Re: [PATCH] virtio-9p: fix QEMU build break

["Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>]

On Mon, 10 Oct 2011 22:05:21 +0530, "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com> wrote:
> On Mon, 10 Oct 2011 18:30:28 +0800, Zhi Yong Wu <wuzhy@linux.vnet.ibm.com> wrote:
> > qemu build break due to the redefinition of struct file_handle. My qemu.git/HEAD is 8acbc9b21d757a6be4f8492e547b8159703a0547
> > 
> > Below is the log:
> > [root@f15 qemu]# make
> >   CC    qapi-generated/qga-qapi-types.o
> >   LINK  qemu-ga
> >   CC    libhw64/9pfs/virtio-9p-handle.o
> > /home/zwu/work/virt/qemu/hw/9pfs/virtio-9p-handle.c:31:8: error: redefinition of "struct file_handle"
> > /usr/include/bits/fcntl.h:254:8: note: originally defined here
> > make[1]: *** [9pfs/virtio-9p-handle.o] Error 1
> > make: *** [subdir-libhw64] Error 2
> > 
> > [root@f15 qemu]# rpm -qf /usr/include/bits/fcntl.h
> > glibc-headers-2.13.90-9.x86_64
> > 
> 
> Is this a backported glibc ? On my ubuntu system glibc 2.13 doesn't
> provide struct file_handle. I also checked glib repo at
> http://repo.or.cz/w/glibc.git. The commit introducing struct file_handle
> is 
> 
> $ git describe --contains 158648c0bdda281e252a27c0200dd0ea6f4e0215
> glibc-2.14~200
> 
> 

How about the below patch. This means that handle driver will only work
with latest glibc. Even if i have latest kernel, with an older glibc
handle fs driver backed will be disabled.

diff --git a/configure b/configure
index 24b8df4..0216c53 100755
--- a/configure
+++ b/configure
@@ -2551,6 +2551,18 @@ EOF
 fi
 
 ##########################################
+# check if we have open_by_handle_at
+
+open_by_hande_at=no
+cat > $TMPC << EOF
+#include <fcntl.h>
+int main(void) { struct file_handle *fh; open_by_handle_at(0, fh, 0); }
+EOF
+if compile_prog "" "" ; then
+    open_by_handle_at=yes
+fi
+
+##########################################
 # End of CC checks
 # After here, no more $cc or $ld runs
 
@@ -3029,6 +3041,10 @@ if test "$ucontext_coroutine" = "yes" ; then
   echo "CONFIG_UCONTEXT_COROUTINE=y" >> $config_host_mak
 fi
 
+if test "$open_by_handle_at" = "yes" ; then
+  echo "CONFIG_OPEN_BY_HANDLE=y" >> $config_host_mak
+fi
+
 # USB host support
 case "$usb" in
 linux)
diff --git a/hw/9pfs/virtio-9p-handle.c b/hw/9pfs/virtio-9p-handle.c
index 68e1d9b..bd73d31 100644
--- a/hw/9pfs/virtio-9p-handle.c
+++ b/hw/9pfs/virtio-9p-handle.c
@@ -30,13 +30,24 @@ struct handle_data {
     int handle_bytes;
 };
 
-#if __GLIBC__ <= 2 && __GLIBC_MINOR__ < 14
+#ifdef CONFIG_OPEN_BY_HANDLE
+static inline int name_to_handle(int dirfd, const char *name,
+                                 struct file_handle *fh, int *mnt_id, int flags)
+{
+    return name_to_handle_at(dirfd, name, fh, mnt_id, flags);
+}
+
+static inline int open_by_handle(int mountfd, const char *fh, int flags)
+{
+    return open_by_handle_at(mountfd, fh, flags);
+}
+#else
+
 struct file_handle {
-        unsigned int handle_bytes;
-        int handle_type;
-        unsigned char handle[0];
+    unsigned int handle_bytes;
+    int handle_type;
+    unsigned char handle[0];
 };
-#endif
 
 #ifndef AT_EMPTY_PATH
 #define AT_EMPTY_PATH   0x1000  /* Allow empty relative pathname */
@@ -45,28 +56,6 @@ struct file_handle {
 #define O_PATH    010000000
 #endif
 
-#ifndef __NR_name_to_handle_at
-#if defined(__i386__)
-#define __NR_name_to_handle_at  341
-#define __NR_open_by_handle_at  342
-#elif defined(__x86_64__)
-#define __NR_name_to_handle_at  303
-#define __NR_open_by_handle_at  304
-#endif
-#endif
-
-#ifdef __NR_name_to_handle_at
-static inline int name_to_handle(int dirfd, const char *name,
-                                 struct file_handle *fh, int *mnt_id, int flags)
-{
-    return syscall(__NR_name_to_handle_at, dirfd, name, fh, mnt_id, flags);
-}
-
-static inline int open_by_handle(int mountfd, const char *fh, int flags)
-{
-    return syscall(__NR_open_by_handle_at, mountfd, fh, flags);
-}
-#else
 static inline int name_to_handle(int dirfd, const char *name,
                                  struct file_handle *fh, int *mnt_id, int flags)
 {