init: Take lock on blocks directory in BlockManager ctor

TheCharlatan · Feb 13, 2025 · 1ba7ff6 · 1ba7ff6
1 parent 9b37088
commit 1ba7ff6
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Showing 4 changed files with 41 additions and 6 deletions.
diff --git a/src/init.cpp b/src/init.cpp
@@ -1109,8 +1109,9 @@ static bool LockDirectory(const fs::path& dir, bool probeOnly)
 }
 static bool LockDirectories(bool probeOnly)
 {
-    return LockDirectory(gArgs.GetDataDirNet(), probeOnly) && \
-           LockDirectory(gArgs.GetBlocksDirPath(), probeOnly);
+    // Only allow probing the blocks directory, the BlockManager takes the lock internally.
+    return LockDirectory(gArgs.GetDataDirNet(), probeOnly) &&
+           (probeOnly ? LockDirectory(gArgs.GetBlocksDirPath(), probeOnly) : true);
 }
 
 bool AppInitSanityChecks(const kernel::Context& kernel)

diff --git a/src/init/common.cpp b/src/init/common.cpp
@@ -117,9 +117,10 @@ bool StartLogging(const ArgsManager& args)
     }
 
     if (!LogInstance().m_log_timestamps)
-        LogPrintf("Startup time: %s\n", FormatISO8601DateTime(GetTime()));
-    LogPrintf("Default data directory %s\n", fs::PathToString(GetDefaultDataDir()));
-    LogPrintf("Using data directory %s\n", fs::PathToString(gArgs.GetDataDirNet()));
+        LogInfo("Startup time: %s", FormatISO8601DateTime(GetTime()));
+    LogInfo("Default data directory %s", fs::PathToString(GetDefaultDataDir()));
+    LogInfo("Using data directory %s", fs::PathToString(gArgs.GetDataDirNet()));
+    LogInfo("Using blocks directory %s", fs::PathToString(gArgs.GetBlocksDirPath()));
 
     // Only log conf file usage message if conf file actually exists.
     fs::path config_file_path = args.GetConfigFilePath();

diff --git a/src/node/blockstorage.cpp b/src/node/blockstorage.cpp
@@ -4,6 +4,8 @@
 
 #include <node/blockstorage.h>
 
+#include <bitcoin-build-config.h> // IWYU pragma: keep
+
 #include <arith_uint256.h>
 #include <chain.h>
 #include <consensus/params.h>
@@ -31,6 +33,7 @@
 #include <util/batchpriority.h>
 #include <util/check.h>
 #include <util/fs.h>
+#include <util/fs_helpers.h>
 #include <util/signalinterrupt.h>
 #include <util/strencodings.h>
 #include <util/translation.h>
@@ -1164,8 +1167,29 @@ static auto InitBlocksdirXorKey(const BlockManager::Options& opts)
     return std::vector<std::byte>{xor_key.begin(), xor_key.end()};
 }
 
+BlockDirLock::BlockDirLock(const fs::path& blocks_dir)
+    : m_path{blocks_dir}
+{
+    // Make sure only a single BlockManager is using the blocks directory.
+    switch (util::LockDirectory(blocks_dir, ".lock", false)) {
+    case util::LockResult::ErrorWrite:
+        throw std::runtime_error(strprintf(_("Cannot write to block directory '%s'; check permissions."), fs::PathToString(blocks_dir)).original);
+    case util::LockResult::ErrorLock:
+        throw std::runtime_error(strprintf(_("Cannot obtain a lock on block directory %s. %s is probably already running."), fs::PathToString(blocks_dir), CLIENT_NAME).original);
+    case util::LockResult::Success:
+        return;
+    } // no default case, so the compiler can warn about missing cases
+    assert(false);
+}
+
+BlockDirLock::~BlockDirLock()
+{
+    UnlockDirectory(m_path, ".lock");
+}
+
 BlockManager::BlockManager(const util::SignalInterrupt& interrupt, Options opts)
-    : m_prune_mode{opts.prune_target > 0},
+    : m_lock{BlockDirLock(opts.blocks_dir)},
+      m_prune_mode{opts.prune_target > 0},
       m_xor_key{InitBlocksdirXorKey(opts)},
       m_opts{std::move(opts)},
       m_block_file_seq{FlatFileSeq{m_opts.blocks_dir, "blk", m_opts.fast_prune ? 0x4000 /* 16kB */ : BLOCKFILE_CHUNK_SIZE}},

diff --git a/src/node/blockstorage.h b/src/node/blockstorage.h
@@ -127,6 +127,14 @@ struct BlockfileCursor {
 
 std::ostream& operator<<(std::ostream& os, const BlockfileCursor& cursor);
 
+class BlockDirLock
+{
+    fs::path m_path;
+
+public:
+    explicit BlockDirLock(const fs::path& blocks_dir);
+    ~BlockDirLock();
+};
 
 /**
  * Maintains a tree of blocks (stored in `m_block_index`) which is consulted
@@ -141,6 +149,7 @@ class BlockManager
     friend ChainstateManager;
 
 private:
+    BlockDirLock m_lock;
     const CChainParams& GetParams() const { return m_opts.chainparams; }
     const Consensus::Params& GetConsensus() const { return m_opts.chainparams.GetConsensus(); }
     /**