On Mon, Oct 28, 2013 at 11:00:16AM -0400, Anna Schumaker wrote:
> + struct nfs42_write_plus_args args = {
> + .wp_fh = NFS_FH(inode),
> + .wp_stable = NFS_FILE_SYNC,
> + .wp_content = NFS4_CONTENT_HOLE,
> + .wp_offset = offset,
> + .wp_length = len,
> + .wp_allocated = (mode == 0),
> + };
After spending some time with draft 21 of the NFSv4.2 spec I don't think
we can use WRITE_PLUS for the prealloc mode of fallocate. The problem
with the NFS4_CONTENT_HOLE arm of WRITE_PLUS is that it is defined to
zero the whole range, while fallocate is defined as being a no-op for
parts of the range that already contain data.
In addition we'll also need more sanity checks on the flags argument,
there already is a FALLOC_FL_KEEP_SIZE not supportable by the NFS
semantics (not that it nessecarily should), and more may be added
in the future. Take a a look at the other fallocate implementations tha
t have a quick check on the top for flags they don't support:
if (mode & ~(FALLOC_FL_KEEP_SIZE | FALLOC_FL_PUNCH_HOLE))
return -EOPNOTSUPP;
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