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nbd: split requests

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qemu-nbd has a limit of slightly less than 1M per request.  Work
around this in the nbd block driver.

Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
This commit is contained in:
Paolo Bonzini 2011-09-10 15:06:52 +02:00
parent ae255e523c
commit d9b09f13ca
1 changed files with 46 additions and 6 deletions
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52
block/nbd.c
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@ -277,8 +277,9 @@ static int nbd_open(BlockDriverState *bs, const char* filename, int flags)
return result;
}
static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
static int nbd_co_readv_1(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov,
int offset)
{
BDRVNBDState *s = bs->opaque;
struct nbd_request request;
@ -292,15 +293,16 @@ static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num,
if (nbd_co_send_request(s, &request, NULL, 0) == -1) {
reply.error = errno;
} else {
nbd_co_receive_reply(s, &request, &reply, qiov->iov, 0);
nbd_co_receive_reply(s, &request, &reply, qiov->iov, offset);
}
nbd_coroutine_end(s, &request);
return -reply.error;
}
static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
static int nbd_co_writev_1(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov,
int offset)
{
BDRVNBDState *s = bs->opaque;
struct nbd_request request;
@ -311,7 +313,7 @@ static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num,
request.len = nb_sectors * 512;
nbd_coroutine_start(s, &request);
if (nbd_co_send_request(s, &request, qiov->iov, 0) == -1) {
if (nbd_co_send_request(s, &request, qiov->iov, offset) == -1) {
reply.error = errno;
} else {
nbd_co_receive_reply(s, &request, &reply, NULL, 0);
@ -320,6 +322,44 @@ static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num,
return -reply.error;
}
/* qemu-nbd has a limit of slightly less than 1M per request. Try to
* remain aligned to 4K. */
#define NBD_MAX_SECTORS 2040
static int nbd_co_readv(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
{
int offset = 0;
int ret;
while (nb_sectors > NBD_MAX_SECTORS) {
ret = nbd_co_readv_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
if (ret < 0) {
return ret;
}
offset += NBD_MAX_SECTORS * 512;
sector_num += NBD_MAX_SECTORS;
nb_sectors -= NBD_MAX_SECTORS;
}
return nbd_co_readv_1(bs, sector_num, nb_sectors, qiov, offset);
}
static int nbd_co_writev(BlockDriverState *bs, int64_t sector_num,
int nb_sectors, QEMUIOVector *qiov)
{
int offset = 0;
int ret;
while (nb_sectors > NBD_MAX_SECTORS) {
ret = nbd_co_writev_1(bs, sector_num, NBD_MAX_SECTORS, qiov, offset);
if (ret < 0) {
return ret;
}
offset += NBD_MAX_SECTORS * 512;
sector_num += NBD_MAX_SECTORS;
nb_sectors -= NBD_MAX_SECTORS;
}
return nbd_co_writev_1(bs, sector_num, nb_sectors, qiov, offset);
}
static void nbd_close(BlockDriverState *bs)
{
BDRVNBDState *s = bs->opaque;