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Subject[PATCH 3/6] cifs: smbd: Avoid allocating iov on the stack
Date
From: Long Li <longli@microsoft.com>

It's not necessary to allocate another iov when going through the buffers
in smbd_send() through RDMA send.

Remove it to reduce stack size.

Signed-off-by: Long Li <longli@microsoft.com>
---
fs/cifs/smbdirect.c | 36 ++++++++++++------------------------
1 file changed, 12 insertions(+), 24 deletions(-)

diff --git a/fs/cifs/smbdirect.c b/fs/cifs/smbdirect.c
index b5c6c0d..f575e9a 100644
--- a/fs/cifs/smbdirect.c
+++ b/fs/cifs/smbdirect.c
@@ -2088,7 +2088,7 @@ int smbd_send(struct smbd_connection *info, struct smb_rqst *rqst)
int start, i, j;
int max_iov_size =
info->max_send_size - sizeof(struct smbd_data_transfer);
- struct kvec iov[SMBDIRECT_MAX_SGE];
+ struct kvec *iov;
int rc;

info->smbd_send_pending++;
@@ -2099,32 +2099,20 @@ int smbd_send(struct smbd_connection *info, struct smb_rqst *rqst)
}

/*
- * This usually means a configuration error
- * We use RDMA read/write for packet size > rdma_readwrite_threshold
- * as long as it's properly configured we should never get into this
- * situation
- */
- if (rqst->rq_nvec + rqst->rq_npages > SMBDIRECT_MAX_SGE) {
- log_write(ERR, "maximum send segment %x exceeding %x\n",
- rqst->rq_nvec + rqst->rq_npages, SMBDIRECT_MAX_SGE);
- rc = -EINVAL;
- goto done;
- }
-
- /*
- * Remove the RFC1002 length defined in MS-SMB2 section 2.1
- * It is used only for TCP transport
+ * Skip the RFC1002 length defined in MS-SMB2 section 2.1
+ * It is used only for TCP transport in the iov[0]
* In future we may want to add a transport layer under protocol
* layer so this will only be issued to TCP transport
*/
- iov[0].iov_base = (char *)rqst->rq_iov[0].iov_base + 4;
- iov[0].iov_len = rqst->rq_iov[0].iov_len - 4;
- buflen += iov[0].iov_len;
+
+ if (rqst->rq_iov[0].iov_len != 4) {
+ log_write(ERR, "expected the pdu length in 1st iov, but got 0x%lu\n", rqst->rq_iov[0].iov_len);
+ return -EINVAL;
+ }
+ iov = &rqst->rq_iov[1];

/* total up iov array first */
- for (i = 1; i < rqst->rq_nvec; i++) {
- iov[i].iov_base = rqst->rq_iov[i].iov_base;
- iov[i].iov_len = rqst->rq_iov[i].iov_len;
+ for (i = 0; i < rqst->rq_nvec-1; i++) {
buflen += iov[i].iov_len;
}

@@ -2197,14 +2185,14 @@ int smbd_send(struct smbd_connection *info, struct smb_rqst *rqst)
goto done;
}
i++;
- if (i == rqst->rq_nvec)
+ if (i == rqst->rq_nvec-1)
break;
}
start = i;
buflen = 0;
} else {
i++;
- if (i == rqst->rq_nvec) {
+ if (i == rqst->rq_nvec-1) {
/* send out all remaining vecs */
remaining_data_length -= buflen;
log_write(INFO,
--
2.7.4
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