From 96b9e739331cea23df263b3c31d92b037feec050 Mon Sep 17 00:00:00 2001 From: Jeffrey Cody Date: Thu, 10 Jul 2014 23:24:21 +0200 Subject: [PATCH 21/44] block: vhdx - add log write support RH-Author: Jeffrey Cody Message-id: Patchwork-id: 59757 O-Subject: [RHEL6-6 qemu-kvm PATCH v2 12/24] block: vhdx - add log write support Bugzilla: 1063559 RH-Acked-by: Stefan Hajnoczi RH-Acked-by: Fam Zheng RH-Acked-by: Markus Armbruster 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 Signed-off-by: Stefan Hajnoczi (cherry picked from commit 8adc52336d9c44ab4c7b9358a7be22ac0ef962bf) --- block/vhdx-log.c | 282 +++++++++++++++++++++++++++++++++++++++++++++++++++++++ block/vhdx.h | 3 + 2 files changed, 285 insertions(+) Signed-off-by: Miroslav Rezanina --- block/vhdx-log.c | 282 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ block/vhdx.h | 3 + 2 files changed, 285 insertions(+), 0 deletions(-) diff --git a/block/vhdx-log.c b/block/vhdx-log.c index 27abde2..bd0d613 100644 --- a/block/vhdx-log.c +++ b/block/vhdx-log.c @@ -156,6 +156,55 @@ exit: return ret; } +/* Writes num_sectors to the log (all log sectors are 4096 bytes), + * from buffer 'buffer'. Upon return, *sectors_written will contain + * the number of sectors successfully written. + * + * It is assumed that 'buffer' is at least 4096*num_sectors large. + * + * 0 is returned on success, -errno otherwise */ +static int vhdx_log_write_sectors(BlockDriverState *bs, VHDXLogEntries *log, + uint32_t *sectors_written, void *buffer, + uint32_t num_sectors) +{ + int ret = 0; + uint64_t offset; + uint32_t write; + void *buffer_tmp; + BDRVVHDXState *s = bs->opaque; + + ret = vhdx_user_visible_write(bs, s); + if (ret < 0) { + goto exit; + } + + write = log->write; + + buffer_tmp = buffer; + while (num_sectors) { + + offset = log->offset + write; + write = vhdx_log_inc_idx(write, log->length); + if (write == log->read) { + /* full */ + break; + } + ret = bdrv_pwrite(bs->file, offset, buffer_tmp, VHDX_LOG_SECTOR_SIZE); + if (ret < 0) { + goto exit; + } + buffer_tmp += VHDX_LOG_SECTOR_SIZE; + + log->write = write; + *sectors_written = *sectors_written + 1; + num_sectors--; + } + +exit: + return ret; +} + + /* Validates a log entry header */ static bool vhdx_log_hdr_is_valid(VHDXLogEntries *log, VHDXLogEntryHeader *hdr, BDRVVHDXState *s) @@ -726,3 +775,236 @@ exit: } + +static void vhdx_log_raw_to_le_sector(VHDXLogDescriptor *desc, + VHDXLogDataSector *sector, void *data, + uint64_t seq) +{ + /* 8 + 4084 + 4 = 4096, 1 log sector */ + memcpy(&desc->leading_bytes, data, 8); + data += 8; + cpu_to_le64s(&desc->leading_bytes); + memcpy(sector->data, data, 4084); + data += 4084; + memcpy(&desc->trailing_bytes, data, 4); + cpu_to_le32s(&desc->trailing_bytes); + data += 4; + + sector->sequence_high = (uint32_t) (seq >> 32); + sector->sequence_low = (uint32_t) (seq & 0xffffffff); + sector->data_signature = VHDX_LOG_DATA_SIGNATURE; + + vhdx_log_desc_le_export(desc); + vhdx_log_data_le_export(sector); +} + + +static int vhdx_log_write(BlockDriverState *bs, BDRVVHDXState *s, + void *data, uint32_t length, uint64_t offset) +{ + int ret = 0; + void *buffer = NULL; + void *merged_sector = NULL; + void *data_tmp, *sector_write; + unsigned int i; + int sector_offset; + uint32_t desc_sectors, sectors, total_length; + uint32_t sectors_written = 0; + uint32_t aligned_length; + uint32_t leading_length = 0; + uint32_t trailing_length = 0; + uint32_t partial_sectors = 0; + uint32_t bytes_written = 0; + uint64_t file_offset; + VHDXHeader *header; + VHDXLogEntryHeader new_hdr; + VHDXLogDescriptor *new_desc = NULL; + VHDXLogDataSector *data_sector = NULL; + MSGUID new_guid = { 0 }; + + header = s->headers[s->curr_header]; + + /* need to have offset read data, and be on 4096 byte boundary */ + + if (length > header->log_length) { + /* no log present. we could create a log here instead of failing */ + ret = -EINVAL; + goto exit; + } + + if (guid_eq(header->log_guid, zero_guid)) { + vhdx_guid_generate(&new_guid); + vhdx_update_headers(bs, s, false, &new_guid); + } else { + /* currently, we require that the log be flushed after + * every write. */ + ret = -ENOTSUP; + goto exit; + } + + /* 0 is an invalid sequence number, but may also represent the first + * log write (or a wrapped seq) */ + if (s->log.sequence == 0) { + s->log.sequence = 1; + } + + sector_offset = offset % VHDX_LOG_SECTOR_SIZE; + file_offset = (offset / VHDX_LOG_SECTOR_SIZE) * VHDX_LOG_SECTOR_SIZE; + + aligned_length = length; + + /* add in the unaligned head and tail bytes */ + if (sector_offset) { + leading_length = (VHDX_LOG_SECTOR_SIZE - sector_offset); + leading_length = leading_length > length ? length : leading_length; + aligned_length -= leading_length; + partial_sectors++; + } + + sectors = aligned_length / VHDX_LOG_SECTOR_SIZE; + trailing_length = aligned_length - (sectors * VHDX_LOG_SECTOR_SIZE); + if (trailing_length) { + partial_sectors++; + } + + sectors += partial_sectors; + + /* sectors is now how many sectors the data itself takes, not + * including the header and descriptor metadata */ + + new_hdr = (VHDXLogEntryHeader) { + .signature = VHDX_LOG_SIGNATURE, + .tail = s->log.tail, + .sequence_number = s->log.sequence, + .descriptor_count = sectors, + .reserved = 0, + .flushed_file_offset = bdrv_getlength(bs->file), + .last_file_offset = bdrv_getlength(bs->file), + }; + + new_hdr.log_guid = header->log_guid; + + desc_sectors = vhdx_compute_desc_sectors(new_hdr.descriptor_count); + + total_length = (desc_sectors + sectors) * VHDX_LOG_SECTOR_SIZE; + new_hdr.entry_length = total_length; + + vhdx_log_entry_hdr_le_export(&new_hdr); + + buffer = qemu_blockalign(bs, total_length); + memcpy(buffer, &new_hdr, sizeof(new_hdr)); + + new_desc = (VHDXLogDescriptor *) (buffer + sizeof(new_hdr)); + data_sector = buffer + (desc_sectors * VHDX_LOG_SECTOR_SIZE); + data_tmp = data; + + /* All log sectors are 4KB, so for any partial sectors we must + * merge the data with preexisting data from the final file + * destination */ + merged_sector = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE); + + for (i = 0; i < sectors; i++) { + new_desc->signature = VHDX_LOG_DESC_SIGNATURE; + new_desc->sequence_number = s->log.sequence; + new_desc->file_offset = file_offset; + + if (i == 0 && leading_length) { + /* partial sector at the front of the buffer */ + ret = bdrv_pread(bs->file, file_offset, merged_sector, + VHDX_LOG_SECTOR_SIZE); + if (ret < 0) { + goto exit; + } + memcpy(merged_sector + sector_offset, data_tmp, leading_length); + bytes_written = leading_length; + sector_write = merged_sector; + } else if (i == sectors - 1 && trailing_length) { + /* partial sector at the end of the buffer */ + ret = bdrv_pread(bs->file, + file_offset, + merged_sector + trailing_length, + VHDX_LOG_SECTOR_SIZE - trailing_length); + if (ret < 0) { + goto exit; + } + memcpy(merged_sector, data_tmp, trailing_length); + bytes_written = trailing_length; + sector_write = merged_sector; + } else { + bytes_written = VHDX_LOG_SECTOR_SIZE; + sector_write = data_tmp; + } + + /* populate the raw sector data into the proper structures, + * as well as update the descriptor, and convert to proper + * endianness */ + vhdx_log_raw_to_le_sector(new_desc, data_sector, sector_write, + s->log.sequence); + + data_tmp += bytes_written; + data_sector++; + new_desc++; + file_offset += VHDX_LOG_SECTOR_SIZE; + } + + /* checksum covers entire entry, from the log header through the + * last data sector */ + vhdx_update_checksum(buffer, total_length, + offsetof(VHDXLogEntryHeader, checksum)); + cpu_to_le32s((uint32_t *)(buffer + 4)); + + /* now write to the log */ + vhdx_log_write_sectors(bs, &s->log, §ors_written, buffer, + desc_sectors + sectors); + if (ret < 0) { + goto exit; + } + + if (sectors_written != desc_sectors + sectors) { + /* instead of failing, we could flush the log here */ + ret = -EINVAL; + goto exit; + } + + s->log.sequence++; + /* write new tail */ + s->log.tail = s->log.write; + +exit: + qemu_vfree(buffer); + qemu_vfree(merged_sector); + return ret; +} + +/* Perform a log write, and then immediately flush the entire log */ +int vhdx_log_write_and_flush(BlockDriverState *bs, BDRVVHDXState *s, + void *data, uint32_t length, uint64_t offset) +{ + int ret = 0; + VHDXLogSequence logs = { .valid = true, + .count = 1, + .hdr = { 0 } }; + + + /* Make sure data written (new and/or changed blocks) is stable + * on disk, before creating log entry */ + bdrv_flush(bs); + ret = vhdx_log_write(bs, s, data, length, offset); + if (ret < 0) { + goto exit; + } + logs.log = s->log; + + /* Make sure log is stable on disk */ + bdrv_flush(bs); + ret = vhdx_log_flush(bs, s, &logs); + if (ret < 0) { + goto exit; + } + + s->log = logs.log; + +exit: + return ret; +} + diff --git a/block/vhdx.h b/block/vhdx.h index 6e57499..4ae8248 100644 --- a/block/vhdx.h +++ b/block/vhdx.h @@ -405,6 +405,9 @@ 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); -- 1.7.1