Re: [Patch v2 3/6] cifs: smbd: Avoid allocating iov on the stack

From: Steve French
Date: Mon Apr 23 2018 - 13:51:21 EST

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I am ok with the other style warning - so I just fixed up the one
error (see attached) and merged into cifs-2.6.git for-next

That leaves two more from your series to review (and for others to
review). Let's just focus on those two.

On Mon, Apr 23, 2018 at 12:33 PM, Long Li <longli@xxxxxxxxxxxxx> wrote:
>> Subject: Re: [Patch v2 3/6] cifs: smbd: Avoid allocating iov on the stack
>>
>> Didn't see any obvious problems, but can you fix the checkpatch warnings
>> and resend to the list (I am more concerned about the last two warnings
>> rather than the first one).
>
> Yes, I will fix it and resend.
>
>>
>> $ scripts/checkpatch.pl 0001-cifs-smbd-Avoid-allocating-iov-on-the-
>> stack.patch
>> WARNING: line over 80 characters
>> #60: FILE: fs/cifs/smbdirect.c:2106:
>> + log_write(ERR, "expected the pdu length in 1st iov, but got
>> 0x%lu\n", rqst->rq_iov[0].iov_len);
>>
>> ERROR: Prefixing 0x with decimal output is defective
>> #60: FILE: fs/cifs/smbdirect.c:2106:
>> + log_write(ERR, "expected the pdu length in 1st iov, but got
>> 0x%lu\n", rqst->rq_iov[0].iov_len);
>>
>> WARNING: braces {} are not necessary for single statement blocks
>> #69: FILE: fs/cifs/smbdirect.c:2112:
>> + for (i = 0; i < rqst->rq_nvec-1; i++) {
>> buflen += iov[i].iov_len;
>> }
>>
>> total: 1 errors, 2 warnings, 65 lines checked
>>
>> NOTE: For some of the reported defects, checkpatch may be able to
>> mechanically convert to the typical style using --fix or --fix-inplace.
>>
>> 0001-cifs-smbd-Avoid-allocating-iov-on-the-stack.patch has style problems,
>> please review.
>>
>> On Tue, Apr 17, 2018 at 2:17 PM, Long Li <longli@xxxxxxxxxxxxxxxxx> wrote:
>> > From: Long Li <longli@xxxxxxxxxxxxx>
>> >
>> > 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@xxxxxxxxxxxxx>
>> > Cc: stable@xxxxxxxxxxxxxxx
>> > ---
>> > 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
>> >
>> > --
>> > To unsubscribe from this list: send the line "unsubscribe linux-cifs"
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>> majordomo
>> > info at
>> >
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>> >
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>> b47%
>> >
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>>
>>
>> --
>> Thanks,
>>
>> Steve
>> --
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--
Thanks,

Steve
From 553018657de265a7c999f4fd12864fd0646319a1 Mon Sep 17 00:00:00 2001
From: Long Li <longli@xxxxxxxxxxxxx>
Date: Tue, 17 Apr 2018 12:17:07 -0700
Subject: [PATCH] cifs: smbd: Avoid allocating iov on the stack

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@xxxxxxxxxxxxx>
Cc: stable@xxxxxxxxxxxxxxx
---
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 87817ddcc096..24cea63e17f5 100644
--- a/fs/cifs/smbdirect.c
+++ b/fs/cifs/smbdirect.c
@@ -2086,7 +2086,7 @@ 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++;
@@ -2096,32 +2096,20 @@ 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 %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;
}

@@ -2198,14 +2186,14 @@ 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,
--
2.14.1

Next message: Tony Lindgren: "[PATCH 05/16] ARM: OMAP2+: Initialize SoC PM later"
Previous message: Tony Lindgren: "[PATCH 06/16] ARM: OMAP2+: Make display related init into device_initcall"
In reply to: Long Li: "RE: [Patch v2 3/6] cifs: smbd: Avoid allocating iov on the stack"
Next in thread: Long Li: "[Patch v2 6/6] cifs: smbd: Dump SMB packet when configured"
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