Files over 128k not of size (N * 128k) create a "file too large for filesystem" error when using rdma about ksmbd

[consp]

Did some digging but I'm now in over my head:

Error -EINVAL originates here:

 static int smb_direct_rdma_xmit(struct smb_direct_transport *t,
                 void *buf, int buf_len,
                 struct smb2_buffer_desc_v1 *desc,
                 unsigned int desc_len,
                 bool is_read)
 {
...
some code
....
for (i = 0; i < desc_len / sizeof(*desc); i++) {
         desc_buf_len = le32_to_cpu(desc[i].length);

         credits_needed += calc_rw_credits(t, desc_buf, desc_buf_len);
         desc_buf += desc_buf_len;
         total_length += desc_buf_len;
         if (desc_buf_len == 0 || total_length > buf_len ||
             total_length > t->max_rdma_rw_size)
         {
             ksmbd_debug(RDMA, "TEST RDMA %08X %08X %08X %08X", desc_buf_len, total_length, buf_len, t->max_rdma_rw_size);
             return -EINVAL;
         }
     }

Logging is my addition.

Is where it errors, seems total_length > buf_len triggers the exit. (hex since I do now know the value representation)
ksmbd: smb_direct: TEST RDMA 00020000 00020000 00000400 01000000

[namjaejeon]

Thanks for your report! I will try to reproduce it.

[consp]

I tried to understand it a bit and this seems to work. I'm not completely sure it is correct but transfering a large sum of files with many different small filesizes seems to work now, it looks like the read descriptor being set to 128k is the issue: (update to match pr)

diff --git a/smb2pdu.c b/smb2pdu.c
index 591d899..e9749fc 100644
--- a/smb2pdu.c
+++ b/smb2pdu.c
@@ -6792,7 +6792,13 @@ static ssize_t smb2_read_rdma_channel(struct ksmbd_work *work,
                                      size_t length)
 {
        int err;
+    struct smb2_buffer_desc_v1 *desc;

+    /* set descriptor lenght to nbytes if less than request size */
+    if (length < req->Length) {
+        desc = (struct smb2_buffer_desc_v1 *)((char *)req + le16_to_cpu(req->ReadChannelInfoOffset));
+        desc->length = cpu_to_le32(length);
+    }
        err = ksmbd_conn_rdma_write(work->conn, data_buf, length,
                                    (struct smb2_buffer_desc_v1 *)
                                    ((char *)req + le16_to_cpu(req->ReadChannelInfoOffset)),

Tested with (all seems to do fine):

#! /bin/bash
for n in {1..1000}; do
    dd if=/dev/zero of=file$( printf %03d "$n" ).bin bs=1024 count=$(( 128 + RANDOM / 1024 ))
done

Result master branch:

Result fix I made later (better place to do it):

[namjaejeon]

@consp Hm.. I can not reproduce it with windows 10 workstation. In my case, multichannel -> RDMA is changed in the middle of copying while a lot of data is being copied. It seems that Windows cannot transfer such small files with RDMA. How did you get RDMA to transfer even for small files?

[namjaejeon]

@consp I have added the patch for this issue? Can you review and verify it(namjaejeon@e255ebe) ?

git clone https://github.com/namjaejeon/ksmbd --branch=rdma

[namjaejeon]

@consp ping ?

[nitroxis]

Hi, I have the same issue. I can't clone your branch though, it says it doesn't exist. Did you delete it, or did you merge the fix into the master branch?

[nitroxis]

I don't know if it's related but ksmbd is also spamming these lines into the kernel log non-stop:

...
[27547.422677] ksmbd: Invalid Buffer Size Requested
[27547.429593] ksmbd: Invalid Buffer Size Requested
[27547.435637] ksmbd: Invalid Buffer Size Requested
...

I'm using Windows 10 and Linux 6.6.0 ksmbd module over RDMA (ConnectX-3)

[nitroxis]

I've tried with the master branch of https://github.com/namjaejeon/ksmbd, I still get these errors. Copying it from Windows onto Linux/ksmbd worked, but moving or renaming the file still produces "file too large" errors:

[namjaejeon]

@nitroxis Can you check the below branch if problem is still happening ?

git clone https://github.com/consp/ksmbd --branch=reduce-descriptor-length

[namjaejeon]

@nitroxis ping?

[nitroxis]

Hi, sorry for the late response. I'm unable to compile that branch against kernel 6.6.0 due to various errors:

make -C /lib/modules/6.6.0-arch1-1-custom/build M=/home/nitroxis/src/ksmbd2 modules
make[1]: Entering directory '/usr/lib/modules/6.6.0-arch1-1-custom/build'
  CC [M]  /home/nitroxis/src/ksmbd2/vfs.o
/home/nitroxis/src/ksmbd2/vfs.c: In function ‘ksmbd_vfs_fill_dentry_attrs’:
/home/nitroxis/src/ksmbd2/vfs.c:3000:33: warning: passing argument 2 of ‘generic_fillattr’ makes integer from pointer without a cast [-Wint-conversion]
 3000 |         generic_fillattr(idmap, d_inode(dentry), ksmbd_kstat->kstat);
      |                                 ^~~~~~~~~~~~~~~
      |                                 |
      |                                 struct inode *
In file included from /home/nitroxis/src/ksmbd2/vfs.c:8:
./include/linux/fs.h:3016:43: note: expected ‘u32’ {aka ‘unsigned int’} but argument is of type ‘struct inode *’
 3016 | void generic_fillattr(struct mnt_idmap *, u32, struct inode *, struct kstat *);
      |                                           ^~~
/home/nitroxis/src/ksmbd2/vfs.c:3000:61: error: passing argument 3 of ‘generic_fillattr’ from incompatible pointer type [-Werror=incompatible-pointer-types]
 3000 |         generic_fillattr(idmap, d_inode(dentry), ksmbd_kstat->kstat);
      |                                                  ~~~~~~~~~~~^~~~~~~
      |                                                             |
      |                                                             struct kstat *
./include/linux/fs.h:3016:48: note: expected ‘struct inode *’ but argument is of type ‘struct kstat *’
 3016 | void generic_fillattr(struct mnt_idmap *, u32, struct inode *, struct kstat *);
      |                                                ^~~~~~~~~~~~~~
/home/nitroxis/src/ksmbd2/vfs.c:3000:9: error: too few arguments to function ‘generic_fillattr’
 3000 |         generic_fillattr(idmap, d_inode(dentry), ksmbd_kstat->kstat);
      |         ^~~~~~~~~~~~~~~~
./include/linux/fs.h:3016:6: note: declared here
 3016 | void generic_fillattr(struct mnt_idmap *, u32, struct inode *, struct kstat *);
      |      ^~~~~~~~~~~~~~~~
cc1: some warnings being treated as errors
make[3]: *** [scripts/Makefile.build:243: /home/nitroxis/src/ksmbd2/vfs.o] Error 1
make[2]: *** [/usr/lib/modules/6.6.0-arch1-1-custom/build/Makefile:1913: /home/nitroxis/src/ksmbd2] Error 2
make[1]: *** [Makefile:234: __sub-make] Error 2
make[1]: Leaving directory '/usr/lib/modules/6.6.0-arch1-1-custom/build'
make: *** [Makefile:47: all] Error 2

[nitroxis]

Nevermind, I merged with cifsd-team/ksmbd master, that compiled successfully. However, loading the new module still leads to the same Windows error message as before.

[nitroxis]

I am not sure if it's related to this issue, but opening files with some programs also leads to errors. For example, opening a small 1kB file in HxD gives me the following error:

Opening text files with VSCode simply shows an empty file. I guess it too encounters an error somewhere, but doesn't propagate it properly in the UI.
Playing a video file with mpv or opening an image with XnView on the other hand works fine, so I'm guessing it's only a specific function/request that fails, which is only triggered by some programs but not by others.

This also happens on master branch, not just the reduce-descriptor-length branch

[nitroxis]

Now VSCode actually displayed the following error:

[namjaejeon]

@nitroxis Can you give me wireshark dump(or tcpdump) on problem situation ? Acutally I didn't reproduce it with windows client before. Once, want to check packets that you will give on your reproduction environment.

[namjaejeon]

@nitroxis please give also me debug prints after enabling RDMA log(sudo ksmbd.control -d rdma).