On Sat, Oct 31, 2015 at 04:46:05PM +0800, Xiao Guangrong wrote:
> On 10/31/2015 01:30 AM, Eduardo Habkost wrote:
> >On Fri, Oct 30, 2015 at 01:56:05PM +0800, Xiao Guangrong wrote:
> >>Use the whole file size if @size is not specified which is useful
> >>if we want to directly pass a file to guest
> >>
> >>Signed-off-by: Xiao Guangrong <guangrong.xiao@xxxxxxxxxxxxxxx>
> >>---
> >> backends/hostmem-file.c | 48 ++++++++++++++++++++++++++++++++++++++++++++----
> >> 1 file changed, 44 insertions(+), 4 deletions(-)
> >>
> >>diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
> >>index 9097a57..e1bc9ff 100644
> >>--- a/backends/hostmem-file.c
> >>+++ b/backends/hostmem-file.c
> >>@@ -9,6 +9,9 @@
> >> * This work is licensed under the terms of the GNU GPL, version 2 or later.
> >> * See the COPYING file in the top-level directory.
> >> */
> >>+#include <sys/ioctl.h>
> >>+#include <linux/fs.h>
> >
> >This code needs to build on other platforms too. e.g. using mingw32:
>
> Err... You did it on Windows? It's surprised that the file is only built
> on Linux:
> common-obj-$(CONFIG_LINUX) += hostmem-file.o
>
> How it can happen...
I did it using mingw32. I don't remember what I did, but I probably tried
something stupid to test just the build of hostmem-file.o and didn't notice it
was conditional on CONFIG_LINUX. Sorry for the noise.
>
> >
> > CC backends/hostmem-file.o
> >/home/ehabkost/rh/proj/virt/qemu/backends/hostmem-file.c:12:23: fatal error: sys/ioctl.h: No such file or directory
> > #include <sys/ioctl.h>
> > ^
> >compilation terminated.
> >/home/ehabkost/rh/proj/virt/qemu/rules.mak:57: recipe for target 'backends/hostmem-file.o' failed
> >make: *** [backends/hostmem-file.o] Error 1
> >
> >
> >>+
> >> #include "qemu-common.h"
> >> #include "sysemu/hostmem.h"
> >> #include "sysemu/sysemu.h"
> >>@@ -33,20 +36,57 @@ struct HostMemoryBackendFile {
> >> char *mem_path;
> >> };
> >>
> >>+static uint64_t get_file_size(const char *file)
> >>+{
> >>+ struct stat stat_buf;
> >>+ uint64_t size = 0;
> >>+ int fd;
> >>+
> >>+ fd = open(file, O_RDONLY);
> >>+ if (fd < 0) {
> >>+ return 0;
> >>+ }
> >>+
> >>+ if (stat(file, &stat_buf) < 0) {
> >>+ goto exit;
> >>+ }
> >>+
> >>+ if ((S_ISBLK(stat_buf.st_mode)) && !ioctl(fd, BLKGETSIZE64, &size)) {
> >>+ goto exit;
> >>+ }
> >>+
I have another question: if our block device code at raw-posix.c doesn't need
the Linux-specific BLKGETSIZE64 call, why exactly do we need it in
hostmem-file.c? In which cases it would break without BLKGETSIZE64?
> >>+ size = lseek(fd, 0, SEEK_END);
> >>+ if (size == -1) {
> >>+ size = 0;
> >>+ }
> >>+exit:
> >>+ close(fd);
> >>+ return size;
> >>+}
> >
> >This code seems to duplicate what block/raw-posix.c:raw_getlength() does
> >(except for the BLKGETSIZE64 part). Have you considered using the same
> >code for both?
> >
> >We can probably move all the raw-posix.c raw_getlength(BlockDriverState
> >*bs) code to fd_getlength(int fd) functions (on osdep.c?), and just
> >implement raw-posix.c:raw_getlength(s) as fd_getlength(s->fd).
> >
>
> Actually, Paolo has the same suggestion before... but
>
> | The function you pointed out is really complex - it mixed 9 platforms and each
> | platform has its own specific implementation. It is hard for us to verify the
> | change.
> |
> | I'd prefer to make it for Linux specific first then share it to other platforms
> | if it's needed in the future.
>
> I do not know if it's really worth doing it. :(
If hostmem-file.c is Linux-specific we don't need to move or reuse the code for
all the other 9 platforms right now, that's true. But now you are adding a new
arch-specific function that does exactly the same thing in a different file to
the mix. What if somebody want to make hostmem-file.c work in another platform
in the future, and begin to duplicate the same #ifdef mess from raw-posix.c?
I was considering this:
1) Move the arch-independent raw_getlength() code to fd_getlength() (at
osdep.c, maybe?), as:
int64_t fd_getlength(int fd)
{
int64_t size;
size = lseek(s->fd, 0, SEEK_END);
if (size < 0) {
return -errno;
}
return size;
}
2) Change the arch-independent version of raw_getlength() to:
[...]
#else
static int64_t raw_getlength(BlockDriverState *bs)
{
BDRVRawState *s = bs->opaque;
int ret;
int64_t size;
ret = fd_open(bs);
if (ret < 0) {
return ret;
}
return fd_getlength(s->fd);
}
#endif
3) Implement get_file_size() using fd_getlength():
uint64_t get_file_size(const char *file, Error **errp)
{
struct stat stat_buf;
int64_t size = 0;
int fd;
fd = open(file, O_RDONLY);
if (fd < 0) {
error_setg_errno(errp, errno, "can't open file %s", file);
return 0;
}
size = fd_getlength(fd);
if (size < 0) {
error_setg_errno(errp, -size, "can't get size of file %s", file);
size = 0;
}
exit:
close(fd);
return size;
}
4) In case BLKGETSIZE64 is really necesary, add a Linux-specific block to
fd_getlength():
int64_t fd_getlength(int fd)
{
int64_t size;
#ifdef CONFIG_LINUX
struct stat stat_buf;
if (fstat(fd, &stat_buf) < 0) {
return -errno;
}
if ((S_ISBLK(stat_buf.st_mode)) && !ioctl(fd, BLKGETSIZE64, &size)) {
if (size < 0) {
return -EOVERFLOW;
}
return size;
}
#endif
size = lseek(fd, 0, SEEK_END);
if (size < 0) {
return -errno;
}
return size;
}
People working on other platforms will be able to move arch-specific code to
fd_getlength() later, if they want to.
--
Eduardo
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