* Re: [PATCH] memory-hotplug: don't BUG() in register_memory_resource()
2015-12-18 14:50 [PATCH] memory-hotplug: don't BUG() in register_memory_resource() Vitaly Kuznetsov
@ 2015-12-18 16:33 ` Igor Mammedov
2015-12-18 22:50 ` Andrew Morton
2015-12-22 21:56 ` David Rientjes
2 siblings, 0 replies; 6+ messages in thread
From: Igor Mammedov @ 2015-12-18 16:33 UTC (permalink / raw)
To: Vitaly Kuznetsov
Cc: linux-mm, linux-kernel, Andrew Morton, Tang Chen,
Naoya Horiguchi, Xishi Qiu, Sheng Yong, David Rientjes,
Zhu Guihua, Dan Williams, David Vrabel
On Fri, 18 Dec 2015 15:50:24 +0100
Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
> Out of memory condition is not a bug and while we can't add new memory in
> such case crashing the system seems wrong. Propagating the return value
> from register_memory_resource() requires interface change.
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: Tang Chen <tangchen@cn.fujitsu.com>
> Cc: Naoya Horiguchi <n-horiguchi@ah.jp.nec.com>
> Cc: Xishi Qiu <qiuxishi@huawei.com>
> Cc: Sheng Yong <shengyong1@huawei.com>
> Cc: David Rientjes <rientjes@google.com>
> Cc: Zhu Guihua <zhugh.fnst@cn.fujitsu.com>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: David Vrabel <david.vrabel@citrix.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
> ---
> mm/memory_hotplug.c | 17 ++++++++++-------
> 1 file changed, 10 insertions(+), 7 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 67d488a..9392f01 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -127,11 +127,13 @@ void mem_hotplug_done(void)
> }
>
> /* add this memory to iomem resource */
> -static struct resource *register_memory_resource(u64 start, u64 size)
> +static int register_memory_resource(u64 start, u64 size,
> + struct resource **resource)
> {
> struct resource *res;
> res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> - BUG_ON(!res);
> + if (!res)
> + return -ENOMEM;
>
> res->name = "System RAM";
> res->start = start;
> @@ -140,9 +142,10 @@ static struct resource *register_memory_resource(u64 start, u64 size)
> if (request_resource(&iomem_resource, res) < 0) {
> pr_debug("System RAM resource %pR cannot be added\n", res);
> kfree(res);
> - res = NULL;
> + return -EEXIST;
> }
> - return res;
> + *resource = res;
> + return 0;
> }
>
> static void release_memory_resource(struct resource *res)
> @@ -1311,9 +1314,9 @@ int __ref add_memory(int nid, u64 start, u64 size)
> struct resource *res;
> int ret;
>
> - res = register_memory_resource(start, size);
> - if (!res)
> - return -EEXIST;
> + ret = register_memory_resource(start, size, &res);
> + if (ret)
> + return ret;
>
> ret = add_memory_resource(nid, res);
> if (ret < 0)
Reviewed-by: Igor Mammedov <imammedo@redhat.com>
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] memory-hotplug: don't BUG() in register_memory_resource()
2015-12-18 14:50 [PATCH] memory-hotplug: don't BUG() in register_memory_resource() Vitaly Kuznetsov
2015-12-18 16:33 ` Igor Mammedov
@ 2015-12-18 22:50 ` Andrew Morton
2015-12-21 10:13 ` Vitaly Kuznetsov
2015-12-22 21:56 ` David Rientjes
2 siblings, 1 reply; 6+ messages in thread
From: Andrew Morton @ 2015-12-18 22:50 UTC (permalink / raw)
To: Vitaly Kuznetsov
Cc: linux-mm, linux-kernel, Tang Chen, Naoya Horiguchi, Xishi Qiu,
Sheng Yong, David Rientjes, Zhu Guihua, Dan Williams,
David Vrabel, Igor Mammedov
On Fri, 18 Dec 2015 15:50:24 +0100 Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
> Out of memory condition is not a bug and while we can't add new memory in
> such case crashing the system seems wrong. Propagating the return value
> from register_memory_resource() requires interface change.
>
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> +static int register_memory_resource(u64 start, u64 size,
> + struct resource **resource)
> {
> struct resource *res;
> res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> - BUG_ON(!res);
> + if (!res)
> + return -ENOMEM;
>
> res->name = "System RAM";
> res->start = start;
> @@ -140,9 +142,10 @@ static struct resource *register_memory_resource(u64 start, u64 size)
> if (request_resource(&iomem_resource, res) < 0) {
> pr_debug("System RAM resource %pR cannot be added\n", res);
> kfree(res);
> - res = NULL;
> + return -EEXIST;
> }
> - return res;
> + *resource = res;
> + return 0;
> }
Was there a reason for overwriting the request_resource() return value?
Ordinarily it should be propagated back to callers.
Please review.
--- a/mm/memory_hotplug.c~memory-hotplug-dont-bug-in-register_memory_resource-fix
+++ a/mm/memory_hotplug.c
@@ -131,7 +131,9 @@ static int register_memory_resource(u64
struct resource **resource)
{
struct resource *res;
+ int ret = 0;
res = kzalloc(sizeof(struct resource), GFP_KERNEL);
+
if (!res)
return -ENOMEM;
@@ -139,13 +141,14 @@ static int register_memory_resource(u64
res->start = start;
res->end = start + size - 1;
res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
- if (request_resource(&iomem_resource, res) < 0) {
+ ret = request_resource(&iomem_resource, res);
+ if (ret < 0) {
pr_debug("System RAM resource %pR cannot be added\n", res);
kfree(res);
- return -EEXIST;
+ } else {
+ *resource = res;
}
- *resource = res;
- return 0;
+ return ret;
}
static void release_memory_resource(struct resource *res)
_
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] memory-hotplug: don't BUG() in register_memory_resource()
2015-12-18 22:50 ` Andrew Morton
@ 2015-12-21 10:13 ` Vitaly Kuznetsov
2015-12-21 23:06 ` Andrew Morton
0 siblings, 1 reply; 6+ messages in thread
From: Vitaly Kuznetsov @ 2015-12-21 10:13 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-mm, linux-kernel, Tang Chen, Naoya Horiguchi, Xishi Qiu,
Sheng Yong, David Rientjes, Zhu Guihua, Dan Williams,
David Vrabel, Igor Mammedov
Andrew Morton <akpm@linux-foundation.org> writes:
> On Fri, 18 Dec 2015 15:50:24 +0100 Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
>
>> Out of memory condition is not a bug and while we can't add new memory in
>> such case crashing the system seems wrong. Propagating the return value
>> from register_memory_resource() requires interface change.
>>
>> --- a/mm/memory_hotplug.c
>> +++ b/mm/memory_hotplug.c
>> +static int register_memory_resource(u64 start, u64 size,
>> + struct resource **resource)
>> {
>> struct resource *res;
>> res = kzalloc(sizeof(struct resource), GFP_KERNEL);
>> - BUG_ON(!res);
>> + if (!res)
>> + return -ENOMEM;
>>
>> res->name = "System RAM";
>> res->start = start;
>> @@ -140,9 +142,10 @@ static struct resource *register_memory_resource(u64 start, u64 size)
>> if (request_resource(&iomem_resource, res) < 0) {
>> pr_debug("System RAM resource %pR cannot be added\n", res);
>> kfree(res);
>> - res = NULL;
>> + return -EEXIST;
>> }
>> - return res;
>> + *resource = res;
>> + return 0;
>> }
>
> Was there a reason for overwriting the request_resource() return
> value?
> Ordinarily it should be propagated back to callers.
>
> Please review.
>
This is a nice-to-have addition but it will break at least ACPI
memhotplug: request_resource() has the following:
conflict = request_resource_conflict(root, new);
return conflict ? -EBUSY : 0;
so we'll end up returning -EBUSY from register_memory_resource() and
add_memory(), at the same time acpi_memory_enable_device() counts on
-EEXIST:
result = add_memory(node, info->start_addr, info->length);
/*
* If the memory block has been used by the kernel, add_memory()
* returns -EEXIST. If add_memory() returns the other error, it
* means that this memory block is not used by the kernel.
*/
if (result && result != -EEXIST)
continue;
So I see 3 options here:
1) Keep the overwrite
2) Change the request_resource() return value to -EEXIST
3) Adapt all add_memory() call sites to -EBUSY.
Please let me know your preference.
> --- a/mm/memory_hotplug.c~memory-hotplug-dont-bug-in-register_memory_resource-fix
> +++ a/mm/memory_hotplug.c
> @@ -131,7 +131,9 @@ static int register_memory_resource(u64
> struct resource **resource)
> {
> struct resource *res;
> + int ret = 0;
> res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> +
> if (!res)
> return -ENOMEM;
>
> @@ -139,13 +141,14 @@ static int register_memory_resource(u64
> res->start = start;
> res->end = start + size - 1;
> res->flags = IORESOURCE_MEM | IORESOURCE_BUSY;
> - if (request_resource(&iomem_resource, res) < 0) {
> + ret = request_resource(&iomem_resource, res);
> + if (ret < 0) {
> pr_debug("System RAM resource %pR cannot be added\n", res);
> kfree(res);
> - return -EEXIST;
> + } else {
> + *resource = res;
> }
> - *resource = res;
> - return 0;
> + return ret;
> }
>
> static void release_memory_resource(struct resource *res)
> _
--
Vitaly
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 6+ messages in thread* Re: [PATCH] memory-hotplug: don't BUG() in register_memory_resource()
2015-12-21 10:13 ` Vitaly Kuznetsov
@ 2015-12-21 23:06 ` Andrew Morton
0 siblings, 0 replies; 6+ messages in thread
From: Andrew Morton @ 2015-12-21 23:06 UTC (permalink / raw)
To: Vitaly Kuznetsov
Cc: linux-mm, linux-kernel, Tang Chen, Naoya Horiguchi, Xishi Qiu,
Sheng Yong, David Rientjes, Zhu Guihua, Dan Williams,
David Vrabel, Igor Mammedov
On Mon, 21 Dec 2015 11:13:15 +0100 Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
> Andrew Morton <akpm@linux-foundation.org> writes:
>
> > On Fri, 18 Dec 2015 15:50:24 +0100 Vitaly Kuznetsov <vkuznets@redhat.com> wrote:
> >
> >> Out of memory condition is not a bug and while we can't add new memory in
> >> such case crashing the system seems wrong. Propagating the return value
> >> from register_memory_resource() requires interface change.
> >>
> >> --- a/mm/memory_hotplug.c
> >> +++ b/mm/memory_hotplug.c
> >> +static int register_memory_resource(u64 start, u64 size,
> >> + struct resource **resource)
> >> {
> >> struct resource *res;
> >> res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> >> - BUG_ON(!res);
> >> + if (!res)
> >> + return -ENOMEM;
> >>
> >> res->name = "System RAM";
> >> res->start = start;
> >> @@ -140,9 +142,10 @@ static struct resource *register_memory_resource(u64 start, u64 size)
> >> if (request_resource(&iomem_resource, res) < 0) {
> >> pr_debug("System RAM resource %pR cannot be added\n", res);
> >> kfree(res);
> >> - res = NULL;
> >> + return -EEXIST;
> >> }
> >> - return res;
> >> + *resource = res;
> >> + return 0;
> >> }
> >
> > Was there a reason for overwriting the request_resource() return
> > value?
> > Ordinarily it should be propagated back to callers.
> >
> > Please review.
> >
>
> This is a nice-to-have addition but it will break at least ACPI
> memhotplug: request_resource() has the following:
>
> conflict = request_resource_conflict(root, new);
> return conflict ? -EBUSY : 0;
>
> so we'll end up returning -EBUSY from register_memory_resource() and
> add_memory(), at the same time acpi_memory_enable_device() counts on
> -EEXIST:
>
> result = add_memory(node, info->start_addr, info->length);
>
> /*
> * If the memory block has been used by the kernel, add_memory()
> * returns -EEXIST. If add_memory() returns the other error, it
> * means that this memory block is not used by the kernel.
> */
> if (result && result != -EEXIST)
> continue;
>
> So I see 3 options here:
> 1) Keep the overwrite
> 2) Change the request_resource() return value to -EEXIST
> 3) Adapt all add_memory() call sites to -EBUSY.
>
> Please let me know your preference.
urgh, what a mess. We should standardize on EBUSY or EEXIST, I don't
see that it matter much which is chosen. And for robustness the
callers should be checking for (err < 0) unless there's a very good
reason otherwise.
But it doesn't seem terribly important.
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH] memory-hotplug: don't BUG() in register_memory_resource()
2015-12-18 14:50 [PATCH] memory-hotplug: don't BUG() in register_memory_resource() Vitaly Kuznetsov
2015-12-18 16:33 ` Igor Mammedov
2015-12-18 22:50 ` Andrew Morton
@ 2015-12-22 21:56 ` David Rientjes
2 siblings, 0 replies; 6+ messages in thread
From: David Rientjes @ 2015-12-22 21:56 UTC (permalink / raw)
To: Vitaly Kuznetsov
Cc: linux-mm, linux-kernel, Andrew Morton, Tang Chen,
Naoya Horiguchi, Xishi Qiu, Sheng Yong, Zhu Guihua, Dan Williams,
David Vrabel, Igor Mammedov
On Fri, 18 Dec 2015, Vitaly Kuznetsov wrote:
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 67d488a..9392f01 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -127,11 +127,13 @@ void mem_hotplug_done(void)
> }
>
> /* add this memory to iomem resource */
> -static struct resource *register_memory_resource(u64 start, u64 size)
> +static int register_memory_resource(u64 start, u64 size,
> + struct resource **resource)
> {
> struct resource *res;
> res = kzalloc(sizeof(struct resource), GFP_KERNEL);
> - BUG_ON(!res);
> + if (!res)
> + return -ENOMEM;
>
> res->name = "System RAM";
> res->start = start;
> @@ -140,9 +142,10 @@ static struct resource *register_memory_resource(u64 start, u64 size)
> if (request_resource(&iomem_resource, res) < 0) {
> pr_debug("System RAM resource %pR cannot be added\n", res);
> kfree(res);
> - res = NULL;
> + return -EEXIST;
> }
> - return res;
> + *resource = res;
> + return 0;
> }
>
> static void release_memory_resource(struct resource *res)
> @@ -1311,9 +1314,9 @@ int __ref add_memory(int nid, u64 start, u64 size)
> struct resource *res;
> int ret;
>
> - res = register_memory_resource(start, size);
> - if (!res)
> - return -EEXIST;
> + ret = register_memory_resource(start, size, &res);
> + if (ret)
> + return ret;
>
> ret = add_memory_resource(nid, res);
> if (ret < 0)
Wouldn't it be simpler and cleaner to keep the return type of
register_memory_resource() the same and return ERR_PTR(-ENOMEM) or
ERR_PTR(-EEXIST) on error? add_memory() can check IS_ERR(res) and return
PTR_ERR(res).
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
^ permalink raw reply [flat|nested] 6+ messages in thread