[bpf-next,v2,2/3] xdp: xdp_umem: replace kmap on vmap for umem map
diff mbox series

Message ID 20190815121356.8848-3-ivan.khoronzhuk@linaro.org
State In Next
Commit 624676e788992e4da8de1fad93bfe51563a7f9a0
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Series
  • xdpsock: allow mmap2 usage for 32bits
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Commit Message

Ivan Khoronzhuk Aug. 15, 2019, 12:13 p.m. UTC
For 64-bit there is no reason to use vmap/vunmap, so use page_address
as it was initially. For 32 bits, in some apps, like in samples
xdpsock_user.c when number of pgs in use is quite big, the kmap
memory can be not enough, despite on this, kmap looks like is
deprecated in such cases as it can block and should be used rather
for dynamic mm.

Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
---
 net/xdp/xdp_umem.c | 36 ++++++++++++++++++++++++++++++------
 1 file changed, 30 insertions(+), 6 deletions(-)

Comments

Jonathan Lemon Aug. 15, 2019, 6:23 p.m. UTC | #1
On 15 Aug 2019, at 5:13, Ivan Khoronzhuk wrote:

> For 64-bit there is no reason to use vmap/vunmap, so use page_address
> as it was initially. For 32 bits, in some apps, like in samples
> xdpsock_user.c when number of pgs in use is quite big, the kmap
> memory can be not enough, despite on this, kmap looks like is
> deprecated in such cases as it can block and should be used rather
> for dynamic mm.
>
> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
> ---
>  net/xdp/xdp_umem.c | 36 ++++++++++++++++++++++++++++++------
>  1 file changed, 30 insertions(+), 6 deletions(-)
>
> diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
> index a0607969f8c0..d740c4f8810c 100644
> --- a/net/xdp/xdp_umem.c
> +++ b/net/xdp/xdp_umem.c
> @@ -14,7 +14,7 @@
>  #include <linux/netdevice.h>
>  #include <linux/rtnetlink.h>
>  #include <linux/idr.h>
> -#include <linux/highmem.h>
> +#include <linux/vmalloc.h>
>
>  #include "xdp_umem.h"
>  #include "xsk_queue.h"
> @@ -170,7 +170,30 @@ static void xdp_umem_unmap_pages(struct xdp_umem 
> *umem)
>  	unsigned int i;
>
>  	for (i = 0; i < umem->npgs; i++)
> -		kunmap(umem->pgs[i]);
> +		if (PageHighMem(umem->pgs[i]))
> +			vunmap(umem->pages[i].addr);
> +}
> +
> +static int xdp_umem_map_pages(struct xdp_umem *umem)
> +{
> +	unsigned int i;
> +	void *addr;
> +
> +	for (i = 0; i < umem->npgs; i++) {
> +		if (PageHighMem(umem->pgs[i]))
> +			addr = vmap(&umem->pgs[i], 1, VM_MAP, PAGE_KERNEL);
> +		else
> +			addr = page_address(umem->pgs[i]);
> +
> +		if (!addr) {
> +			xdp_umem_unmap_pages(umem);
> +			return -ENOMEM;
> +		}
> +
> +		umem->pages[i].addr = addr;
> +	}
> +
> +	return 0;
>  }

You'll want a __xdp_umem_unmap_pages() helper here that takes an
count of the number of pages to unmap, so it can be called from
xdp_umem_unmap_pages() in the normal case, and xdp_umem_map_pages()
in the error case.  Otherwise the error case ends up calling
PageHighMem on a null page.
Ivan Khoronzhuk Aug. 15, 2019, 7:19 p.m. UTC | #2
On Thu, Aug 15, 2019 at 11:23:16AM -0700, Jonathan Lemon wrote:
>On 15 Aug 2019, at 5:13, Ivan Khoronzhuk wrote:
>
>>For 64-bit there is no reason to use vmap/vunmap, so use page_address
>>as it was initially. For 32 bits, in some apps, like in samples
>>xdpsock_user.c when number of pgs in use is quite big, the kmap
>>memory can be not enough, despite on this, kmap looks like is
>>deprecated in such cases as it can block and should be used rather
>>for dynamic mm.
>>
>>Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
>>---
>> net/xdp/xdp_umem.c | 36 ++++++++++++++++++++++++++++++------
>> 1 file changed, 30 insertions(+), 6 deletions(-)
>>
>>diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
>>index a0607969f8c0..d740c4f8810c 100644
>>--- a/net/xdp/xdp_umem.c
>>+++ b/net/xdp/xdp_umem.c
>>@@ -14,7 +14,7 @@
>> #include <linux/netdevice.h>
>> #include <linux/rtnetlink.h>
>> #include <linux/idr.h>
>>-#include <linux/highmem.h>
>>+#include <linux/vmalloc.h>
>>
>> #include "xdp_umem.h"
>> #include "xsk_queue.h"
>>@@ -170,7 +170,30 @@ static void xdp_umem_unmap_pages(struct 
>>xdp_umem *umem)
>> 	unsigned int i;
>>
>> 	for (i = 0; i < umem->npgs; i++)
>>-		kunmap(umem->pgs[i]);
>>+		if (PageHighMem(umem->pgs[i]))
>>+			vunmap(umem->pages[i].addr);
>>+}
>>+
>>+static int xdp_umem_map_pages(struct xdp_umem *umem)
>>+{
>>+	unsigned int i;
>>+	void *addr;
>>+
>>+	for (i = 0; i < umem->npgs; i++) {
>>+		if (PageHighMem(umem->pgs[i]))
>>+			addr = vmap(&umem->pgs[i], 1, VM_MAP, PAGE_KERNEL);
>>+		else
>>+			addr = page_address(umem->pgs[i]);
>>+
>>+		if (!addr) {
>>+			xdp_umem_unmap_pages(umem);
>>+			return -ENOMEM;
>>+		}
>>+
>>+		umem->pages[i].addr = addr;
>>+	}
>>+
>>+	return 0;
>> }
>
>You'll want a __xdp_umem_unmap_pages() helper here that takes an
>count of the number of pages to unmap, so it can be called from
>xdp_umem_unmap_pages() in the normal case, and xdp_umem_map_pages()
>in the error case.  Otherwise the error case ends up calling
>PageHighMem on a null page.
>-- 
>Jonathan

Do you mean null address?
If so, then vunmap do nothing if it's null, and addr is null if it's not
assigned... and it's not assigned w/o correct mapping...

If you mean null page, then it is not possible after all they are
pinned above, here: xdp_umem_pin_pages(), thus assigned.

Or I missed smth?

Despite of this, seems like here should be one more patch, adding unpinning page
in error path, but this not related to this change. Will do this in follow up
fix patch, if no objection to my explanation, ofc.
Jonathan Lemon Aug. 15, 2019, 7:32 p.m. UTC | #3
On 15 Aug 2019, at 12:19, Ivan Khoronzhuk wrote:

> On Thu, Aug 15, 2019 at 11:23:16AM -0700, Jonathan Lemon wrote:
>> On 15 Aug 2019, at 5:13, Ivan Khoronzhuk wrote:
>>
>>> For 64-bit there is no reason to use vmap/vunmap, so use 
>>> page_address
>>> as it was initially. For 32 bits, in some apps, like in samples
>>> xdpsock_user.c when number of pgs in use is quite big, the kmap
>>> memory can be not enough, despite on this, kmap looks like is
>>> deprecated in such cases as it can block and should be used rather
>>> for dynamic mm.
>>>
>>> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>
>>> ---
>>> net/xdp/xdp_umem.c | 36 ++++++++++++++++++++++++++++++------
>>> 1 file changed, 30 insertions(+), 6 deletions(-)
>>>
>>> diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
>>> index a0607969f8c0..d740c4f8810c 100644
>>> --- a/net/xdp/xdp_umem.c
>>> +++ b/net/xdp/xdp_umem.c
>>> @@ -14,7 +14,7 @@
>>> #include <linux/netdevice.h>
>>> #include <linux/rtnetlink.h>
>>> #include <linux/idr.h>
>>> -#include <linux/highmem.h>
>>> +#include <linux/vmalloc.h>
>>>
>>> #include "xdp_umem.h"
>>> #include "xsk_queue.h"
>>> @@ -170,7 +170,30 @@ static void xdp_umem_unmap_pages(struct 
>>> xdp_umem *umem)
>>> 	unsigned int i;
>>>
>>> 	for (i = 0; i < umem->npgs; i++)
>>> -		kunmap(umem->pgs[i]);
>>> +		if (PageHighMem(umem->pgs[i]))
>>> +			vunmap(umem->pages[i].addr);
>>> +}
>>> +
>>> +static int xdp_umem_map_pages(struct xdp_umem *umem)
>>> +{
>>> +	unsigned int i;
>>> +	void *addr;
>>> +
>>> +	for (i = 0; i < umem->npgs; i++) {
>>> +		if (PageHighMem(umem->pgs[i]))
>>> +			addr = vmap(&umem->pgs[i], 1, VM_MAP, PAGE_KERNEL);
>>> +		else
>>> +			addr = page_address(umem->pgs[i]);
>>> +
>>> +		if (!addr) {
>>> +			xdp_umem_unmap_pages(umem);
>>> +			return -ENOMEM;
>>> +		}
>>> +
>>> +		umem->pages[i].addr = addr;
>>> +	}
>>> +
>>> +	return 0;
>>> }
>>
>> You'll want a __xdp_umem_unmap_pages() helper here that takes an
>> count of the number of pages to unmap, so it can be called from
>> xdp_umem_unmap_pages() in the normal case, and xdp_umem_map_pages()
>> in the error case.  Otherwise the error case ends up calling
>> PageHighMem on a null page.
>> -- 
>> Jonathan
>
> Do you mean null address?
> If so, then vunmap do nothing if it's null, and addr is null if it's 
> not
> assigned... and it's not assigned w/o correct mapping...
>
> If you mean null page, then it is not possible after all they are
> pinned above, here: xdp_umem_pin_pages(), thus assigned.
>
> Or I missed smth?

No - I forgot about umem_pin_pages() - feel free to ignore my comments.
--
Jonathan

>
> Despite of this, seems like here should be one more patch, adding 
> unpinning page
> in error path, but this not related to this change. Will do this in 
> follow up
> fix patch, if no objection to my explanation, ofc.
>
> -- 
> Regards,
> Ivan Khoronzhuk
Jonathan Lemon Aug. 15, 2019, 7:33 p.m. UTC | #4
On 15 Aug 2019, at 5:13, Ivan Khoronzhuk wrote:

> For 64-bit there is no reason to use vmap/vunmap, so use page_address
> as it was initially. For 32 bits, in some apps, like in samples
> xdpsock_user.c when number of pgs in use is quite big, the kmap
> memory can be not enough, despite on this, kmap looks like is
> deprecated in such cases as it can block and should be used rather
> for dynamic mm.
>
> Signed-off-by: Ivan Khoronzhuk <ivan.khoronzhuk@linaro.org>

Acked-by: Jonathan Lemon <jonathan.lemon@gmail.com>

Patch
diff mbox series

diff --git a/net/xdp/xdp_umem.c b/net/xdp/xdp_umem.c
index a0607969f8c0..d740c4f8810c 100644
--- a/net/xdp/xdp_umem.c
+++ b/net/xdp/xdp_umem.c
@@ -14,7 +14,7 @@ 
 #include <linux/netdevice.h>
 #include <linux/rtnetlink.h>
 #include <linux/idr.h>
-#include <linux/highmem.h>
+#include <linux/vmalloc.h>
 
 #include "xdp_umem.h"
 #include "xsk_queue.h"
@@ -170,7 +170,30 @@  static void xdp_umem_unmap_pages(struct xdp_umem *umem)
 	unsigned int i;
 
 	for (i = 0; i < umem->npgs; i++)
-		kunmap(umem->pgs[i]);
+		if (PageHighMem(umem->pgs[i]))
+			vunmap(umem->pages[i].addr);
+}
+
+static int xdp_umem_map_pages(struct xdp_umem *umem)
+{
+	unsigned int i;
+	void *addr;
+
+	for (i = 0; i < umem->npgs; i++) {
+		if (PageHighMem(umem->pgs[i]))
+			addr = vmap(&umem->pgs[i], 1, VM_MAP, PAGE_KERNEL);
+		else
+			addr = page_address(umem->pgs[i]);
+
+		if (!addr) {
+			xdp_umem_unmap_pages(umem);
+			return -ENOMEM;
+		}
+
+		umem->pages[i].addr = addr;
+	}
+
+	return 0;
 }
 
 static void xdp_umem_unpin_pages(struct xdp_umem *umem)
@@ -312,7 +335,7 @@  static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 	u32 chunk_size = mr->chunk_size, headroom = mr->headroom;
 	unsigned int chunks, chunks_per_page;
 	u64 addr = mr->addr, size = mr->len;
-	int size_chk, err, i;
+	int size_chk, err;
 
 	if (chunk_size < XDP_UMEM_MIN_CHUNK_SIZE || chunk_size > PAGE_SIZE) {
 		/* Strictly speaking we could support this, if:
@@ -378,10 +401,11 @@  static int xdp_umem_reg(struct xdp_umem *umem, struct xdp_umem_reg *mr)
 		goto out_account;
 	}
 
-	for (i = 0; i < umem->npgs; i++)
-		umem->pages[i].addr = kmap(umem->pgs[i]);
+	err = xdp_umem_map_pages(umem);
+	if (!err)
+		return 0;
 
-	return 0;
+	kfree(umem->pages);
 
 out_account:
 	xdp_umem_unaccount_pages(umem);