Re: [libvirt] [PATCH 1/1] storage: Fix a vol-clone bug for ppc64

On 11/08/2013 06:25 AM, Li Zhang wrote: > On 2013年11月07日 18:41, Ján Tomko wrote: >> On 11/07/2013 09:35 AM, Li Zhang wrote: >>> Currently, wbytes is defined as size_t type which is 8 bytes on ppc64, >>> but args's value in ioctl(fd, args..) in kernel is unsigned int. >>> So it will read more 4 bytes by ioctl() with size_t from memory which >>> gets a large number and causes out of memory error. >> On x86_64 size_t is 8 bytes and int is 4 bytes, I guess this is an >> endianness issue. > It doesn't look like the endianness issue. > It appends more 32 0s to the value. > I need to trace kernel to see how this happens. > > Here is what I get on PPC64. > blksz = 0x1000000000000, pbsz = 0x20000000000 > > Actually, they should be : > blksz = 0x10000, pbsz = 0x200 > > On x86_64, they can get right value. > That looks like endianness to me :) 0x200 on little endian: 4-byte int: 0x00 0x02 0x00 0x00 8-byte size_t: 0x00 0x02 0x00 0x00 0x00 0x00 0x00 0x00 0x200 on big endian: 4-byte int: 0x00 0x00 0x02 0x00 8-byte size_t: 0x00 0x00 0x00 0x00 0x00 0x00 0x02 0x00 8-byte size_t with the int written in the first four bytes: 0x00 0x00 0x02 0x00 0x00 0x00 0x00 0x00 Which is what you get in pbsz on PPC64.

>>> This patch changes size_t to unsigned int to synchronize with kernel. >> The type in the kernel seems to be int: >> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/bloc... >> >> https://lkml.org/lkml/2013/11/1/620 > Ah, you are right, should be int. :) > >>> Signed-off-by: Li Zhang <zhlcindy(a)linux.vnet.ibm.com&gt; >>> --- >>> src/storage/storage_backend.c | 2 +- >>> 1 file changed, 1 insertion(+), 1 deletion(-) >>> >>> diff --git a/src/storage/storage_backend.c b/src/storage/storage_backend.c >>> index 4b1b00d..f510080 100644 >>> --- a/src/storage/storage_backend.c >>> +++ b/src/storage/storage_backend.c >>> @@ -135,7 +135,7 @@ virStorageBackendCopyToFD(virStorageVolDefPtr vol, >>> int amtread = -1; >>> int ret = 0; >>> size_t rbytes = READ_BLOCK_SIZE_DEFAULT; >>> - size_t wbytes = 0; >>> + unsigned int wbytes = 0; >>> int interval; >>> char *zerobuf = NULL; >>> char *buf = NULL; >>> >> I'll push this with s/unsigned // later, unless someone has a different >> opinion. > Got it, thanks. > Now pushed. Jan