Kevin Wolf b94a261057 block: Avoid unecessary drv->bdrv_getlength() calls ... The block layer generally keeps the size of an image cached in bs->total_sectors so that it doesn't have to perform expensive operations to get the size whenever it needs it. This doesn't work however when using a backend that can change its size without qemu being aware of it, i.e. passthrough of removable media like CD-ROMs or floppy disks. For this reason, the caching is disabled when a removable device is used. It is obvious that checking whether the _guest_ device has removable media isn't the right thing to do when we want to know whether the size of the host backend can change. To make things worse, non-top-level BlockDriverStates never have any device attached, which makes qemu assume they are removable, so drv->bdrv_getlength() is always called on the protocol layer. In the case of raw-posix, this causes unnecessary lseek() system calls, which turned out to be rather expensive. This patch completely changes the logic and disables bs->total_sectors caching only for certain block driver types, for which a size change is expected: host_cdrom and host_floppy on POSIX, host_device on win32; also the raw format in case it sits on top of one of these protocols, but in the common case the nested bdrv_getlength() call on the protocol driver will use the cache again and avoid an expensive drv->bdrv_getlength() call. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>		2013-10-29 13:10:26 +01:00
..
backup.c	qapi: make use of new BlockJobType	2013-10-11 10:52:54 +02:00
blkdebug.c	blkdebug: Employ error parameter	2013-10-11 16:50:00 +02:00
blkverify.c	blkverify: Employ error parameter	2013-10-11 16:50:00 +02:00
bochs.c	bdrv: Use "Error" for opening images	2013-09-12 10:12:47 +02:00
cloop.c	bdrv: Use "Error" for opening images	2013-09-12 10:12:47 +02:00
commit.c	qapi: make use of new BlockJobType	2013-10-11 10:52:54 +02:00
cow.c	block: Error parameter for create functions	2013-09-12 10:12:48 +02:00
curl.c	bdrv: Use "Error" for opening images	2013-09-12 10:12:47 +02:00
dmg.c	bdrv: Use "Error" for opening images	2013-09-12 10:12:47 +02:00
gluster.c	block: introduce BlockDriver.bdrv_needs_filename to enable some drivers.	2013-09-25 16:21:28 +02:00
iscsi.c	block/iscsi: reenable iscsi_co_get_block_status	2013-10-09 10:43:42 +02:00
linux-aio.c	aio: drop io_flush argument	2013-08-19 15:52:19 +02:00
Makefile.objs	switch raw block driver from "raw.o" to "raw_bsd.o"	2013-08-30 15:28:52 +02:00
mirror.c	qapi: make use of new BlockJobType	2013-10-11 10:52:54 +02:00
nbd.c	bdrv: Use "Error" for opening images	2013-09-12 10:12:47 +02:00
parallels.c	bdrv: Use "Error" for opening images	2013-09-12 10:12:47 +02:00
qapi.c	block/qapi: Human-readable ImageInfoSpecific dump	2013-10-11 10:52:54 +02:00
qcow.c	block: Error parameter for create functions	2013-09-12 10:12:48 +02:00
qcow2-cache.c	qcow2: Use negated overflow check mask	2013-10-11 16:50:00 +02:00
qcow2-cluster.c	qcow2: Use negated overflow check mask	2013-10-11 16:50:00 +02:00
qcow2-refcount.c	qcow2: Make overlap check mask variable	2013-10-11 16:50:00 +02:00
qcow2-snapshot.c	qcow2: Use negated overflow check mask	2013-10-11 16:50:00 +02:00
qcow2.c	qcow2: Flush image after creation	2013-10-28 17:34:32 +01:00
qcow2.h	qcow2: Add more overlap check bitmask macros	2013-10-11 16:50:00 +02:00
qed-check.c	qed: mark image clean after repair succeeds	2012-08-10 10:25:12 +02:00
qed-cluster.c	Use glib memory allocation and free functions	2011-08-20 23:01:08 -05:00
qed-gencb.c	Use glib memory allocation and free functions	2011-08-20 23:01:08 -05:00
qed-l2-cache.c	qed: do not evict in-use L2 table cache entries	2012-03-12 15:14:06 +01:00
qed-table.c	misc: move include files to include/qemu/	2012-12-19 08:32:39 +01:00
qed.c	block: Error parameter for create functions	2013-09-12 10:12:48 +02:00
qed.h	block: qed - use QEMU_PACKED for on-disk structures	2013-09-25 20:51:15 +02:00
raw-aio.h	block: make discard asynchronous	2013-01-15 10:03:47 +01:00
raw-posix.c	block: Avoid unecessary drv->bdrv_getlength() calls	2013-10-29 13:10:26 +01:00
raw-win32.c	block: Avoid unecessary drv->bdrv_getlength() calls	2013-10-29 13:10:26 +01:00
raw_bsd.c	block: Avoid unecessary drv->bdrv_getlength() calls	2013-10-29 13:10:26 +01:00
rbd.c	rbd: avoid qemu_rbd_snap_list() memory leaks	2013-09-25 16:22:00 +02:00
sheepdog.c	sheepdog: pass copy_policy in the request	2013-10-28 17:40:00 +01:00
snapshot.c	bdrv: Use "Error" for opening images	2013-09-12 10:12:47 +02:00
ssh.c	bdrv: Use "Error" for creating images	2013-09-12 10:12:48 +02:00
stream.c	qapi: make use of new BlockJobType	2013-10-11 10:52:54 +02:00
vdi.c	block: vdi - use QEMU_PACKED for on-disk structures	2013-09-25 20:51:05 +02:00
vhdx.c	block: vhdx - add migration blocker	2013-10-02 15:24:39 +02:00
vhdx.h	misc: Fix new typos in comments and strings	2013-07-27 11:22:54 +04:00
vmdk.c	vmdk: fix VMFS extent parsing	2013-10-18 13:41:36 +02:00
vpc.c	block/vpc: check that the image has not been truncated	2013-10-24 17:34:48 +02:00
vvfat.c	block: Error parameter for create functions	2013-09-12 10:12:48 +02:00
win32-aio.c	win32-aio: drop win32_aio_flush_cb()	2013-08-22 22:05:04 +02:00