@@ -526,15 +526,10 @@ more:
io_align = pos & ~PAGE_MASK;
buf_align = (unsigned long)data & ~PAGE_MASK;
len = left;
- if (file->f_flags & O_DIRECT) {
- /* write from beginning of first page, regardless of
- io alignment */
- page_align = (pos - io_align + buf_align) & ~PAGE_MASK;
- num_pages = calc_pages_for((unsigned long)data, len);
- } else {
- page_align = pos & ~PAGE_MASK;
- num_pages = calc_pages_for(pos, len);
- }
+
+ /* write from beginning of first page, regardless of io alignment */
+ page_align = file->f_flags & O_DIRECT ? buf_align : io_align;
+ num_pages = calc_pages_for(page_align, len);
req = ceph_osdc_new_request(&fsc->client->osdc, &ci->i_layout,
ceph_vino(inode), pos, &len,
CEPH_OSD_OP_WRITE, flags,
(This is being reposted. The first one had a problem because it erroneously added a similar change elsewhere; that change has been dropped.) The next patch in this series points out that the calculation for the number of pages in an osd request is getting done twice. It is not obvious, but the result of both calculations is identical. This patch simplifies one of them--as a separate step--to make it clear that the transformation in the next patch is valid. In ceph_sync_write() there is some magic that computes page_align for an osd request. But a little analysis shows it can be simplified. First, we have: io_align = pos & ~PAGE_MASK; which is used here: page_align = (pos - io_align + buf_align) & ~PAGE_MASK; Note (pos - io_align) simply rounds "pos" down to the nearest multiple of the page size. We also have: buf_align = (unsigned long)data & ~PAGE_MASK; Adding buf_align to that rounded-down "pos" value will stay within the same page; the result will just be offset by the page offset for the "data" pointer. The final mask therefore leaves just the value of "buf_align". One more simplification. Note that the result of calc_pages_for() is invariant of which page the offset starts in--the only thing that matters is the offset within the starting page. We will have put the proper page offset to use into "page_align", so just use that in calculating num_pages. This resolves: http://tracker.ceph.com/issues/4166 Signed-off-by: Alex Elder <elder@inktank.com> Reviewed-by: Josh Durgin <josh.durgin@inktank.com> --- fs/ceph/file.c | 13 ++++--------- 1 file changed, 4 insertions(+), 9 deletions(-)