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

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

> Yes, ofcourse.
Thank you!

> 
> 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;
> >         }
> >