For environments where space must be guaranteed in advance
use the -p flag to remove sparseness from the qcow file.
Signed-off-by: Julian Chesterfield <julian@xensource.com>
with I/O errors.
There are a number of flaws in the blktap userspace daemon when dealing
with I/O errors.
- The backends which use AIO check the io_events.res member to determine
if an I/O error occurred. Which is good. But when calling the callback
to signal completion of the I/O, they pass the io_events.res2 member
Now this seems fine at first glance[1]
"res is the usual result of an I/O operation: the number of bytes
transfered, or a negative error code. res2 is a second status
value which will be returned to the user"
Except that
"currently (2.6.0-test9), callers of aio_complete() within the
kernel always set res2 to zero."
And this hasn't changed anytime since 2.6.0, so by passing through
the status from 'res2', the callback thinks the I/O operation succeeded
even when it failed :-(
The fix is simple instead of passing 'res2', just pass
ep->res == io->u.c.nbytes ? 0 : 1
This would solve the error reporting to the guest, except that there
is a second flaw...
- The tapdisk I/O completion callback checks the status parameter
passed in, syslog's it and then returns. It never bothers to send
the I/O completion response back to the blktap kernel driver when
a failure occurrs.
Fortunately the fix for this is also simple. Instead of returning
from the callback when dealing with an error, we simply toggle the
status field for the pending response to BLKIF_RSP_ERROR and then
continue with the normal codepath. So the error eventually gets
back to the guest.
The scenario I used to discover the problem and test the patch is thus:
- In dom0 create a filesystem with only 200 MB of free space
- Create a 1 GB sparse file on this volume.
- Configure the guest so this sparse file appears as /dev/xvdb
- In the domU create a single partition on /dev/xvdb and format
it with ext3.
- In the DomU, mount /dev/xvdb1 on /mnt and then run
dd if=/dev/zero of=/mnt/data.bin bs=1GB count=1
Without this patch, the 'dd' command would succeed in writing 1 GB of data
even though the underlying disk in Dom0 was only 200 MB in size. More complex
tests of copying a whole directory heirarchy across resulted in catastrophic
data corruption of the filessytem itself. Manual fsck was needed to fixup
the filesystem & there were many very bad errors needing fixing.
With this patch applied the DomU sees the I/O failures and kernel logs
messages
Dec 1 11:02:53 dhcp-5-203 kernel: end_request: I/O error, dev xvdc, sector 722127
Dec 1 11:02:53 dhcp-5-203 kernel: end_request: I/O error, dev xvdc, sector 730327
Dec 1 11:02:53 dhcp-5-203 kernel: end_request: I/O error, dev xvdc, sector 738527
Dec 1 11:02:53 dhcp-5-203 kernel: end_request: I/O error, dev xvdc, sector 746727
Dec 1 11:02:53 dhcp-5-203 kernel: end_request: I/O error, dev xvdc, sector 754927
Dec 1 11:02:53 dhcp-5-203 kernel: end_request: I/O error, dev xvdc, sector 763127
Dec 1 11:02:53 dhcp-5-203 kernel: end_request: I/O error, dev xvdc, sector 771327
Dec 1 11:02:53 dhcp-5-203 kernel: end_request: I/O error, dev xvdc, sector 779527
Dec 1 11:02:53 dhcp-5-203 kernel: end_request: I/O error, dev xvdc, sector 792399
It will retry the I/O operation until it runs out of sectors to try, and then
fail the operation. The filesystem is not seriously damaged - ext3 journal
recovery will trivially cleanup if the guest is rebooted after the disk in
Dom0 is enlarged.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
[1] http://lwn.net/Articles/24366/
While the kernel side of blktap drivers is using 64-bit sector numbers
correctly when reporting disk sizing, the userspace parts where this
dat is actually generated is truncating at 32-bit. There are 3 variables
related to disk sizing which are used in the kernel/userspace code
'size', 'sector size' & 'info'. In kernel space these are treated as being
unsigned long long, unsigned long, and unsigned int, respectively. In
the blktap userspace code this were all varyingly long, unsigned long.
This mismatch caused 32-bit wraparound on large disks. The attached
patch updates the blktap userspace to use the same data types as
kernel space for all these params, thus both fixing the 32-bit bug &
giving the code consistency.
This patch has been tested both by comparing /proc/partitions in the
guest, with the image size seen in the host, and by using Stephen
Tweedie's 'verify-data' tool on a variety of multi-TB sized disks.
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
- remove magic number 8 and 64.
page size / sector size is 8 on x86, however on ia64 page size is
16kb.
blkring size is 64 on x86. however it's 128 on ia64.
- replace 0xFFFF with INVALID_GRANT_HANDLE
- don't map io ring into user space with uncachable.
kernel access the page with cacable and tapdisk uses memory barrier
so that it isn't necessary.
- remove printk warning and inserted new line.
- remove unused variable, page.
- add one BUG()
Signed-off-by: Isaku Yamahata <yamahata@valinux.co.jp>
tapdisk was using a 1msec select() timeout in its main event loop. On
timeout, the loop does nothing except repeat, so the timeout achieves
nothing; worse, on a machine with HZ set to less than 1000, a msec
timeout returns immediately, sending tapdisk into a 100%-CPU-
utilisation loop.
Simply remove the timeout entirely; everything still works fine, and
much more efficiently when idle.
Signed-off-by: Stephen Tweedie <sct@redhat.com>
blktap currently uses a hardcoded major of 254 for the device. This is
not robust in anyway and needs to be dynamic.
Note: it is better not to have the daemon create the node, and have udev
create it instead. But since the daemon currently creates the node
anyway, it is still the way this is done. That change needs to be made
at another time.
Signed-off-by: Steven Rostedt <srostedt@redhat.com>
the sources under the tools directory. This patch became necessary
after qemu-dm is updated to a newer version.
Signed-off-by: Hiroya INAKOSHI <inakoshi.hiroya@jp.fujitsu.com>
* Move .PHONY directives next to targets,
this makes them a lot harder to miss
* Add missing .PHONY directives
* Remove nonexistent .PHONY directives
* Hopefully I didn'T miss anything...
Signed-Off-By: Horms <horms@verge.net.au>
interface defintions for future extensibility. In particular,
grant references are now 32 bits and this has some knock-on
effects on split-driver interfaces.
Signed-off-by: Keir Fraser <keir@xensource.com>
transient information regarding a domain. This allows live localhost migration,
which is important for testing migration, and also allows migration when we
have a distributed store. The backend paths in the store now refer to the
frontend domain ID, not its UUID, and blktap has changed to match.
To support this split in the information, the cleanup procedure has been split
to match.
Change the save-restore interface between XendDomain, XendDomainInfo, and
XendCheckpoint, to remove some intermingling, in particular taking XendDomain
out of the loop for the restore procedure.
Improved the recovery procedure to avoid trying to destroy dom0 when recovering.
Added a lock around XendDomain.refresh and one around
XendDomainInfo.refreshShutdown, to improve the behaviour when recreating
domains at startup. There are still races here, so more thought needs to be
given to the locking.
Live reconfiguration of an existing domain is temporarily broken.
Signed-off-by: Ewan Mellor <ewan@xensource.com>
xs_write with O_CREAT|O_EXCL causes problems over daemon restarts, since
it's not idempotent.
It turns out noone really needs the flags word at all, so get rid of it.
It's now as if everyone specified "O_CREAT".
Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>
Signed-off-by: Christian Limpach <Christian.Limpach@cl.cam.ac.uk>
