {
		struct srcu_struct io_barrier;
		struct mutex suspend_lock;

		/*
		@@ -127,6 +126,8 @@ struct mapped_device {
		struct blk_mq_tag_set *tag_set;
		bool use_blk_mq:1;
		bool init_tio_pdu:1;

		struct srcu_struct io_barrier;
		};

		void dm_init_md_queue(struct mapped_device *md);

drivers/md/dm.c

+3 −3

Original line number	Diff line number	Diff line
		@@ -1697,7 +1697,7 @@ static struct mapped_device *alloc_dev(int minor)
		struct mapped_device *md;
		void *old_md;

		md = kzalloc_node(sizeof(*md), GFP_KERNEL, numa_node_id);
		md = kvzalloc_node(sizeof(*md), GFP_KERNEL, numa_node_id);
		if (!md) {
		DMWARN("unable to allocate device, out of memory.");
		return NULL;
		@@ -1797,7 +1797,7 @@ bad_io_barrier:
		bad_minor:
		module_put(THIS_MODULE);
		bad_module_get:
		kfree(md);
		kvfree(md);
		return NULL;
		}

		@@ -1816,7 +1816,7 @@ static void free_dev(struct mapped_device *md)
		free_minor(minor);

		module_put(THIS_MODULE);
		kfree(md);
		kvfree(md);
		}

		static void __bind_mempools(struct mapped_device md, struct dm_table t)

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