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authorKevin Wolf <kwolf@redhat.com>2019-03-22 13:38:43 +0100
committerKevin Wolf <kwolf@redhat.com>2019-03-26 11:37:51 +0100
commitfe0480d6294270ff0d6fb60e66bb725a6aad2043 (patch)
tree86c0e0d0d3582b8cce53b18b0b3ecc7f942bf84b /block/io.c
parent48ce986096bb70354b12f0becb253a06bcf9c434 (diff)
block: Add BDRV_REQ_NO_FALLBACK
For qemu-img convert, we want an operation that zeroes out the whole image if this can be done efficiently, but that returns an error otherwise so we don't write explicit zeroes and immediately overwrite them with the real data, potentially doubling the amount of data to be written. Signed-off-by: Kevin Wolf <kwolf@redhat.com> Acked-by: Eric Blake <eblake@redhat.com>
Diffstat (limited to 'block/io.c')
-rw-r--r--block/io.c12
1 files changed, 11 insertions, 1 deletions
diff --git a/block/io.c b/block/io.c
index 952372c2bb..dfc153b8d8 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1015,6 +1015,7 @@ static int coroutine_fn bdrv_driver_preadv(BlockDriverState *bs,
unsigned int nb_sectors;
assert(!(flags & ~BDRV_REQ_MASK));
+ assert(!(flags & BDRV_REQ_NO_FALLBACK));
if (!drv) {
return -ENOMEDIUM;
@@ -1061,6 +1062,7 @@ static int coroutine_fn bdrv_driver_pwritev(BlockDriverState *bs,
int ret;
assert(!(flags & ~BDRV_REQ_MASK));
+ assert(!(flags & BDRV_REQ_NO_FALLBACK));
if (!drv) {
return -ENOMEDIUM;
@@ -1467,6 +1469,10 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
return -ENOMEDIUM;
}
+ if ((flags & ~bs->supported_zero_flags) & BDRV_REQ_NO_FALLBACK) {
+ return -ENOTSUP;
+ }
+
assert(alignment % bs->bl.request_alignment == 0);
head = offset % alignment;
tail = (offset + bytes) % alignment;
@@ -1510,7 +1516,7 @@ static int coroutine_fn bdrv_co_do_pwrite_zeroes(BlockDriverState *bs,
assert(!bs->supported_zero_flags);
}
- if (ret == -ENOTSUP) {
+ if (ret == -ENOTSUP && !(flags & BDRV_REQ_NO_FALLBACK)) {
/* Fall back to bounce buffer if write zeroes is unsupported */
BdrvRequestFlags write_flags = flags & ~BDRV_REQ_ZERO_WRITE;
@@ -2949,6 +2955,10 @@ static int coroutine_fn bdrv_co_copy_range_internal(
BdrvTrackedRequest req;
int ret;
+ /* TODO We can support BDRV_REQ_NO_FALLBACK here */
+ assert(!(read_flags & BDRV_REQ_NO_FALLBACK));
+ assert(!(write_flags & BDRV_REQ_NO_FALLBACK));
+
if (!dst || !dst->bs) {
return -ENOMEDIUM;
}