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From db9d361c509aea4ce8aca7b7f16a1808880bad29 Mon Sep 17 00:00:00 2001
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From: Jeffrey Cody <jcody@redhat.com>
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Date: Wed, 20 Nov 2013 19:43:59 +0100
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Subject: [PATCH 16/25] block: vhdx - add log write support
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RH-Author: Jeffrey Cody <jcody@redhat.com>
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Message-id: <376bced13e2a7e1069a50bcbd09f3d822306865a.1384975172.git.jcody@redhat.com>
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Patchwork-id: 55809
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O-Subject: [RHEL7 qemu-kvm PATCH 16/26] block: vhdx - add log write support
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Bugzilla: 879234
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RH-Acked-by: Stefan Hajnoczi <stefanha@redhat.com>
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RH-Acked-by: Paolo Bonzini <pbonzini@redhat.com>
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RH-Acked-by: Fam Zheng <famz@redhat.com>
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This adds support for writing to the VHDX log.
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For spec details, see VHDX Specification Format v1.00:
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https://www.microsoft.com/en-us/download/details.aspx?id=34750
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There are a few limitations to this log support:
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1.) There is no caching yet
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2.) The log is flushed after each entry
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The primary write interface, vhdx_log_write_and_flush(), performs a log
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write followed by an immediate flush of the log.
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As each log entry sector is a minimum of 4KB, partial sector writes are
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filled in with data from the disk write destination.
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If the current file log GUID is 0, a new GUID is generated and updated
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in the header.
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Signed-off-by: Jeff Cody <jcody@redhat.com>
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Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
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(cherry picked from commit 8adc52336d9c44ab4c7b9358a7be22ac0ef962bf)
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---
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 block/vhdx-log.c | 282 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
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 block/vhdx.h     |   3 +
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 2 files changed, 285 insertions(+)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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 block/vhdx-log.c |  282 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
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 block/vhdx.h     |    3 +
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 2 files changed, 285 insertions(+), 0 deletions(-)
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diff --git a/block/vhdx-log.c b/block/vhdx-log.c
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index 0284729..ee5583c 100644
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--- a/block/vhdx-log.c
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+++ b/block/vhdx-log.c
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@@ -156,6 +156,55 @@ exit:
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     return ret;
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 }
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+/* Writes num_sectors to the log (all log sectors are 4096 bytes),
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+ * from buffer 'buffer'.  Upon return, *sectors_written will contain
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+ * the number of sectors successfully written.
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+ *
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+ * It is assumed that 'buffer' is at least 4096*num_sectors large.
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+ *
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+ * 0 is returned on success, -errno otherwise */
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+static int vhdx_log_write_sectors(BlockDriverState *bs, VHDXLogEntries *log,
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+                                  uint32_t *sectors_written, void *buffer,
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+                                  uint32_t num_sectors)
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+{
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+    int ret = 0;
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+    uint64_t offset;
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+    uint32_t write;
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+    void *buffer_tmp;
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+    BDRVVHDXState *s = bs->opaque;
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+
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+    ret = vhdx_user_visible_write(bs, s);
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+    if (ret < 0) {
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+        goto exit;
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+    }
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+
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+    write = log->write;
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+
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+    buffer_tmp = buffer;
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+    while (num_sectors) {
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+
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+        offset = log->offset + write;
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+        write = vhdx_log_inc_idx(write, log->length);
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+        if (write == log->read) {
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+            /* full */
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+            break;
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+        }
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+        ret = bdrv_pwrite(bs->file, offset, buffer_tmp, VHDX_LOG_SECTOR_SIZE);
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+        if (ret < 0) {
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+            goto exit;
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+        }
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+        buffer_tmp += VHDX_LOG_SECTOR_SIZE;
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+
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+        log->write = write;
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+        *sectors_written = *sectors_written + 1;
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+        num_sectors--;
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+    }
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+
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+exit:
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+    return ret;
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+}
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+
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+
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 /* Validates a log entry header */
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 static bool vhdx_log_hdr_is_valid(VHDXLogEntries *log, VHDXLogEntryHeader *hdr,
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                                   BDRVVHDXState *s)
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@@ -726,3 +775,236 @@ exit:
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 }
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+
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+static void vhdx_log_raw_to_le_sector(VHDXLogDescriptor *desc,
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+                                      VHDXLogDataSector *sector, void *data,
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+                                      uint64_t seq)
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+{
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+    /* 8 + 4084 + 4 = 4096, 1 log sector */
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+    memcpy(&desc->leading_bytes, data, 8);
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+    data += 8;
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+    cpu_to_le64s(&desc->leading_bytes);
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+    memcpy(sector->data, data, 4084);
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+    data += 4084;
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+    memcpy(&desc->trailing_bytes, data, 4);
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+    cpu_to_le32s(&desc->trailing_bytes);
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+    data += 4;
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+
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+    sector->sequence_high  = (uint32_t) (seq >> 32);
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+    sector->sequence_low   = (uint32_t) (seq & 0xffffffff);
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+    sector->data_signature = VHDX_LOG_DATA_SIGNATURE;
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+
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+    vhdx_log_desc_le_export(desc);
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+    vhdx_log_data_le_export(sector);
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+}
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+
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+
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+static int vhdx_log_write(BlockDriverState *bs, BDRVVHDXState *s,
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+                          void *data, uint32_t length, uint64_t offset)
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+{
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+    int ret = 0;
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+    void *buffer = NULL;
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+    void *merged_sector = NULL;
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+    void *data_tmp, *sector_write;
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+    unsigned int i;
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+    int sector_offset;
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+    uint32_t desc_sectors, sectors, total_length;
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+    uint32_t sectors_written = 0;
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+    uint32_t aligned_length;
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+    uint32_t leading_length = 0;
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+    uint32_t trailing_length = 0;
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+    uint32_t partial_sectors = 0;
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+    uint32_t bytes_written = 0;
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+    uint64_t file_offset;
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+    VHDXHeader *header;
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+    VHDXLogEntryHeader new_hdr;
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+    VHDXLogDescriptor *new_desc = NULL;
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+    VHDXLogDataSector *data_sector = NULL;
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+    MSGUID new_guid = { 0 };
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+
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+    header = s->headers[s->curr_header];
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+
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+    /* need to have offset read data, and be on 4096 byte boundary */
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+
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+    if (length > header->log_length) {
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+        /* no log present.  we could create a log here instead of failing */
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+        ret = -EINVAL;
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+        goto exit;
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+    }
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+
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+    if (guid_eq(header->log_guid, zero_guid)) {
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+        vhdx_guid_generate(&new_guid);
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+        vhdx_update_headers(bs, s, false, &new_guid);
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+    } else {
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+        /* currently, we require that the log be flushed after
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+         * every write. */
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+        ret = -ENOTSUP;
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+        goto exit;
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+    }
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+
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+    /* 0 is an invalid sequence number, but may also represent the first
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+     * log write (or a wrapped seq) */
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+    if (s->log.sequence == 0) {
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+        s->log.sequence = 1;
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+    }
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+
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+    sector_offset = offset % VHDX_LOG_SECTOR_SIZE;
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+    file_offset = (offset / VHDX_LOG_SECTOR_SIZE) * VHDX_LOG_SECTOR_SIZE;
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+
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+    aligned_length = length;
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+
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+    /* add in the unaligned head and tail bytes */
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+    if (sector_offset) {
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+        leading_length = (VHDX_LOG_SECTOR_SIZE - sector_offset);
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+        leading_length = leading_length > length ? length : leading_length;
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+        aligned_length -= leading_length;
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+        partial_sectors++;
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+    }
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+
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+    sectors = aligned_length / VHDX_LOG_SECTOR_SIZE;
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+    trailing_length = aligned_length - (sectors * VHDX_LOG_SECTOR_SIZE);
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+    if (trailing_length) {
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+        partial_sectors++;
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+    }
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+
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+    sectors += partial_sectors;
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+
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+    /* sectors is now how many sectors the data itself takes, not
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+     * including the header and descriptor metadata */
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+
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+    new_hdr = (VHDXLogEntryHeader) {
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+                .signature           = VHDX_LOG_SIGNATURE,
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+                .tail                = s->log.tail,
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+                .sequence_number     = s->log.sequence,
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+                .descriptor_count    = sectors,
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+                .reserved            = 0,
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+                .flushed_file_offset = bdrv_getlength(bs->file),
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+                .last_file_offset    = bdrv_getlength(bs->file),
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+              };
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+
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+    new_hdr.log_guid = header->log_guid;
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+
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+    desc_sectors = vhdx_compute_desc_sectors(new_hdr.descriptor_count);
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+
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+    total_length = (desc_sectors + sectors) * VHDX_LOG_SECTOR_SIZE;
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+    new_hdr.entry_length = total_length;
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+
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+    vhdx_log_entry_hdr_le_export(&new_hdr);
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+
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+    buffer = qemu_blockalign(bs, total_length);
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+    memcpy(buffer, &new_hdr, sizeof(new_hdr));
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+
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+    new_desc = (VHDXLogDescriptor *) (buffer + sizeof(new_hdr));
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+    data_sector = buffer + (desc_sectors * VHDX_LOG_SECTOR_SIZE);
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+    data_tmp = data;
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+
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+    /* All log sectors are 4KB, so for any partial sectors we must
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+     * merge the data with preexisting data from the final file
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+     * destination */
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+    merged_sector = qemu_blockalign(bs, VHDX_LOG_SECTOR_SIZE);
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+
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+    for (i = 0; i < sectors; i++) {
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+        new_desc->signature       = VHDX_LOG_DESC_SIGNATURE;
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+        new_desc->sequence_number = s->log.sequence;
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+        new_desc->file_offset     = file_offset;
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+
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+        if (i == 0 && leading_length) {
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+            /* partial sector at the front of the buffer */
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+            ret = bdrv_pread(bs->file, file_offset, merged_sector,
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+                             VHDX_LOG_SECTOR_SIZE);
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+            if (ret < 0) {
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+                goto exit;
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+            }
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+            memcpy(merged_sector + sector_offset, data_tmp, leading_length);
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+            bytes_written = leading_length;
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+            sector_write = merged_sector;
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+        } else if (i == sectors - 1 && trailing_length) {
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+            /* partial sector at the end of the buffer */
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+            ret = bdrv_pread(bs->file,
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+                            file_offset,
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+                            merged_sector + trailing_length,
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+                            VHDX_LOG_SECTOR_SIZE - trailing_length);
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+            if (ret < 0) {
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+                goto exit;
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+            }
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+            memcpy(merged_sector, data_tmp, trailing_length);
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+            bytes_written = trailing_length;
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+            sector_write = merged_sector;
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+        } else {
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+            bytes_written = VHDX_LOG_SECTOR_SIZE;
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+            sector_write = data_tmp;
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+        }
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+
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+        /* populate the raw sector data into the proper structures,
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+         * as well as update the descriptor, and convert to proper
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+         * endianness */
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+        vhdx_log_raw_to_le_sector(new_desc, data_sector, sector_write,
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+                                  s->log.sequence);
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+
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+        data_tmp += bytes_written;
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+        data_sector++;
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+        new_desc++;
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+        file_offset += VHDX_LOG_SECTOR_SIZE;
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+    }
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+
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+    /* checksum covers entire entry, from the log header through the
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+     * last data sector */
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+    vhdx_update_checksum(buffer, total_length,
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+                         offsetof(VHDXLogEntryHeader, checksum));
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+    cpu_to_le32s((uint32_t *)(buffer + 4));
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+
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+    /* now write to the log */
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+    vhdx_log_write_sectors(bs, &s->log, &sectors_written, buffer,
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+                           desc_sectors + sectors);
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+    if (ret < 0) {
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+        goto exit;
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+    }
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+
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+    if (sectors_written != desc_sectors + sectors) {
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+        /* instead of failing, we could flush the log here */
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+        ret = -EINVAL;
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+        goto exit;
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+    }
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+
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+    s->log.sequence++;
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+    /* write new tail */
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+    s->log.tail = s->log.write;
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+
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+exit:
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+    qemu_vfree(buffer);
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+    qemu_vfree(merged_sector);
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+    return ret;
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+}
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+
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+/* Perform a log write, and then immediately flush the entire log */
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+int vhdx_log_write_and_flush(BlockDriverState *bs, BDRVVHDXState *s,
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+                             void *data, uint32_t length, uint64_t offset)
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+{
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+    int ret = 0;
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+    VHDXLogSequence logs = { .valid = true,
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+                             .count = 1,
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+                             .hdr = { 0 } };
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+
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+
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+    /* Make sure data written (new and/or changed blocks) is stable
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+     * on disk, before creating log entry */
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+    bdrv_flush(bs);
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+    ret = vhdx_log_write(bs, s, data, length, offset);
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+    if (ret < 0) {
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+        goto exit;
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+    }
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+    logs.log = s->log;
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+
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+    /* Make sure log is stable on disk */
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+    bdrv_flush(bs);
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+    ret = vhdx_log_flush(bs, s, &logs);
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+    if (ret < 0) {
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+        goto exit;
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+    }
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+
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+    s->log = logs.log;
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+
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+exit:
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+    return ret;
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+}
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+
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diff --git a/block/vhdx.h b/block/vhdx.h
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index 91ef8fe..4bb83de 100644
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--- a/block/vhdx.h
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+++ b/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);
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 int vhdx_parse_log(BlockDriverState *bs, BDRVVHDXState *s, bool *flushed);
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+int vhdx_log_write_and_flush(BlockDriverState *bs, BDRVVHDXState *s,
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+                             void *data, uint32_t length, uint64_t offset);
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+
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 static inline void leguid_to_cpus(MSGUID *guid)
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 {
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     le32_to_cpus(&guid->data1);
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-- 
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1.7.1
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