Re: [PATCH] vhost-scsi: Depend on NET for memcpy_fromiovec

[Rusty Russell <rusty@rustcorp.com.au>]

Joe Perches <joe@perches.com> writes:
> On Thu, 2013-05-16 at 13:04 +0930, Rusty Russell wrote:
>> Asias He <asias@redhat.com> writes:
>> > On Wed, May 15, 2013 at 02:47:53PM +0930, Rusty Russell wrote:
> []
>> > Other users are using memcpy_fromiovec and friends outside net. It seems
>> > a good idea to put it in a util library. e.g.  crypto/algif_skcipher.c
>> > which also depends on NET for it.
>
> []
>> Subject: Hoist memcpy_fromiovec into lib/
>
> You'll need the "friends" memcpy_toiovec too.
>
> $ git grep -E \bmemcpy\w+iovec\w*"
> crypto/algif_hash.c:    err = memcpy_toiovec(msg->msg_iov, ctx->result, len);
> crypto/algif_skcipher.c:                        err = memcpy_fromiovec(page_address(sg_page(sg)) +
> crypto/algif_skcipher.c:                        err = memcpy_fromiovec(page_address(sg_page(sg + i)),
> drivers/dma/iovlock.c:#include <net/tcp.h> /* for memcpy_toiovec */
> drivers/dma/iovlock.c:          return memcpy_toiovec(iov, kdata, len);
> drivers/dma/iovlock.c:          err = memcpy_toiovec(iov, vaddr + offset, len);
> drivers/isdn/mISDN/socket.c:    if (memcpy_fromiovec(skb_put(skb, len), msg->msg_iov, len)) {
> drivers/misc/vmw_vmci/vmci_queue_pair.c:                        err = memcpy_fromiovec((u8 *)va + page_o
> drivers/misc/vmw_vmci/vmci_queue_pair.c:                        err = memcpy_toiovec(iov, (u8 *)va + pag

Fascinating.  These all indirectly depend on NET, so there's no problem
at the moment.  But it is a bit weird...

crypto/algif_hash.c: depends on CRYPTO_USER_API_HASH -> NET
crypto/algif_skcipher.c: depends on CRYPTO_USER_API_SKCIPHER -> NET
drivers/dma/iovlock.c: depends on NET_DMA -> NET
drivers/isdn/mISDN/socket.c: depends on MISDN -> ISDN -> NET
drivers/misc/vmw_vmci/vmci_queue_pair.c: depends on VMCI -> NET

Patch welcome.

Meanwhile, to avoid more bikeshedding I've put the patch I posted with
all acks in my fixes branch.  One cycle through linux-next, then
straight to Linus.

Subject: Hoist memcpy_fromiovec into lib/

ERROR: "memcpy_fromiovec" [drivers/vhost/vhost_scsi.ko] undefined!

That function is only present with CONFIG_NET.  Turns out that
crypto/algif_skcipher.c also uses that outside net, but it actually
needs sockets anyway.

socket.h already include uio.h, so no callers need updating.

Reported-by: Randy Dunlap <rdunlap@infradead.org>
Acked-by: David S. Miller <davem@davemloft.net>
Acked-by: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

diff --git a/include/linux/socket.h b/include/linux/socket.h
index 428c37a..7266775 100644
--- a/include/linux/socket.h
+++ b/include/linux/socket.h
@@ -305,7 +305,6 @@ struct ucred {
 
 extern void cred_to_ucred(struct pid *pid, const struct cred *cred, struct ucred *ucred);
 
-extern int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len);
 extern int memcpy_fromiovecend(unsigned char *kdata, const struct iovec *iov,
 			       int offset, int len);
 extern int csum_partial_copy_fromiovecend(unsigned char *kdata, 
diff --git a/include/linux/uio.h b/include/linux/uio.h
index 629aaf5..21628d3 100644
--- a/include/linux/uio.h
+++ b/include/linux/uio.h
@@ -35,4 +35,6 @@ static inline size_t iov_length(const struct iovec *iov, unsigned long nr_segs)
 }
 
 unsigned long iov_shorten(struct iovec *iov, unsigned long nr_segs, size_t to);
+
+int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len);
 #endif
diff --git a/lib/Makefile b/lib/Makefile
index e9c52e1..2377211 100644
--- a/lib/Makefile
+++ b/lib/Makefile
@@ -9,7 +9,7 @@ endif
 
 lib-y := ctype.o string.o vsprintf.o cmdline.o \
 	 rbtree.o radix-tree.o dump_stack.o timerqueue.o\
-	 idr.o int_sqrt.o extable.o \
+	 idr.o int_sqrt.o extable.o iovec.o \
 	 sha1.o md5.o irq_regs.o reciprocal_div.o argv_split.o \
 	 proportions.o flex_proportions.o prio_heap.o ratelimit.o show_mem.o \
 	 is_single_threaded.o plist.o decompress.o kobject_uevent.o \
diff --git a/lib/iovec.c b/lib/iovec.c
new file mode 100644
index 0000000..632c5ea
--- /dev/null
+++ b/lib/iovec.c
@@ -0,0 +1,29 @@
+#include <linux/uaccess.h>
+#include <linux/export.h>
+#include <linux/uio.h>
+
+/*
+ *	Copy iovec to kernel. Returns -EFAULT on error.
+ *
+ *	Note: this modifies the original iovec.
+ */
+
+int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len)
+{
+	while (len > 0) {
+		if (iov->iov_len) {
+			int copy = min_t(unsigned int, len, iov->iov_len);
+			if (copy_from_user(kdata, iov->iov_base, copy))
+				return -EFAULT;
+			len -= copy;
+			kdata += copy;
+			iov->iov_base += copy;
+			iov->iov_len -= copy;
+		}
+		iov++;
+	}
+
+	return 0;
+}
+EXPORT_SYMBOL(memcpy_fromiovec);
+
diff --git a/net/core/iovec.c b/net/core/iovec.c
index 7e7aeb0..d81257f 100644
--- a/net/core/iovec.c
+++ b/net/core/iovec.c
@@ -125,31 +125,6 @@ int memcpy_toiovecend(const struct iovec *iov, unsigned char *kdata,
 EXPORT_SYMBOL(memcpy_toiovecend);
 
 /*
- *	Copy iovec to kernel. Returns -EFAULT on error.
- *
- *	Note: this modifies the original iovec.
- */
-
-int memcpy_fromiovec(unsigned char *kdata, struct iovec *iov, int len)
-{
-	while (len > 0) {
-		if (iov->iov_len) {
-			int copy = min_t(unsigned int, len, iov->iov_len);
-			if (copy_from_user(kdata, iov->iov_base, copy))
-				return -EFAULT;
-			len -= copy;
-			kdata += copy;
-			iov->iov_base += copy;
-			iov->iov_len -= copy;
-		}
-		iov++;
-	}
-
-	return 0;
-}
-EXPORT_SYMBOL(memcpy_fromiovec);
-
-/*
  *	Copy iovec from kernel. Returns -EFAULT on error.
  */