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From a6db5931947acb807b37cac9c832d68cd66fbc2a Mon Sep 17 00:00:00 2001
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From: Jan Janssen <medhefgo@web.de>
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Date: Fri, 1 May 2015 15:15:16 +0200
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Subject: [PATCH] journalctl: Improve boot ID lookup
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This method should greatly improve offset based lookup, by simply jumping
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from one boot to the next boot. It starts at the journal head to get the
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a boot ID, makes a _BOOT_ID match and then comes from the opposite
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journal direction (tail) to get to the end that boot. After flushing the matches
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and advancing the journal from that exact position, we arrive at the start
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of next boot. Rinse and repeat.
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This is faster than the old method of aggregating the full boot listing just
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so we can jump to a specific boot, which can be a real pain on big journals
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just for a mere "-b -1" case.
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As an additional benefit --list-boots should improve slightly too, because
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it does less seeking.
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Note that there can be a change in boot order with this lookup method
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because it will use the order of boots in the journal, not the realtime stamp
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stored in them. That's arguably better, though.
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Another deficiency is that it will get confused with boots interleaving in the
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journal, therefore, it will refuse operation in --merge, --file and --directory mode.
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https://bugs.freedesktop.org/show_bug.cgi?id=72601
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Conflicts:
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	src/journal/journalctl.c
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Cherry-picked from: 596a23293d28f93843aef86721b90043e74d3081
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Related: #1318994
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---
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 src/journal/journalctl.c | 7 +++----
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 1 file changed, 3 insertions(+), 4 deletions(-)
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diff --git a/src/journal/journalctl.c b/src/journal/journalctl.c
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index f60e6415f8..c7a19f236c 100644
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--- a/src/journal/journalctl.c
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+++ b/src/journal/journalctl.c
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@@ -1166,11 +1166,10 @@ static int add_boot(sd_journal *j) {
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                 const char *reason = (r == 0) ? "No such boot ID in journal" : strerror(-r);
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                 if (sd_id128_is_null(arg_boot_id))
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-                        log_error("Data from the specified boot (%+i) is not available: %s",
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-                                  arg_boot_offset, reason);
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+                        log_error("Failed to look up boot %+i: %s", arg_boot_offset, reason);
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                 else
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-                        log_error("Data from the specified boot ("SD_ID128_FORMAT_STR") is not available: %s",
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-                                  SD_ID128_FORMAT_VAL(arg_boot_id), reason);
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+                        log_error("Failed to look up boot ID "SD_ID128_FORMAT_STR"%+i: %s",
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+                                  SD_ID128_FORMAT_VAL(arg_boot_id), arg_boot_offset, reason);
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                 return r == 0 ? -ENODATA : r;
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         }