Hi Sam, Thanks for the explanation. I misread the third case, my description was incorrect. I amended https://github.com/ceph/ceph/pull/340 accordingly. Cheers On 06/03/2013 10:28 PM, Samuel Just wrote: > In all three cases, we know the authoritative log does not contain an > entry for oe.soid, therefore: > > If oe.prior_version > log.tail, we must already have processed an > earlier entry for that object resulting in the object being correctly > marked missing (or not) (specifically, the entry for > oe.prior_version). > > If log.tail >= oe.prior_version > eversion_t(), the missing entry > should have need set at oe.prior_version (revise_need). > oe.prior_version cannot be divergent because all divergent entries > must fall within the log (otherwise, we would have backfilled). > > If oe.prior_version == eversion_t(), the object no longer exists, and > the object should be removed from the missing set. > > Hope that helps. > -Sam > > On Sun, Jun 2, 2013 at 4:09 AM, Loic Dachary <loic@xxxxxxxxxxx> wrote: >> Hi Sam, >> >> TL;DR: >> >> When there no new entry, what is the rationale for merge_old_entry to remove the object from missing only if the tail is eversion_t() and the object prior_version is also eversion_t() ? >> https://github.com/dachary/ceph/blob/f58299db098d5f18c817b516fa6ffaa76245e57d/src/osd/PGLog.cc#L330 >> >> Long version: >> >> The conditions are created with: >> >> info.log_tail = eversion_t(); >> oe.soid.hash = 1; >> oe.op = pg_log_entry_t::DELETE; >> oe.prior_version = eversion_t(); >> >> missing.add(oe.soid, eversion_t(1,1), eversion_t()); >> >> as shown in >> https://github.com/dachary/ceph/blob/f58299db098d5f18c817b516fa6ffaa76245e57d/src/test/osd/TestPGLog.cc#L467 >> I double checked with gdb and when called with >> >> EXPECT_FALSE(merge_old_entry(t, oe, info, remove_snap, dirty_log)); >> https://github.com/dachary/ceph/blob/f58299db098d5f18c817b516fa6ffaa76245e57d/src/test/osd/TestPGLog.cc#L481 >> >> it reaches >> >> missing.rm(oe.soid, missing.missing[oe.soid].need); >> https://github.com/dachary/ceph/blob/f58299db098d5f18c817b516fa6ffaa76245e57d/src/osd/PGLog.cc#L330 >> >> and the expected side effects are observed: >> >> EXPECT_FALSE(dirty_log); >> EXPECT_TRUE(remove_snap.empty()); >> EXPECT_TRUE(t.empty()); >> EXPECT_FALSE(missing.have_missing()); >> EXPECT_TRUE(log.empty()); >> EXPECT_EQ(0U, ondisklog.length()); >> https://github.com/dachary/ceph/blob/f58299db098d5f18c817b516fa6ffaa76245e57d/src/test/osd/TestPGLog.cc#L483 >> >> Cheers >> >> -- >> Loïc Dachary, Artisan Logiciel Libre >> All that is necessary for the triumph of evil is that good people do nothing. >> -- Loïc Dachary, Artisan Logiciel Libre All that is necessary for the triumph of evil is that good people do nothing.
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