On 05.01.2015 12:51, Denis V. Lunev wrote:
On 05/01/15 14:29, Peter Lieven wrote:
If bs->bl.max_write_zeroes is large and we end up in the unsupported
path we might allocate a lot of memory for the iovector and/or even
generate an oversized requests.
Fix this by limiting the request by the minimum of the reported
maximum transfer size or 16MB (32768 sectors).
Reported-by: Denis V. Lunev <d...@openvz.org>
Signed-off-by: Peter Lieven <p...@kamp.de>
---
block.c | 5 ++++-
1 file changed, 4 insertions(+), 1 deletion(-)
diff --git a/block.c b/block.c
index a612594..8009478 100644
--- a/block.c
+++ b/block.c
@@ -3203,6 +3203,9 @@ static int coroutine_fn
bdrv_co_do_write_zeroes(BlockDriverState *bs,
if (ret == -ENOTSUP) {
/* Fall back to bounce buffer if write zeroes is unsupported */
+ int max_xfer_len = MIN_NON_ZERO(bs->bl.max_transfer_length,
+ MAX_WRITE_ZEROES_DEFAULT);
+ num = MIN(num, max_xfer_len);
iov.iov_len = num * BDRV_SECTOR_SIZE;
if (iov.iov_base == NULL) {
iov.iov_base = qemu_try_blockalign(bs, num *
BDRV_SECTOR_SIZE);
@@ -3219,7 +3222,7 @@ static int coroutine_fn
bdrv_co_do_write_zeroes(BlockDriverState *bs,
/* Keep bounce buffer around if it is big enough for all
* all future requests.
*/
- if (num < max_write_zeroes) {
+ if (num < max_xfer_len) {
qemu_vfree(iov.iov_base);
iov.iov_base = NULL;
}
this is not going to work IMHO. num is the number in sectors.
max_xfer_len is in bytes.
bs->bl.max_transfer_length is in sectors.
Peter
I will send my updated version using your approach in a
couple of minutes. Would like to test it a bit.
--
Mit freundlichen Grüßen
Peter Lieven
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Tel: +49 (0) 208.89 402-50 | Fax: +49 (0) 208.89 402-40
p...@kamp.de | http://www.kamp.de
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