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@xxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
drivers/md/dm-core.h | 3 ++-
drivers/md/dm.c | 6 +++---
2 files changed, 5 insertions(+), 4 deletions(-)
Index: linux-2.6/drivers/md/dm-core.h
===================================================================
--- linux-2.6.orig/drivers/md/dm-core.h
+++ linux-2.6/drivers/md/dm-core.h
@@ -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);
Index: linux-2.6/drivers/md/dm.c
===================================================================
--- linux-2.6.orig/drivers/md/dm.c
+++ linux-2.6/drivers/md/dm.c
@@ -1695,7 +1695,7 @@ static struct mapped_device *alloc_dev(i
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;
@@ -1795,7 +1795,7 @@ bad_io_barrier:
bad_minor:
module_put(THIS_MODULE);
bad_module_get:
- kfree(md);
+ kvfree(md);
return NULL;
}
@@ -1814,7 +1814,7 @@ static void free_dev(struct mapped_devic
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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