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block: vhdx - add log write support

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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>
This commit is contained in:
Jeff Cody 2013-10-30 10:44:47 -04:00 • committed by Stefan Hajnoczi
parent 1a848fd451
commit 8adc52336d
2 changed files with 285 additions and 0 deletions
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3
block/vhdx.h
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@ -398,6 +398,9 @@ bool vhdx_checksum_is_valid(uint8_t *buf, size_t size, int crc_offset);
int vhdx_parse_log(BlockDriverState *bs, BDRVVHDXState *s, bool *flushed);
int vhdx_log_write_and_flush(BlockDriverState *bs, BDRVVHDXState *s,
void *data, uint32_t length, uint64_t offset);
static inline void leguid_to_cpus(MSGUID *guid)
{
le32_to_cpus(&guid->data1);