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[Qemu-block] [PATCH v4 1/1] qemu-img: check block status of backing file
From: |
Ren Kimura |
Subject: |
[Qemu-block] [PATCH v4 1/1] qemu-img: check block status of backing file when converting. |
Date: |
Sat, 23 Apr 2016 15:26:27 +0900 |
When converting images, check the block status of its backing file chain
to avoid needlessly reading zeros.
Signed-off-by: Ren Kimura <address@hidden>
---
qemu-img.c | 31 +++++++++++++++++++++++++++++--
1 file changed, 29 insertions(+), 2 deletions(-)
diff --git a/qemu-img.c b/qemu-img.c
index 06264d9..b771227 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1451,6 +1451,22 @@ static void convert_select_part(ImgConvertState *s,
int64_t sector_num)
}
}
+static int64_t get_backing_status(BlockDriverState *bs,
+ int64_t sector_num,
+ int nb_sectors, int *pnum)
+{
+ while (bs->backing) {
+ int64_t ret;
+ BlockDriverState *file;
+ bs = bs->backing->bs;
+ ret = bdrv_get_block_status(bs, sector_num, nb_sectors, pnum, &file);
+ if (ret < 0 || ret & (BDRV_BLOCK_DATA | BDRV_BLOCK_ZERO)) {
+ return ret;
+ }
+ }
+ return -1;
+}
+
static int convert_iteration_sectors(ImgConvertState *s, int64_t sector_num)
{
int64_t ret;
@@ -1477,10 +1493,21 @@ static int convert_iteration_sectors(ImgConvertState
*s, int64_t sector_num)
} else if (!s->target_has_backing) {
/* Without a target backing file we must copy over the contents of
* the backing file as well. */
- /* TODO Check block status of the backing file chain to avoid
+ /* Check block status of the backing file chain to avoid
* needlessly reading zeroes and limiting the iteration to the
* buffer size */
- s->status = BLK_DATA;
+ ret = get_backing_status(blk_bs(s->src[s->src_cur]),
+ sector_num - s->src_cur_offset,
+ n, &n);
+ if (ret < 0) {
+ return ret;
+ }
+
+ if (ret & BDRV_BLOCK_ZERO) {
+ s->status = BLK_ZERO;
+ } else {
+ s->status = BLK_DATA;
+ }
} else {
s->status = BLK_BACKING_FILE;
}
--
2.5.0