2:07 a.m.
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(a)infradead.org>
Cc: Dan Williams <dan.j.williams(a)intel.com>
Cc: Sachin Sant <sachinp(a)linux.vnet.ibm.com>
Cc: linux-nvdimm(a)lists.01.org
Cc: Ira Weiny <ira.weiny(a)intel.com>
Cc: Jason Gunthorpe <jgg(a)mellanox.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.ibm.com>
---
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;
+ }
dev_pagemap_kill(pgmap);
for (i = 0; i < pgmap->nr_range; i++)
@@ -169,7 +179,8 @@ void memunmap_pages(struct dev_pagemap *pgmap)
pageunmap_range(pgmap, i);
WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved pages\n");
- devmap_managed_enable_put();
+ if (need_devmap_managed)
+ devmap_managed_enable_put();
}
EXPORT_SYMBOL_GPL(memunmap_pages);
@@ -307,7 +318,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
.pgprot = PAGE_KERNEL,
};
const int nr_range = pgmap->nr_range;
- bool need_devmap_managed = true;
+ bool need_devmap_managed = false;
int error, i;
if (WARN_ONCE(!nr_range, "nr_range must be specified\n"))
@@ -327,6 +338,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
WARN(1, "Missing owner\n");
return ERR_PTR(-EINVAL);
}
+ need_devmap_managed = true;
break;
case MEMORY_DEVICE_FS_DAX:
if (!IS_ENABLED(CONFIG_ZONE_DEVICE) ||
@@ -334,13 +346,12 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
WARN(1, "File system DAX not supported\n");
return ERR_PTR(-EINVAL);
}
+ need_devmap_managed = true;
break;
case MEMORY_DEVICE_GENERIC:
- need_devmap_managed = false;
break;
case MEMORY_DEVICE_PCI_P2PDMA:
params.pgprot = pgprot_noncached(params.pgprot);
- need_devmap_managed = false;
break;
default:
WARN(1, "Invalid pgmap type %d\n", pgmap->type);
--
2.26.2
4:34 a.m.
New subject: [PATCH] mm/mremap_pages: Fix static key devmap_managed_key
updates
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:
….
Cc: Christoph Hellwig <hch(a)infradead.org>
Cc: Dan Williams <dan.j.williams(a)intel.com>
Cc: Sachin Sant <sachinp(a)linux.vnet.ibm.com>
Cc: linux-nvdimm(a)lists.01.org
Cc: Ira Weiny <ira.weiny(a)intel.com>
Cc: Jason Gunthorpe <jgg(a)mellanox.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.ibm.com>
—
Tested-by: Sachin Sant <sachinp(a)linux.vnet.ibm.com>
-Sachin
9:26 a.m.
New subject: [PATCH] mm/mremap_pages: Fix static key devmap_managed_key
updates
Looks good,
Reviewed-by: Christoph Hellwig <hch(a)lst.de>
11:41 a.m.
New subject: [PATCH] mm/mremap_pages: Fix static key devmap_managed_key
updates
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(a)infradead.org>
Cc: Dan Williams <dan.j.williams(a)intel.com>
Cc: Sachin Sant <sachinp(a)linux.vnet.ibm.com>
Cc: linux-nvdimm(a)lists.01.org
Cc: Ira Weiny <ira.weiny(a)intel.com>
Cc: Jason Gunthorpe <jgg(a)mellanox.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.ibm.com>
---
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?
dev_pagemap_kill(pgmap);
for (i = 0; i < pgmap->nr_range; i++)
@@ -169,7 +179,8 @@ void memunmap_pages(struct dev_pagemap *pgmap)
pageunmap_range(pgmap, i);
WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved pages\n");
- devmap_managed_enable_put();
+ if (need_devmap_managed)
+ devmap_managed_enable_put();
}
EXPORT_SYMBOL_GPL(memunmap_pages);
@@ -307,7 +318,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
.pgprot = PAGE_KERNEL,
};
const int nr_range = pgmap->nr_range;
- bool need_devmap_managed = true;
+ bool need_devmap_managed = false;
I'm CC'ing Ralph Campbell because I think some of his work has proposed this
same change.
Ira
> int error, i;
>
> if (WARN_ONCE(!nr_range, "nr_range must be specified\n"))
> @@ -327,6 +338,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
> WARN(1, "Missing owner\n");
> return ERR_PTR(-EINVAL);
> }
> + need_devmap_managed = true;
> break;
> case MEMORY_DEVICE_FS_DAX:
> if (!IS_ENABLED(CONFIG_ZONE_DEVICE) ||
> @@ -334,13 +346,12 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
> WARN(1, "File system DAX not supported\n");
> return ERR_PTR(-EINVAL);
> }
> + need_devmap_managed = true;
> break;
> case MEMORY_DEVICE_GENERIC:
> - need_devmap_managed = false;
> break;
> case MEMORY_DEVICE_PCI_P2PDMA:
> params.pgprot = pgprot_noncached(params.pgprot);
> - need_devmap_managed = false;
> break;
> default:
> WARN(1, "Invalid pgmap type %d\n", pgmap->type);
> --
> 2.26.2
>
2:19 p.m.
New subject: [PATCH] mm/mremap_pages: Fix static key devmap_managed_key
updates
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(a)infradead.org>
> Cc: Dan Williams <dan.j.williams(a)intel.com>
> Cc: Sachin Sant <sachinp(a)linux.vnet.ibm.com>
> Cc: linux-nvdimm(a)lists.01.org
> Cc: Ira Weiny <ira.weiny(a)intel.com>
> Cc: Jason Gunthorpe <jgg(a)mellanox.com>
> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.ibm.com>
> ---
> 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(a)nvidia.com>
---
mm/memremap.c | 39 ++++++++++++++++-----------------------
1 file changed, 16 insertions(+), 23 deletions(-)
diff --git a/mm/memremap.c b/mm/memremap.c
index 73a206d0f645..16b2fb482da1 100644
--- a/mm/memremap.c
+++ b/mm/memremap.c
@@ -41,28 +41,24 @@ EXPORT_SYMBOL_GPL(memremap_compat_align);
DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
EXPORT_SYMBOL(devmap_managed_key);
-static void devmap_managed_enable_put(void)
+static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
{
- static_branch_dec(&devmap_managed_key);
+ if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
+ pgmap->type == MEMORY_DEVICE_FS_DAX)
+ static_branch_dec(&devmap_managed_key);
}
-static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
+static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
{
- if (pgmap->type == MEMORY_DEVICE_PRIVATE &&
- (!pgmap->ops || !pgmap->ops->page_free)) {
- WARN(1, "Missing page_free method\n");
- return -EINVAL;
- }
-
- static_branch_inc(&devmap_managed_key);
- return 0;
+ if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
+ pgmap->type == MEMORY_DEVICE_FS_DAX)
+ static_branch_inc(&devmap_managed_key);
}
#else
-static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
+static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
{
- return -EINVAL;
}
-static void devmap_managed_enable_put(void)
+static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
{
}
#endif /* CONFIG_DEV_PAGEMAP_OPS */
@@ -169,7 +165,7 @@ void memunmap_pages(struct dev_pagemap *pgmap)
pageunmap_range(pgmap, i);
WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved pages\n");
- devmap_managed_enable_put();
+ devmap_managed_enable_put(pgmap);
}
EXPORT_SYMBOL_GPL(memunmap_pages);
@@ -307,7 +303,6 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
.pgprot = PAGE_KERNEL,
};
const int nr_range = pgmap->nr_range;
- bool need_devmap_managed = true;
int error, i;
if (WARN_ONCE(!nr_range, "nr_range must be specified\n"))
@@ -323,6 +318,10 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
WARN(1, "Missing migrate_to_ram method\n");
return ERR_PTR(-EINVAL);
}
+ if (!pgmap->ops->page_free) {
+ WARN(1, "Missing page_free method\n");
+ return ERR_PTR(-EINVAL);
+ }
if (!pgmap->owner) {
WARN(1, "Missing owner\n");
return ERR_PTR(-EINVAL);
@@ -336,11 +335,9 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
}
break;
case MEMORY_DEVICE_GENERIC:
- need_devmap_managed = false;
break;
case MEMORY_DEVICE_PCI_P2PDMA:
params.pgprot = pgprot_noncached(params.pgprot);
- need_devmap_managed = false;
break;
default:
WARN(1, "Invalid pgmap type %d\n", pgmap->type);
@@ -364,11 +361,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
}
}
- if (need_devmap_managed) {
- error = devmap_managed_enable_get(pgmap);
- if (error)
- return ERR_PTR(error);
- }
+ devmap_managed_enable_get(pgmap);
/*
* Clear the pgmap nr_range as it will be incremented for each
--
2.20.1
>
> dev_pagemap_kill(pgmap);
> for (i = 0; i < pgmap->nr_range; i++)
> @@ -169,7 +179,8 @@ void memunmap_pages(struct dev_pagemap *pgmap)
> pageunmap_range(pgmap, i);
>
> WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved
pages\n");
> - devmap_managed_enable_put();
> + if (need_devmap_managed)
> + devmap_managed_enable_put();
> }
> EXPORT_SYMBOL_GPL(memunmap_pages);
>
> @@ -307,7 +318,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
> .pgprot = PAGE_KERNEL,
> };
> const int nr_range = pgmap->nr_range;
> - bool need_devmap_managed = true;
> + bool need_devmap_managed = false;
I'm CC'ing Ralph Campbell because I think some of his work has proposed this
same change.
Ira
This part of the patch isn't strictly needed, it just reverses the default value of
need_devmap_managed.
>> int error, i;
>>
>> if (WARN_ONCE(!nr_range, "nr_range must be specified\n"))
>> @@ -327,6 +338,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
>> WARN(1, "Missing owner\n");
>> return ERR_PTR(-EINVAL);
>> }
>> + need_devmap_managed = true;
>> break;
>> case MEMORY_DEVICE_FS_DAX:
>> if (!IS_ENABLED(CONFIG_ZONE_DEVICE) ||
>> @@ -334,13 +346,12 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
>> WARN(1, "File system DAX not supported\n");
>> return ERR_PTR(-EINVAL);
>> }
>> + need_devmap_managed = true;
>> break;
>> case MEMORY_DEVICE_GENERIC:
>> - need_devmap_managed = false;
>> break;
>> case MEMORY_DEVICE_PCI_P2PDMA:
>> params.pgprot = pgprot_noncached(params.pgprot);
>> - need_devmap_managed = false;
>> break;
>> default:
>> WARN(1, "Invalid pgmap type %d\n", pgmap->type);
>> --
>> 2.26.2
>>
3:10 p.m.
New subject: [PATCH] mm/mremap_pages: Fix static key devmap_managed_key
updates
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(a)infradead.org>
> > Cc: Dan Williams <dan.j.williams(a)intel.com>
> > Cc: Sachin Sant <sachinp(a)linux.vnet.ibm.com>
> > Cc: linux-nvdimm(a)lists.01.org
> > Cc: Ira Weiny <ira.weiny(a)intel.com>
> > Cc: Jason Gunthorpe <jgg(a)mellanox.com>
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.ibm.com>
> > ---
> > 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.
This looks cleaner to me. Aneesh?
FWIW:
Reviewed-by: Ira Weiny <ira.weiny(a)intel.com>
Ira
>
> Signed-off-by: Ralph Campbell <rcampbell(a)nvidia.com>
> ---
> mm/memremap.c | 39 ++++++++++++++++-----------------------
> 1 file changed, 16 insertions(+), 23 deletions(-)
>
> diff --git a/mm/memremap.c b/mm/memremap.c
> index 73a206d0f645..16b2fb482da1 100644
> --- a/mm/memremap.c
> +++ b/mm/memremap.c
> @@ -41,28 +41,24 @@ EXPORT_SYMBOL_GPL(memremap_compat_align);
> DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
> EXPORT_SYMBOL(devmap_managed_key);
> -static void devmap_managed_enable_put(void)
> +static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
> {
> - static_branch_dec(&devmap_managed_key);
> + if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
> + pgmap->type == MEMORY_DEVICE_FS_DAX)
> + static_branch_dec(&devmap_managed_key);
> }
> -static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
> +static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
> {
> - if (pgmap->type == MEMORY_DEVICE_PRIVATE &&
> - (!pgmap->ops || !pgmap->ops->page_free)) {
> - WARN(1, "Missing page_free method\n");
> - return -EINVAL;
> - }
> -
> - static_branch_inc(&devmap_managed_key);
> - return 0;
> + if (pgmap->type == MEMORY_DEVICE_PRIVATE ||
> + pgmap->type == MEMORY_DEVICE_FS_DAX)
> + static_branch_inc(&devmap_managed_key);
> }
> #else
> -static int devmap_managed_enable_get(struct dev_pagemap *pgmap)
> +static void devmap_managed_enable_get(struct dev_pagemap *pgmap)
> {
> - return -EINVAL;
> }
> -static void devmap_managed_enable_put(void)
> +static void devmap_managed_enable_put(struct dev_pagemap *pgmap)
> {
> }
> #endif /* CONFIG_DEV_PAGEMAP_OPS */
> @@ -169,7 +165,7 @@ void memunmap_pages(struct dev_pagemap *pgmap)
> pageunmap_range(pgmap, i);
> WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved
pages\n");
> - devmap_managed_enable_put();
> + devmap_managed_enable_put(pgmap);
> }
> EXPORT_SYMBOL_GPL(memunmap_pages);
> @@ -307,7 +303,6 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
> .pgprot = PAGE_KERNEL,
> };
> const int nr_range = pgmap->nr_range;
> - bool need_devmap_managed = true;
> int error, i;
> if (WARN_ONCE(!nr_range, "nr_range must be specified\n"))
> @@ -323,6 +318,10 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
> WARN(1, "Missing migrate_to_ram method\n");
> return ERR_PTR(-EINVAL);
> }
> + if (!pgmap->ops->page_free) {
> + WARN(1, "Missing page_free method\n");
> + return ERR_PTR(-EINVAL);
> + }
> if (!pgmap->owner) {
> WARN(1, "Missing owner\n");
> return ERR_PTR(-EINVAL);
> @@ -336,11 +335,9 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
> }
> break;
> case MEMORY_DEVICE_GENERIC:
> - need_devmap_managed = false;
> break;
> case MEMORY_DEVICE_PCI_P2PDMA:
> params.pgprot = pgprot_noncached(params.pgprot);
> - need_devmap_managed = false;
> break;
> default:
> WARN(1, "Invalid pgmap type %d\n", pgmap->type);
> @@ -364,11 +361,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int nid)
> }
> }
> - if (need_devmap_managed) {
> - error = devmap_managed_enable_get(pgmap);
> - if (error)
> - return ERR_PTR(error);
> - }
> + devmap_managed_enable_get(pgmap);
> /*
> * Clear the pgmap nr_range as it will be incremented for each
> --
> 2.20.1
>
> > > dev_pagemap_kill(pgmap);
> > > for (i = 0; i < pgmap->nr_range; i++)
> > > @@ -169,7 +179,8 @@ void memunmap_pages(struct dev_pagemap *pgmap)
> > > pageunmap_range(pgmap, i);
> > > WARN_ONCE(pgmap->altmap.alloc, "failed to free all reserved
pages\n");
> > > - devmap_managed_enable_put();
> > > + if (need_devmap_managed)
> > > + devmap_managed_enable_put();
> > > }
> > > EXPORT_SYMBOL_GPL(memunmap_pages);
> > > @@ -307,7 +318,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int
nid)
> > > .pgprot = PAGE_KERNEL,
> > > };
> > > const int nr_range = pgmap->nr_range;
> > > - bool need_devmap_managed = true;
> > > + bool need_devmap_managed = false;
> >
> > I'm CC'ing Ralph Campbell because I think some of his work has proposed
this
> > same change.
> >
> > Ira
>
> This part of the patch isn't strictly needed, it just reverses the default value
of
> need_devmap_managed.
>
> > > int error, i;
> > > if (WARN_ONCE(!nr_range, "nr_range must be specified\n"))
> > > @@ -327,6 +338,7 @@ void *memremap_pages(struct dev_pagemap *pgmap, int
nid)
> > > WARN(1, "Missing owner\n");
> > > return ERR_PTR(-EINVAL);
> > > }
> > > + need_devmap_managed = true;
> > > break;
> > > case MEMORY_DEVICE_FS_DAX:
> > > if (!IS_ENABLED(CONFIG_ZONE_DEVICE) ||
> > > @@ -334,13 +346,12 @@ void *memremap_pages(struct dev_pagemap *pgmap, int
nid)
> > > WARN(1, "File system DAX not supported\n");
> > > return ERR_PTR(-EINVAL);
> > > }
> > > + need_devmap_managed = true;
> > > break;
> > > case MEMORY_DEVICE_GENERIC:
> > > - need_devmap_managed = false;
> > > break;
> > > case MEMORY_DEVICE_PCI_P2PDMA:
> > > params.pgprot = pgprot_noncached(params.pgprot);
> > > - need_devmap_managed = false;
> > > break;
> > > default:
> > > WARN(1, "Invalid pgmap type %d\n", pgmap->type);
> > > --
> > > 2.26.2
> > >
10:52 p.m.
New subject: [PATCH] mm/mremap_pages: Fix static key devmap_managed_key
updates
On 10/23/20 12:40 AM, Ira Weiny 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(a)infradead.org>
>>> Cc: Dan Williams <dan.j.williams(a)intel.com>
>>> Cc: Sachin Sant <sachinp(a)linux.vnet.ibm.com>
>>> Cc: linux-nvdimm(a)lists.01.org
>>> Cc: Ira Weiny <ira.weiny(a)intel.com>
>>> Cc: Jason Gunthorpe <jgg(a)mellanox.com>
>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.ibm.com>
>>> ---
>>> 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.
This looks cleaner to me. Aneesh?
FWIW:
Reviewed-by: Ira Weiny <ira.weiny(a)intel.com>
Yes. You can add
Reviewed-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.ibm.com>
-aneesh
2:38 a.m.
New subject: [PATCH] mm/mremap_pages: Fix static key devmap_managed_key
updates
> 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(a)nvidia.com>
—
This patch fixes the warning for me.
Tested-by: Sachin Sant <sachinp(a)linux.vnet.ibm.com>
-Sachin
2:46 a.m.
New subject: [PATCH] mm/mremap_pages: Fix static key devmap_managed_key
updates
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(a)infradead.org>
> > Cc: Dan Williams <dan.j.williams(a)intel.com>
> > Cc: Sachin Sant <sachinp(a)linux.vnet.ibm.com>
> > Cc: linux-nvdimm(a)lists.01.org
> > Cc: Ira Weiny <ira.weiny(a)intel.com>
> > Cc: Jason Gunthorpe <jgg(a)mellanox.com>
> > Signed-off-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.ibm.com>
> > ---
> > 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(a)nvidia.com>
This looks ok as well. Can you submit it as a proper standalone patch?
1:29 p.m.
New subject: [PATCH] mm/mremap_pages: Fix static key devmap_managed_key
updates
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(a)infradead.org>
>>> Cc: Dan Williams <dan.j.williams(a)intel.com>
>>> Cc: Sachin Sant <sachinp(a)linux.vnet.ibm.com>
>>> Cc: linux-nvdimm(a)lists.01.org
>>> Cc: Ira Weiny <ira.weiny(a)intel.com>
>>> Cc: Jason Gunthorpe <jgg(a)mellanox.com>
>>> Signed-off-by: Aneesh Kumar K.V <aneesh.kumar(a)linux.ibm.com>
>>> ---
>>> 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(a)nvidia.com>
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.
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participants (5)
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Aneesh Kumar K.V -
Christoph Hellwig -
Ira Weiny -
Ralph Campbell -
Sachin Sant