Don't increase limits when prefetching metadata for added magnets

Adjusting limits was made based on the belief that "forced" torrents (internally used for prefetching metadata)
are still under limits, but ignore only the queue. This is not really the case. "Forced" torrents ignore the limits
like "maximum active torrents/downloads", so adjusting limits is not required, and what's more, it really causes the
problem of unexpectedly activated previously queued torrents when adding some magnet using "Add new torrent" dialog.

PR #18503.
Fixes #18490.

src/base/bittorrent/sessionimpl.cpp

@@ -1086,18 +1086,6 @@ void SessionImpl::setGlobalMaxSeedingMinutes(int minutes)
     }
 }
 
-void SessionImpl::adjustLimits()
-{
-    if (isQueueingSystemEnabled())
-    {
-        lt::settings_pack settingsPack;
-        // Internally increase the queue limits to ensure that the magnet is started
-        settingsPack.set_int(lt::settings_pack::active_downloads, adjustLimit(maxActiveDownloads()));
-        settingsPack.set_int(lt::settings_pack::active_limit, adjustLimit(maxActiveTorrents()));
-        m_nativeSession->apply_settings(std::move(settingsPack));
-    }
-}
-
 void SessionImpl::applyBandwidthLimits()
 {
     lt::settings_pack settingsPack;
@@ -1540,16 +1528,6 @@ void SessionImpl::processBannedIPs(lt::ip_filter &filter)
     }
 }
 
-int SessionImpl::adjustLimit(const int limit) const
-{
-    if (limit <= -1)
-        return limit;
-    // check for overflow: (limit + m_extraLimit) < std::numeric_limits<int>::max()
-    return (m_extraLimit < (std::numeric_limits<int>::max() - limit))
-        ? (limit + m_extraLimit)
-        : std::numeric_limits<int>::max();
-}
-
 void SessionImpl::initMetrics()
 {
     const auto findMetricIndex = [](const char *name) -> int
@@ -1751,10 +1729,8 @@ lt::settings_pack SessionImpl::loadLTSettings() const
     // Queueing System
     if (isQueueingSystemEnabled())
     {
-        // Internally increase the queue limits to ensure that the magnet is started
-        settingsPack.set_int(lt::settings_pack::active_downloads, adjustLimit(maxActiveDownloads()));
-        settingsPack.set_int(lt::settings_pack::active_limit, adjustLimit(maxActiveTorrents()));
-
+        settingsPack.set_int(lt::settings_pack::active_downloads, maxActiveDownloads());
+        settingsPack.set_int(lt::settings_pack::active_limit, maxActiveTorrents());
         settingsPack.set_int(lt::settings_pack::active_seeds, maxActiveUploads());
         settingsPack.set_bool(lt::settings_pack::dont_count_slow_torrents, ignoreSlowTorrentsForQueueing());
         settingsPack.set_int(lt::settings_pack::inactive_down_rate, downloadRateForSlowTorrents() * 1024); // KiB to Bytes
@@ -2333,8 +2309,6 @@ bool SessionImpl::cancelDownloadMetadata(const TorrentID &id)
     }
 #endif
     m_downloadedMetadata.erase(downloadedMetadataIter);
-    --m_extraLimit;
-    adjustLimits();
     m_nativeSession->remove_torrent(nativeHandle, lt::session::delete_files);
     return true;
 }
@@ -5212,9 +5186,6 @@ void SessionImpl::handleAddTorrentAlerts(const std::vector<lt::alert *> &alerts)
         else if (const auto downloadedMetadataIter = m_downloadedMetadata.find(torrentID)
                  ; downloadedMetadataIter != m_downloadedMetadata.end())
         {
-            ++m_extraLimit;
-            adjustLimits();
-
             downloadedMetadataIter.value() = alert->handle;
             if (infoHash.isHybrid())
             {
@@ -5493,9 +5464,6 @@ void SessionImpl::handleMetadataReceivedAlert(const lt::metadata_received_alert
     if (found)
     {
         const TorrentInfo metadata {*p->handle.torrent_file()};
-
-        --m_extraLimit;
-        adjustLimits();
         m_nativeSession->remove_torrent(p->handle, lt::session::delete_files);
 
         emit metadataDownloaded(metadata);

src/base/bittorrent/sessionimpl.h

@@ -492,9 +492,7 @@ namespace BitTorrent
         lt::settings_pack loadLTSettings() const;
         void applyNetworkInterfacesSettings(lt::settings_pack &settingsPack) const;
         void configurePeerClasses();
-        int adjustLimit(int limit) const;
         void initMetrics();
-        void adjustLimits();
         void applyBandwidthLimits();
         void processBannedIPs(lt::ip_filter &filter);
         QStringList getListeningIPs() const;
@@ -686,7 +684,6 @@ namespace BitTorrent
         const bool m_wasPexEnabled = m_isPeXEnabled;
 
         int m_numResumeData = 0;
-        int m_extraLimit = 0;
         QVector<TrackerEntry> m_additionalTrackerList;
         QVector<QRegularExpression> m_excludedFileNamesRegExpList;