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authorPeter Lieven <pl@kamp.de>2013-10-24 12:07:03 +0200
committerKevin Wolf <kwolf@redhat.com>2013-11-28 10:30:52 +0100
commitd75cbb5e68f5a7d64248ba89399a7f2073231de5 (patch)
tree16296a172363a83acc43298de189ffbc0d5aa413 /block.c
parentd4cd961507e6f013fd0f9b1dc609f15ed2aaa40d (diff)
downloadhqemu-d75cbb5e68f5a7d64248ba89399a7f2073231de5.zip
hqemu-d75cbb5e68f5a7d64248ba89399a7f2073231de5.tar.gz
block: introduce bdrv_make_zero
this patch adds a call to completely zero out a block device. the operation is sped up by checking the block status and only writing zeroes to the device if they currently do not return zeroes. optionally the zero writing can be sped up by setting the flag BDRV_REQ_MAY_UNMAP to emulate the zero write by unmapping if the driver supports it. Signed-off-by: Peter Lieven <pl@kamp.de> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'block.c')
-rw-r--r--block.c37
1 files changed, 37 insertions, 0 deletions
diff --git a/block.c b/block.c
index df5a603..c390f20 100644
--- a/block.c
+++ b/block.c
@@ -2399,6 +2399,43 @@ int bdrv_write_zeroes(BlockDriverState *bs, int64_t sector_num,
BDRV_REQ_ZERO_WRITE | flags);
}
+/*
+ * Completely zero out a block device with the help of bdrv_write_zeroes.
+ * The operation is sped up by checking the block status and only writing
+ * zeroes to the device if they currently do not return zeroes. Optional
+ * flags are passed through to bdrv_write_zeroes (e.g. BDRV_REQ_MAY_UNMAP).
+ *
+ * Returns < 0 on error, 0 on success. For error codes see bdrv_write().
+ */
+int bdrv_make_zero(BlockDriverState *bs, BdrvRequestFlags flags)
+{
+ int64_t target_size = bdrv_getlength(bs) / BDRV_SECTOR_SIZE;
+ int64_t ret, nb_sectors, sector_num = 0;
+ int n;
+
+ for (;;) {
+ nb_sectors = target_size - sector_num;
+ if (nb_sectors <= 0) {
+ return 0;
+ }
+ if (nb_sectors > INT_MAX) {
+ nb_sectors = INT_MAX;
+ }
+ ret = bdrv_get_block_status(bs, sector_num, nb_sectors, &n);
+ if (ret & BDRV_BLOCK_ZERO) {
+ sector_num += n;
+ continue;
+ }
+ ret = bdrv_write_zeroes(bs, sector_num, n, flags);
+ if (ret < 0) {
+ error_report("error writing zeroes at sector %" PRId64 ": %s",
+ sector_num, strerror(-ret));
+ return ret;
+ }
+ sector_num += n;
+ }
+}
+
int bdrv_pread(BlockDriverState *bs, int64_t offset,
void *buf, int count1)
{
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