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From 989d971046a36afa7acb67855f565603297ad2e8 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 19:44:01 +0100
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Subject: [PATCH 18/25] block: vhdx - remove BAT file offset bit shifting
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RH-Author: Jeffrey Cody <jcody@redhat.com>
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Message-id: <348f6a1952aa68e9a5cfefb56a7e86f5ff1d01c9.1384975172.git.jcody@redhat.com>
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Patchwork-id: 55811
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O-Subject: [RHEL7 qemu-kvm PATCH 18/26] block: vhdx - remove BAT file offset bit shifting
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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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Bit shifting can be fun, but in this case it was unnecessary. The
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upper 44 bits of the 64-bit BAT entry is specifies the File Offset,
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so we shifted the bits to get access to the value.
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However, per the spec the value is in MB. So we dutifully shifted back
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to the left by 20 bits, to convert to a true uint64_t file offset.
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This replaces those steps with just a bit mask, to get rid of the lower
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20 bits instead.
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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 0b7da092b40734538631c3ad461c1753a87535fc)
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---
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block/vhdx.c | 6 ++----
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block/vhdx.h | 1 -
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2 files changed, 2 insertions(+), 5 deletions(-)
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Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>
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---
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block/vhdx.c | 6 ++----
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block/vhdx.h | 1 -
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2 files changed, 2 insertions(+), 5 deletions(-)
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diff --git a/block/vhdx.c b/block/vhdx.c
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index baf8970..97099aa 100644
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--- a/block/vhdx.c
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+++ b/block/vhdx.c
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@@ -985,7 +985,7 @@ static void vhdx_block_translate(BDRVVHDXState *s, int64_t sector_num,
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sinfo->bytes_avail = sinfo->sectors_avail << s->logical_sector_size_bits;
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- sinfo->file_offset = s->bat[sinfo->bat_idx] >> VHDX_BAT_FILE_OFF_BITS;
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+ sinfo->file_offset = s->bat[sinfo->bat_idx] & VHDX_BAT_FILE_OFF_MASK;
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sinfo->block_offset = block_offset << s->logical_sector_size_bits;
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@@ -999,7 +999,6 @@ static void vhdx_block_translate(BDRVVHDXState *s, int64_t sector_num,
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* in the block, and add in the payload data block offset
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* in the file, in bytes, to get the final read address */
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- sinfo->file_offset <<= 20; /* now in bytes, rather than 1MB units */
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sinfo->file_offset += sinfo->block_offset;
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}
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@@ -1110,8 +1109,7 @@ static void vhdx_update_bat_table_entry(BlockDriverState *bs, BDRVVHDXState *s,
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{
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/* The BAT entry is a uint64, with 44 bits for the file offset in units of
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* 1MB, and 3 bits for the block state. */
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- s->bat[sinfo->bat_idx] = ((sinfo->file_offset>>20) <<
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- VHDX_BAT_FILE_OFF_BITS);
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+ s->bat[sinfo->bat_idx] = sinfo->file_offset;
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s->bat[sinfo->bat_idx] |= state & VHDX_BAT_STATE_BIT_MASK;
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diff --git a/block/vhdx.h b/block/vhdx.h
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index a85c5c8..7deb7fd 100644
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--- a/block/vhdx.h
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+++ b/block/vhdx.h
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@@ -229,7 +229,6 @@ typedef struct QEMU_PACKED VHDXLogDataSector {
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/* upper 44 bits are the file offset in 1MB units lower 3 bits are the state
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other bits are reserved */
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#define VHDX_BAT_STATE_BIT_MASK 0x07
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-#define VHDX_BAT_FILE_OFF_BITS (64 - 44)
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#define VHDX_BAT_FILE_OFF_MASK 0xFFFFFFFFFFF00000 /* upper 44 bits */
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typedef uint64_t VHDXBatEntry;
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--
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1.7.1
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