Skip to content

Q
qemu

openeuler / qemu

通知 10
Star 0
Fork 0
Q
qemu

体验新版 GitCode，发现更多精彩内容 >>

切换分支/标签
  1. 16 6月, 2017 8 次提交
  3. 25 5月, 2017 1 次提交
  5. 12 5月, 2017 1 次提交
  7. 27 4月, 2017 3 次提交
  9. 18 4月, 2017 1 次提交
    • F
      block: Walk bs->children carefully in bdrv_drain_recurse · 178bd438
      由 Fam Zheng 提交于 
      The recursive bdrv_drain_recurse may run a block job completion BH that
drops nodes. The coming changes will make that more likely and use-after-free
would happen without this patch

Stash the bs pointer and use bdrv_ref/bdrv_unref in addition to
QLIST_FOREACH_SAFE to prevent such a case from happening.

Since bdrv_unref accesses global state that is not protected by the AioContext
lock, we cannot use bdrv_ref/bdrv_unref unconditionally.  Fortunately the
protection is not needed in IOThread because only main loop can modify a graph
with the AioContext lock held.
Signed-off-by: NFam Zheng <famz@redhat.com>
Message-Id: <20170418143044.12187-2-famz@redhat.com>
Reviewed-by: NJeff Cody <jcody@redhat.com>
Tested-by: NJeff Cody <jcody@redhat.com>
Signed-off-by: NFam Zheng <famz@redhat.com>
      178bd438
  11. 11 4月, 2017 4 次提交
  13. 07 4月, 2017 1 次提交
  15. 13 3月, 2017 1 次提交
  17. 01 3月, 2017 3 次提交
  19. 21 2月, 2017 5 次提交
  21. 16 1月, 2017 1 次提交
    • P
      block: get rid of bdrv_io_unplugged_begin/end · 8f90b5e9
      由 Paolo Bonzini 提交于 
      bdrv_io_plug and bdrv_io_unplug are only called (via their
BlockBackend equivalents) after starting asynchronous I/O.
bdrv_drain is not going to be called while they are running,
because---even if a coroutine runs for some reason---it will
only drain in the next iteration of the event loop through
bdrv_co_yield_to_drain.

So this mechanism is unnecessary, get rid of it.
Signed-off-by: NPaolo Bonzini <pbonzini@redhat.com>
Message-id: 20161129113334.605-1-pbonzini@redhat.com
Signed-off-by: NStefan Hajnoczi <stefanha@redhat.com>
      8f90b5e9
  23. 22 11月, 2016 2 次提交
    • E
      block: Pass unaligned discard requests to drivers · 3482b9bc
      由 Eric Blake 提交于 
      Discard is advisory, so rounding the requests to alignment
boundaries is never semantically wrong from the data that
the guest sees.  But at least the Dell Equallogic iSCSI SANs
has an interesting property that its advertised discard
alignment is 15M, yet documents that discarding a sequence
of 1M slices will eventually result in the 15M page being
marked as discarded, and it is possible to observe which
pages have been discarded.

Between commits 9f1963b3 and b8d0a980, we converted the block
layer to a byte-based interface that ultimately ignores any
unaligned head or tail based on the driver's advertised
discard granularity, which means that qemu 2.7 refuses to
pass any discard request smaller than 15M down to the Dell
Equallogic hardware.  This is a slight regression in behavior
compared to earlier qemu, where a guest executing discards
in power-of-2 chunks used to be able to get every page
discarded, but is now left with various pages still allocated
because the guest requests did not align with the hardware's
15M pages.

Since the SCSI specification says nothing about a minimum
discard granularity, and only documents the preferred
alignment, it is best if the block layer gives the driver
every bit of information about discard requests, rather than
rounding it to alignment boundaries early.

Rework the block layer discard algorithm to mirror the write
zero algorithm: always peel off any unaligned head or tail
and manage that in isolation, then do the bulk of the request
on an aligned boundary.  The fallback when the driver returns
-ENOTSUP for an unaligned request is to silently ignore that
portion of the discard request; but for devices that can pass
the partial request all the way down to hardware, this can
result in the hardware coalescing requests and discarding
aligned pages after all.

Reported by: Peter Lieven <pl@kamp.de>
CC: qemu-stable@nongnu.org
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
      3482b9bc
    • E
      block: Let write zeroes fallback work even with small max_transfer · b2f95fee
      由 Eric Blake 提交于 
      Commit 443668ca rewrote the write_zeroes logic to guarantee that
an unaligned request never crosses a cluster boundary.  But
in the rewrite, the new code assumed that at most one iteration
would be needed to get to an alignment boundary.

However, it is easy to trigger an assertion failure: the Linux
kernel limits loopback devices to advertise a max_transfer of
only 64k.  Any operation that requires falling back to writes
rather than more efficient zeroing must obey max_transfer during
that fallback, which means an unaligned head may require multiple
iterations of the write fallbacks before reaching the aligned
boundaries, when layering a format with clusters larger than 64k
atop the protocol of file access to a loopback device.

Test case:

$ qemu-img create -f qcow2 -o cluster_size=1M file 10M
$ losetup /dev/loop2 /path/to/file
$ qemu-io -f qcow2 /dev/loop2
qemu-io> w 7m 1k
qemu-io> w -z 8003584 2093056

In fairness to Denis (as the original listed author of the culprit
commit), the faulty logic for at most one iteration is probably all
my fault in reworking his idea.  But the solution is to restore what
was in place prior to that commit: when dealing with an unaligned
head or tail, iterate as many times as necessary while fragmenting
the operation at max_transfer boundaries.
Reported-by: NEd Swierk <eswierk@skyportsystems.com>
CC: qemu-stable@nongnu.org
CC: Denis V. Lunev <den@openvz.org>
Signed-off-by: NEric Blake <eblake@redhat.com>
Reviewed-by: NMax Reitz <mreitz@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
      b2f95fee
  25. 09 11月, 2016 1 次提交
  27. 31 10月, 2016 1 次提交
    • A
      block: Add bdrv_drain_all_{begin,end}() · c0778f66
      由 Alberto Garcia 提交于 
      bdrv_drain_all() doesn't allow the caller to do anything after all
pending requests have been completed but before block jobs are
resumed.

This patch splits bdrv_drain_all() into _begin() and _end() for that
purpose. It also adds aio_{disable,enable}_external() calls to disable
external clients in the meantime.

An important restriction of this split is that no new block jobs or
BlockDriverStates can be created between the bdrv_drain_all_begin()
and bdrv_drain_all_end() calls. This is not a concern now because
we'll only be using this in bdrv_reopen_multiple(), but it must be
dealt with if we ever have other uses cases in the future.
Signed-off-by: NAlberto Garcia <berto@igalia.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: NKevin Wolf <kwolf@redhat.com>
Signed-off-by: NKevin Wolf <kwolf@redhat.com>
      c0778f66
  29. 28 10月, 2016 7 次提交