On Mon, Nov 02, 2015 at 05:13:14PM +0800, Xiao Guangrong wrote: > lseek can not work for all block devices as the man page says: > | Some devices are incapable of seeking and POSIX does not specify > | which devices must support lseek(). > > This patch tries to add the support on Linux by using BLKGETSIZE64 > ioctl > > Signed-off-by: Xiao Guangrong <guangrong.x...@linux.intel.com>
On which cases is this patch necessary? Do you know any examples of Linux block devices that won't work with lseek(SEEK_END)? > --- > util/osdep.c | 20 ++++++++++++++++++++ > 1 file changed, 20 insertions(+) > > diff --git a/util/osdep.c b/util/osdep.c > index 5a61e19..b20c793 100644 > --- a/util/osdep.c > +++ b/util/osdep.c > @@ -45,6 +45,11 @@ > extern int madvise(caddr_t, size_t, int); > #endif > > +#ifdef CONFIG_LINUX > +#include <sys/ioctl.h> > +#include <linux/fs.h> > +#endif > + > #include "qemu-common.h" > #include "qemu/sockets.h" > #include "qemu/error-report.h" > @@ -433,6 +438,21 @@ int64_t qemu_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)) { > + /* The size of block device is larger than max int64_t? */ > + if (size < 0) { > + return -EOVERFLOW; > + } > + return size; > + } > +#endif > + > size = lseek(fd, 0, SEEK_END); > if (size < 0) { > return -errno; > -- > 1.8.3.1 > -- Eduardo -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html