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Diffstat (limited to 'src/common/file_utils.c')
| -rw-r--r-- | src/common/file_utils.c | 485 |
1 files changed, 485 insertions, 0 deletions
diff --git a/src/common/file_utils.c b/src/common/file_utils.c new file mode 100644 index 0000000..fd2d113 --- /dev/null +++ b/src/common/file_utils.c @@ -0,0 +1,485 @@ +/*------------------------------------------------------------------------- + * + * File-processing utility routines. + * + * Assorted utility functions to work on files. + * + * + * Portions Copyright (c) 1996-2021, PostgreSQL Global Development Group + * Portions Copyright (c) 1994, Regents of the University of California + * + * src/common/file_utils.c + * + *------------------------------------------------------------------------- + */ + +#ifndef FRONTEND +#include "postgres.h" +#else +#include "postgres_fe.h" +#endif + +#include <dirent.h> +#include <fcntl.h> +#include <sys/stat.h> +#include <unistd.h> + +#include "common/file_utils.h" +#ifdef FRONTEND +#include "common/logging.h" +#endif + +#ifdef FRONTEND + +/* Define PG_FLUSH_DATA_WORKS if we have an implementation for pg_flush_data */ +#if defined(HAVE_SYNC_FILE_RANGE) +#define PG_FLUSH_DATA_WORKS 1 +#elif defined(USE_POSIX_FADVISE) && defined(POSIX_FADV_DONTNEED) +#define PG_FLUSH_DATA_WORKS 1 +#endif + +/* + * pg_xlog has been renamed to pg_wal in version 10. + */ +#define MINIMUM_VERSION_FOR_PG_WAL 100000 + +#ifdef PG_FLUSH_DATA_WORKS +static int pre_sync_fname(const char *fname, bool isdir); +#endif +static void walkdir(const char *path, + int (*action) (const char *fname, bool isdir), + bool process_symlinks); + +/* + * Issue fsync recursively on PGDATA and all its contents. + * + * We fsync regular files and directories wherever they are, but we follow + * symlinks only for pg_wal (or pg_xlog) and immediately under pg_tblspc. + * Other symlinks are presumed to point at files we're not responsible for + * fsyncing, and might not have privileges to write at all. + * + * serverVersion indicates the version of the server to be fsync'd. + */ +void +fsync_pgdata(const char *pg_data, + int serverVersion) +{ + bool xlog_is_symlink; + char pg_wal[MAXPGPATH]; + char pg_tblspc[MAXPGPATH]; + + /* handle renaming of pg_xlog to pg_wal in post-10 clusters */ + snprintf(pg_wal, MAXPGPATH, "%s/%s", pg_data, + serverVersion < MINIMUM_VERSION_FOR_PG_WAL ? "pg_xlog" : "pg_wal"); + snprintf(pg_tblspc, MAXPGPATH, "%s/pg_tblspc", pg_data); + + /* + * If pg_wal is a symlink, we'll need to recurse into it separately, + * because the first walkdir below will ignore it. + */ + xlog_is_symlink = false; + +#ifndef WIN32 + { + struct stat st; + + if (lstat(pg_wal, &st) < 0) + pg_log_error("could not stat file \"%s\": %m", pg_wal); + else if (S_ISLNK(st.st_mode)) + xlog_is_symlink = true; + } +#else + if (pgwin32_is_junction(pg_wal)) + xlog_is_symlink = true; +#endif + + /* + * If possible, hint to the kernel that we're soon going to fsync the data + * directory and its contents. + */ +#ifdef PG_FLUSH_DATA_WORKS + walkdir(pg_data, pre_sync_fname, false); + if (xlog_is_symlink) + walkdir(pg_wal, pre_sync_fname, false); + walkdir(pg_tblspc, pre_sync_fname, true); +#endif + + /* + * Now we do the fsync()s in the same order. + * + * The main call ignores symlinks, so in addition to specially processing + * pg_wal if it's a symlink, pg_tblspc has to be visited separately with + * process_symlinks = true. Note that if there are any plain directories + * in pg_tblspc, they'll get fsync'd twice. That's not an expected case + * so we don't worry about optimizing it. + */ + walkdir(pg_data, fsync_fname, false); + if (xlog_is_symlink) + walkdir(pg_wal, fsync_fname, false); + walkdir(pg_tblspc, fsync_fname, true); +} + +/* + * Issue fsync recursively on the given directory and all its contents. + * + * This is a convenient wrapper on top of walkdir(). + */ +void +fsync_dir_recurse(const char *dir) +{ + /* + * If possible, hint to the kernel that we're soon going to fsync the data + * directory and its contents. + */ +#ifdef PG_FLUSH_DATA_WORKS + walkdir(dir, pre_sync_fname, false); +#endif + + walkdir(dir, fsync_fname, false); +} + +/* + * walkdir: recursively walk a directory, applying the action to each + * regular file and directory (including the named directory itself). + * + * If process_symlinks is true, the action and recursion are also applied + * to regular files and directories that are pointed to by symlinks in the + * given directory; otherwise symlinks are ignored. Symlinks are always + * ignored in subdirectories, ie we intentionally don't pass down the + * process_symlinks flag to recursive calls. + * + * Errors are reported but not considered fatal. + * + * See also walkdir in fd.c, which is a backend version of this logic. + */ +static void +walkdir(const char *path, + int (*action) (const char *fname, bool isdir), + bool process_symlinks) +{ + DIR *dir; + struct dirent *de; + + dir = opendir(path); + if (dir == NULL) + { + pg_log_error("could not open directory \"%s\": %m", path); + return; + } + + while (errno = 0, (de = readdir(dir)) != NULL) + { + char subpath[MAXPGPATH * 2]; + + if (strcmp(de->d_name, ".") == 0 || + strcmp(de->d_name, "..") == 0) + continue; + + snprintf(subpath, sizeof(subpath), "%s/%s", path, de->d_name); + + switch (get_dirent_type(subpath, de, process_symlinks, PG_LOG_ERROR)) + { + case PGFILETYPE_REG: + (*action) (subpath, false); + break; + case PGFILETYPE_DIR: + walkdir(subpath, action, false); + break; + default: + + /* + * Errors are already reported directly by get_dirent_type(), + * and any remaining symlinks and unknown file types are + * ignored. + */ + break; + } + } + + if (errno) + pg_log_error("could not read directory \"%s\": %m", path); + + (void) closedir(dir); + + /* + * It's important to fsync the destination directory itself as individual + * file fsyncs don't guarantee that the directory entry for the file is + * synced. Recent versions of ext4 have made the window much wider but + * it's been an issue for ext3 and other filesystems in the past. + */ + (*action) (path, true); +} + +/* + * Hint to the OS that it should get ready to fsync() this file. + * + * Ignores errors trying to open unreadable files, and reports other errors + * non-fatally. + */ +#ifdef PG_FLUSH_DATA_WORKS + +static int +pre_sync_fname(const char *fname, bool isdir) +{ + int fd; + + fd = open(fname, O_RDONLY | PG_BINARY, 0); + + if (fd < 0) + { + if (errno == EACCES || (isdir && errno == EISDIR)) + return 0; + pg_log_error("could not open file \"%s\": %m", fname); + return -1; + } + + /* + * We do what pg_flush_data() would do in the backend: prefer to use + * sync_file_range, but fall back to posix_fadvise. We ignore errors + * because this is only a hint. + */ +#if defined(HAVE_SYNC_FILE_RANGE) + (void) sync_file_range(fd, 0, 0, SYNC_FILE_RANGE_WRITE); +#elif defined(USE_POSIX_FADVISE) && defined(POSIX_FADV_DONTNEED) + (void) posix_fadvise(fd, 0, 0, POSIX_FADV_DONTNEED); +#else +#error PG_FLUSH_DATA_WORKS should not have been defined +#endif + + (void) close(fd); + return 0; +} + +#endif /* PG_FLUSH_DATA_WORKS */ + +/* + * fsync_fname -- Try to fsync a file or directory + * + * Ignores errors trying to open unreadable files, or trying to fsync + * directories on systems where that isn't allowed/required. All other errors + * are fatal. + */ +int +fsync_fname(const char *fname, bool isdir) +{ + int fd; + int flags; + int returncode; + + /* + * Some OSs require directories to be opened read-only whereas other + * systems don't allow us to fsync files opened read-only; so we need both + * cases here. Using O_RDWR will cause us to fail to fsync files that are + * not writable by our userid, but we assume that's OK. + */ + flags = PG_BINARY; + if (!isdir) + flags |= O_RDWR; + else + flags |= O_RDONLY; + + /* + * Open the file, silently ignoring errors about unreadable files (or + * unsupported operations, e.g. opening a directory under Windows), and + * logging others. + */ + fd = open(fname, flags, 0); + if (fd < 0) + { + if (errno == EACCES || (isdir && errno == EISDIR)) + return 0; + pg_log_error("could not open file \"%s\": %m", fname); + return -1; + } + + returncode = fsync(fd); + + /* + * Some OSes don't allow us to fsync directories at all, so we can ignore + * those errors. Anything else needs to be reported. + */ + if (returncode != 0 && !(isdir && (errno == EBADF || errno == EINVAL))) + { + pg_log_fatal("could not fsync file \"%s\": %m", fname); + (void) close(fd); + exit(EXIT_FAILURE); + } + + (void) close(fd); + return 0; +} + +/* + * fsync_parent_path -- fsync the parent path of a file or directory + * + * This is aimed at making file operations persistent on disk in case of + * an OS crash or power failure. + */ +int +fsync_parent_path(const char *fname) +{ + char parentpath[MAXPGPATH]; + + strlcpy(parentpath, fname, MAXPGPATH); + get_parent_directory(parentpath); + + /* + * get_parent_directory() returns an empty string if the input argument is + * just a file name (see comments in path.c), so handle that as being the + * current directory. + */ + if (strlen(parentpath) == 0) + strlcpy(parentpath, ".", MAXPGPATH); + + if (fsync_fname(parentpath, true) != 0) + return -1; + + return 0; +} + +/* + * durable_rename -- rename(2) wrapper, issuing fsyncs required for durability + * + * Wrapper around rename, similar to the backend version. + */ +int +durable_rename(const char *oldfile, const char *newfile) +{ + int fd; + + /* + * First fsync the old and target path (if it exists), to ensure that they + * are properly persistent on disk. Syncing the target file is not + * strictly necessary, but it makes it easier to reason about crashes; + * because it's then guaranteed that either source or target file exists + * after a crash. + */ + if (fsync_fname(oldfile, false) != 0) + return -1; + + fd = open(newfile, PG_BINARY | O_RDWR, 0); + if (fd < 0) + { + if (errno != ENOENT) + { + pg_log_error("could not open file \"%s\": %m", newfile); + return -1; + } + } + else + { + if (fsync(fd) != 0) + { + pg_log_fatal("could not fsync file \"%s\": %m", newfile); + close(fd); + exit(EXIT_FAILURE); + } + close(fd); + } + + /* Time to do the real deal... */ + if (rename(oldfile, newfile) != 0) + { + pg_log_error("could not rename file \"%s\" to \"%s\": %m", + oldfile, newfile); + return -1; + } + + /* + * To guarantee renaming the file is persistent, fsync the file with its + * new name, and its containing directory. + */ + if (fsync_fname(newfile, false) != 0) + return -1; + + if (fsync_parent_path(newfile) != 0) + return -1; + + return 0; +} + +#endif /* FRONTEND */ + +/* + * Return the type of a directory entry. + * + * In frontend code, elevel should be a level from logging.h; in backend code + * it should be a level from elog.h. + */ +PGFileType +get_dirent_type(const char *path, + const struct dirent *de, + bool look_through_symlinks, + int elevel) +{ + PGFileType result; + + /* + * Some systems tell us the type directly in the dirent struct, but that's + * a BSD and Linux extension not required by POSIX. Even when the + * interface is present, sometimes the type is unknown, depending on the + * filesystem. + */ +#if defined(DT_REG) && defined(DT_DIR) && defined(DT_LNK) + if (de->d_type == DT_REG) + result = PGFILETYPE_REG; + else if (de->d_type == DT_DIR) + result = PGFILETYPE_DIR; + else if (de->d_type == DT_LNK && !look_through_symlinks) + result = PGFILETYPE_LNK; + else + result = PGFILETYPE_UNKNOWN; +#else + result = PGFILETYPE_UNKNOWN; +#endif + + if (result == PGFILETYPE_UNKNOWN) + { + struct stat fst; + int sret; + + + if (look_through_symlinks) + sret = stat(path, &fst); + else + sret = lstat(path, &fst); + + if (sret < 0) + { + result = PGFILETYPE_ERROR; +#ifdef FRONTEND + pg_log_generic(elevel, "could not stat file \"%s\": %m", path); +#else + ereport(elevel, + (errcode_for_file_access(), + errmsg("could not stat file \"%s\": %m", path))); +#endif + } + else if (S_ISREG(fst.st_mode)) + result = PGFILETYPE_REG; + else if (S_ISDIR(fst.st_mode)) + result = PGFILETYPE_DIR; +#ifdef S_ISLNK + else if (S_ISLNK(fst.st_mode)) + result = PGFILETYPE_LNK; +#endif + } + +#if defined(WIN32) && !defined(_MSC_VER) + + /* + * If we're on native Windows (not Cygwin, which has its own POSIX + * symlinks), but not using the MSVC compiler, then we're using a + * readdir() emulation provided by the MinGW runtime that has no d_type. + * Since the lstat() fallback code reports junction points as directories, + * we need an extra system call to check if we should report them as + * symlinks instead, following our convention. + */ + if (result == PGFILETYPE_DIR && + !look_through_symlinks && + pgwin32_is_junction(path)) + result = PGFILETYPE_LNK; +#endif + + return result; +} |