[Xen-devel] [PATCH]Fix memory leak for copy-receiver of netfront

[Kasai Takanori <kasai.takanori@xxxxxxxxxxxxxx>]

Hi all,

We found the problem of the memory leak when working with copy-
receiver of netfront.

The source of a problem is that the fragment page is not released with 
dev_kfree_skb() because the nr_frags variable of skb is set to 0. 

This is the patch to fix memory leak in netfront.

Signed-off-by: Kazuhiro Suzuki <kaz@xxxxxxxxxxxxxx>
Signed-off-by: Hirofumi Tsujimura <tsujimura.hirof@xxxxxxxxxxxxxx>
Signed-off-by: Takanori Kasai <kasai.takanori@xxxxxxxxxxxxxx>


A guest kernel does panic if attaching and detaching VNIF is repeated.
Because guest memory becomes empty, and OOM killer is run.
It is a log of that time as follows. 

------------------------------------------------------------------------
<dom0 log>
# xm network-attach guest
# xm network-detach guest 0
# xm network-attach guest
# xm network-detach guest 1
... repeat ...
# xm network-attach guest
# xm network-detach guest 179
# xm network-attach guest
# xm network-detach guest 180
Error: Domain 'guest' does not exist.


<guest log>
# free -m
             total       used       free     shared    buffers     
cached
Mem:           512        504          8          0         23        
174
-/+ buffers/cache:        305        206
Swap:          511          0        511
... repeat ...
# free -m
             total       used       free     shared    buffers     
cached
Mem:           512        509          2          0          0          
1
-/+ buffers/cache:        507          4
Swap:          511         50        461
awk invoked oom-killer: gfp_mask=0x201d2, order=0, oomkilladj=-17

Call Trace:
 [<a00000010001d160>] show_stack+0x40/0xa0
                                sp=e00000001e0a7a70 bsp=e00000001e0a1480
 [<a00000010001d1f0>] dump_stack+0x30/0x60
                                sp=e00000001e0a7c40 bsp=e00000001e0a1468
 [<a00000010011b1b0>] out_of_memory+0xf0/0x780
                                sp=e00000001e0a7c40 bsp=e00000001e0a1430
 [<a000000100121040>] __alloc_pages+0x420/0x540
                                sp=e00000001e0a7cd0 bsp=e00000001e0a13b8
... snip ...
Kernel panic - not syncing: Out of memory and no killable processes...
------------------------------------------------------------------------

Best Regards,

---
Takanori Kasai

Attachment: fix-netfront-memory-leak.patch
Description: Binary data

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