crucible: add missing template specializations of pwrite helper functions

I got a little too enthusiastic when redacting the code, and removed some
overloaded functions bees was using.  C++ silently found replacements,
and the result was a bug that prevented any data from being persisted
from the hash table.

Fixes: https://github.com/Zygo/bees/issues/7

README.md

@@ -1,31 +1,52 @@
 BEES
 ====
 
-Best-Effort Extent-Same, a btrfs deduplication daemon.
+Best-Effort Extent-Same, a btrfs dedup agent.
 
 About Bees
 ----------
 
-Bees is a daemon designed to run continuously on live file servers.
-Bees consumes entire filesystems and deduplicates in a single pass, using
-minimal RAM to store data.  Bees maintains persistent state so it can be
-interrupted and resumed, whether by planned upgrades or unplanned crashes.
-Bees makes continuous incremental progress instead of using separate
-scan and dedup phases.  Bees uses the Linux kernel's `dedupe_file_range`
-system call to ensure data is handled safely even if other applications
-concurrently modify it.
+Bees is a block-oriented userspace dedup agent designed to avoid
+scalability problems on large filesystems.
 
-Bees is intentionally btrfs-specific for performance and capability.
-Bees uses the btrfs `SEARCH_V2` ioctl to scan for new data 
-without the overhead of repeatedly walking filesystem trees with the
-POSIX API.  Bees uses `LOGICAL_INO` and `INO_PATHS` to leverage btrfs's
-existing metadata instead of building its own redundant data structures.
-Bees can cope with Btrfs filesystem compression.  Bees can reassemble
-Btrfs extents to deduplicate extents that contain a mix of duplicate
-and unique data blocks.
+Bees is designed to degrade gracefully when underprovisioned with RAM.
+Bees does not use more RAM or storage as filesystem data size increases.
+The dedup hash table size is fixed at creation time and does not change.
+The effective dedup block size is dynamic and adjusts automatically to
+fit the hash table into the configured RAM limit.  Hash table overflow
+is not implemented to eliminate the IO overhead of hash table overflow.
+Hash table entries are only 16 bytes per dedup block to keep the average
+dedup block size small.
 
-Bees includes a number of workarounds for Btrfs kernel bugs to (try to)
-avoid ruining your day.  You're welcome.
+Bees does not require alignment between dedup blocks or extent boundaries
+(i.e. it can handle any multiple-of-4K offset between dup block pairs).
+Bees rearranges blocks into shared and unique extents if required to
+work within current btrfs kernel dedup limitations.
+
+Bees can dedup any combination of compressed and uncompressed extents.
+
+Bees operates in a single pass which removes duplicate extents immediately
+during scan.  There are no separate scanning and dedup phases.
+
+Bees uses only data-safe btrfs kernel operations, so it can dedup live
+data (e.g. build servers, sqlite databases, VM disk images).  It does
+not modify file attributes or timestamps.
+
+Bees does not store any information about filesystem structure, so it is
+not affected by the number or size of files (except to the extent that
+these cause performance problems for btrfs in general).  It retrieves such
+information on demand through btrfs SEARCH_V2 and LOGICAL_INO ioctls.
+This eliminates the storage required to maintain the equivalents of
+these functions in userspace.  It's also why bees has no XFS support.
+
+Bees is a daemon designed to run continuously and maintain its state
+across crahes and reboots.  Bees uses checkpoints for persistence to
+eliminate the IO overhead of a transactional data store.  On restart,
+bees will dedup any data that was added to the filesystem since the
+last checkpoint.
+
+Bees is used to dedup filesystems ranging in size from 16GB to 35TB, with
+hash tables ranging in size from 128MB to 11GB.
 
 How Bees Works
 --------------
@@ -37,7 +58,8 @@ using a weighted sampling algorithm.  This allows Bees to adapt itself
 to its filesystem size without forcing admins to do math at install time.
 At the same time, the duplicate block alignment constraint can be as low
 as 4K, allowing efficient deduplication of files with narrowly-aligned
-duplicate block offsets (e.g. compiled binaries and VM/disk images).
+duplicate block offsets (e.g. compiled binaries and VM/disk images)
+even if the effective block size is much larger.
 
 The Bees hash table is loaded into RAM at startup (using hugepages if
 available), mlocked, and synced to persistent storage by trickle-writing
@@ -78,6 +100,12 @@ and some metadata bits).  Each entry represents a minimum of 4K on disk.
         1TB                16MB               1024K
        64TB                 1GB               1024K
 
+It is possible to resize the hash table by changing the size of
+`beeshash.dat` (e.g. with `truncate`) and restarting `bees`.  This
+does not preserve all the existing hash table entries, but it does
+preserve more than zero of them--especially if the old and new sizes
+are a power-of-two multiple of each other.
+
 Things You Might Expect That Bees Doesn't Have
 ----------------------------------------------
 
@@ -113,6 +141,16 @@ this was removed because it made Bees too aggressive to coexist with
 other applications on the same machine.  It also hit the *slow backrefs*
 on N CPU cores instead of just one.
 
+* Block reads are currently more allocation- and CPU-intensive than they
+should be, especially for filesystems on SSD where the IO overhead is
+much smaller.  This is a problem for power-constrained environments
+(e.g. laptops with slow CPU).
+
+* Bees can currently fragment extents when required to remove duplicate
+blocks, but has no defragmentation capability yet.  When possible, Bees
+will attempt to work with existing extent boundaries, but it will not
+aggregate blocks together from multiple extents to create larger ones.
+
 Good Btrfs Feature Interactions
 -------------------------------
 
@@ -175,7 +213,7 @@ Other Caveats
   unallocated space (see `btrfs fi df`) on the filesystem before running
   Bees for the first time.  Use
 
-	btrfs balance start -dusage=100,limit=1 /your/filesystem
+        btrfs balance start -dusage=100,limit=1 /your/filesystem
 
   If possible, raise the `limit` parameter to the current size of metadata
   usage (from `btrfs fi df`) plus 1.
@@ -254,9 +292,10 @@ Not really a bug, but a gotcha nonetheless:
 Requirements
 ------------
 
-* C++11 compiler (tested with GCC 4.9)
+* C++11 compiler (tested with GCC 4.9 and 6.2.0)
 
-  Sorry.  I really like closures.
+  Sorry.  I really like closures and shared_ptr, so support
+  for earlier compiler versions is unlikely.
 
 * btrfs-progs (tested with 4.1..4.7)
 
@@ -295,14 +334,14 @@ Setup
 
 Create a directory for bees state files:
 
-	export BEESHOME=/some/path
-	mkdir -p "$BEESHOME"
+        export BEESHOME=/some/path
+        mkdir -p "$BEESHOME"
 
 Create an empty hash table (your choice of size, but it must be a multiple
 of 16M).  This example creates a 1GB hash table:
 
-	truncate -s 1g "$BEESHOME/beeshash.dat"
-	chmod 700 "$BEESHOME/beeshash.dat"
+        truncate -s 1g "$BEESHOME/beeshash.dat"
+        chmod 700 "$BEESHOME/beeshash.dat"
 
 Configuration
 -------------
@@ -324,11 +363,11 @@ Running
 
 We created this directory in the previous section:
 
-	export BEESHOME=/some/path
+        export BEESHOME=/some/path
 
 Use a tmpfs for BEESSTATUS, it updates once per second:
 
-	export BEESSTATUS=/run/bees.status
+        export BEESSTATUS=/run/bees.status
 
 bees can only process the root subvol of a btrfs (seriously--if the
 argument is not the root subvol directory, Bees will just throw an
@@ -336,20 +375,20 @@ exception and stop).
 
 Use a bind mount, and let only bees access it:
 
-	mount -osubvol=/ /dev/<your-filesystem> /var/lib/bees/root
+        mount -osubvol=/ /dev/<your-filesystem> /var/lib/bees/root
 
 Reduce CPU and IO priority to be kinder to other applications
 sharing this host (or raise them for more aggressive disk space
-recovery).  If you use cgroups, put bees in its own cgroup, then reduce
+recovery).  If you use cgroups, put `bees` in its own cgroup, then reduce
 the `blkio.weight` and `cpu.shares` parameters.  You can also use
-`schedtool` and `ionice in the shell script that launches bees:
+`schedtool` and `ionice` in the shell script that launches `bees`:
 
-	schedtool -D -n20 $$
-	ionice -c3 -p $$
+        schedtool -D -n20 $$
+        ionice -c3 -p $$
 
 Let the bees fly:
 
-	bees /var/lib/bees/root >> /var/log/bees.log 2>&1
+        bees /var/lib/bees/root >> /var/log/bees.log 2>&1
 
 You'll probably want to arrange for /var/log/bees.log to be rotated
 periodically.  You may also want to set umask to 077 to prevent disclosure
@@ -363,7 +402,7 @@ Email bug reports and patches to Zygo Blaxell <bees@furryterror.org>.
 
 You can also use Github:
 
-	https://github.com/Zygo/bees
+        https://github.com/Zygo/bees
 
 
 

include/crucible/cache.h

@@ -8,6 +8,7 @@
 #include <map>
 #include <mutex>
 #include <tuple>
+#include <vector>
 
 namespace crucible {
 	using namespace std;

include/crucible/chatter.h

@@ -86,16 +86,6 @@ namespace crucible {
 		}
 	};
 
-	template <>
-	struct ChatterTraits<ostream &> {
-		Chatter &
-		operator()(Chatter &c, ostream & arg)
-		{
-			c.get_os() << arg;
-			return c;
-		}
-	};
-
 	class ChatterBox {
 		string m_file;
 		int m_line;

include/crucible/fd.h

@@ -120,6 +120,9 @@ namespace crucible {
 	template<> void pread_or_die<string>(int fd, string& str, off_t offset);
 	template<> void pread_or_die<vector<char>>(int fd, vector<char>& str, off_t offset);
 	template<> void pread_or_die<vector<uint8_t>>(int fd, vector<uint8_t>& str, off_t offset);
+	template<> void pwrite_or_die<string>(int fd, const string& str, off_t offset);
+	template<> void pwrite_or_die<vector<char>>(int fd, const vector<char>& str, off_t offset);
+	template<> void pwrite_or_die<vector<uint8_t>>(int fd, const vector<uint8_t>& str, off_t offset);
 
 	// A different approach to reading a simple string
 	string read_string(int fd, size_t size);

include/crucible/fs.h

@@ -171,7 +171,7 @@ namespace crucible {
 	ostream & operator<<(ostream &os, const BtrfsIoctlSearchKey &key);
 
 	string btrfs_search_type_ntoa(unsigned type);
-	string btrfs_search_objectid_ntoa(unsigned objectid);
+	string btrfs_search_objectid_ntoa(uint64_t objectid);
 
 	uint64_t btrfs_get_root_id(int fd);
 	uint64_t btrfs_get_root_transid(int fd);

include/crucible/ntoa.h

@@ -7,12 +7,12 @@ namespace crucible {
 	using namespace std;
 
 	struct bits_ntoa_table {
-		unsigned long n;
-		unsigned long mask;
+		unsigned long long n;
+		unsigned long long mask;
 		const char *a;
 	};
 
-	string bits_ntoa(unsigned long n, const bits_ntoa_table *a);
+	string bits_ntoa(unsigned long long n, const bits_ntoa_table *a);
 
 };
 

include/crucible/timequeue.h

@@ -23,7 +23,7 @@ namespace crucible {
 	private:
 		struct Item {
 			Timestamp m_time;
-			unsigned m_id;
+			unsigned long m_id;
 			Task m_task;
 
 			bool operator<(const Item &that) const {

lib/chatter.cc

@@ -15,7 +15,7 @@
 namespace crucible {
 	using namespace std;
 
-	static auto_ptr<set<string>> chatter_names;
+	static shared_ptr<set<string>> chatter_names;
 	static const char *SPACETAB = " \t";
 
 	static

lib/execpipe.cc

@@ -72,14 +72,10 @@ namespace crucible {
 			catch_all([&]() {
 				parent_fd->close();
 				import_fd_fn(child_fd);
-				// system("ls -l /proc/$$/fd/ >&2");
 
 				rv = f();
 			});
 			_exit(rv);
-			cerr << "PID " << getpid() << " TID " << gettid() << "STILL ALIVE" << endl;
-			system("ls -l /proc/$$/task/ >&2");
-			exit(EXIT_FAILURE);
 		}
 	}
 

lib/fd.cc

@@ -426,6 +426,27 @@ namespace crucible {
 		return pread_or_die(fd, text.data(), text.size(), offset);
 	}
 
+	template<>
+	void
+	pwrite_or_die<vector<uint8_t>>(int fd, const vector<uint8_t> &text, off_t offset)
+	{
+		return pwrite_or_die(fd, text.data(), text.size(), offset);
+	}
+
+	template<>
+	void
+	pwrite_or_die<vector<char>>(int fd, const vector<char> &text, off_t offset)
+	{
+		return pwrite_or_die(fd, text.data(), text.size(), offset);
+	}
+
+	template<>
+	void
+	pwrite_or_die<string>(int fd, const string &text, off_t offset)
+	{
+		return pwrite_or_die(fd, text.data(), text.size(), offset);
+	}
+
 	Stat::Stat()
 	{
 		memset_zero<stat>(this);

lib/fs.cc

@@ -834,7 +834,7 @@ namespace crucible {
 	}
 
 	string
-	btrfs_search_objectid_ntoa(unsigned objectid)
+	btrfs_search_objectid_ntoa(uint64_t objectid)
 	{
 		static const bits_ntoa_table table[] = {
 			NTOA_TABLE_ENTRY_ENUM(BTRFS_ROOT_TREE_OBJECTID),

lib/ntoa.cc

@@ -7,7 +7,7 @@
 namespace crucible {
 	using namespace std;
 
-	string bits_ntoa(unsigned long n, const bits_ntoa_table *table)
+	string bits_ntoa(unsigned long long n, const bits_ntoa_table *table)
 	{
 		string out;
 		while (n && table->a) {

src/bees-context.cc

@@ -5,6 +5,7 @@
 
 #include <fstream>
 #include <iostream>
+#include <vector>
 
 using namespace crucible;
 using namespace std;

src/bees-roots.cc

@@ -50,9 +50,18 @@ string
 BeesRoots::crawl_state_filename() const
 {
 	string rv;
+
+	// Legacy filename included UUID
 	rv += "beescrawl.";
 	rv += m_ctx->root_uuid();
 	rv += ".dat";
+
+	struct stat buf;
+	if (fstatat(m_ctx->home_fd(), rv.c_str(), &buf, AT_SYMLINK_NOFOLLOW)) {
+		// Use new filename
+		rv = "beescrawl.dat";
+	}
+
 	return rv;
 }
 
@@ -101,6 +110,12 @@ BeesRoots::state_save()
 
 	m_crawl_state_file.write(ofs.str());
 
+	// Renaming things is hard after release
+	if (m_crawl_state_file.name() != "beescrawl.dat") {
+		renameat(m_ctx->home_fd(), m_crawl_state_file.name().c_str(), m_ctx->home_fd(), "beescrawl.dat");
+		m_crawl_state_file.name("beescrawl.dat");
+	}
+
 	BEESNOTE("relocking crawl state");
 	lock.lock();
 	// Not really correct but probably close enough

src/bees.cc

@@ -351,6 +351,18 @@ BeesStringFile::BeesStringFile(Fd dir_fd, string name, size_t limit) :
 	BEESLOG("BeesStringFile " << name_fd(m_dir_fd) << "/" << m_name << " max size " << pretty(m_limit));
 }
 
+void
+BeesStringFile::name(const string &new_name)
+{
+	m_name = new_name;
+}
+
+string
+BeesStringFile::name() const
+{
+	return m_name;
+}
+
 string
 BeesStringFile::read()
 {

src/bees.h

@@ -374,6 +374,8 @@ public:
 	BeesStringFile(Fd dir_fd, string name, size_t limit = 1024 * 1024);
 	string read();
 	void write(string contents);
+	void name(const string &new_name);
+	string name() const;
 };
 
 class BeesHashTable {

test/limits.cc

@@ -126,7 +126,13 @@ test_cast_0x80000000_to_things()
 {
 	auto sv = 0x80000000LL;
 	auto uv = 0x80000000ULL;
-	SHOULD_PASS(ranged_cast<off_t>(sv), sv);
+	if (sizeof(off_t) == 4) {
+		SHOULD_FAIL(ranged_cast<off_t>(sv));
+	} else if (sizeof(off_t) == 8) {
+		SHOULD_PASS(ranged_cast<off_t>(sv), sv);
+	} else {
+		assert(!"unhandled case, please add code for off_t here");
+	}
 	SHOULD_PASS(ranged_cast<uint64_t>(uv), uv);
 	SHOULD_PASS(ranged_cast<uint32_t>(uv), uv);
 	SHOULD_FAIL(ranged_cast<uint16_t>(uv));
@@ -141,7 +147,13 @@ test_cast_0x80000000_to_things()
 	SHOULD_FAIL(ranged_cast<unsigned short>(uv));
 	SHOULD_FAIL(ranged_cast<unsigned char>(uv));
 	SHOULD_PASS(ranged_cast<signed long long>(sv), sv);
-	SHOULD_PASS(ranged_cast<signed long>(sv), sv);
+	if (sizeof(long) == 4) {
+		SHOULD_FAIL(ranged_cast<signed long>(sv));
+	} else if (sizeof(long) == 8) {
+		SHOULD_PASS(ranged_cast<signed long>(sv), sv);
+	} else {
+		assert(!"unhandled case, please add code for long here");
+	}
 	SHOULD_FAIL(ranged_cast<signed short>(sv));
 	SHOULD_FAIL(ranged_cast<signed char>(sv));
 	if (sizeof(int) == 4) {
@@ -149,7 +161,7 @@ test_cast_0x80000000_to_things()
 	} else if (sizeof(int) == 8) {
 		SHOULD_PASS(ranged_cast<signed int>(sv), sv);
 	} else {
-		assert(!"unhandled case, please add code here");
+		assert(!"unhandled case, please add code for int here");
 	}
 }
 
@@ -159,7 +171,13 @@ test_cast_0xffffffff_to_things()
 {
 	auto sv = 0xffffffffLL;
 	auto uv = 0xffffffffULL;
-	SHOULD_PASS(ranged_cast<off_t>(sv), sv);
+	if (sizeof(off_t) == 4) {
+		SHOULD_FAIL(ranged_cast<off_t>(sv));
+	} else if (sizeof(off_t) == 8) {
+		SHOULD_PASS(ranged_cast<off_t>(sv), sv);
+	} else {
+		assert(!"unhandled case, please add code for off_t here");
+	}
 	SHOULD_PASS(ranged_cast<uint64_t>(uv), uv);
 	SHOULD_PASS(ranged_cast<uint32_t>(uv), uv);
 	SHOULD_FAIL(ranged_cast<uint16_t>(uv));
@@ -174,7 +192,13 @@ test_cast_0xffffffff_to_things()
 	SHOULD_FAIL(ranged_cast<unsigned short>(uv));
 	SHOULD_FAIL(ranged_cast<unsigned char>(uv));
 	SHOULD_PASS(ranged_cast<signed long long>(sv), sv);
-	SHOULD_PASS(ranged_cast<signed long>(sv), sv);
+	if (sizeof(long) == 4) {
+		SHOULD_FAIL(ranged_cast<signed long>(sv));
+	} else if (sizeof(long) == 8) {
+		SHOULD_PASS(ranged_cast<signed long>(sv), sv);
+	} else {
+		assert(!"unhandled case, please add code for long here");
+	}
 	SHOULD_FAIL(ranged_cast<signed short>(sv));
 	SHOULD_FAIL(ranged_cast<signed char>(sv));
 	if (sizeof(int) == 4) {
@@ -182,7 +206,7 @@ test_cast_0xffffffff_to_things()
 	} else if (sizeof(int) == 8) {
 		SHOULD_PASS(ranged_cast<signed int>(sv), sv);
 	} else {
-		assert(!"unhandled case, please add code here");
+		assert(!"unhandled case, please add code for int here");
 	}
 }
 
@@ -192,7 +216,13 @@ test_cast_0xfffffffff_to_things()
 {
 	auto sv = 0xfffffffffLL;
 	auto uv = 0xfffffffffULL;
-	SHOULD_PASS(ranged_cast<off_t>(sv), sv);
+	if (sizeof(off_t) == 4) {
+		SHOULD_FAIL(ranged_cast<off_t>(sv));
+	} else if (sizeof(off_t) == 8) {
+		SHOULD_PASS(ranged_cast<off_t>(sv), sv);
+	} else {
+		assert(!"unhandled case, please add code for off_t here");
+	}
 	SHOULD_PASS(ranged_cast<uint64_t>(uv), uv);
 	SHOULD_FAIL(ranged_cast<uint32_t>(uv));
 	SHOULD_FAIL(ranged_cast<uint16_t>(uv));