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commit c00b984fcd53f679ca2dafcd1aee2c89836e6e73
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Author: Florian Weimer <fweimer@redhat.com>
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Date: Tue Aug 29 08:28:31 2023 +0200
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nscd: Skip unusable entries in first pass in prune_cache (bug 30800)
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Previously, if an entry was marked unusable for any reason, but had
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not timed out yet, the assert would trigger.
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One way to get into such state is if a data change is detected during
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re-validation of an entry. This causes the entry to be marked as not
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usable. If exits nscd soon after that, then the clock jumps
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backwards, and nscd restarted, the cache re-validation run after
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startup triggers the removed assert.
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The change is more complicated than just the removal of the assert
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because entries marked as not usable should be garbage-collected in
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the second pass. To make this happen, it is necessary to update some
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book-keeping data.
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Reviewed-by: DJ Delorie <dj@redhat.com>
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diff --git a/nscd/cache.c b/nscd/cache.c
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index efe4214d953edb30..2fd3f78ebb567bbe 100644
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--- a/nscd/cache.c
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+++ b/nscd/cache.c
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@@ -371,8 +371,11 @@ prune_cache (struct database_dyn *table, time_t now, int fd)
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serv2str[runp->type], str, dh->timeout);
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}
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- /* Check whether the entry timed out. */
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- if (dh->timeout < now)
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+ /* Check whether the entry timed out. Timed out entries
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+ will be revalidated. For unusable records, it is still
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+ necessary to record that the bucket needs to be scanned
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+ again below. */
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+ if (dh->timeout < now || !dh->usable)
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{
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/* This hash bucket could contain entries which need to
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be looked at. */
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@@ -384,7 +387,7 @@ prune_cache (struct database_dyn *table, time_t now, int fd)
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/* We only have to look at the data of the first entries
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since the count information is kept in the data part
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which is shared. */
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- if (runp->first)
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+ if (runp->first && dh->usable)
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{
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/* At this point there are two choices: we reload the
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@@ -400,9 +403,6 @@ prune_cache (struct database_dyn *table, time_t now, int fd)
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{
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/* Remove the value. */
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dh->usable = false;
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-
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- /* We definitely have some garbage entries now. */
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- any = true;
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}
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else
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{
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@@ -414,18 +414,15 @@ prune_cache (struct database_dyn *table, time_t now, int fd)
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time_t timeout = readdfcts[runp->type] (table, runp, dh);
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next_timeout = MIN (next_timeout, timeout);
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-
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- /* If the entry has been replaced, we might need
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- cleanup. */
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- any |= !dh->usable;
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}
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}
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+
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+ /* If the entry has been replaced, we might need cleanup. */
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+ any |= !dh->usable;
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}
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else
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- {
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- assert (dh->usable);
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- next_timeout = MIN (next_timeout, dh->timeout);
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- }
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+ /* Entry has not timed out and is usable. */
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+ next_timeout = MIN (next_timeout, dh->timeout);
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run = runp->next;
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}
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