On 10/22/20 11:46 PM, Christoph Hellwig wrote:
On Thu, Oct 22, 2020 at 11:19:43AM -0700, Ralph Campbell wrote:
On 10/22/20 8:41 AM, Ira Weiny wrote:
On Thu, Oct 22, 2020 at 11:37:53AM +0530, Aneesh Kumar K.V wrote:
commit 6f42193fd86e ("memremap: don't use a separate devm action for
devmap_managed_enable_get") changed the static key updates such that we
now call devmap_managed_enable_put() without doing the equivalent
devmap_managed_enable_get().
devmap_managed_enable_get() is only called for MEMORY_DEVICE_PRIVATE and
MEMORY_DEVICE_FS_DAX, But memunmap_pages() get called for other pgmap
types too. This results in the below warning when switching between
system-ram and devdax mode for devdax namespace.
jump label: negative count!
WARNING: CPU: 52 PID: 1335 at kernel/jump_label.c:235 static_key_slow_try_dec+0x88/0xa0
Modules linked in:
....
NIP [c000000000433318] static_key_slow_try_dec+0x88/0xa0
LR [c000000000433314] static_key_slow_try_dec+0x84/0xa0
Call Trace:
[c000000025c1f660] [c000000000433314] static_key_slow_try_dec+0x84/0xa0 (unreliable)
[c000000025c1f6d0] [c000000000433664] __static_key_slow_dec_cpuslocked+0x34/0xd0
[c000000025c1f700] [c0000000004337a4] static_key_slow_dec+0x54/0xf0
[c000000025c1f770] [c00000000059c49c] memunmap_pages+0x36c/0x500
[c000000025c1f820] [c000000000d91d10] devm_action_release+0x30/0x50
[c000000025c1f840] [c000000000d92e34] release_nodes+0x2f4/0x3e0
[c000000025c1f8f0] [c000000000d8b15c] device_release_driver_internal+0x17c/0x280
[c000000025c1f930] [c000000000d883a4] bus_remove_device+0x124/0x210
[c000000025c1f9b0] [c000000000d80ef4] device_del+0x1d4/0x530
[c000000025c1fa70] [c000000000e341e8] unregister_dev_dax+0x48/0xe0
[c000000025c1fae0] [c000000000d91d10] devm_action_release+0x30/0x50
[c000000025c1fb00] [c000000000d92e34] release_nodes+0x2f4/0x3e0
[c000000025c1fbb0] [c000000000d8b15c] device_release_driver_internal+0x17c/0x280
[c000000025c1fbf0] [c000000000d87000] unbind_store+0x130/0x170
[c000000025c1fc30] [c000000000d862a0] drv_attr_store+0x40/0x60
[c000000025c1fc50] [c0000000006d316c] sysfs_kf_write+0x6c/0xb0
[c000000025c1fc90] [c0000000006d2328] kernfs_fop_write+0x118/0x280
[c000000025c1fce0] [c0000000005a79f8] vfs_write+0xe8/0x2a0
[c000000025c1fd30] [c0000000005a7d94] ksys_write+0x84/0x140
[c000000025c1fd80] [c00000000003a430] system_call_exception+0x120/0x270
[c000000025c1fe20] [c00000000000c540] system_call_common+0xf0/0x27c
Cc: Christoph Hellwig <hch@xxxxxxxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Sachin Sant <sachinp@xxxxxxxxxxxxxxxxxx>
Cc: linux-nvdimm@xxxxxxxxxxxx
Cc: Ira Weiny <ira.weiny@xxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxxxxxx>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@xxxxxxxxxxxxx>
---
mm/memremap.c | 19 +++++++++++++++----
1 file changed, 15 insertions(+), 4 deletions(-)
diff --git a/mm/memremap.c b/mm/memremap.c
index 73a206d0f645..d4402ff3e467 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -158,6 +158,16 @@ void memunmap_pages(struct dev_pagemap *pgmap)
{
unsigned long pfn;
int i;
+ bool need_devmap_managed = false;
+
+ switch (pgmap->type) {
+ case MEMORY_DEVICE_PRIVATE:
+ case MEMORY_DEVICE_FS_DAX:
+ need_devmap_managed = true;
+ break;
+ default:
+ break;
+ }
Is it overkill to avoid duplicating this switch logic in
page_is_devmap_managed() by creating another call which can be used here?
Perhaps. I can imagine a helper defined in include/linux/mm.h which
page_is_devmap_managed() could also call but that would impact a lot of
places that include mm.h. Since memremap.c already has to have intimate
knowledge of the pgmap->type, I think limiting the change to just what
is needed is better for now. So the patch looks OK to me.
Looking at this some more, I would suggest changing devmap_managed_enable_get()
and devmap_managed_enable_put() to do the special case checking instead of
doing it in memremap_pages() and memunmap_pages().
Then devmap_managed_enable_get() doesn't need to return an error if
CONFIG_DEV_PAGEMAP_OPS isn't defined. I have only compile tested the
following.
Signed-off-by: Ralph Campbell <rcampbell@xxxxxxxxxx>
This looks ok as well. Can you submit it as a proper standalone patch?
Yes. I was just about to ask whether I should do that and you beat me to it.
