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librbd: handle diff from clone

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If we have a parent image, and the reference is from snap 0 (beginning of
time) we need to look at the diff on the parent from the beginning of time
and report that when we get an ENOENT.

Signed-off-by: Sage Weil <sage@inktank.com>
This commit is contained in:
Sage Weil 2013-03-28 09:26:11 -07:00 committed by Josh Durgin
parent 186ddda58c
commit 4d02e17f36
1 changed files with 42 additions and 1 deletions
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43
src/librbd/internal.cc
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@ -2256,6 +2256,14 @@ reprotect_and_return_err:
return total_read;
}
int simple_diff_cb(uint64_t off, size_t len, bool exists, void *arg)
{
interval_set<uint64_t> *diff = static_cast<interval_set<uint64_t> *>(arg);
diff->insert(off, len);
return 0;
}
int64_t diff_iterate(ImageCtx *ictx, const char *fromsnapname,
uint64_t off, size_t len,
int (*cb)(uint64_t, size_t, bool, void *),
@ -2307,6 +2315,22 @@ reprotect_and_return_err:
// FIXME: if end_size > from_size, we could read_iterate for the
// final part, and skip the listsnaps op.
// check parent overlap only if we are comparing to the beginning of time
interval_set<uint64_t> parent_diff;
if (from_snap_id == 0) {
ictx->parent_lock.get_read();
uint64_t overlap = end_size;
ictx->get_parent_overlap(from_snap_id, &overlap);
r = 0;
if (ictx->parent && overlap > 0) {
ldout(ictx->cct, 10) << " first getting parent diff" << dendl;
r = diff_iterate(ictx->parent, NULL, 0, overlap, simple_diff_cb, &parent_diff);
}
ictx->parent_lock.put_read();
if (r < 0)
return r;
}
int64_t total_read = 0;
uint64_t period = ictx->get_stripe_period();
uint64_t left = mylen;
@ -2334,8 +2358,25 @@ reprotect_and_return_err:
op.stat(&size, NULL, NULL);
op.list_snaps(&snap_set, NULL);
int r = head_ctx.operate(p->first.name, &op, NULL);
if (r == -ENOENT)
if (r == -ENOENT) {
if (from_snap_id == 0 && !parent_diff.empty()) {
// report parent diff instead
for (vector<ObjectExtent>::iterator q = p->second.begin(); q != p->second.end(); ++q) {
for (vector<pair<uint64_t,uint64_t> >::iterator r = q->buffer_extents.begin();
r != q->buffer_extents.end();
++r) {
interval_set<uint64_t> o;
o.insert(off + r->first, r->second);
o.intersection_of(parent_diff);
ldout(ictx->cct, 20) << " reporting parent overlap " << o << dendl;
for (interval_set<uint64_t>::iterator s = o.begin(); s != o.end(); ++s) {
cb(s.get_start(), s.get_len(), false, arg);
}
}
}
}
continue;
}
if (r < 0)
return r;