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Storing the lseek() result in an int results in it overflowing when the
file is at least 2 GB big. Then, we have a 50 % chance of the result
being "negative" and thus thinking an error occurred when actually
everything went just fine.
So we should use the correct type for storing the result: off_t.
Reported-by: Daniel P. Berrange <berrange@redhat.com>
Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1549231
Cc: qemu-stable@nongnu.org
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20180228131315.30194-2-mreitz@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
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In commit 223a23c198787328ae75bc65d84edf5fde33c0b6, we implemented a
workaround in the gluster driver to handle invalid values returned for
SEEK_DATA or SEEK_HOLE.
In some instances, these same invalid values can be seen in the posix
file handler as well - for example, it has been reported on FUSE gluster
mounts.
Calling assert() for these invalid values is overly harsh; we can safely
return -EIO and allow this case to be treated as a "learned nothing"
case (e.g., D4 / H4, as commented in the code).
This patch does the same thing that 223a23c198787 did for gluster.c,
except in file-posix.c
Signed-off-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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If bdrv_truncate() is called, but the requested size is the same as
before, don't call posix_fallocate(), which returns -EINVAL for length
zero and would therefore make bdrv_truncate() fail.
The problem can be triggered by creating a zero-sized raw image with
'falloc' preallocation mode.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
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This adds the .bdrv_co_create driver callback to file, which enables
image creation over QMP.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
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BlockDriver->bdrv_create() has been called from coroutine context since
commit 5b7e1542cfa41a281af9629d31cef03704d976e6 ("block: make
bdrv_create adopt coroutine").
Make this explicit by renaming to .bdrv_co_create_opts() and add the
coroutine_fn annotation. This makes it obvious to block driver authors
that they may yield, use CoMutex, or other coroutine_fn APIs.
bdrv_co_create is reserved for the QAPI-based version that Kevin is
working on.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-Id: <20170705102231.20711-2-stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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We are gradually moving away from sector-based interfaces, towards
byte-based. Update the file protocol driver accordingly.
In want_zero mode, we continue to report fine-grained hole
information (the caller wants as much mapping detail as possible);
but when not in that mode, the caller prefers larger *pnum and
merely cares about what offsets are allocated at this layer, rather
than where the holes live. Since holes still read as zeroes at
this layer (rather than deferring to a backing layer), we can take
the shortcut of skipping lseek(), and merely state that all bytes
are allocated.
We can also drop redundant bounds checks that are already
guaranteed by the block layer.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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We don't need the can_write_zeroes_with_unmap field in
BlockDriverInfo, because it is redundant information with
supported_zero_flags & BDRV_REQ_MAY_UNMAP. Note that
BlockDriverInfo and supported_zero_flags are both per-device
settings, rather than global state about the driver as a
whole, which means one or both of these bits of information
can already be conditional. Let's audit how they were set:
crypto: always setting can_write_ to false is pointless (the
struct starts life zero-initialized), no use of supported_
nbd: just recently fixed to set can_write_ if supported_
includes MAY_UNMAP (thus this commit effectively reverts
bca80059e and solves the problem mentioned there in a more
global way)
file-posix, iscsi, qcow2: can_write_ is conditional, while
supported_ was unconditional; but passing MAY_UNMAP would
fail with ENOTSUP if the condition wasn't met
qed: can_write_ is unconditional, but pwrite_zeroes lacks
support for MAY_UNMAP and supported_ is not set. Perhaps
support can be added later (since it would be similar to
qcow2), but for now claiming false is no real loss
all other drivers: can_write_ is not set, and supported_ is
either unset or a passthrough
Simplify the code by moving the conditional into
supported_zero_flags for all drivers, then dropping the
now-unused BDI field. For callers that relied on
bdrv_can_write_zeroes_with_unmap(), we return the same
per-device settings for drivers that had conditions (no
observable change in behavior there); and can now return
true (instead of false) for drivers that support passthrough
(for example, the commit driver) which gives those drivers
the same fix as nbd just got in bca80059e. For callers that
relied on supported_zero_flags, we now have a few more places
that can avoid a wasted call to pwrite_zeroes() that will
just fail with ENOTSUP.
Suggested-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <20180126193439.20219-1-eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
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qemu-common.h includes qemu/option.h, but most places that include the
former don't actually need the latter. Drop the include, and add it
to the places that actually need it.
While there, drop superfluous includes of both headers, and
separate #include from file comment with a blank line.
This cleanup makes the number of objects depending on qemu/option.h
drop from 4545 (out of 4743) to 284 in my "build everything" tree.
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180201111846.21846-20-armbru@redhat.com>
[Semantic conflict with commit bdd6a90a9e in block/nvme.c resolved]
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This cleanup makes the number of objects depending on qapi/qmp/qdict.h
drop from 4550 (out of 4743) to 368 in my "build everything" tree.
For qapi/qmp/qobject.h, the number drops from 4552 to 390.
While there, separate #include from file comment with a blank line.
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20180201111846.21846-13-armbru@redhat.com>
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People get surprised when, after "qemu-img create -f raw /dev/sdX", they
still see qcow2 with "qemu-img info", if previously the bdev had a qcow2
header. While this is natural because raw doesn't need to write any
magic bytes during creation, hdev_create is free to clear out the first
sector to make sure the stale qcow2 header doesn't cause such confusion.
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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It is a common requirement for virtual machine to send persistent
reservations, but this currently requires either running QEMU with
CAP_SYS_RAWIO, or using out-of-tree patches that let an unprivileged
QEMU bypass Linux's filter on SG_IO commands.
As an alternative mechanism, the next patches will introduce a
privileged helper to run persistent reservation commands without
expanding QEMU's attack surface unnecessarily.
The helper is invoked through a "pr-manager" QOM object, to which
file-posix.c passes SG_IO requests for PERSISTENT RESERVE OUT and
PERSISTENT RESERVE IN commands. For example:
$ qemu-system-x86_64
-device virtio-scsi \
-object pr-manager-helper,id=helper0,path=/var/run/qemu-pr-helper.sock
-drive if=none,id=hd,driver=raw,file.filename=/dev/sdb,file.pr-manager=helper0
-device scsi-block,drive=hd
or:
$ qemu-system-x86_64
-device virtio-scsi \
-object pr-manager-helper,id=helper0,path=/var/run/qemu-pr-helper.sock
-blockdev node-name=hd,driver=raw,file.driver=host_device,file.filename=/dev/sdb,file.pr-manager=helper0
-device scsi-block,drive=hd
Multiple pr-manager implementations are conceivable and possible, though
only one is implemented right now. For example, a pr-manager could:
- talk directly to the multipath daemon from a privileged QEMU
(i.e. QEMU links to libmpathpersist); this makes reservation work
properly with multipath, but still requires CAP_SYS_RAWIO
- use the Linux IOC_PR_* ioctls (they require CAP_SYS_ADMIN though)
- more interestingly, implement reservations directly in QEMU
through file system locks or a shared database (e.g. sqlite)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Currently, a FOO_lookup is an array of strings terminated by a NULL
sentinel.
A future patch will generate enums with "holes". NULL-termination
will cease to work then.
To prepare for that, store the length in the FOO_lookup by wrapping it
in a struct and adding a member for the length.
The sentinel will be dropped next.
Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Message-Id: <20170822132255.23945-13-marcandre.lureau@redhat.com>
[Basically redone]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503564371-26090-16-git-send-email-armbru@redhat.com>
[Rebased]
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Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503564371-26090-14-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
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The next commit will put it to use. May look pointless now, but we're
going to change the FOO_lookup's type, and then it'll help.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503564371-26090-13-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
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The lookup tables have a sentinel, no need to make callers pass their
size.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <1503564371-26090-3-git-send-email-armbru@redhat.com>
Reviewed-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
[Rebased, commit message corrected]
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It is reported that on Windows Subsystem for Linux, ofd operations fail
with -EINVAL. In other words, QEMU binary built with system headers that
exports F_OFD_SETLK doesn't necessarily run in an environment that
actually supports it:
$ qemu-system-aarch64 ... -drive file=test.vhdx,if=none,id=hd0 \
-device virtio-blk-pci,drive=hd0
qemu-system-aarch64: -drive file=test.vhdx,if=none,id=hd0: Failed to unlock byte 100
qemu-system-aarch64: -drive file=test.vhdx,if=none,id=hd0: Failed to unlock byte 100
qemu-system-aarch64: -drive file=test.vhdx,if=none,id=hd0: Failed to lock byte 100
As a matter of fact this is not WSL specific. It can happen when running
a QEMU compiled against a newer glibc on an older kernel, such as in
a containerized environment.
Let's do a runtime check to cope with that.
Reported-by: Andrew Baumann <Andrew.Baumann@microsoft.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Original idea beyond the code in question was the following: we have failed
to write zeroes with fallocate(FALLOC_FL_ZERO_RANGE) as the simplest
approach and via fallocate(FALLOC_FL_PUNCH_HOLE)/fallocate(0). We have the
only chance now: if the request comes beyond end of the file. Thus we
should calculate file length and respect the error code from that op.
Signed-off-by: Denis V. Lunev <den@openvz.org>
CC: Markus Armbruster <armbru@redhat.com>
CC: Kevin Wolf <kwolf@redhat.com>
CC: Max Reitz <mreitz@redhat.com>
CC: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
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By using raw_regular_truncate() in raw_truncate(), we can now easily
support preallocation.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170613202107.10125-9-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
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Currently, raw_regular_truncate() is intended for setting the size of a
newly created file. However, we also want to use it for truncating an
existing file in which case only the newly added space (when growing)
should be preallocated.
This also means that if resizing failed, we should try to restore the
original file size. This is important when using preallocation.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170613202107.10125-8-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
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This functionality is part of raw_create() which we will be able to
reuse nicely in raw_truncate().
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20170613202107.10125-7-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
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Variables should be declared at the start of a block, and if a certain
parameter value is not supported it may be better to return -ENOTSUP
instead of -EINVAL.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Message-id: 20170613202107.10125-6-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
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Add a PreallocMode parameter to the bdrv_truncate() function implemented
by each block driver. Currently, we always pass PREALLOC_MODE_OFF and no
driver accepts anything else.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 20170613202107.10125-2-mreitz@redhat.com
Signed-off-by: Max Reitz <mreitz@redhat.com>
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Change the 'int count' parameter in *pwrite_zeros, *pdiscard related
functions (and some others) to 'int bytes', as they both refer to bytes.
This helps with code legibility.
Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Message-id: 20170609101808.13506-1-el13635@mail.ntua.gr
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
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The file drivers' *_parse_filename() implementations just strip the
optional protocol prefix off the filename. However, for e.g.
"file:foo:bar", this would lead to "foo:bar" being stored as the BDS's
filename which looks like it should be managed using the "foo" protocol.
This is especially troublesome if you then try to resolve a backing
filename based on "foo:bar".
This issue can only occur if the stripped part is a relative filename
("file:/foo:bar" will be shortened to "/foo:bar" and having a slash
before the first colon means that "/foo" is not recognized as a protocol
part). Therefore, we can easily fix it by prepending "./" to such
filenames.
Before this patch:
$ ./qemu-img create -f qcow2 backing.qcow2 64M
Formatting 'backing.qcow2', fmt=qcow2 size=67108864 encryption=off
cluster_size=65536 lazy_refcounts=off refcount_bits=16
$ ./qemu-img create -f qcow2 -b backing.qcow2 file:top:image.qcow2
Formatting 'file:top:image.qcow2', fmt=qcow2 size=67108864
backing_file=backing.qcow2 encryption=off cluster_size=65536
lazy_refcounts=off refcount_bits=16
$ ./qemu-io file:top:image.qcow2
can't open device file:top:image.qcow2: Could not open backing file:
Unknown protocol 'top'
After this patch:
$ ./qemu-io file:top:image.qcow2
[no error]
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20170522195217.12991-3-mreitz@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
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Now that the block layer takes care to request a lot less permissions
for inactive nodes, the special-casing in file-posix isn't necessary any
more.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
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This extends the permission bits of op blocker API to external using
Linux OFD locks.
Each permission in @perm and @shared_perm is represented by a locked
byte in the image file. Requesting a permission in @perm is translated
to a shared lock of the corresponding byte; rejecting to share the same
permission is translated to a shared lock of a separate byte. With that,
we use 2x number of bytes of distinct permission types.
virtlockd in libvirt locks the first byte, so we do locking from a
higher offset.
Suggested-by: Kevin Wolf <kwolf@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Making this option available even before implementing it will let
converting tests easier: in coming patches they can specify the option
already when necessary, before we actually write code to lock the
images.
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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We now have macros in place to make it less verbose to add a scalar
to QDict and QList, so use them.
Patch created mechanically via:
spatch --sp-file scripts/coccinelle/qobject.cocci \
--macro-file scripts/cocci-macro-file.h --dir . --in-place
then touched up manually to fix a couple of '?:' back to original
spacing, as well as avoiding a long line in monitor.c.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20170427215821.19397-7-eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
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We have macros in place to make it less verbose to add a subtype
of QObject to both QDict and QList. While we have made cleanups
like this in the past (see commit fcfcd8ffc, for example), having
it be automated by Coccinelle makes it easier to maintain.
Patch created mechanically via:
spatch --sp-file scripts/coccinelle/qobject.cocci \
--macro-file scripts/cocci-macro-file.h --dir . --in-place
then I verified that no manual touchups were required.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20170427215821.19397-5-eblake@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
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Add missing error messages for the block driver implementations of
.bdrv_truncate(); drop the generic one from block.c's bdrv_truncate().
Since one of these changes touches a mis-indented block in
block/file-posix.c, this patch fixes that coding style issue along the
way.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20170328205129.15138-5-mreitz@redhat.com
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
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Add an Error parameter to the block drivers' bdrv_truncate() interface.
If a block driver does not set this in case of an error, the generic
bdrv_truncate() implementation will do so.
Where it is obvious, this patch also makes some block drivers set this
value.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Message-id: 20170328205129.15138-4-mreitz@redhat.com
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
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Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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-blockdev and blockdev_add convert their arguments via QObject to
BlockdevOptions for qmp_blockdev_add(), which converts them back to
QObject, then to a flattened QDict. The QDict's members are typed
according to the QAPI schema.
-drive converts its argument via QemuOpts to a (flat) QDict. This
QDict's members are all QString.
Thus, the QType of a flat QDict member depends on whether it comes
from -drive or -blockdev/blockdev_add, except when the QAPI type maps
to QString, which is the case for 'str' and enumeration types.
The block layer core extracts generic configuration from the flat
QDict, and the block driver extracts driver-specific configuration.
Both commonly do so by converting (parts of) the flat QDict to
QemuOpts, which turns all values into strings. Not exactly elegant,
but correct.
However, A few places access the flat QDict directly:
* Most of them access members that are always QString. Correct.
* bdrv_open_inherit() accesses a boolean, carefully. Correct.
* nfs_config() uses a QObject input visitor. Correct only because the
visited type contains nothing but QStrings.
* nbd_config() and ssh_config() use a QObject input visitor, and the
visited types contain non-QStrings: InetSocketAddress members
@numeric, @to, @ipv4, @ipv6. -drive works as long as you don't try
to use them (they're all optional). @to is ignored anyway.
Reproducer:
-drive driver=ssh,server.host=h,server.port=22,server.ipv4,path=p
-drive driver=nbd,server.type=inet,server.data.host=h,server.data.port=22,server.data.ipv4
both fail with "Invalid parameter type for 'data.ipv4', expected: boolean"
Add suitable comments to all these places. Mark the buggy ones FIXME.
"Fortunately", -drive's driver-specific options are entirely
undocumented.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-id: 1490895797-29094-5-git-send-email-armbru@redhat.com
[mreitz: Fixed two typos]
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
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On OpenBSD none of the ioctls probe_logical_blocksize() tries
exist, so the variable sector_size is unused. Refactor the
code to avoid this (and reduce the duplicated code).
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Message-id: 1490279788-12995-1-git-send-email-peter.maydell@linaro.org
Signed-off-by: Max Reitz <mreitz@redhat.com>
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Success for bdrv_flush() means that all previously written data is safe
on disk. For fdatasync(), the best semantics we can hope for on Linux
(without O_DIRECT) is that all data that was written since the last call
was successfully written back. Therefore, and because we can't redo all
writes after a flush failure, we have to give up after a single
fdatasync() failure. After this failure, we would never be able to make
the promise that a successful bdrv_flush() makes.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 20170322210005.16533-1-kwolf@redhat.com
Reviewed-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Max Reitz <mreitz@redhat.com>
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This fixes a leaked fd introduced in commit 9103f1ce.
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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The following pattern is unsafe:
char buf[32];
ret = read(fd, buf, sizeof(buf));
...
buf[ret] = 0;
If read(2) returns 32 then a byte beyond the end of the buffer is
zeroed.
In practice this buffer overflow does not occur because the sysfs
max_segments file only contains an unsigned short + '\n'. The string is
always shorter than 32 bytes.
Regardless, avoid this pattern because static analysis tools might
complain and it could lead to real buffer overflows if copy-pasted
elsewhere in the codebase.
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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BlockLimits.max_transfer can be too high without this fix, guest will
encounter I/O error or even get paused with werror=stop or rerror=stop. The
cause is explained below.
Linux has a separate limit, /sys/block/.../queue/max_segments, which in
the worst case can be more restrictive than the BLKSECTGET which we
already consider (note that they are two different things). So, the
failure scenario before this patch is:
1) host device has max_sectors_kb = 4096 and max_segments = 64;
2) guest learns max_sectors_kb limit from QEMU, but doesn't know
max_segments;
3) guest issues e.g. a 512KB request thinking it's okay, but actually
it's not, because it will be passed through to host device as an
SG_IO req that has niov > 64;
4) host kernel doesn't like the segmenting of the request, and returns
-EINVAL;
This patch checks the max_segments sysfs entry for the host device and
calculates a "conservative" bytes limit using the page size, which is
then merged into the existing max_transfer limit. Guest will discover
this from the usual virtual block device interfaces. (In the case of
scsi-generic, it will be done in the INQUIRY reply interception in
device model.)
The other possibility is to actually propagate it as a separate limit,
but it's not better. On the one hand, there is a big complication: the
limit is per-LUN in QEMU PoV (because we can attach LUNs from different
host HBAs to the same virtio-scsi bus), but the channel to communicate
it in a per-LUN manner is missing down the stack; on the other hand,
two limits versus one doesn't change much about the valid size of I/O
(because guest has no control over host segmenting).
Also, the idea to fall back to bounce buffering in QEMU, upon -EINVAL,
was explored. Unfortunately there is no neat way to ensure the bounce
buffer is less segmented (in terms of DMA addr) than the guest buffer.
Practically, this bug is not very common. It is only reported on a
Emulex (lpfc), so it's okay to get it fixed in the easier way.
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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Now that we are truncating the file in both PREALLOC_MODE_FULL and
PREALLOC_MODE_OFF, not truncating in PREALLOC_MODE_FALLOC looks odd.
Add a comment explaining why we do not truncate in this case.
Signed-off-by: Nir Soffer <nirsof@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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In a previous commit (qemu-img: Do not truncate before preallocation) we
moved truncate to the PREALLOC_MODE_OFF branch to avoid slowdown in
posix_fallocate().
However this change is not optimal when using PREALLOC_MODE_FULL, since
knowing the final size from the beginning could allow the file system
driver to do less allocations and possibly avoid fragmentation of the
file.
Now we truncate also before doing full preallocation.
Signed-off-by: Nir Soffer <nirsof@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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When using file system that does not support fallocate() (e.g. NFS <
4.2), truncating the file only when preallocation=OFF speeds up creating
raw file.
Here is example run, tested on Fedora 24 machine, creating raw file on
NFS version 3 server.
$ time ./qemu-img-master create -f raw -o preallocation=falloc mnt/test 1g
Formatting 'mnt/test', fmt=raw size=1073741824 preallocation=falloc
real 0m21.185s
user 0m0.022s
sys 0m0.574s
$ time ./qemu-img-fix create -f raw -o preallocation=falloc mnt/test 1g
Formatting 'mnt/test', fmt=raw size=1073741824 preallocation=falloc
real 0m11.601s
user 0m0.016s
sys 0m0.525s
$ time dd if=/dev/zero of=mnt/test bs=1M count=1024 oflag=direct
1024+0 records in
1024+0 records out
1073741824 bytes (1.1 GB, 1.0 GiB) copied, 15.6627 s, 68.6 MB/s
real 0m16.104s
user 0m0.009s
sys 0m0.220s
Running with strace we can see that without this change we do one
pread() and one pwrite() for each block. With this change, we do only
one pwrite() per block.
$ strace ./qemu-img-master create -f raw -o preallocation=falloc mnt/test 8192
...
pread64(9, "\0", 1, 4095) = 1
pwrite64(9, "\0", 1, 4095) = 1
pread64(9, "\0", 1, 8191) = 1
pwrite64(9, "\0", 1, 8191) = 1
$ strace ./qemu-img-fix create -f raw -o preallocation=falloc mnt/test 8192
...
pwrite64(9, "\0", 1, 4095) = 1
pwrite64(9, "\0", 1, 8191) = 1
This happens because posix_fallocate is checking if each block is
allocated before writing a byte to the block, and when truncating the
file before preallocation, all blocks are unallocated.
Signed-off-by: Nir Soffer <nirsof@gmail.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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We can get the maximum number of bytes for a single I/O transfer
from the BLKSECTGET ioctl, but we only perform this for block
devices. scsi-generic devices are represented as character devices,
and so do not issue this today. Update this, so that virtio-scsi
devices using the scsi-generic interface can return the same data.
Signed-off-by: Eric Farman <farman@linux.vnet.ibm.com>
Message-Id: <20170120162527.66075-4-farman@linux.vnet.ibm.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Commit 6f6071745bd0 ("raw-posix: Fetch max sectors for host block device")
introduced a routine to call the kernel BLKSECTGET ioctl, which stores the
result back to user space. However, the size of the data returned depends
on the routine handling the ioctl. The (compat_)blkdev_ioctl returns a
short, while sg_ioctl returns an int. Thus, on big-endian systems, we can
find ourselves accidentally shifting the result to a much larger value.
(On s390x, a short is 16 bits while an int is 32 bits.)
Also, the two ioctl handlers return values in different scales (block
returns sectors, while sg returns bytes), so some tweaking of the outputs
is required such that hdev_get_max_transfer_length returns a value in a
consistent set of units.
Signed-off-by: Eric Farman <farman@linux.vnet.ibm.com>
Message-Id: <20170120162527.66075-3-farman@linux.vnet.ibm.com>
Reviewed-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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These files deal with the file protocol, not the raw format (the
file protocol is often used with other formats, and the raw
format is not forced to use the file protocol). Rename things
to make it a bit easier to follow.
Suggested-by: Daniel P. Berrange <berrange@redhat.com>
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>
Reviewed-by: Laszlo Ersek <lersek@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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