PG-1444 Move relation key deleteion to smgr_unlink()

Replaces the old way we deleted keys which was built for tde_heap_basic
with deleting the the relation key when smgr_unlink() is called on the
main fork. This function is always called after commit/abort when a
relation deletion has been registered, even if no main fork would exist.

This approach means we do not need to WAL log any event for deleting
relation keys, the normal SMGR unlink also handles that which fits well
into the current approach of doing most of the encryption at the SMGR
layer.

Author: jeltz

contrib/pg_tde/Makefile

@@ -33,7 +33,6 @@ src/encryption/enc_aes.o \
 src/access/pg_tde_tdemap.o \
 src/access/pg_tde_xlog.o \
 src/access/pg_tde_xlog_encrypt.o \
-src/transam/pg_tde_xact_handler.o \
 src/keyring/keyring_curl.o \
 src/keyring/keyring_file.o \
 src/keyring/keyring_vault.o \

contrib/pg_tde/meson.build

@@ -21,7 +21,6 @@ pg_tde_sources = files(
   'src/pg_tde_event_capture.c',
   'src/pg_tde_guc.c',
   'src/smgr/pg_tde_smgr.c',
-  'src/transam/pg_tde_xact_handler.c',
 )
 
 tde_frontend_sources = files(

contrib/pg_tde/src/access/pg_tde_tdemap.c

@@ -13,7 +13,6 @@
 #include "postgres.h"
 #include "access/pg_tde_tdemap.h"
 #include "common/file_perm.h"
-#include "transam/pg_tde_xact_handler.h"
 #include "storage/fd.h"
 #include "utils/wait_event.h"
 #include "utils/memutils.h"
@@ -129,7 +128,6 @@ static int	pg_tde_file_header_write(const char *tde_filename, int fd, const TDES
 static void pg_tde_sign_principal_key_info(TDESignedPrincipalKeyInfo *signed_key_info, const TDEPrincipalKey *principal_key);
 static off_t pg_tde_write_one_map_entry(int fd, const TDEMapEntry *map_entry, off_t *offset, const char *db_map_path);
 static void pg_tde_write_key_map_entry(const RelFileLocator *rlocator, InternalKey *rel_key_data, TDEPrincipalKey *principal_key, bool write_xlog);
-static bool pg_tde_delete_map_entry(const RelFileLocator *rlocator, char *db_map_path, off_t offset);
 static int	keyrotation_init_file(const TDESignedPrincipalKeyInfo *signed_key_info, char *rotated_filename, const char *filename, off_t *curr_pos);
 static void finalize_key_rotation(const char *path_old, const char *path_new);
 static int	pg_tde_open_file_write(const char *tde_filename, const TDESignedPrincipalKeyInfo *signed_key_info, bool truncate, off_t *curr_pos);
@@ -486,9 +484,6 @@ pg_tde_write_key_map_entry(const RelFileLocator *rlocator, InternalKey *rel_key_
 
 	/* Let's close the file. */
 	close(map_fd);
-
-	/* Register the entry to be freed in case the transaction aborts */
-	RegisterEntryForDeletion(rlocator, curr_pos, false);
 }
 
 /*
@@ -548,51 +543,40 @@ pg_tde_write_key_map_entry_redo(const TDEMapEntry *write_map_entry, TDESignedPri
 	LWLockRelease(tde_lwlock_enc_keys());
 }
 
-static bool
-pg_tde_delete_map_entry(const RelFileLocator *rlocator, char *db_map_path, off_t offset)
+/*
+ * Mark relation map entry as free and overwrite the key
+ *
+ * This fucntion is called by the pg_tde SMGR when storage is unlinked on
+ * transaction commit/abort.
+ */
+void
+pg_tde_free_key_map_entry(const RelFileLocator *rlocator)
 {
+	char		db_map_path[MAXPGPATH];
 	File		map_fd;
-	bool		found = false;
 	off_t		curr_pos = 0;
 
-	/* Open and validate file for basic correctness. */
-	map_fd = pg_tde_open_file_write(db_map_path, NULL, false, &curr_pos);
+	Assert(rlocator);
 
-	/*
-	 * If we need to delete an entry, we expect an offset value to the start
-	 * of the entry to speed up the operation. Otherwise, we'd be sequentially
-	 * scanning the entire map file.
-	 */
-	if (offset > 0)
-	{
-		curr_pos = lseek(map_fd, offset, SEEK_SET);
+	pg_tde_set_db_file_path(rlocator->dbOid, db_map_path);
 
-		if (curr_pos == -1)
-		{
-			ereport(ERROR,
-					errcode_for_file_access(),
-					errmsg("could not seek in tde map file \"%s\": %m",
-						   db_map_path));
-		}
-	}
+	LWLockAcquire(tde_lwlock_enc_keys(), LW_EXCLUSIVE);
+
+	/* Open and validate file for basic correctness. */
+	map_fd = pg_tde_open_file_write(db_map_path, NULL, false, &curr_pos);
 
-	/*
-	 * Read until we find an empty slot. Otherwise, read until end. This seems
-	 * to be less frequent than vacuum. So let's keep this function here
-	 * rather than overloading the vacuum process.
-	 */
 	while (1)
 	{
 		TDEMapEntry read_map_entry;
 		off_t		prev_pos = curr_pos;
+		bool		found;
 
 		found = pg_tde_read_one_map_entry(map_fd, rlocator, MAP_ENTRY_VALID, &read_map_entry, &curr_pos);
 
 		/* We've reached EOF */
 		if (curr_pos == prev_pos)
 			break;
 
-		/* We found a valid entry for the relation */
 		if (found)
 		{
 			TDEMapEntry empty_map_entry = {
@@ -607,52 +591,9 @@ pg_tde_delete_map_entry(const RelFileLocator *rlocator, char *db_map_path, off_t
 		}
 	}
 
-	/* Let's close the file. */
 	close(map_fd);
 
-	/* Return -1 indicating that no entry was removed */
-	return found;
-}
-
-/*
- * Called when transaction is being completed; either committed or aborted.
- * By default, when a transaction creates an entry, we mark it as MAP_ENTRY_VALID.
- * Only during the abort phase of the transaction that we are proceed on with
- * marking the entry as MAP_ENTRY_FREE. This optimistic strategy that assumes
- * that transaction will commit more often then getting aborted avoids
- * unnecessary locking.
- *
- * The offset allows us to simply seek to the desired location and mark the entry
- * as MAP_ENTRY_FREE without needing any further processing.
- */
-void
-pg_tde_free_key_map_entry(const RelFileLocator *rlocator, off_t offset)
-{
-	bool		found;
-	char		db_map_path[MAXPGPATH] = {0};
-
-	Assert(rlocator);
-
-	/* Get the file paths */
-	pg_tde_set_db_file_path(rlocator->dbOid, db_map_path);
-
-	LWLockAcquire(tde_lwlock_enc_keys(), LW_EXCLUSIVE);
-
-	/* Remove the map entry if found */
-	found = pg_tde_delete_map_entry(rlocator, db_map_path, offset);
-
 	LWLockRelease(tde_lwlock_enc_keys());
-
-	if (!found)
-	{
-		ereport(WARNING,
-				errcode(ERRCODE_NO_DATA_FOUND),
-				errmsg("could not find the required map entry for deletion of relation %d in tablespace %d in tde map file \"%s\": %m",
-					   rlocator->relNumber,
-					   rlocator->spcOid,
-					   db_map_path));
-
-	}
 }
 
 /*

contrib/pg_tde/src/include/access/pg_tde_tdemap.h

@@ -101,7 +101,7 @@ extern void pg_tde_wal_last_key_set_lsn(XLogRecPtr lsn, const char *keyfile_path
 
 extern InternalKey *pg_tde_create_smgr_key(const RelFileLocatorBackend *newrlocator);
 extern void pg_tde_create_wal_key(InternalKey *rel_key_data, const RelFileLocator *newrlocator, uint32 flags);
-extern void pg_tde_free_key_map_entry(const RelFileLocator *rlocator, off_t offset);
+extern void pg_tde_free_key_map_entry(const RelFileLocator *rlocator);
 extern void pg_tde_write_key_map_entry_redo(const TDEMapEntry *write_map_entry, TDESignedPrincipalKeyInfo *signed_key_info);
 
 #define PG_TDE_MAP_FILENAME			"pg_tde_%d_map"

contrib/pg_tde/src/include/transam/pg_tde_xact_handler.h

@@ -13,7 +13,6 @@
 #include "postgres.h"
 #include "funcapi.h"
 #include "pg_tde.h"
-#include "transam/pg_tde_xact_handler.h"
 #include "miscadmin.h"
 #include "storage/ipc.h"
 #include "storage/lwlock.h"
@@ -121,7 +120,6 @@ _PG_init(void)
 	prev_shmem_startup_hook = shmem_startup_hook;
 	shmem_startup_hook = tde_shmem_startup;
 
-	RegisterTdeXactCallbacks();
 	InstallFileKeyring();
 	InstallVaultV2Keyring();
 	InstallKmipKeyring();

contrib/pg_tde/src/pg_tde.c

@@ -115,6 +115,28 @@ tde_mdwritev(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
 	}
 }
 
+static void
+tde_mdunlink(RelFileLocatorBackend rlocator, ForkNumber forknum, bool isRedo)
+{
+	mdunlink(rlocator, forknum, isRedo);
+
+	/*
+	 * As of PostgreSQL 17 we are only ever called once for all forks, no
+	 * matter if they exist or not, from smgrdounlinkall() so deleting the
+	 * relation key on attempting to delete the init fork is safe.
+	 * Additionally since we unlink the files after commit/abort we do not
+	 * need to care about current accesses.
+	 *
+	 * We support InvalidForkNumber to be similar to mdunlink() but it can
+	 * actually never happen.
+	 */
+	if (forknum == INIT_FORKNUM || forknum == InvalidForkNumber)
+	{
+		if (!RelFileLocatorBackendIsTemp(rlocator) && GetSMGRRelationKey(rlocator))
+			pg_tde_free_key_map_entry(&rlocator.locator);
+	}
+}
+
 static void
 tde_mdextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum,
 			 const void *buffer, bool skipFsync)
@@ -274,7 +296,7 @@ static const struct f_smgr tde_smgr = {
 	.smgr_close = mdclose,
 	.smgr_create = tde_mdcreate,
 	.smgr_exists = mdexists,
-	.smgr_unlink = mdunlink,
+	.smgr_unlink = tde_mdunlink,
 	.smgr_extend = tde_mdextend,
 	.smgr_zeroextend = mdzeroextend,
 	.smgr_prefetch = mdprefetch,