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2023-11-08vhdx: Take locks for accessing bs->fileKevin Wolf
This updates the vhdx code to add GRAPH_RDLOCK annotations for all places that read bs->file. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Message-ID: <20231027155333.420094-23-kwolf@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-06-28vhdx: mark more functions as coroutine_fns and GRAPH_RDLOCKPaolo Bonzini
Mark functions as coroutine_fn when they are only called by other coroutine_fns and they can suspend. Change calls to co_wrappers to use the non-wrapped functions, which in turn requires adding GRAPH_RDLOCK annotations. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> Message-ID: <20230601115145.196465-10-pbonzini@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-04-11block/vhdx: fix dynamic VHDX BAT corruptionLukas Tschoke
The corruption occurs when a BAT entry aligned to 4096 bytes is changed. Specifically, the corruption occurs during the creation of the LOG Data Descriptor. The incorrect behavior involves copying 4088 bytes from the original 4096 bytes aligned offset to `tmp[8..4096]` and then copying the new value for the first BAT entry to the beginning `tmp[0..8]`. This results in all existing BAT entries inside the 4K region being incorrectly moved by 8 bytes and the last entry being lost. This bug did not cause noticeable corruption when only sequentially writing once to an empty dynamic VHDX (e.g. using `qemu-img convert -O vhdx -o subformat=dynamic ...`), but it still resulted in invalid values for the (unused) Sector Bitmap BAT entries. Importantly, this corruption would only become noticeable after the corrupted BAT is re-read from the file. Resolves: https://gitlab.com/qemu-project/qemu/-/issues/727 Cc: qemu-stable@nongnu.org Signed-off-by: Lukas Tschoke <lukts330@gmail.com> Message-Id: <6cfb6d6b-adc5-7772-c8a5-6bae9a0ad668@gmail.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2023-01-20include/block: Untangle inclusion loopsMarkus Armbruster
We have two inclusion loops: block/block.h -> block/block-global-state.h -> block/block-common.h -> block/blockjob.h -> block/block.h block/block.h -> block/block-io.h -> block/block-common.h -> block/blockjob.h -> block/block.h I believe these go back to Emanuele's reorganization of the block API, merged a few months ago in commit d7e2fe4aac8. Fortunately, breaking them is merely a matter of deleting unnecessary includes from headers, and adding them back in places where they are now missing. Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20221221133551.3967339-2-armbru@redhat.com>
2022-07-12block: Change bdrv_{pread,pwrite,pwrite_sync}() param orderAlberto Faria
Swap 'buf' and 'bytes' around for consistency with bdrv_co_{pread,pwrite}(), and in preparation to implement these functions using generated_co_wrapper. Callers were updated using this Coccinelle script: @@ expression child, offset, buf, bytes, flags; @@ - bdrv_pread(child, offset, buf, bytes, flags) + bdrv_pread(child, offset, bytes, buf, flags) @@ expression child, offset, buf, bytes, flags; @@ - bdrv_pwrite(child, offset, buf, bytes, flags) + bdrv_pwrite(child, offset, bytes, buf, flags) @@ expression child, offset, buf, bytes, flags; @@ - bdrv_pwrite_sync(child, offset, buf, bytes, flags) + bdrv_pwrite_sync(child, offset, bytes, buf, flags) Resulting overly-long lines were then fixed by hand. Signed-off-by: Alberto Faria <afaria@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> Message-Id: <20220609152744.3891847-3-afaria@redhat.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2022-07-12block: Add a 'flags' param to bdrv_{pread,pwrite,pwrite_sync}()Alberto Faria
For consistency with other I/O functions, and in preparation to implement them using generated_co_wrapper. Callers were updated using this Coccinelle script: @@ expression child, offset, buf, bytes; @@ - bdrv_pread(child, offset, buf, bytes) + bdrv_pread(child, offset, buf, bytes, 0) @@ expression child, offset, buf, bytes; @@ - bdrv_pwrite(child, offset, buf, bytes) + bdrv_pwrite(child, offset, buf, bytes, 0) @@ expression child, offset, buf, bytes; @@ - bdrv_pwrite_sync(child, offset, buf, bytes) + bdrv_pwrite_sync(child, offset, buf, bytes, 0) Resulting overly-long lines were then fixed by hand. Signed-off-by: Alberto Faria <afaria@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@yandex-team.ru> Message-Id: <20220609152744.3891847-2-afaria@redhat.com> Reviewed-by: Hanna Reitz <hreitz@redhat.com> Signed-off-by: Hanna Reitz <hreitz@redhat.com>
2022-03-07osdep: Move memalign-related functions to their own headerPeter Maydell
Move the various memalign-related functions out of osdep.h and into their own header, which we include only where they are used. While we're doing this, add some brief documentation comments. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Richard Henderson <richard.henderson@linaro.org> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Message-id: 20220226180723.1706285-10-peter.maydell@linaro.org
2021-06-02block: consistently use bdrv_is_read_only()Vladimir Sementsov-Ogievskiy
It's better to use accessor function instead of bs->read_only directly. In some places use bdrv_is_writable() instead of checking both BDRV_O_RDWR set and BDRV_O_INACTIVE not set. In bdrv_open_common() it's a bit strange to add one more variable, but we are going to drop bs->read_only in the next patch, so new ro local variable substitutes it here. Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Message-Id: <20210527154056.70294-2-vsementsov@virtuozzo.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2020-04-30block: Add flags to bdrv(_co)_truncate()Kevin Wolf
Now that block drivers can support flags for .bdrv_co_truncate, expose the parameter in the node level interfaces bdrv_co_truncate() and bdrv_truncate(). Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Message-Id: <20200424125448.63318-3-kwolf@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2019-10-28block: Add @exact parameter to bdrv_co_truncate()Max Reitz
We have two drivers (iscsi and file-posix) that (in some cases) return success from their .bdrv_co_truncate() implementation if the block device is larger than the requested offset, but cannot be shrunk. Some callers do not want that behavior, so this patch adds a new parameter that they can use to turn off that behavior. This patch just adds the parameter and lets the block/io.c and block/block-backend.c functions pass it around. All other callers always pass false and none of the implementations evaluate it, so that this patch does not change existing behavior. Future patches take care of that. Suggested-by: Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com> Message-id: 20190918095144.955-5-mreitz@redhat.com Reviewed-by: Maxim Levitsky <mlevitsk@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2019-06-12Include qemu/module.h where needed, drop it from qemu-common.hMarkus Armbruster
Signed-off-by: Markus Armbruster <armbru@redhat.com> Message-Id: <20190523143508.25387-4-armbru@redhat.com> [Rebased with conflicts resolved automatically, except for hw/usb/dev-hub.c hw/misc/exynos4210_rng.c hw/misc/bcm2835_rng.c hw/misc/aspeed_scu.c hw/display/virtio-vga.c hw/arm/stm32f205_soc.c; ui/cocoa.m fixed up]
2019-04-30block/vhdx: Use IEC binary prefixes for size constantsStefano Garzarella
Using IEC binary prefixes in order to make the code more readable, with the exception of DEFAULT_LOG_SIZE because it's passed to stringify(). Signed-off-by: Stefano Garzarella <sgarzare@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Reviewed-by: John Snow <jsnow@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2019-02-25block: Use bdrv_refresh_filename() to pullMax Reitz
Before this patch, bdrv_refresh_filename() is used in a pushing manner: Whenever the BDS graph is modified, the parents of the modified edges are supposed to be updated (recursively upwards). However, that is nonviable, considering that we want child changes not to concern parents. Also, in the long run we want a pull model anyway: Here, we would have a bdrv_filename() function which returns a BDS's filename, freshly constructed. This patch is an intermediate step. It adds bdrv_refresh_filename() calls before every place a BDS.filename value is used. The only exceptions are protocol drivers that use their own filename, which clearly would not profit from refreshing that filename before. Also, bdrv_get_encrypted_filename() is removed along the way (as a user of BDS.filename), since it is completely unused. In turn, all of the calls to bdrv_refresh_filename() before this patch are removed, because we no longer have to call this function on graph changes. Signed-off-by: Max Reitz <mreitz@redhat.com> Message-id: 20190201192935.18394-2-mreitz@redhat.com Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2018-11-05block/vhdx: Don't take address of fields in packed structsPeter Maydell
Taking the address of a field in a packed struct is a bad idea, because it might not be actually aligned enough for that pointer type (and thus cause a crash on dereference on some host architectures). Newer versions of clang warn about this. Avoid the bug by not using the "modify in place" byte swapping functions. There are a few places where the in-place swap function is used on something other than a packed struct field; we convert those anyway, for consistency. Patch produced with scripts/coccinelle/inplace-byteswaps.cocci. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2018-05-31block: use local path for local headersMichael S. Tsirkin
When pulling in headers that are in the same directory as the C file (as opposed to one in include/), we should use its relative path, without a directory. Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Tested-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
2017-08-31vhdx: use QEMU_ALIGN_DOWNMarc-André Lureau
I used the clang-tidy qemu-round check to generate the fix: https://github.com/elmarco/clang-tools-extra Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Richard Henderson <rth@twiddle.net>
2017-08-08block/vhdx: check error return of bdrv_truncate()Jeff Cody
Signed-off-by: Jeff Cody <jcody@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-08-08block/vhdx: check error return of bdrv_flush()Jeff Cody
Reported-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Jeff Cody <jcody@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-08-08block/vhdx: check for offset overflow to bdrv_truncate()Jeff Cody
VHDX uses uint64_t types for most offsets, following the VHDX spec. However, bdrv_truncate() takes an int64_t value for the truncating offset. Check for overflow before calling bdrv_truncate(). While we are here, replace the bit shifting with QEMU_ALIGN_UP as well. N.B.: For a compliant image this is not an issue, as the maximum VHDX image size is defined per the spec to be 64TB. Reviewed-by: Eric Blake <eblake@redhat.com> Reviewed-by: Kevin Wolf <kwolf@redhat.com> Signed-off-by: Jeff Cody <jcody@redhat.com> Reviewed-by: Philippe Mathieu-Daudé <f4bug@amsat.org> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-08-08block/vhdx: check error return of bdrv_getlength()Jeff Cody
Calls to bdrv_getlength() were not checking for error. In vhdx.c, this can lead to truncating an image file, so it is a definite bug. In vhdx-log.c, the path for improper behavior is less clear, but it is best to check in any case. Some minor code movement of the log_guid intialization, as well. Reported-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2017-07-11block: Add PreallocMode to bdrv_truncate()Max Reitz
For block drivers that just pass a truncate request to the underlying protocol, we can now pass the preallocation mode instead of aborting if it is not PREALLOC_MODE_OFF. Signed-off-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Message-id: 20170613202107.10125-3-mreitz@redhat.com Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-04-28block: Add errp to b{lk,drv}_truncate()Max Reitz
For one thing, this allows us to drop the error message generation from qemu-img.c and blockdev.c and instead have it unified in bdrv_truncate(). Signed-off-by: Max Reitz <mreitz@redhat.com> Message-id: 20170328205129.15138-3-mreitz@redhat.com Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Max Reitz <mreitz@redhat.com>
2017-02-24block: Pass BdrvChild to bdrv_truncate()Kevin Wolf
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com>
2016-07-05block: Convert bdrv_pwrite(v/_sync) to BdrvChildKevin Wolf
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-07-05block: Convert bdrv_pread(v) to BdrvChildKevin Wolf
Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
2016-05-19qemu-common: stop including qemu/bswap.h from qemu-common.hPaolo Bonzini
Move it to the actual users. There are still a few includes of qemu/bswap.h in headers; removing them is left for future work. Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-03-22include/qemu/osdep.h: Don't include qapi/error.hMarkus Armbruster
Commit 57cb38b included qapi/error.h into qemu/osdep.h to get the Error typedef. Since then, we've moved to include qemu/osdep.h everywhere. Its file comment explains: "To avoid getting into possible circular include dependencies, this file should not include any other QEMU headers, with the exceptions of config-host.h, compiler.h, os-posix.h and os-win32.h, all of which are doing a similar job to this file and are under similar constraints." qapi/error.h doesn't do a similar job, and it doesn't adhere to similar constraints: it includes qapi-types.h. That's in excess of 100KiB of crap most .c files don't actually need. Add the typedef to qemu/typedefs.h, and include that instead of qapi/error.h. Include qapi/error.h in .c files that need it and don't get it now. Include qapi-types.h in qom/object.h for uint16List. Update scripts/clean-includes accordingly. Update it further to match reality: replace config.h by config-target.h, add sysemu/os-posix.h, sysemu/os-win32.h. Update the list of includes in the qemu/osdep.h comment quoted above similarly. This reduces the number of objects depending on qapi/error.h from "all of them" to less than a third. Unfortunately, the number depending on qapi-types.h shrinks only a little. More work is needed for that one. Signed-off-by: Markus Armbruster <armbru@redhat.com> [Fix compilation without the spice devel packages. - Paolo] Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
2016-01-20block: Clean up includesPeter Maydell
Clean up includes so that osdep.h is included first and headers which it implies are not included manually. This commit was created with scripts/clean-includes. Signed-off-by: Peter Maydell <peter.maydell@linaro.org> Reviewed-by: Eric Blake <eblake@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2016-01-13vhdx: Fix "log that needs to be replayed" error messageMarkus Armbruster
The arguments of error_setg_errno() should yield a short error string without newlines. Here, we try to append additional help to the error message by embedding newlines in the error string. That's nice, but it's doesn't play nicely with the errno part. tests/qemu-iotests/070.out shows the resulting mess: can't open device TEST_DIR/iotest-dirtylog-10G-4M.vhdx: VHDX image file 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx' opened read-only, but contains a log that needs to be replayed. To replay the log, execute: qemu-img check -r all 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx': Operation not permitted Switch to error_setg() and error_append_hint(). Result: can't open device TEST_DIR/iotest-dirtylog-10G-4M.vhdx: VHDX image file 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx' opened read-only, but contains a log that needs to be replayed To replay the log, run: qemu-img check -r all 'TEST_DIR/iotest-dirtylog-10G-4M.vhdx' Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Eric Blake <eblake@redhat.com> Message-Id: <1450452927-8346-21-git-send-email-armbru@redhat.com>
2015-10-16block: Convert bs->file to BdrvChildKevin Wolf
This patch removes the temporary duplication between bs->file and bs->file_child by converting everything to BdrvChild. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Alberto Garcia <berto@igalia.com> Reviewed-by: Fam Zheng <famz@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
2015-06-22qerror: Move #include out of qerror.hMarkus Armbruster
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>
2014-08-20block: Drop some superfluous casts from void *Markus Armbruster
They clutter the code. Unfortunately, I can't figure out how to make Coccinelle drop all of them, so I have to settle for common special cases: @@ type T; T *pt; void *pv; @@ - pt = (T *)pv; + pt = pv; @@ type T; @@ - (T *) (\(g_malloc\|g_malloc0\|g_realloc\|g_new\|g_new0\|g_renew\| g_try_malloc\|g_try_malloc0\|g_try_realloc\| g_try_new\|g_try_new0\|g_try_renew\)(...)) Topped off with minor manual style cleanups. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Max Reitz <mreitz@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-08-15vhdx: Handle failure for potentially large allocationsKevin Wolf
Some code in the block layer makes potentially huge allocations. Failure is not completely unexpected there, so avoid aborting qemu and handle out-of-memory situations gracefully. This patch addresses the allocations in the vhdx block driver. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Reviewed-by: Benoit Canet <benoit@irqsave.net>
2014-08-15block: VHDX endian fixesJeff Cody
This patch contains several changes for endian conversion fixes for VHDX, particularly for big-endian machines (multibyte values in VHDX are all on disk in LE format). Tests were done with existing qemu-iotests on an IBM POWER7 (8406-71Y). This includes sample images created by Hyper-V, both with dirty logs and without. In addition, VHDX image files created (and written to) on a BE machine were tested on a LE machine, and vice-versa. Reported-by: Markus Armburster <armbru@redhat.com> Reported-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Jeff Cody <jcody@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-08-15block: vhdx - add error checkJeff Cody
This add an error check for an invalid descriptor entry signature, when flushing the log descriptor entries. Signed-off-by: Jeff Cody <jcody@redhat.com> Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
2014-03-25Fixed various typosDeepak Kathayat
Signed-off-by: Deepak Kathayat <deepak.mk17@gmail.com> Reviewed-by: Andreas Färber <afaerber@suse.de> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2014-01-31block/vhdx: Error checking fixesMarkus Armbruster
Errors are inadvertently ignored in a few places. Has always been broken. Spotted by Coverity. Signed-off-by: Markus Armbruster <armbru@redhat.com> Reviewed-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-12-20block: vhdx - improve error message, and .bdrv_check implementationJeff Cody
If there is a dirty log file to be replayed in a VHDX image, it is replayed in .vhdx_open(). However, if the file is opened read-only, then a somewhat cryptic error message results. This adds a more helpful error message for the user. If an image file contains a log to be replayed, and is opened read-only, the user is instructed to run 'qemu-img check -r all' on the image file. Running qemu-img check -r all will cause the image file to be opened r/w, which will replay the log file. If a log file replay is detected, this is flagged, and bdrv_check will increase the corruptions_fixed count for the image. [Fixed typo in error message that was pointed out by Eric Blake <eblake@redhat.com>. --Stefan] Signed-off-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-07block: vhdx - add log write supportJeff Cody
This adds support for writing to the VHDX log. For spec details, see VHDX Specification Format v1.00: https://www.microsoft.com/en-us/download/details.aspx?id=34750 There are a few limitations to this log support: 1.) There is no caching yet 2.) The log is flushed after each entry The primary write interface, vhdx_log_write_and_flush(), performs a log write followed by an immediate flush of the log. As each log entry sector is a minimum of 4KB, partial sector writes are filled in with data from the disk write destination. If the current file log GUID is 0, a new GUID is generated and updated in the header. Signed-off-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2013-11-07block: vhdx - log parsing, replay, and flush supportJeff Cody
This adds support for VHDX v0 logs, as specified in Microsoft's VHDX Specification Format v1.00: https://www.microsoft.com/en-us/download/details.aspx?id=34750 The following support is added: * Log parsing, and validation - validate that an existing log is correct. * Log search - search through an existing log, to find any valid sequence of entries. * Log replay and flush - replay an existing log, and flush/clear the log when complete. The VHDX log is a circular buffer, with elements (sectors) of 4KB. A log entry is a variably-length number of sectors, that is comprised of a header and 'descriptors', that describe each sector. A log may contain multiple entries, know as a log sequence. In a log sequence, each log entry immediately follows the previous entry, with an incrementing sequence number. There can only ever be one active and valid sequence in the log. Each log entry must match the file log GUID in order to be valid (along with other criteria). Once we have flushed all valid log entries, we marked the file log GUID to be zero, which indicates a buffer with no valid entries. Signed-off-by: Jeff Cody <jcody@redhat.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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