Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2019-09-03' into staging

Block patches:
- qemu-io now accepts a file to read a write pattern from
- Ensure that raw files have their fi

Merge remote-tracking branch 'remotes/maxreitz/tags/pull-block-2019-09-03' into staging

Block patches:
- qemu-io now accepts a file to read a write pattern from
- Ensure that raw files have their first block allocated so we can probe
the O_DIRECT alignment if necessary
- Various fixes

# gpg: Signature made Tue 03 Sep 2019 13:58:57 BST
# gpg: using RSA key 91BEB60A30DB3E8857D11829F407DB0061D5CF40
# gpg: issuer "mreitz@redhat.com"
# gpg: Good signature from "Max Reitz <mreitz@redhat.com>" [full]
# Primary key fingerprint: 91BE B60A 30DB 3E88 57D1 1829 F407 DB00 61D5 CF40

* remotes/maxreitz/tags/pull-block-2019-09-03:
iotests: Unify cache mode quoting
tests/check-block: Skip iotests when sanitizers are enabled
iotests: Check for enabled drivers before testing them
iotests: Add -display none to the qemu options
file-posix: fix request_alignment typo
iotests: Disable 126 for flat vmdk subformats
iotests: Disable 110 for vmdk.twoGbMaxExtentSparse
iotests: Disable broken streamOptimized tests
vmdk: Reject invalid compressed writes
iotests: Keep testing broken relative extent paths
vmdk: Use bdrv_dirname() for relative extent paths
iotests: Fix _filter_img_create()
iotests: Test allocate_first_block() with O_DIRECT
block: posix: Always allocate the first block
block: fix permission update in bdrv_replace_node
qemu-io: add pattern file for write command

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

show more ...

block: posix: Always allocate the first block

When creating an image with preallocation "off" or "falloc", the first
block of the image is typically not allocated. When using Gluster
storage backed

block: posix: Always allocate the first block

When creating an image with preallocation "off" or "falloc", the first
block of the image is typically not allocated. When using Gluster
storage backed by XFS filesystem, reading this block using direct I/O
succeeds regardless of request length, fooling alignment detection.

In this case we fallback to a safe value (4096) instead of the optimal
value (512), which may lead to unneeded data copying when aligning
requests. Allocating the first block avoids the fallback.

Since we allocate the first block even with preallocation=off, we no
longer create images with zero disk size:

$ ./qemu-img create -f raw test.raw 1g
Formatting 'test.raw', fmt=raw size=1073741824

$ ls -lhs test.raw
4.0K -rw-r--r--. 1 nsoffer nsoffer 1.0G Aug 16 23:48 test.raw

And converting the image requires additional cluster:

$ ./qemu-img measure -f raw -O qcow2 test.raw
required size: 458752
fully allocated size: 1074135040

When using format like vmdk with multiple files per image, we allocate
one block per file:

$ ./qemu-img create -f vmdk -o subformat=twoGbMaxExtentFlat test.vmdk 4g
Formatting 'test.vmdk', fmt=vmdk size=4294967296 compat6=off hwversion=undefined subformat=twoGbMaxExtentFlat

$ ls -lhs test*.vmdk
4.0K -rw-r--r--. 1 nsoffer nsoffer 2.0G Aug 27 03:23 test-f001.vmdk
4.0K -rw-r--r--. 1 nsoffer nsoffer 2.0G Aug 27 03:23 test-f002.vmdk
4.0K -rw-r--r--. 1 nsoffer nsoffer 353 Aug 27 03:23 test.vmdk

I did quick performance test for copying disks with qemu-img convert to
new raw target image to Gluster storage with sector size of 512 bytes:

for i in $(seq 10); do
rm -f dst.raw
sleep 10
time ./qemu-img convert -f raw -O raw -t none -T none src.raw dst.raw
done

Here is a table comparing the total time spent:

Type Before(s) After(s) Diff(%)
---------------------------------------
real 530.028 469.123 -11.4
user 17.204 10.768 -37.4
sys 17.881 7.011 -60.7

We can see very clear improvement in CPU usage.

Signed-off-by: Nir Soffer <nsoffer@redhat.com>
Message-id: 20190827010528.8818-2-nsoffer@redhat.com
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>

show more ...