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

["Namjae Jeon" <namjae.jeon@samsung.com>]

> 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;
        }