[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[PULL 29/30] vhdx: Rework truncation logic
From: |
Kevin Wolf |
Subject: |
[PULL 29/30] vhdx: Rework truncation logic |
Date: |
Fri, 8 May 2020 14:41:34 +0200 |
From: Eric Blake <address@hidden>
The vhdx driver uses truncation for image growth, with a special case
for blocks that already read as zero but which are only being
partially written. But with a bit of rearranging, it's just as easy
to defer the decision on whether truncation resulted in zeroes to the
actual allocation attempt, reducing the number of places that still
use bdrv_has_zero_init_truncate.
Signed-off-by: Eric Blake <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
block/vhdx.c | 89 ++++++++++++++++++++++++++++++----------------------
1 file changed, 51 insertions(+), 38 deletions(-)
diff --git a/block/vhdx.c b/block/vhdx.c
index e11fb7413a..53e756438a 100644
--- a/block/vhdx.c
+++ b/block/vhdx.c
@@ -1240,12 +1240,16 @@ exit:
/*
* Allocate a new payload block at the end of the file.
*
- * Allocation will happen at 1MB alignment inside the file
+ * Allocation will happen at 1MB alignment inside the file.
+ *
+ * If @need_zero is set on entry but not cleared on return, then truncation
+ * could not guarantee that the new portion reads as zero, and the caller
+ * will take care of it instead.
*
* Returns the file offset start of the new payload block
*/
static int vhdx_allocate_block(BlockDriverState *bs, BDRVVHDXState *s,
- uint64_t *new_offset)
+ uint64_t *new_offset, bool *need_zero)
{
int64_t current_len;
@@ -1262,6 +1266,17 @@ static int vhdx_allocate_block(BlockDriverState *bs,
BDRVVHDXState *s,
return -EINVAL;
}
+ if (*need_zero) {
+ int ret;
+
+ ret = bdrv_truncate(bs->file, *new_offset + s->block_size, false,
+ PREALLOC_MODE_OFF, BDRV_REQ_ZERO_WRITE, NULL);
+ if (ret != -ENOTSUP) {
+ *need_zero = false;
+ return ret;
+ }
+ }
+
return bdrv_truncate(bs->file, *new_offset + s->block_size, false,
PREALLOC_MODE_OFF, 0, NULL);
}
@@ -1355,18 +1370,38 @@ static coroutine_fn int vhdx_co_writev(BlockDriverState
*bs, int64_t sector_num,
/* in this case, we need to preserve zero writes for
* data that is not part of this write, so we must pad
* the rest of the buffer to zeroes */
-
- /* if we are on a posix system with ftruncate() that extends
- * a file, then it is zero-filled for us. On Win32, the raw
- * layer uses SetFilePointer and SetFileEnd, which does not
- * zero fill AFAIK */
-
- /* Queue another write of zero buffers if the underlying file
- * does not zero-fill on file extension */
-
- if (bdrv_has_zero_init_truncate(bs->file->bs) == 0) {
- use_zero_buffers = true;
-
+ use_zero_buffers = true;
+ /* fall through */
+ case PAYLOAD_BLOCK_NOT_PRESENT: /* fall through */
+ case PAYLOAD_BLOCK_UNMAPPED:
+ case PAYLOAD_BLOCK_UNMAPPED_v095:
+ case PAYLOAD_BLOCK_UNDEFINED:
+ bat_prior_offset = sinfo.file_offset;
+ ret = vhdx_allocate_block(bs, s, &sinfo.file_offset,
+ &use_zero_buffers);
+ if (ret < 0) {
+ goto exit;
+ }
+ /*
+ * once we support differencing files, this may also be
+ * partially present
+ */
+ /* update block state to the newly specified state */
+ vhdx_update_bat_table_entry(bs, s, &sinfo, &bat_entry,
+ &bat_entry_offset,
+ PAYLOAD_BLOCK_FULLY_PRESENT);
+ bat_update = true;
+ /*
+ * Since we just allocated a block, file_offset is the
+ * beginning of the payload block. It needs to be the
+ * write address, which includes the offset into the
+ * block, unless the entire block needs to read as
+ * zeroes but truncation was not able to provide them,
+ * in which case we need to fill in the rest.
+ */
+ if (!use_zero_buffers) {
+ sinfo.file_offset += sinfo.block_offset;
+ } else {
/* zero fill the front, if any */
if (sinfo.block_offset) {
iov1.iov_len = sinfo.block_offset;
@@ -1378,7 +1413,7 @@ static coroutine_fn int vhdx_co_writev(BlockDriverState
*bs, int64_t sector_num,
}
/* our actual data */
- qemu_iovec_concat(&hd_qiov, qiov, bytes_done,
+ qemu_iovec_concat(&hd_qiov, qiov, bytes_done,
sinfo.bytes_avail);
/* zero fill the back, if any */
@@ -1393,29 +1428,7 @@ static coroutine_fn int vhdx_co_writev(BlockDriverState
*bs, int64_t sector_num,
sectors_to_write += iov2.iov_len >> BDRV_SECTOR_BITS;
}
}
- /* fall through */
- case PAYLOAD_BLOCK_NOT_PRESENT: /* fall through */
- case PAYLOAD_BLOCK_UNMAPPED:
- case PAYLOAD_BLOCK_UNMAPPED_v095:
- case PAYLOAD_BLOCK_UNDEFINED:
- bat_prior_offset = sinfo.file_offset;
- ret = vhdx_allocate_block(bs, s, &sinfo.file_offset);
- if (ret < 0) {
- goto exit;
- }
- /* once we support differencing files, this may also be
- * partially present */
- /* update block state to the newly specified state */
- vhdx_update_bat_table_entry(bs, s, &sinfo, &bat_entry,
- &bat_entry_offset,
- PAYLOAD_BLOCK_FULLY_PRESENT);
- bat_update = true;
- /* since we just allocated a block, file_offset is the
- * beginning of the payload block. It needs to be the
- * write address, which includes the offset into the block */
- if (!use_zero_buffers) {
- sinfo.file_offset += sinfo.block_offset;
- }
+
/* fall through */
case PAYLOAD_BLOCK_FULLY_PRESENT:
/* if the file offset address is in the header zone,
--
2.25.3
- [PULL 09/30] qcow2: Avoid integer wraparound in qcow2_co_truncate(), (continued)
- [PULL 09/30] qcow2: Avoid integer wraparound in qcow2_co_truncate(), Kevin Wolf, 2020/05/08
- [PULL 14/30] vmdk: Flush only once in vmdk_L2update(), Kevin Wolf, 2020/05/08
- [PULL 16/30] iotests/283: Use consistent size for source and target, Kevin Wolf, 2020/05/08
- [PULL 15/30] iotests: vmdk: Enable zeroed_grained=on by default, Kevin Wolf, 2020/05/08
- [PULL 21/30] qcow2: Fix preallocation on block devices, Kevin Wolf, 2020/05/08
- [PULL 27/30] ssh: Support BDRV_REQ_ZERO_WRITE for truncate, Kevin Wolf, 2020/05/08
- [PULL 22/30] gluster: Drop useless has_zero_init callback, Kevin Wolf, 2020/05/08
- [PULL 17/30] backup: Improve error for bdrv_getlength() failure, Kevin Wolf, 2020/05/08
- [PULL 20/30] iotests/055: Use cache.no-flush for vmdk target, Kevin Wolf, 2020/05/08
- [PULL 18/30] backup: Make sure that source and target size match, Kevin Wolf, 2020/05/08
- [PULL 29/30] vhdx: Rework truncation logic,
Kevin Wolf <=
- [PULL 19/30] iotests: Backup with different source/target size, Kevin Wolf, 2020/05/08
- [PULL 24/30] nfs: Support BDRV_REQ_ZERO_WRITE for truncate, Kevin Wolf, 2020/05/08
- [PULL 25/30] rbd: Support BDRV_REQ_ZERO_WRITE for truncate, Kevin Wolf, 2020/05/08
- [PULL 23/30] file-win32: Support BDRV_REQ_ZERO_WRITE for truncate, Kevin Wolf, 2020/05/08
- [PULL 28/30] parallels: Rework truncation logic, Kevin Wolf, 2020/05/08
- [PULL 30/30] block: Drop unused .bdrv_has_zero_init_truncate, Kevin Wolf, 2020/05/08
- [PULL 26/30] sheepdog: Support BDRV_REQ_ZERO_WRITE for truncate, Kevin Wolf, 2020/05/08
- Re: [PULL 00/30] Block layer patches, Peter Maydell, 2020/05/08