tree e3d774b9ff1a2cb3577b8e3c1ba127cba456345e
parent 5df521b1eecf276c4bae8ffb7945acef45530449
author Alex Elder <elder@inktank.com> 1364705215 -0500
committer Sage Weil <sage@inktank.com> 1367468260 -0700

libceph: account for alignment in pages cursor

When a cursor for a page array data message is initialized it needs
to determine the initial value for cursor->last_piece.  Currently it
just checks if length is less than a page, but that's not correct.
The data in the first page in the array will be offset by a page
offset based on the alignment recorded for the data.  (All pages
thereafter will be aligned at the base of the page, so there's
no need to account for this except for the first page.)

Because this was wrong, there was a case where the length of a piece
would be calculated as all of the residual bytes in the message and
that plus the page offset could exceed the length of a page.

So fix this case.  Make sure the sum won't wrap.

This resolves a third issue described in:
    http://tracker.ceph.com/issues/4598

Signed-off-by: Alex Elder <elder@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>