From 33a4e7173f4a71d5739a608193175184984e9da7 Mon Sep 17 00:00:00 2001 From: Thomas Munro Date: Mon, 1 Mar 2021 17:14:11 +1300 Subject: [PATCH v7] Fix DROP {DATABASE,TABLESPACE} on Windows. Previously, it was possible for DROP DATABASE and DROP TABLESPACE to fail because other backends still had open file handles. Windows won't allow a directory containing unlinked-but-still-open files to be unlinked. Tackle this problem by forcing all backends to close all fds at appropriate times. No change for Unix systems, which didn't suffer from the problem, but simulate the need to do it in assertion builds just to exercise the code. Reviewed-by: Andres Freund Reviewed-by: Daniel Gustafsson Discussion: https://postgr.es/m/CA+hUKGLdemy2gBm80kz20GTe6hNVwoErE8KwcJk6-U56oStjtg@mail.gmail.com --- src/backend/commands/dbcommands.c | 19 +++++++++++++++--- src/backend/commands/tablespace.c | 29 +++++++++++++++++++++------- src/backend/storage/ipc/procsignal.c | 24 +++-------------------- src/backend/storage/smgr/md.c | 6 ++++++ src/backend/storage/smgr/smgr.c | 18 +++++++++++++++++ src/include/storage/md.h | 1 + src/include/storage/procsignal.h | 7 +------ src/include/storage/smgr.h | 1 + 8 files changed, 68 insertions(+), 37 deletions(-) diff --git a/src/backend/commands/dbcommands.c b/src/backend/commands/dbcommands.c index 2b159b60eb..d533558fa3 100644 --- a/src/backend/commands/dbcommands.c +++ b/src/backend/commands/dbcommands.c @@ -985,12 +985,15 @@ dropdb(const char *dbname, bool missing_ok, bool force) /* * Force a checkpoint to make sure the checkpointer has received the - * message sent by ForgetDatabaseSyncRequests. On Windows, this also - * ensures that background procs don't hold any open files, which would - * cause rmdir() to fail. + * message sent by ForgetDatabaseSyncRequests. */ RequestCheckpoint(CHECKPOINT_IMMEDIATE | CHECKPOINT_FORCE | CHECKPOINT_WAIT); +#if defined(WIN32) || defined(USE_ASSERT_CHECKING) + /* Close all fds in other Windows processes. */ + WaitForProcSignalBarrier(EmitProcSignalBarrier(PROCSIGNAL_BARRIER_SMGRRELEASE)); +#endif + /* * Remove all tablespace subdirs belonging to the database. */ @@ -1239,6 +1242,11 @@ movedb(const char *dbname, const char *tblspcname) RequestCheckpoint(CHECKPOINT_IMMEDIATE | CHECKPOINT_FORCE | CHECKPOINT_WAIT | CHECKPOINT_FLUSH_ALL); +#if defined(WIN32) || defined(USE_ASSERT_CHECKING) + /* Close all fds in other Windows processes. */ + WaitForProcSignalBarrier(EmitProcSignalBarrier(PROCSIGNAL_BARRIER_SMGRRELEASE)); +#endif + /* * Now drop all buffers holding data of the target database; they should * no longer be dirty so DropDatabaseBuffers is safe. @@ -2251,6 +2259,11 @@ dbase_redo(XLogReaderState *record) /* Clean out the xlog relcache too */ XLogDropDatabase(xlrec->db_id); +#if defined(WIN32) || defined(USE_ASSERT_CHECKING) + /* Close all fds in other Windows processes. */ + WaitForProcSignalBarrier(EmitProcSignalBarrier(PROCSIGNAL_BARRIER_SMGRRELEASE)); +#endif + for (i = 0; i < xlrec->ntablespaces; i++) { dst_path = GetDatabasePath(xlrec->db_id, xlrec->tablespace_ids[i]); diff --git a/src/backend/commands/tablespace.c b/src/backend/commands/tablespace.c index 69ea155d50..2ce8966af0 100644 --- a/src/backend/commands/tablespace.c +++ b/src/backend/commands/tablespace.c @@ -520,15 +520,25 @@ DropTableSpace(DropTableSpaceStmt *stmt) * but we can't tell them apart from important data files that we * mustn't delete. So instead, we force a checkpoint which will clean * out any lingering files, and try again. - * - * XXX On Windows, an unlinked file persists in the directory listing - * until no process retains an open handle for the file. The DDL - * commands that schedule files for unlink send invalidation messages - * directing other PostgreSQL processes to close the files. DROP - * TABLESPACE should not give up on the tablespace becoming empty - * until all relevant invalidation processing is complete. */ RequestCheckpoint(CHECKPOINT_IMMEDIATE | CHECKPOINT_FORCE | CHECKPOINT_WAIT); + /* + * On Windows, an unlinked file persists in the directory listing until + * no process retains an open handle for the file. The DDL + * commands that schedule files for unlink send invalidation messages + * directing other PostgreSQL processes to close the files, but nothing + * guarantees they'll be processed in time. So, we'll also use a + * global barrier to ask all backends to close all files, and wait + * until they're finished. + * + * For test coverage, also do this on Unix systems in assert builds. + */ +#if defined(WIN32) || defined(USE_ASSERT_CHECKING) + LWLockRelease(TablespaceCreateLock); + WaitForProcSignalBarrier(EmitProcSignalBarrier(PROCSIGNAL_BARRIER_SMGRRELEASE)); + LWLockAcquire(TablespaceCreateLock, LW_EXCLUSIVE); +#endif + /* And now try again. */ if (!destroy_tablespace_directories(tablespaceoid, false)) { /* Still not empty, the files must be important then */ @@ -1550,6 +1560,11 @@ tblspc_redo(XLogReaderState *record) */ if (!destroy_tablespace_directories(xlrec->ts_id, true)) { +#if defined(WIN32) || defined(USE_ASSERT_CHECKING) + /* Close fds in other Windows processes. */ + WaitForProcSignalBarrier(EmitProcSignalBarrier(PROCSIGNAL_BARRIER_SMGRRELEASE)); +#endif + ResolveRecoveryConflictWithTablespace(xlrec->ts_id); /* diff --git a/src/backend/storage/ipc/procsignal.c b/src/backend/storage/ipc/procsignal.c index c6a8d4611e..dd27f1bb8f 100644 --- a/src/backend/storage/ipc/procsignal.c +++ b/src/backend/storage/ipc/procsignal.c @@ -28,6 +28,7 @@ #include "storage/latch.h" #include "storage/proc.h" #include "storage/shmem.h" +#include "storage/smgr.h" #include "storage/sinval.h" #include "tcop/tcopprot.h" @@ -100,7 +101,6 @@ static ProcSignalSlot *MyProcSignalSlot = NULL; static bool CheckProcSignal(ProcSignalReason reason); static void CleanupProcSignalState(int status, Datum arg); static void ResetProcSignalBarrierBits(uint32 flags); -static bool ProcessBarrierPlaceholder(void); /* * ProcSignalShmemSize @@ -526,8 +526,8 @@ ProcessProcSignalBarrier(void) type = (ProcSignalBarrierType) pg_rightmost_one_pos32(flags); switch (type) { - case PROCSIGNAL_BARRIER_PLACEHOLDER: - processed = ProcessBarrierPlaceholder(); + case PROCSIGNAL_BARRIER_SMGRRELEASE: + processed = ProcessBarrierSmgrRelease(); break; } @@ -593,24 +593,6 @@ ResetProcSignalBarrierBits(uint32 flags) InterruptPending = true; } -static bool -ProcessBarrierPlaceholder(void) -{ - /* - * XXX. This is just a placeholder until the first real user of this - * machinery gets committed. Rename PROCSIGNAL_BARRIER_PLACEHOLDER to - * PROCSIGNAL_BARRIER_SOMETHING_ELSE where SOMETHING_ELSE is something - * appropriately descriptive. Get rid of this function and instead have - * ProcessBarrierSomethingElse. Most likely, that function should live in - * the file pertaining to that subsystem, rather than here. - * - * The return value should be 'true' if the barrier was successfully - * absorbed and 'false' if not. Note that returning 'false' can lead to - * very frequent retries, so try hard to make that an uncommon case. - */ - return true; -} - /* * CheckProcSignal - check to see if a particular reason has been * signaled, and clear the signal flag. Should be called after receiving diff --git a/src/backend/storage/smgr/md.c b/src/backend/storage/smgr/md.c index 1e12cfad8e..1b751205b1 100644 --- a/src/backend/storage/smgr/md.c +++ b/src/backend/storage/smgr/md.c @@ -548,6 +548,12 @@ mdclose(SMgrRelation reln, ForkNumber forknum) } } +void +mdrelease(void) +{ + closeAllVfds(); +} + /* * mdprefetch() -- Initiate asynchronous read of the specified block of a relation */ diff --git a/src/backend/storage/smgr/smgr.c b/src/backend/storage/smgr/smgr.c index 4dc24649df..91cf3cef48 100644 --- a/src/backend/storage/smgr/smgr.c +++ b/src/backend/storage/smgr/smgr.c @@ -41,6 +41,7 @@ typedef struct f_smgr { void (*smgr_init) (void); /* may be NULL */ void (*smgr_shutdown) (void); /* may be NULL */ + void (*smgr_release) (void); /* may be NULL */ void (*smgr_open) (SMgrRelation reln); void (*smgr_close) (SMgrRelation reln, ForkNumber forknum); void (*smgr_create) (SMgrRelation reln, ForkNumber forknum, @@ -69,6 +70,7 @@ static const f_smgr smgrsw[] = { { .smgr_init = mdinit, .smgr_shutdown = NULL, + .smgr_release = mdrelease, .smgr_open = mdopen, .smgr_close = mdclose, .smgr_create = mdcreate, @@ -693,3 +695,19 @@ AtEOXact_SMgr(void) smgrclose(rel); } } + +/* + * This routine is called when we are ordered to release all open files by a + * ProcSignalBarrier. + */ +bool +ProcessBarrierSmgrRelease(void) +{ + for (int i = 0; i < NSmgr; i++) + { + if (smgrsw[i].smgr_release) + smgrsw[i].smgr_release(); + } + + return true; +} diff --git a/src/include/storage/md.h b/src/include/storage/md.h index 752b440864..7685367b97 100644 --- a/src/include/storage/md.h +++ b/src/include/storage/md.h @@ -23,6 +23,7 @@ extern void mdinit(void); extern void mdopen(SMgrRelation reln); extern void mdclose(SMgrRelation reln, ForkNumber forknum); +extern void mdrelease(void); extern void mdcreate(SMgrRelation reln, ForkNumber forknum, bool isRedo); extern bool mdexists(SMgrRelation reln, ForkNumber forknum); extern void mdunlink(RelFileNodeBackend rnode, ForkNumber forknum, bool isRedo); diff --git a/src/include/storage/procsignal.h b/src/include/storage/procsignal.h index 4ae7dc33b8..aaaa8ed07c 100644 --- a/src/include/storage/procsignal.h +++ b/src/include/storage/procsignal.h @@ -48,12 +48,7 @@ typedef enum typedef enum { - /* - * XXX. PROCSIGNAL_BARRIER_PLACEHOLDER should be replaced when the first - * real user of the ProcSignalBarrier mechanism is added. It's just here - * for now because we can't have an empty enum. - */ - PROCSIGNAL_BARRIER_PLACEHOLDER = 0 + PROCSIGNAL_BARRIER_SMGRRELEASE /* ask smgr to close files */ } ProcSignalBarrierType; /* diff --git a/src/include/storage/smgr.h b/src/include/storage/smgr.h index a6fbf7b6a6..8da5139b03 100644 --- a/src/include/storage/smgr.h +++ b/src/include/storage/smgr.h @@ -104,5 +104,6 @@ extern void smgrtruncate(SMgrRelation reln, ForkNumber *forknum, int nforks, BlockNumber *nblocks); extern void smgrimmedsync(SMgrRelation reln, ForkNumber forknum); extern void AtEOXact_SMgr(void); +extern bool ProcessBarrierSmgrRelease(void); #endif /* SMGR_H */ -- 2.30.1