Re: [PATCH] cifs: only write 64kb at a time when fallocating a small region of a file

[ronnie sahlberg <ronniesahlberg@gmail.com>]

Yes, ofcourse.

Steve, can you revert that deletion in the patch?

On Thu, Jul 22, 2021 at 4:55 PM Namjae Jeon <namjae.jeon@samsung.com> wrote:
>
> > This code is actually bogus and does the opposite of what the comment says.
> > If out_data_len is 0 then that means that the entire region is unallocated and then we should not
> > bail out but proceed and allocate the hole.
>
> > generic/071 works against a windows server for me.
>
>
> > If it fails with this code removed it might mean that generic/071 never worked with cifs.ko correctly.
>
> generic/071 create preallocated extent by calling fallocate with keep size flags.
> It means the file size should not be increased.
> But if (out_buf_len == 0) check is removed, 1MB write is performed using SMB2_write loop().
> It means the file size becomes 1MB.
>
> And then, generic/071 call again fallocate(0, 512K) which mean file size should be 512K.
> but SMB2_set_eof() in cifs is not called due to the code below(->i_size is bigger than off + len),
> So 071 test failed as file size remains 1MB.
>
>         /*
>          * Extending the file
>          */
>         if ((keep_size == false) && i_size_read(inode) < off + len) {
>                 rc = inode_newsize_ok(inode, off + len);
>                 if (rc)
>                         goto out;
>
>                 if ((cifsi->cifsAttrs & FILE_ATTRIBUTE_SPARSE_FILE) == 0)
>                         smb2_set_sparse(xid, tcon, cfile, inode, false);
>
>                 eof = cpu_to_le64(off + len);
>                 rc = SMB2_set_eof(xid, tcon, cfile->fid.persistent_fid,
>                                   cfile->fid.volatile_fid, cfile->pid, &eof);
>                 if (rc == 0) {
>                         cifsi->server_eof = off + len;
>                         cifs_setsize(inode, off + len);
>                         cifs_truncate_page(inode->i_mapping, inode->i_size);
>                         truncate_setsize(inode, off + len);
>                 }
>                 goto out;
>         }
>