Re: [Qemu-devel] [PATCH v2 2/5] block: Avoid BlockDriverState.filename

[Max Reitz <mreitz@redhat.com>]

On 06.08.2015 04:27, Wen Congyang wrote:
> On 08/06/2015 04:52 AM, Max Reitz wrote:
>> In places which directly pass a filename to the OS, we should not use
>> the filename field at all but exact_filename instead (although the
>> former currently equals the latter if that is set).
>>
>> In qemu-img's map command, we should be using the filename field; but
>> since this commit prepares to remove that field, using exact_filename is
>> fine, too (this is the only user of BlockDriverState.filename which
>> frequently queries that field).
>>
>> Signed-off-by: Max Reitz <mreitz@redhat.com>
>> ---
>>   block.c           | 4 ++--
>>   block/gluster.c   | 2 +-
>>   block/raw-posix.c | 8 ++++----
>>   block/raw-win32.c | 4 ++--
>>   qemu-img.c        | 2 +-
>>   5 files changed, 10 insertions(+), 10 deletions(-)
>>
>> diff --git a/block.c b/block.c
>> index e7dd2f1..5a1dc16 100644
>> --- a/block.c
>> +++ b/block.c
>> @@ -918,8 +918,8 @@ static int bdrv_open_common(BlockDriverState *bs, BlockDriverState *file,
>>       if (ret < 0) {
>>           if (local_err) {
>>               error_propagate(errp, local_err);
>> -        } else if (bs->filename[0]) {
>> -            error_setg_errno(errp, -ret, "Could not open '%s'", bs->filename);
>> +        } else if (bs->exact_filename[0]) {
>> +            error_setg_errno(errp, -ret, "Could not open '%s'", bs->exact_filename);
>>           } else {
>>               error_setg_errno(errp, -ret, "Could not open image");
>>           }
>> diff --git a/block/gluster.c b/block/gluster.c
>> index 1eb3a8c..176682b 100644
>> --- a/block/gluster.c
>> +++ b/block/gluster.c
>> @@ -358,7 +358,7 @@ static int qemu_gluster_reopen_prepare(BDRVReopenState *state,
>>
>>       gconf = g_new0(GlusterConf, 1);
>>
>> -    reop_s->glfs = qemu_gluster_init(gconf, state->bs->filename, errp);
>> +    reop_s->glfs = qemu_gluster_init(gconf, state->bs->exact_filename, errp);
>>       if (reop_s->glfs == NULL) {
>>           ret = -errno;
>>           goto exit;
>> diff --git a/block/raw-posix.c b/block/raw-posix.c
>> index 855febe..b61c11f 100644
>> --- a/block/raw-posix.c
>> +++ b/block/raw-posix.c
>> @@ -671,7 +671,7 @@ static int raw_reopen_prepare(BDRVReopenState *state,
>>       /* If we cannot use fcntl, or fcntl failed, fall back to qemu_open() */
>>       if (raw_s->fd == -1) {
>>           assert(!(raw_s->open_flags & O_CREAT));
>> -        raw_s->fd = qemu_open(state->bs->filename, raw_s->open_flags);
>> +        raw_s->fd = qemu_open(state->bs->exact_filename, raw_s->open_flags);
>
> In raw_open_common(), we call raw_normalize_devicepath(). Why don't we call it
> here?

Ideally because bs->exact_filename is normalized already, whereas 
raw_open_common() takes the filename from the options QDict (which was 
specified by the user). The question now is whether bs->exact_filename 
is indeed normalized.

Looking into bdrv_open_common(), where that field is initially set, it 
doesn't look that way.

One way to fix this would be to implement bdrv_refresh_filename() for 
raw-posix. However, then we still have the issue of bs->filename usage 
in raw_open_common() (for an error message, although in reality, that 
message can only appear on Linux where raw_normalize_devicepath() won't 
do anything).

So the easy way to fix it would be to copy the normalized filename into 
bs->filename at the beginning of raw_open_common(). I'll think about it, 
but in any case, I think this issue is not related to this series and 
the fix will work independently.

I'll work something out, thanks for spotting this!

Max

>
> Thanks
> Wen Congyang
>
>>           if (raw_s->fd == -1) {
>>               error_setg_errno(errp, errno, "Could not reopen file");
>>               ret = -1;
>> @@ -2195,7 +2195,7 @@ static int fd_open(BlockDriverState *bs)
>>               DPRINTF("No floppy (open delayed)\n");
>>               return -EIO;
>>           }
>> -        s->fd = qemu_open(bs->filename, s->open_flags & ~O_NONBLOCK);
>> +        s->fd = qemu_open(bs->exact_filename, s->open_flags & ~O_NONBLOCK);
>>           if (s->fd < 0) {
>>               s->fd_error_time = qemu_clock_get_ns(QEMU_CLOCK_REALTIME);
>>               s->fd_got_error = 1;
>> @@ -2486,7 +2486,7 @@ static void floppy_eject(BlockDriverState *bs, bool eject_flag)
>>           qemu_close(s->fd);
>>           s->fd = -1;
>>       }
>> -    fd = qemu_open(bs->filename, s->open_flags | O_NONBLOCK);
>> +    fd = qemu_open(bs->exact_filename, s->open_flags | O_NONBLOCK);
>>       if (fd >= 0) {
>>           if (ioctl(fd, FDEJECT, 0) < 0)
>>               perror("FDEJECT");
>> @@ -2710,7 +2710,7 @@ static int cdrom_reopen(BlockDriverState *bs)
>>        */
>>       if (s->fd >= 0)
>>           qemu_close(s->fd);
>> -    fd = qemu_open(bs->filename, s->open_flags, 0644);
>> +    fd = qemu_open(bs->exact_filename, s->open_flags, 0644);
>>       if (fd < 0) {
>>           s->fd = -1;
>>           return -EIO;
>> diff --git a/block/raw-win32.c b/block/raw-win32.c
>> index 68f2338..5c8a894 100644
>> --- a/block/raw-win32.c
>> +++ b/block/raw-win32.c
>> @@ -417,7 +417,7 @@ static void raw_close(BlockDriverState *bs)
>>
>>       CloseHandle(s->hfile);
>>       if (bs->open_flags & BDRV_O_TEMPORARY) {
>> -        unlink(bs->filename);
>> +        unlink(bs->exact_filename);
>>       }
>>   }
>>
>> @@ -485,7 +485,7 @@ static int64_t raw_get_allocated_file_size(BlockDriverState *bs)
>>                                                 DWORD * high);
>>       get_compressed_t get_compressed;
>>       struct _stati64 st;
>> -    const char *filename = bs->filename;
>> +    const char *filename = bs->exact_filename;
>>       /* WinNT support GetCompressedFileSize to determine allocate size */
>>       get_compressed =
>>           (get_compressed_t) GetProcAddress(GetModuleHandle("kernel32"),
>> diff --git a/qemu-img.c b/qemu-img.c
>> index 75f4ee4..3d5587a 100644
>> --- a/qemu-img.c
>> +++ b/qemu-img.c
>> @@ -2155,7 +2155,7 @@ static void dump_map_entry(OutputFormat output_format, MapEntry *e,
>>           }
>>           if ((e->flags & (BDRV_BLOCK_DATA|BDRV_BLOCK_ZERO)) == BDRV_BLOCK_DATA) {
>>               printf("%#-16"PRIx64"%#-16"PRIx64"%#-16"PRIx64"%s\n",
>> -                   e->start, e->length, e->offset, e->bs->filename);
>> +                   e->start, e->length, e->offset, e->bs->exact_filename);
>>           }
>>           /* This format ignores the distinction between 0, ZERO and ZERO|DATA.
>>            * Modify the flags here to allow more coalescing.
>>
>