提交 46a4e4e6 编写于 作者: S Stefan Hajnoczi 提交者: Kevin Wolf

block: Do not cache device size for removable media

The block layer caches the device size to avoid doing lseek(fd, 0,
SEEK_END) every time this value is needed.  For removable media the
device size becomes stale if a new medium is inserted.  This patch
simply prevents device size caching for removable media.

A smarter solution is to update the cached device size when a new medium
is inserted.  Given that there are currently bugs with CD-ROM media
change I do not want to implement that approach until we've gotten
things correct first.
Signed-off-by: NStefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
上级 b8c6d095
......@@ -1161,14 +1161,12 @@ int64_t bdrv_getlength(BlockDriverState *bs)
if (!drv)
return -ENOMEDIUM;
/* Fixed size devices use the total_sectors value for speed instead of
issuing a length query (like lseek) on each call. Also, legacy block
drivers don't provide a bdrv_getlength function and must use
total_sectors. */
if (!bs->growable || !drv->bdrv_getlength) {
return bs->total_sectors * BDRV_SECTOR_SIZE;
}
return drv->bdrv_getlength(bs);
if (bs->growable || bs->removable) {
if (drv->bdrv_getlength) {
return drv->bdrv_getlength(bs);
}
}
return bs->total_sectors * BDRV_SECTOR_SIZE;
}
/* return 0 as number of sectors if no device present or error */
......
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