fd.c

PostgreSQL7.4.6 for Linux

{
	Assert(FileIsValid(file));

	DO_DB(elog(LOG, "FileUnlink: %d (%s)",
			   file, VfdCache[file].fileName));

	/* force FileClose to delete it */
	VfdCache[file].fdstate |= FD_TEMPORARY;

	FileClose(file);
}

int
FileRead(File file, char *buffer, int amount)
{
	int			returnCode;

	Assert(FileIsValid(file));

	DO_DB(elog(LOG, "FileRead: %d (%s) %ld %d %p",
			   file, VfdCache[file].fileName,
			   VfdCache[file].seekPos, amount, buffer));

	FileAccess(file);
	returnCode = read(VfdCache[file].fd, buffer, amount);
	if (returnCode > 0)
		VfdCache[file].seekPos += returnCode;
	else
		VfdCache[file].seekPos = FileUnknownPos;

	return returnCode;
}

int
FileWrite(File file, char *buffer, int amount)
{
	int			returnCode;

	Assert(FileIsValid(file));

	DO_DB(elog(LOG, "FileWrite: %d (%s) %ld %d %p",
			   file, VfdCache[file].fileName,
			   VfdCache[file].seekPos, amount, buffer));

	FileAccess(file);

	errno = 0;
	returnCode = write(VfdCache[file].fd, buffer, amount);

	/* if write didn't set errno, assume problem is no disk space */
	if (returnCode != amount && errno == 0)
		errno = ENOSPC;

	if (returnCode > 0)
		VfdCache[file].seekPos += returnCode;
	else
		VfdCache[file].seekPos = FileUnknownPos;

	return returnCode;
}

long
FileSeek(File file, long offset, int whence)
{
	Assert(FileIsValid(file));

	DO_DB(elog(LOG, "FileSeek: %d (%s) %ld %ld %d",
			   file, VfdCache[file].fileName,
			   VfdCache[file].seekPos, offset, whence));

	if (FileIsNotOpen(file))
	{
		switch (whence)
		{
			case SEEK_SET:
				if (offset < 0)
					elog(ERROR, "invalid seek offset: %ld", offset);
				VfdCache[file].seekPos = offset;
				break;
			case SEEK_CUR:
				VfdCache[file].seekPos += offset;
				break;
			case SEEK_END:
				FileAccess(file);
				VfdCache[file].seekPos = lseek(VfdCache[file].fd, offset, whence);
				break;
			default:
				elog(ERROR, "invalid whence: %d", whence);
				break;
		}
	}
	else
	{
		switch (whence)
		{
			case SEEK_SET:
				if (offset < 0)
					elog(ERROR, "invalid seek offset: %ld", offset);
				if (VfdCache[file].seekPos != offset)
					VfdCache[file].seekPos = lseek(VfdCache[file].fd, offset, whence);
				break;
			case SEEK_CUR:
				if (offset != 0 || VfdCache[file].seekPos == FileUnknownPos)
					VfdCache[file].seekPos = lseek(VfdCache[file].fd, offset, whence);
				break;
			case SEEK_END:
				VfdCache[file].seekPos = lseek(VfdCache[file].fd, offset, whence);
				break;
			default:
				elog(ERROR, "invalid whence: %d", whence);
				break;
		}
	}
	return VfdCache[file].seekPos;
}

/*
 * XXX not actually used but here for completeness
 */
#ifdef NOT_USED
long
FileTell(File file)
{
	Assert(FileIsValid(file));
	DO_DB(elog(LOG, "FileTell %d (%s)",
			   file, VfdCache[file].fileName));
	return VfdCache[file].seekPos;
}
#endif

int
FileTruncate(File file, long offset)
{
	int			returnCode;

	Assert(FileIsValid(file));

	DO_DB(elog(LOG, "FileTruncate %d (%s)",
			   file, VfdCache[file].fileName));

	FileAccess(file);
	returnCode = ftruncate(VfdCache[file].fd, (size_t) offset);
	return returnCode;
}


/*
 * Routines that want to use stdio (ie, FILE*) should use AllocateFile
 * rather than plain fopen().  This lets fd.c deal with freeing FDs if
 * necessary to open the file.	When done, call FreeFile rather than fclose.
 *
 * Note that files that will be open for any significant length of time
 * should NOT be handled this way, since they cannot share kernel file
 * descriptors with other files; there is grave risk of running out of FDs
 * if anyone locks down too many FDs.  Most callers of this routine are
 * simply reading a config file that they will read and close immediately.
 *
 * fd.c will automatically close all files opened with AllocateFile at
 * transaction commit or abort; this prevents FD leakage if a routine
 * that calls AllocateFile is terminated prematurely by ereport(ERROR).
 *
 * Ideally this should be the *only* direct call of fopen() in the backend.
 */
FILE *
AllocateFile(char *name, char *mode)
{
	FILE	   *file;

	DO_DB(elog(LOG, "AllocateFile: Allocated %d", numAllocatedFiles));

	/*
	 * The test against MAX_ALLOCATED_FILES prevents us from overflowing
	 * allocatedFiles[]; the test against max_safe_fds prevents AllocateFile
	 * from hogging every one of the available FDs, which'd lead to infinite
	 * looping.
	 */
	if (numAllocatedFiles >= MAX_ALLOCATED_FILES ||
		numAllocatedFiles + numAllocatedDirs >= max_safe_fds - 1)
		elog(ERROR, "too many private files demanded");

TryAgain:
	if ((file = fopen(name, mode)) != NULL)
	{
		allocatedFiles[numAllocatedFiles] = file;
		numAllocatedFiles++;
		return file;
	}

	if (errno == EMFILE || errno == ENFILE)
	{
		int			save_errno = errno;

		ereport(LOG,
				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
			  errmsg("out of file descriptors: %m; release and retry")));
		errno = 0;
		if (ReleaseLruFile())
			goto TryAgain;
		errno = save_errno;
	}

	return NULL;
}

void
FreeFile(FILE *file)
{
	int			i;

	DO_DB(elog(LOG, "FreeFile: Allocated %d", numAllocatedFiles));

	/* Remove file from list of allocated files, if it's present */
	for (i = numAllocatedFiles; --i >= 0;)
	{
		if (allocatedFiles[i] == file)
		{
			numAllocatedFiles--;
			allocatedFiles[i] = allocatedFiles[numAllocatedFiles];
			break;
		}
	}
	if (i < 0)
		elog(WARNING, "file passed to FreeFile was not obtained from AllocateFile");

	fclose(file);
}


/*
 * Routines that want to use <dirent.h> (ie, DIR*) should use AllocateDir
 * rather than plain opendir().  This lets fd.c deal with freeing FDs if
 * necessary to open the directory, and with closing it after an elog.
 * When done, call FreeDir rather than closedir.
 *
 * Ideally this should be the *only* direct call of opendir() in the backend.
 */
DIR *
AllocateDir(const char *dirname)
{
	DIR	   *dir;

	DO_DB(elog(LOG, "AllocateDir: Allocated %d", numAllocatedDirs));

	/*
	 * The test against MAX_ALLOCATED_DIRS prevents us from overflowing
	 * allocatedDirs[]; the test against max_safe_fds prevents AllocateDir
	 * from hogging every one of the available FDs, which'd lead to infinite
	 * looping.
	 */
	if (numAllocatedDirs >= MAX_ALLOCATED_DIRS ||
		numAllocatedDirs + numAllocatedFiles >= max_safe_fds - 1)
		elog(ERROR, "too many private dirs demanded");

TryAgain:
	if ((dir = opendir(dirname)) != NULL)
	{
		allocatedDirs[numAllocatedDirs] = dir;
		numAllocatedDirs++;
		return dir;
	}

	if (errno == EMFILE || errno == ENFILE)
	{
		int			save_errno = errno;

		ereport(LOG,
				(errcode(ERRCODE_INSUFFICIENT_RESOURCES),
			  errmsg("out of file descriptors: %m; release and retry")));
		errno = 0;
		if (ReleaseLruFile())
			goto TryAgain;
		errno = save_errno;
	}

	return NULL;
}

/*
 * Close a directory opened with AllocateDir.
 *
 * Note we do not check closedir's return value --- it is up to the caller
 * to handle close errors.
 */
int
FreeDir(DIR *dir)
{
	int			i;

	DO_DB(elog(LOG, "FreeDir: Allocated %d", numAllocatedDirs));

	/* Remove dir from list of allocated dirs, if it's present */
	for (i = numAllocatedDirs; --i >= 0;)
	{
		if (allocatedDirs[i] == dir)
		{
			numAllocatedDirs--;
			allocatedDirs[i] = allocatedDirs[numAllocatedDirs];
			break;
		}
	}
	if (i < 0)
		elog(WARNING, "dir passed to FreeDir was not obtained from AllocateDir");

	return closedir(dir);
}


/*
 * closeAllVfds
 *
 * Force all VFDs into the physically-closed state, so that the fewest
 * possible number of kernel file descriptors are in use.  There is no
 * change in the logical state of the VFDs.
 */
void
closeAllVfds(void)
{
	Index		i;

	if (SizeVfdCache > 0)
	{
		Assert(FileIsNotOpen(0));		/* Make sure ring not corrupted */
		for (i = 1; i < SizeVfdCache; i++)
		{
			if (!FileIsNotOpen(i))
				LruDelete(i);
		}
	}
}

/*
 * AtEOXact_Files
 *
 * This routine is called during transaction commit or abort (it doesn't
 * particularly care which).  All still-open per-transaction temporary file
 * VFDs are closed, which also causes the underlying files to be
 * deleted. Furthermore, all "allocated" stdio files are closed.
 */
void
AtEOXact_Files(void)
{
	CleanupTempFiles(false);
}

/*
 * AtProcExit_Files
 *
 * on_proc_exit hook to clean up temp files during backend shutdown.
 * Here, we want to clean up *all* temp files including interXact ones.
 */
static void
AtProcExit_Files(void)
{
	CleanupTempFiles(true);
}

/*
 * Close temporary files and delete their underlying files.
 *
 * isProcExit: if true, this is being called as the backend process is
 * exiting. If that's the case, we should remove all temporary files; if
 * that's not the case, we are being called for transaction commit/abort
 * and should only remove transaction-local temp files.  In either case,
 * also clean up "allocated" stdio files and dirs.
 */
static void
CleanupTempFiles(bool isProcExit)
{
	Index		i;

	if (SizeVfdCache > 0)
	{
		Assert(FileIsNotOpen(0));		/* Make sure ring not corrupted */
		for (i = 1; i < SizeVfdCache; i++)
		{
			unsigned short fdstate = VfdCache[i].fdstate;

			if ((fdstate & FD_TEMPORARY) && VfdCache[i].fileName != NULL)
			{
				/*
				 * If we're in the process of exiting a backend process,
				 * close all temporary files. Otherwise, only close
				 * temporary files local to the current transaction.
				 */
				if (isProcExit || (fdstate & FD_XACT_TEMPORARY))
					FileClose(i);
			}
		}
	}

	while (numAllocatedFiles > 0)
		FreeFile(allocatedFiles[0]);

	while (numAllocatedDirs > 0)
		FreeDir(allocatedDirs[0]);
}


/*
 * Remove temporary files left over from a prior postmaster session
 *
 * This should be called during postmaster startup.  It will forcibly
 * remove any leftover files created by OpenTemporaryFile.
 *
 * NOTE: we could, but don't, call this during a post-backend-crash restart
 * cycle.  The argument for not doing it is that someone might want to examine
 * the temp files for debugging purposes.  This does however mean that
 * OpenTemporaryFile had better allow for collision with an existing temp
 * file name.
 */
void
RemovePgTempFiles(void)
{
	char		db_path[MAXPGPATH];
	char		temp_path[MAXPGPATH];
	char		rm_path[MAXPGPATH];
	DIR		   *db_dir;
	DIR		   *temp_dir;
	struct dirent *db_de;
	struct dirent *temp_de;

	/*
	 * Cycle through pg_tempfiles for all databases and remove old temp
	 * files.
	 */
	snprintf(db_path, sizeof(db_path), "%s/base", DataDir);
	if ((db_dir = AllocateDir(db_path)) != NULL)
	{
		while ((db_de = readdir(db_dir)) != NULL)
		{
			if (strcmp(db_de->d_name, ".") == 0 ||
				strcmp(db_de->d_name, "..") == 0)
				continue;

			snprintf(temp_path, sizeof(temp_path),
					 "%s/%s/%s",
					 db_path, db_de->d_name,
					 PG_TEMP_FILES_DIR);
			if ((temp_dir = AllocateDir(temp_path)) != NULL)
			{
				while ((temp_de = readdir(temp_dir)) != NULL)
				{
					if (strcmp(temp_de->d_name, ".") == 0 ||
						strcmp(temp_de->d_name, "..") == 0)
						continue;

					snprintf(rm_path, sizeof(temp_path),
							 "%s/%s/%s/%s",
							 db_path, db_de->d_name,
							 PG_TEMP_FILES_DIR,
							 temp_de->d_name);

					if (strncmp(temp_de->d_name,
								PG_TEMP_FILE_PREFIX,
								strlen(PG_TEMP_FILE_PREFIX)) == 0)
						unlink(rm_path);
					else
						elog(LOG,
							 "unexpected file found in temporary-files directory: \"%s\"",
							 rm_path);
				}
				FreeDir(temp_dir);
			}
		}
		FreeDir(db_dir);
	}
}