-/*
- * prepare a page for being written to
- */
-static int afs_prepare_page(struct afs_vnode *vnode, struct page *page,
- struct key *key, unsigned offset, unsigned to)
-{
- unsigned eof, tail, start, stop, len;
- loff_t i_size, pos;
- void *p;
- int ret;
-
- _enter("");
-
- if (offset == 0 && to == PAGE_SIZE)
- return 0;
-
- p = kmap_atomic(page, KM_USER0);
-
- i_size = i_size_read(&vnode->vfs_inode);
- pos = (loff_t) page->index << PAGE_SHIFT;
- if (pos >= i_size) {
- /* partial write, page beyond EOF */
- _debug("beyond");
- if (offset > 0)
- memset(p, 0, offset);
- if (to < PAGE_SIZE)
- memset(p + to, 0, PAGE_SIZE - to);
- kunmap_atomic(p, KM_USER0);
- return 0;
- }
-
- if (i_size - pos >= PAGE_SIZE) {
- /* partial write, page entirely before EOF */
- _debug("before");
- tail = eof = PAGE_SIZE;
- } else {
- /* partial write, page overlaps EOF */
- eof = i_size - pos;
- _debug("overlap %u", eof);
- tail = max(eof, to);
- if (tail < PAGE_SIZE)
- memset(p + tail, 0, PAGE_SIZE - tail);
- if (offset > eof)
- memset(p + eof, 0, PAGE_SIZE - eof);
- }
-
- kunmap_atomic(p, KM_USER0);
-
- ret = 0;
- if (offset > 0 || eof > to) {
- /* need to fill one or two bits that aren't going to be written
- * (cover both fillers in one read if there are two) */
- start = (offset > 0) ? 0 : to;
- stop = (eof > to) ? eof : offset;
- len = stop - start;
- _debug("wr=%u-%u av=0-%u rd=%u@%u",
- offset, to, eof, start, len);
- ret = afs_fill_page(vnode, key, start, len, page);
- }
-
- _leave(" = %d", ret);
- return ret;
-}
-