The maximum number of struct iovec elements depends on the
BlockDriverState. The raw-posix and iSCSI protocols have a maximum of
IOV_MAX but others could have different values.
Cc: Peter Lieven <p...@kamp.de>
Suggested-by: Kevin Wolf <kw...@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com>
---
v2:
* Change default from INT_MAX to IOV_MAX [Peter Lieven]
---
block/io.c | 5 +++++
include/block/block_int.h | 3 +++
2 files changed, 8 insertions(+)
diff --git a/block/io.c b/block/io.c
index d4bc83b..37bc0dc 100644
--- a/block/io.c
+++ b/block/io.c
@@ -165,9 +165,13 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error
**errp)
bs->bl.max_transfer_length = bs->file->bl.max_transfer_length;
bs->bl.min_mem_alignment = bs->file->bl.min_mem_alignment;
bs->bl.opt_mem_alignment = bs->file->bl.opt_mem_alignment;
+ bs->bl.max_iov = bs->file->bl.max_iov;
} else {
bs->bl.min_mem_alignment = 512;
bs->bl.opt_mem_alignment = getpagesize();
+
+ /* Safe default since most protocols use readv()/writev()/etc */
+ bs->bl.max_iov = IOV_MAX;
}
if (bs->backing_hd) {
@@ -188,6 +192,7 @@ void bdrv_refresh_limits(BlockDriverState *bs, Error **errp)
bs->bl.min_mem_alignment =
MAX(bs->bl.min_mem_alignment,
bs->backing_hd->bl.min_mem_alignment);
+ bs->bl.max_iov = MIN(bs->bl.max_iov, bs->backing_hd->bl.max_iov);
}
/* Then let the driver override it */
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 8996baf..7d578c4 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -315,6 +315,9 @@ typedef struct BlockLimits {
/* memory alignment for bounce buffer */
size_t opt_mem_alignment;
+
+ /* maximum number of iovec elements */
+ int max_iov;
} BlockLimits;
typedef struct BdrvOpBlocker BdrvOpBlocker;
--
2.4.3
