Re: [PATCH v7 11/35] util: introduce qemu_file_getlength()

[Eduardo Habkost]

On Mon, Nov 09, 2015 at 12:44:55PM +0800, Xiao Guangrong wrote:
> On 11/06/2015 11:50 PM, Eduardo Habkost wrote:
> >As this patch affects raw_getlength(), CCing the raw block driver
> >maintainer and the qemu-block mailing list.
> 
> Eduardo, thanks for your reminder. I will keep CCing Kevin and qemu-block mail
> list for future version.
> 
> >
> >On Mon, Nov 02, 2015 at 05:13:13PM +0800, Xiao Guangrong wrote:
> >>It is used to get the size of the specified file, also qemu_fd_getlength()
> >>is introduced to unify the code with raw_getlength() in block/raw-posix.c
> >>
> >>Signed-off-by: Xiao Guangrong 
> >>---
> >>  block/raw-posix.c|  7 +--
> >>  include/qemu/osdep.h |  2 ++
> >>  util/osdep.c | 31 +++
> >
> >I know I was the one who suggested osdep.c, but maybe oslib-posix.c is a
> >more appropriate place for the new function?
> >
> 
> Since the function we introduced here can work on both windows and posix, so
> i thing osdep.c is the right place. Otherwise we should implement it for 
> multiple
> platforms.

I didn't notice it was going to be used by a platform-independent
qemu_file_getlength() function in addition to the posix-specific
raw_getlength(). Have you tested it on Windows, though?

If you didn't test it on Windows, what about keeping
qemu_file_getlength() available only on posix, by now? The only
users are raw-posix.c and hostmem-file.c, currently. If in the
future somebody need it on Windows, they can decide between
moving the SEEK_END code to osdep.c (after testing it), or moving
the existing raw-win32.c:raw_getlength() code to a
oslib-win32.c:qemu_file_getlength() function.

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Re: [PATCH v7 11/35] util: introduce qemu_file_getlength()

[Xiao Guangrong]

On 11/06/2015 11:50 PM, Eduardo Habkost wrote:

As this patch affects raw_getlength(), CCing the raw block driver
maintainer and the qemu-block mailing list.


Eduardo, thanks for your reminder. I will keep CCing Kevin and qemu-block mail
list for future version.



On Mon, Nov 02, 2015 at 05:13:13PM +0800, Xiao Guangrong wrote:

It is used to get the size of the specified file, also qemu_fd_getlength()
is introduced to unify the code with raw_getlength() in block/raw-posix.c

Signed-off-by: Xiao Guangrong 
---
  block/raw-posix.c|  7 +--
  include/qemu/osdep.h |  2 ++
  util/osdep.c | 31 +++


I know I was the one who suggested osdep.c, but maybe oslib-posix.c is a
more appropriate place for the new function?



Since the function we introduced here can work on both windows and posix, so
i thing osdep.c is the right place. Otherwise we should implement it for 
multiple
platforms.
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Re: [PATCH v7 11/35] util: introduce qemu_file_getlength()

[Eduardo Habkost]

As this patch affects raw_getlength(), CCing the raw block driver
maintainer and the qemu-block mailing list.

On Mon, Nov 02, 2015 at 05:13:13PM +0800, Xiao Guangrong wrote:
> It is used to get the size of the specified file, also qemu_fd_getlength()
> is introduced to unify the code with raw_getlength() in block/raw-posix.c
> 
> Signed-off-by: Xiao Guangrong 
> ---
>  block/raw-posix.c|  7 +--
>  include/qemu/osdep.h |  2 ++
>  util/osdep.c | 31 +++

I know I was the one who suggested osdep.c, but maybe oslib-posix.c is a
more appropriate place for the new function?


>  3 files changed, 34 insertions(+), 6 deletions(-)
> 
> diff --git a/block/raw-posix.c b/block/raw-posix.c
> index 918c756..734e6dd 100644
> --- a/block/raw-posix.c
> +++ b/block/raw-posix.c
> @@ -1592,18 +1592,13 @@ 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;
>  }
>  
> -size = lseek(s->fd, 0, SEEK_END);
> -if (size < 0) {
> -return -errno;
> -}
> -return size;
> +return qemu_fd_getlength(s->fd);
>  }
>  #endif
>  
> diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
> index dbc17dc..ca4c3fa 100644
> --- a/include/qemu/osdep.h
> +++ b/include/qemu/osdep.h
> @@ -303,4 +303,6 @@ int qemu_read_password(char *buf, int buf_size);
>  pid_t qemu_fork(Error **errp);
>  
>  size_t qemu_file_get_page_size(const char *mem_path, Error **errp);
> +int64_t qemu_fd_getlength(int fd);
> +size_t qemu_file_getlength(const char *file, Error **errp);
>  #endif
> diff --git a/util/osdep.c b/util/osdep.c
> index 0092bb6..5a61e19 100644
> --- a/util/osdep.c
> +++ b/util/osdep.c
> @@ -428,3 +428,34 @@ writev(int fd, const struct iovec *iov, int iov_cnt)
>  return readv_writev(fd, iov, iov_cnt, true);
>  }
>  #endif
> +
> +int64_t qemu_fd_getlength(int fd)
> +{
> +int64_t size;
> +
> +size = lseek(fd, 0, SEEK_END);
> +if (size < 0) {
> +return -errno;
> +}
> +return size;
> +}
> +
> +size_t qemu_file_getlength(const char *file, Error **errp)
> +{
> +int64_t size;
> +int fd = qemu_open(file, O_RDONLY);
> +
> +if (fd < 0) {
> +error_setg_file_open(errp, errno, file);
> +return 0;
> +}
> +
> +size = qemu_fd_getlength(fd);
> +if (size < 0) {
> +error_setg_errno(errp, -size, "can't get size of file %s", file);
> +size = 0;
> +}
> +
> +qemu_close(fd);
> +return size;
> +}
> -- 
> 1.8.3.1
> 

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Re: [PATCH v7 11/35] util: introduce qemu_file_getlength()

[Eduardo Habkost]

On Wed, Nov 04, 2015 at 11:17:09AM +0800, Xiao Guangrong wrote:
> 
> 
> On 11/04/2015 07:21 AM, Eduardo Habkost wrote:
> >On Mon, Nov 02, 2015 at 05:13:13PM +0800, Xiao Guangrong wrote:
> >[...]
> >>+size_t qemu_file_getlength(const char *file, Error **errp)
> >>+{
> >>+int64_t size;
> >[...]
> >>+return size;
> >
> >Can you guarantee that SIZE_MAX >= INT64_MAX on all platforms supported
> >by QEMU?
> >
> 
> Actually, this function is abstracted from the common function, 
> raw_getlength(),
> in raw-posix.c whose return value is int64_t.
> 
> And i think int64_t is large enough for block devices.

int64_t should be enough, but I don't know if size_t is large enough on
all platforms.

I believe it's going to be either one of those cases:

* If you are absolutely sure SIZE_MAX >= INT64_MAX on all platforms,
  please explain why (and maybe add a QEMU_BUILD_BUG_ON?). (I don't
  think this will be the case)
* If SIZE_MAX < INT64_MAX is possible but you believe
  size <= SIZE_MAX is always true here, please explain why (and maybe
  add an assert()).
* Otherwise, we need to set an appropriate error if size > SIZE_MAX
  or change the type of qemu_file_getlength(). What about making it
  uint64_t?

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Re: [PATCH v7 11/35] util: introduce qemu_file_getlength()

[Xiao Guangrong]

On 11/04/2015 10:44 PM, Eduardo Habkost wrote:

On Wed, Nov 04, 2015 at 11:17:09AM +0800, Xiao Guangrong wrote:



On 11/04/2015 07:21 AM, Eduardo Habkost wrote:

On Mon, Nov 02, 2015 at 05:13:13PM +0800, Xiao Guangrong wrote:
[...]

+size_t qemu_file_getlength(const char *file, Error **errp)
+{
+int64_t size;

[...]

+return size;


Can you guarantee that SIZE_MAX >= INT64_MAX on all platforms supported
by QEMU?



Actually, this function is abstracted from the common function, raw_getlength(),
in raw-posix.c whose return value is int64_t.

And i think int64_t is large enough for block devices.


int64_t should be enough, but I don't know if size_t is large enough on
all platforms.

I believe it's going to be either one of those cases:

* If you are absolutely sure SIZE_MAX >= INT64_MAX on all platforms,
   please explain why (and maybe add a QEMU_BUILD_BUG_ON?). (I don't
   think this will be the case)
* If SIZE_MAX < INT64_MAX is possible but you believe
   size <= SIZE_MAX is always true here, please explain why (and maybe
   add an assert()).
* Otherwise, we need to set an appropriate error if size > SIZE_MAX
   or change the type of qemu_file_getlength(). What about making it
   uint64_t?



It sounds better, I will change the return value from size_t to uint64_t.

Thank you for pointing it out, Eduardo!



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Re: [PATCH v7 11/35] util: introduce qemu_file_getlength()

[Eduardo Habkost]

On Mon, Nov 02, 2015 at 05:13:13PM +0800, Xiao Guangrong wrote:
[...]
> +size_t qemu_file_getlength(const char *file, Error **errp)
> +{
> +int64_t size;
[...]
> +return size;

Can you guarantee that SIZE_MAX >= INT64_MAX on all platforms supported
by QEMU?

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Re: [PATCH v7 11/35] util: introduce qemu_file_getlength()

[Xiao Guangrong]

On 11/04/2015 07:21 AM, Eduardo Habkost wrote:

On Mon, Nov 02, 2015 at 05:13:13PM +0800, Xiao Guangrong wrote:
[...]

+size_t qemu_file_getlength(const char *file, Error **errp)
+{
+int64_t size;

[...]

+return size;


Can you guarantee that SIZE_MAX >= INT64_MAX on all platforms supported
by QEMU?



Actually, this function is abstracted from the common function, raw_getlength(),
in raw-posix.c whose return value is int64_t.

And i think int64_t is large enough for block devices.



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Re: [PATCH v7 11/35] util: introduce qemu_file_getlength()

[Vladimir Sementsov-Ogievskiy]

On 02.11.2015 12:13, Xiao Guangrong wrote:

It is used to get the size of the specified file, also qemu_fd_getlength()
is introduced to unify the code with raw_getlength() in block/raw-posix.c

Signed-off-by: Xiao Guangrong 
---
  block/raw-posix.c|  7 +--
  include/qemu/osdep.h |  2 ++
  util/osdep.c | 31 +++
  3 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index 918c756..734e6dd 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -1592,18 +1592,13 @@ 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;
  }
  
-size = lseek(s->fd, 0, SEEK_END);

-if (size < 0) {
-return -errno;
-}
-return size;
+return qemu_fd_getlength(s->fd);
  }
  #endif
  
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h

index dbc17dc..ca4c3fa 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -303,4 +303,6 @@ int qemu_read_password(char *buf, int buf_size);
  pid_t qemu_fork(Error **errp);
  
  size_t qemu_file_get_page_size(const char *mem_path, Error **errp);

+int64_t qemu_fd_getlength(int fd);
+size_t qemu_file_getlength(const char *file, Error **errp);
  #endif
diff --git a/util/osdep.c b/util/osdep.c
index 0092bb6..5a61e19 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -428,3 +428,34 @@ writev(int fd, const struct iovec *iov, int iov_cnt)
  return readv_writev(fd, iov, iov_cnt, true);
  }
  #endif
+
+int64_t qemu_fd_getlength(int fd)
+{
+int64_t size;
+
+size = lseek(fd, 0, SEEK_END);
+if (size < 0) {
+return -errno;
+}
+return size;
+}
+
+size_t qemu_file_getlength(const char *file, Error **errp)
+{
+int64_t size;
+int fd = qemu_open(file, O_RDONLY);
+
+if (fd < 0) {
+error_setg_file_open(errp, errno, file);
+return 0;
+}
+
+size = qemu_fd_getlength(fd);
+if (size < 0) {
+error_setg_errno(errp, -size, "can't get size of file %s", file);
+size = 0;
+}
+
+qemu_close(fd);
+return size;
+}


Reviewed-by: Vladimir Sementsov-Ogievskiy 

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Best regards,
Vladimir
* now, @virtuozzo.com instead of @parallels.com. Sorry for this inconvenience.

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[PATCH v7 11/35] util: introduce qemu_file_getlength()

[Xiao Guangrong]

It is used to get the size of the specified file, also qemu_fd_getlength()
is introduced to unify the code with raw_getlength() in block/raw-posix.c

Signed-off-by: Xiao Guangrong 
---
 block/raw-posix.c|  7 +--
 include/qemu/osdep.h |  2 ++
 util/osdep.c | 31 +++
 3 files changed, 34 insertions(+), 6 deletions(-)

diff --git a/block/raw-posix.c b/block/raw-posix.c
index 918c756..734e6dd 100644
--- a/block/raw-posix.c
+++ b/block/raw-posix.c
@@ -1592,18 +1592,13 @@ 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;
 }
 
-size = lseek(s->fd, 0, SEEK_END);
-if (size < 0) {
-return -errno;
-}
-return size;
+return qemu_fd_getlength(s->fd);
 }
 #endif
 
diff --git a/include/qemu/osdep.h b/include/qemu/osdep.h
index dbc17dc..ca4c3fa 100644
--- a/include/qemu/osdep.h
+++ b/include/qemu/osdep.h
@@ -303,4 +303,6 @@ int qemu_read_password(char *buf, int buf_size);
 pid_t qemu_fork(Error **errp);
 
 size_t qemu_file_get_page_size(const char *mem_path, Error **errp);
+int64_t qemu_fd_getlength(int fd);
+size_t qemu_file_getlength(const char *file, Error **errp);
 #endif
diff --git a/util/osdep.c b/util/osdep.c
index 0092bb6..5a61e19 100644
--- a/util/osdep.c
+++ b/util/osdep.c
@@ -428,3 +428,34 @@ writev(int fd, const struct iovec *iov, int iov_cnt)
 return readv_writev(fd, iov, iov_cnt, true);
 }
 #endif
+
+int64_t qemu_fd_getlength(int fd)
+{
+int64_t size;
+
+size = lseek(fd, 0, SEEK_END);
+if (size < 0) {
+return -errno;
+}
+return size;
+}
+
+size_t qemu_file_getlength(const char *file, Error **errp)
+{
+int64_t size;
+int fd = qemu_open(file, O_RDONLY);
+
+if (fd < 0) {
+error_setg_file_open(errp, errno, file);
+return 0;
+}
+
+size = qemu_fd_getlength(fd);
+if (size < 0) {
+error_setg_errno(errp, -size, "can't get size of file %s", file);
+size = 0;
+}
+
+qemu_close(fd);
+return size;
+}
-- 
1.8.3.1

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