An empty GSList is represented by a NULL pointer, therefore it's a
perfectly valid argument for g_slist_find() and there's no need to
make any additional check.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Message-id: 1435583533-5758-1-git-send-email-berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
a malicious caller could otherwise specify a very
large value via the URI and force libnfs to allocate
a large amount of memory for the readahead buffer.
Cc: qemu-stable@nongnu.org
Signed-off-by: Peter Lieven <pl@kamp.de>
Message-id: 1435317241-25585-1-git-send-email-pl@kamp.de
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
RHEL7 and others are stuck with libiscsi 1.9.0 since there
unfortunately was an ABI breakage after that release.
Signed-off-by: Peter Lieven <pl@kamp.de>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Message-id: 1435313881-19366-1-git-send-email-pl@kamp.de
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Unsetting dirty globally with discard is not very correct. The discard may zero
out sectors (depending on can_write_zeroes_with_unmap), we should replicate
this change to destination side to make sure that the guest sees the same data.
Calling bdrv_reset_dirty also troubles mirror job because the hbitmap iterator
doesn't expect unsetting of bits after current position.
So let's do it the opposite way which fixes both problems: set the dirty bits
if we are to discard it.
Reported-by: wangxiaolong@ucloud.cn
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
If guest discards a source cluster, mirroring with bdrv_aio_readv is overkill.
Some protocols do zero upon discard, where it's best to use
bdrv_aio_write_zeroes, otherwise, bdrv_aio_discard will be enough.
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
If specified as "true", it allows discarding on target sectors where source is
not allocated.
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Like bdrv_is_allocated_above, this function follows the backing chain until seeing
BDRV_BLOCK_ALLOCATED. Base is not included.
Reimplement bdrv_is_allocated on top.
[Initialized bdrv_co_get_block_status_above() ret to 0 to silence
mingw64 compiler warning about the unitialized variable. assert(bs !=
base) prevents that case but I suppose the program could be compiled
with -DNDEBUG.
--Stefan]
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
If we wish to make differential backups a feature that's easy to access,
it might be pertinent to rename the "dirty-bitmap" mode to "incremental"
to make it clear what /type/ of backup the dirty-bitmap is helping us
perform.
This is an API breaking change, but 2.4 has not yet gone live,
so we have this flexibility.
Signed-off-by: John Snow <jsnow@redhat.com>
Message-id: 1433463642-21840-2-git-send-email-jsnow@redhat.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Fixes a crash during image compression
Signed-off-by: Jindřich Makovička <makovick@gmail.com>
Tested-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
libiscsi starting with 1.15 will properly support timeout of iscsi
commands. The default will remain no timeout, but this can
be changed via cmdline parameters, e.g.:
qemu -iscsi timeout=30 -drive file=iscsi://...
If a timeout occurs a reconnect is scheduled and the timed out command
will be requeued for processing after a successful reconnect.
The required API call iscsi_set_timeout is present since libiscsi
1.10 which was released in October 2013. However, due to some bugs
in the libiscsi code the use is not recommended before version 1.15.
Please note that this patch bumps the libiscsi requirement to 1.10
to have all function and macros defined. The patch fixes also a
off-by-one error in the NOP timeout calculation which was fixed
while touching these code parts.
Signed-off-by: Peter Lieven <pl@kamp.de>
Message-id: 1434455107-19328-1-git-send-email-pl@kamp.de
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Until now, an SG device was identified only by checking if its path
started with "/dev/sg". Then, hdev_open() would set the bs->sg flag
accordingly. The patch relies on the actual properties of the device
instead of the specified file path.
To this end, test for an SG device (e.g. /dev/sg0) by ensuring that
all of the following holds:
- The specified file name corresponds to a character device
- The device supports the SG_GET_VERSION_NUM ioctl
- The device supports the SG_GET_SCSI_ID ioctl
Signed-off-by: Dimitris Aragiorgis <dimara@arrikto.com>
Message-id: 1435056300-14924-6-git-send-email-dimara@arrikto.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Get rid of several #ifdef DEBUG_FLOPPY and substitute them with
DPRINTF.
Signed-off-by: Dimitris Aragiorgis <dimara@arrikto.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1435056300-14924-5-git-send-email-dimara@arrikto.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Building the QEMU tools fails if we #define DEBUG_BLOCK inside
block/raw-posix.c. Here instead of adding qemu-log.o in block-obj-y
so that DEBUG_BLOCK_PRINT can be used, we substitute the latter with
a simple DPRINTF() (that does not cause bit-rot).
Signed-off-by: Dimitris Aragiorgis <dimara@arrikto.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1435056300-14924-4-git-send-email-dimara@arrikto.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
During migration, QEMU uses fsync()/fdatasync() on the open file
descriptor for read-write block devices to flush data just before
stopping the VM.
However, fsync() on a scsi-generic device returns -EINVAL which
causes the migration to fail. This patch skips flushing data in case
of an SG device, since submitting SCSI commands directly via an SG
character device (e.g. /dev/sg0) bypasses the page cache completely,
anyway.
Note that fsync() not only flushes the page cache but also the disk
cache. The scsi-generic device never sends flushes, and for
migration it assumes that the same SCSI device is used by the
destination host, so it does not issue any SCSI SYNCHRONIZE CACHE
(10) command.
Finally, remove the bdrv_is_sg() test from iscsi_co_flush() since
this is now redundant (we flush the underlying protocol at the end
of bdrv_co_flush() which, with this patch, we never reach).
Signed-off-by: Dimitris Aragiorgis <dimara@arrikto.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1435056300-14924-3-git-send-email-dimara@arrikto.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Instead of checking bs->sg use bdrv_is_sg() consistently throughout
the code.
Signed-off-by: Dimitris Aragiorgis <dimara@arrikto.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 1435056300-14924-2-git-send-email-dimara@arrikto.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Until now the vvfat volume label was hardcoded to be
"QEMU VVFAT", now you can pass a file.label=labelname option
to the -drive to change it.
The FAT structure defines the volume label to be limited to
11 bytes and is filled up spaces when shorter than that. The
trailing spaces however aren't exposed to the user by
operating systems.
[Added missing comment '#' characters in block-core.json to fix build
errors.
--Stefan]
Signed-off-by: Wolfgang Bumiller <w.bumiller@proxmox.com>
Message-id: 1434706529-13895-2-git-send-email-w.bumiller@proxmox.com
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
This patch introduces the blk_drain() function which allows to replace
blk_drain_all() when only one BlockDriverState needs to be drained.
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Acked-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 1434537440-28236-2-git-send-email-yarygin@linux.vnet.ibm.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Calling throttle_group_config() cancels all timers from a particular
BlockDriverState, so any_timer_armed[] should be updated accordingly.
However, with the current code it may happen that a timer is armed in
a different BlockDriverState from the same group, so any_timer_armed[]
would be set to false in a situation where there is still a timer
armed.
The consequence is that we might end up with two timers armed. This
should not have any noticeable impact however, since all accesses to
the ThrottleGroup are protected by a lock, and the situation would
become normal again shortly thereafter as soon as all timers have been
fired.
The correct way to solve this is to check that we're actually
cancelling a timer before updating any_timer_armed[].
Signed-off-by: Alberto Garcia <berto@igalia.com>
Message-id: 1434382875-3998-1-git-send-email-berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
After the commit 9b536adc ("block: acquire AioContext in
bdrv_drain_all()") the aio_poll() function got called for every
BlockDriverState, in assumption that every device may have its own
AioContext. If we have thousands of disks attached, there are a lot of
BlockDriverStates but only a few AioContexts, leading to tons of
unnecessary aio_poll() calls.
This patch changes the bdrv_drain_all() function allowing it find shared
AioContexts and to call aio_poll() only for unique ones.
Cc: Christian Borntraeger <borntraeger@de.ibm.com>
Cc: Cornelia Huck <cornelia.huck@de.ibm.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Alexander Yarygin <yarygin@linux.vnet.ibm.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Tested-by: Christian Borntraeger <borntraeger@de.ibm.com>
Message-id: 1433936297-7098-4-git-send-email-yarygin@linux.vnet.ibm.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
In particular, don't include it into headers.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
Remove it except for two things in qerror.h:
* Two #include to be cleaned up separately to avoid cluttering this
patch.
* The QERR_ macros. Mark as obsolete.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
These macros expand into error class enumeration constant, comma,
string. Unclean. Has been that way since commit 13f59ae.
The error class is always ERROR_CLASS_GENERIC_ERROR since the previous
commit.
Clean up as follows:
* Prepend every use of a QERR_ macro by ERROR_CLASS_GENERIC_ERROR, and
delete it from the QERR_ macro. No change after preprocessing.
* Rewrite error_set(ERROR_CLASS_GENERIC_ERROR, ...) into
error_setg(...). Again, no change after preprocessing.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
We require a C99 compiler, so let's use 'bool' instead of 'int'
when dealing with boolean values. There are few enough clients
to fix them all in one pass.
Signed-off-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Andreas Färber <afaerber@suse.de>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Acked-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Markus Armbruster <armbru@redhat.com>
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Merge remote-tracking branch 'remotes/kevin/tags/for-upstream' into staging
Block layer core and image format patches
# gpg: Signature made Fri Jun 12 16:08:53 2015 BST using RSA key ID C88F2FD6
# gpg: Good signature from "Kevin Wolf <kwolf@redhat.com>"
* remotes/kevin/tags/for-upstream: (25 commits)
block: Fix reopen flag inheritance
block: Add BlockDriverState.inherits_from
block: Add list of children to BlockDriverState
queue.h: Add QLIST_FIX_HEAD_PTR()
block: Drain requests before swapping nodes in bdrv_swap()
block: Move flag inheritance to bdrv_open_inherit()
block: Use QemuOpts in bdrv_open_common()
block: Use macro for cache option names
vmdk: Use bdrv_open_image()
quorum: Use bdrv_open_image()
check-qdict: Test cases for new functions
qdict: Add qdict_{set,copy}_default()
qdict: Add qdict_array_entries()
iotests: Add tests for overriding BDRV_O_PROTOCOL
block: driver should override flags in bdrv_open()
block: Change bitmap truncate conditional to assertion
block: record new size in bdrv_dirty_bitmap_truncate
raw-posix: Fix .bdrv_co_get_block_status() for unaligned image size
vmdk: Use vmdk_find_index_in_cluster everywhere
vmdk: Fix index_in_cluster calculation in vmdk_co_get_block_status
...
Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
When reopening an image, the block layer already takes care to reopen
bs->file as well with recalculated inherited flags. The same must happen
for any other child (most notably missing before this patch: backing
files).
If bs->file (or any other child) didn't originally inherit from bs, e.g.
because it was created separately and then only referenced, it must not
inherit flags on reopen either, so check the inherited_from field before
propagation the reopen down.
VMDK already reopened its extents manually; this code can now be
dropped.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Instead of letting every caller of bdrv_open() determine the right flags
for its child node manually and pass them to the function, pass the
parent node and the role of the newly opened child (like backing file,
protocol layer, etc.).
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Besides standardising on a single interface for opening child nodes,
this patch allows the user to specify options to individual extent
nodes. Overriding file names isn't possible with this yet, so it's of
limited usefulness, but still a step forward.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Besides standardising on a single interface for opening child nodes,
this simplifies the .bdrv_open() implementation of the quorum block
driver by using block layer functionality for handling BlockdevRefs.
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Jeff Cody <jcody@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Image files with an unaligned image size have a final hole that starts
at EOF, i.e. in the middle of a sector. Currently, *pnum == 0 is
returned when checking the status of this sector. In qemu-img, this
triggers an assertion failure.
In order to fix this, one type for the sector that contains EOF must be
found. Treating a hole as data is safe, so this patch rounds the
calculated number of data sectors up, so that a partial sector at EOF is
treated as a full data sector.
This fixes https://bugzilla.redhat.com/show_bug.cgi?id=1229394
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Tested-by: Cole Robinson <crobinso@redhat.com>
It has the similar issue with b1649fae49. Since the calculation
is repeated for a few times already, introduce a function so it can be
reused.
Signed-off-by: Fam Zheng <famz@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
If a relatively large cluster size is chosen, the default of 1 MB L2
cache is not really appropriate. In this case, unless overridden by the
user, the default cache size should not be determined by its size in
bytes but by the number of L2 tables (clusters) it is supposed to
contain.
Note that without this patch, MIN_L2_CACHE_SIZE will effectively take
over the same role. However, providing space for just two L2 tables is
not enough to be the default.
Signed-off-by: Max Reitz <mreitz@redhat.com>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The L2 cache must cover at least two L2 tables, because during COW two
L2 tables are accessed simultaneously.
Reported-by: Alexander Graf <agraf@suse.de>
Cc: qemu-stable <qemu-stable@nongnu.org>
Signed-off-by: Max Reitz <mreitz@redhat.com>
Tested-by: Alexander Graf <agraf@suse.de>
Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
bdrv_swap() touches the fields of a BlockDriverState that are
protected by the ThrottleGroup lock. Although those fields end up in
their original place, they are temporarily swapped in the process,
so there's a chance that an operation on a member of the same group
happening on a different thread can try to use them.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: d92dc40d7c4f1fc5cda5cbbf4ffb7a4670b79d17.1433779731.git.berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
The throttle group support use a cooperative round robin scheduling
algorithm.
The principles of the algorithm are simple:
- Each BDS of the group is used as a token in a circular way.
- The active BDS computes if a wait must be done and arms the right
timer.
- If a wait must be done the token timer will be armed so the token
will become the next active BDS.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: f0082a86f3ac01c46170f7eafe2101a92e8fde39.1433779731.git.berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Group throttling will share ThrottleState between multiple bs.
As a consequence the ThrottleState will be accessed by multiple aio
context.
Timers are tied to their aio context so they must go out of the
ThrottleState structure.
This commit paves the way for each bs of a common ThrottleState to
have its own timer.
Signed-off-by: Benoit Canet <benoit.canet@nodalink.com>
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Message-id: 6cf9ea96d8b32ae2f8769cead38f68a6a0c8c909.1433779731.git.berto@igalia.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Image files with an unaligned image size have a final hole that starts
at EOF, i.e. in the middle of a sector. Currently, *pnum == 0 is
returned when checking the status of this sector. In qemu-img, this
triggers an assertion failure.
In order to fix this, one type for the sector that contains EOF must be
found. Treating a hole as data is safe, so this patch rounds the
calculated number of data sectors up, so that a partial sector at EOF is
treated as a full data sector.
This fixes https://bugzilla.redhat.com/show_bug.cgi?id=1229394
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Message-id: 1433840108-9996-1-git-send-email-kwolf@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Kevin Wolf <kwolf@redhat.com>
Cc: qemu-block@nongnu.org
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Kevin Wolf <kwolf@redhat.com>
Retain the function value for now, to permit selective conversion of
its callers.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Kevin Wolf <kwolf@redhat.com>
When the argument is non-zero, qemu_opts_foreach() stops on callback
returning non-zero, and returns that value.
When the argument is zero, it doesn't stop, and returns the bit-wise
inclusive or of all the return values. Funky :)
The callers that pass zero could just as well pass one, because their
callbacks can't return anything but zero:
* qemu_add_globals()'s callback qdev_add_one_global()
* qemu_config_write()'s callback config_write_opts()
* main()'s callbacks default_driver_check(), drive_enable_snapshot(),
vnc_init_func()
Drop the parameter, and always stop.
Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Acked-by: Kevin Wolf <kwolf@redhat.com>
raw_bsd already has QEMU_BUILD_BUG_ON(BDRV_SECTOR_SIZE != 512), so iscsi
should relax.
Signed-off-by: Fam Zheng <famz@redhat.com>
Signed-off-by: Michael Tokarev <mjt@tls.msk.ru>
When a qcow[2] file is opened, if the header reports an
encryption method, this is used to set the 'crypt_method_header'
field on the BDRVQcow[2]State struct, and the 'encrypted' flag
in the BDRVState struct.
When doing I/O operations, the 'crypt_method' field on the
BDRVQcow[2]State struct is checked to determine if encryption
needs to be applied.
The crypt_method_header value is copied into crypt_method when
the bdrv_set_key() method is called.
The QEMU code which opens a block device is expected to always
do a check
if (bdrv_is_encrypted(bs)) {
bdrv_set_key(bs, ....key...);
}
If code forgets to do this, then 'crypt_method' is never set
and so when I/O is performed, QEMU writes plain text data
into a sector which is expected to contain cipher text, or
when reading, will return cipher text instead of plain
text.
Change the qcow[2] code to consult bs->encrypted when deciding
whether encryption is required, and assert(s->crypt_method)
to protect against cases where the caller forgets to set the
encryption key.
Also put an assert in the set_key methods to protect against
the case where the caller sets an encryption key on a block
device that does not have encryption
Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Fix pointer declaration to make it consistent with the rest of the
code.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This function never receives an invalid table pointer, so we can make
it void and remove all the error checking code.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The current cache algorithm traverses the array starting always from
the beginning, so the average number of comparisons needed to perform
a lookup is proportional to the size of the array.
By using a hash of the offset as the starting point, lookups are
faster and independent from the array size.
The hash is computed using the cluster number of the table, multiplied
by 4 to make it perform better when there are collisions.
In my tests, using a cache with 2048 entries, this reduces the average
number of comparisons per lookup from 430 to 2.5.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
A cache miss means that the whole array was traversed and the entry
we were looking for was not found, so there's no need to traverse it
again in order to select an entry to replace.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
The current algorithm to evict entries from the cache gives always
preference to those in the lowest positions. As the size of the cache
increases, the chances of the later elements of being removed decrease
exponentially.
In a scenario with random I/O and lots of cache misses, entries in
positions 8 and higher are rarely (if ever) evicted. This can be seen
even with the default cache size, but with larger caches the problem
becomes more obvious.
Using an LRU algorithm makes the chances of being removed from the
cache independent from the position.
Signed-off-by: Alberto Garcia <berto@igalia.com>
Reviewed-by: Max Reitz <mreitz@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
