Commit 46a4e4e6 authored Mar 29, 2011 by Stefan Hajnoczi Committed by Kevin Wolf Apr 07, 2011

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: Stefan Hajnoczi <stefanha@linux.vnet.ibm.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>

parent b8c6d095

block.c

+6 −8

Original line number	Diff line number	Diff line
		@@ -1161,15 +1161,13 @@ 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;
		}
		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 */
		void bdrv_get_geometry(BlockDriverState bs, uint64_t nb_sectors_ptr)