Re: [Qemu-devel] [PATCH v3 11/32] hostmem-file: use whole file size if possible

[Xiao Guangrong <guangrong.xiao@linux.intel.com>]

On 10/13/2015 07:50 PM, Vladimir Sementsov-Ogievskiy wrote:
> On 11.10.2015 06:52, 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@linux.intel.com>
>> ---
>>   backends/hostmem-file.c | 47 +++++++++++++++++++++++++++++++++++++++++++----
>>   1 file changed, 43 insertions(+), 4 deletions(-)
>>
>> diff --git a/backends/hostmem-file.c b/backends/hostmem-file.c
>> index 9097a57..adf2835 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>
>> +
>>   #include "qemu-common.h"
>>   #include "sysemu/hostmem.h"
>>   #include "sysemu/sysemu.h"
>> @@ -33,20 +36,56 @@ 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;
>> +    }
>> +
>> +    size = lseek(fd, 0, SEEK_END);
>> +    if (size == -1) {
>> +        size = 0;
>> +    }
>> +exit:
>> +    close(fd);
>> +    return size;
>> +}
>> +
>>   static void
>>   file_backend_memory_alloc(HostMemoryBackend *backend, Error **errp)
>>   {
>>       HostMemoryBackendFile *fb = MEMORY_BACKEND_FILE(backend);
>> -    if (!backend->size) {
>> -        error_setg(errp, "can't create backend with size 0");
>> -        return;
>> -    }
>>       if (!fb->mem_path) {
>>           error_setg(errp, "mem-path property not set");
>>           return;
>>       }
>> +    if (!backend->size) {
>> +        /*
>> +         * use the whole file size if @size is not specified.
>> +         */
>> +        backend->size = get_file_size(fb->mem_path);
>> +    }
>> +
>> +    if (!backend->size) {
>> +        error_setg(errp, "can't create backend with size 0");
>> +        return;
>> +    }
>
> in case of any error in get_file_size (open, stat, lseek) it will write about "backend with size 0"
> which may be not appropriate..

Okay, i will change it to:
("failed to get file size for %s, can't create backend on it", mem_path);