copydir.c

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/*-------------------------------------------------------------------------
 *
 * copydir.c
 *    copies a directory
 *
 * Portions Copyright (c) 1996-2013, PostgreSQL Global Development Group
 * Portions Copyright (c) 1994, Regents of the University of California
 *
 *  While "xcopy /e /i /q" works fine for copying directories, on Windows XP
 *  it requires a Window handle which prevents it from working when invoked
 *  as a service.
 *
 * IDENTIFICATION
 *    src/backend/storage/file/copydir.c
 *
 *-------------------------------------------------------------------------
 */

#include "postgres.h"

#include <fcntl.h>
#include <unistd.h>
#include <sys/stat.h>

#include "storage/copydir.h"
#include "storage/fd.h"
#include "miscadmin.h"


static void fsync_fname(char *fname, bool isdir);


/*
 * copydir: copy a directory
 *
 * If recurse is false, subdirectories are ignored.  Anything that's not
 * a directory or a regular file is ignored.
 */
void
copydir(char *fromdir, char *todir, bool recurse)
{
    DIR        *xldir;
    struct dirent *xlde;
    char        fromfile[MAXPGPATH];
    char        tofile[MAXPGPATH];

    if (mkdir(todir, S_IRWXU) != 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not create directory \"%s\": %m", todir)));

    xldir = AllocateDir(fromdir);
    if (xldir == NULL)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not open directory \"%s\": %m", fromdir)));

    while ((xlde = ReadDir(xldir, fromdir)) != NULL)
    {
        struct stat fst;

        /* If we got a cancel signal during the copy of the directory, quit */
        CHECK_FOR_INTERRUPTS();

        if (strcmp(xlde->d_name, ".") == 0 ||
            strcmp(xlde->d_name, "..") == 0)
            continue;

        snprintf(fromfile, MAXPGPATH, "%s/%s", fromdir, xlde->d_name);
        snprintf(tofile, MAXPGPATH, "%s/%s", todir, xlde->d_name);

        if (lstat(fromfile, &fst) < 0)
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not stat file \"%s\": %m", fromfile)));

        if (S_ISDIR(fst.st_mode))
        {
            /* recurse to handle subdirectories */
            if (recurse)
                copydir(fromfile, tofile, true);
        }
        else if (S_ISREG(fst.st_mode))
            copy_file(fromfile, tofile);
    }
    FreeDir(xldir);

    /*
     * Be paranoid here and fsync all files to ensure the copy is really done.
     * But if fsync is disabled, we're done.
     */
    if (!enableFsync)
        return;

    xldir = AllocateDir(todir);
    if (xldir == NULL)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not open directory \"%s\": %m", todir)));

    while ((xlde = ReadDir(xldir, todir)) != NULL)
    {
        struct stat fst;

        if (strcmp(xlde->d_name, ".") == 0 ||
            strcmp(xlde->d_name, "..") == 0)
            continue;

        snprintf(tofile, MAXPGPATH, "%s/%s", todir, xlde->d_name);

        /*
         * We don't need to sync subdirectories here since the recursive
         * copydir will do it before it returns
         */
        if (lstat(tofile, &fst) < 0)
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not stat file \"%s\": %m", tofile)));

        if (S_ISREG(fst.st_mode))
            fsync_fname(tofile, false);
    }
    FreeDir(xldir);

    /*
     * 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 true for ext3 and other filesystems in the past.
     */
    fsync_fname(todir, true);
}

/*
 * copy one file
 */
void
copy_file(char *fromfile, char *tofile)
{
    char       *buffer;
    int         srcfd;
    int         dstfd;
    int         nbytes;
    off_t       offset;

    /* Use palloc to ensure we get a maxaligned buffer */
#define COPY_BUF_SIZE (8 * BLCKSZ)

    buffer = palloc(COPY_BUF_SIZE);

    /*
     * Open the files
     */
    srcfd = OpenTransientFile(fromfile, O_RDONLY | PG_BINARY, 0);
    if (srcfd < 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not open file \"%s\": %m", fromfile)));

    dstfd = OpenTransientFile(tofile, O_RDWR | O_CREAT | O_EXCL | PG_BINARY,
                              S_IRUSR | S_IWUSR);
    if (dstfd < 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not create file \"%s\": %m", tofile)));

    /*
     * Do the data copying.
     */
    for (offset = 0;; offset += nbytes)
    {
        /* If we got a cancel signal during the copy of the file, quit */
        CHECK_FOR_INTERRUPTS();

        nbytes = read(srcfd, buffer, COPY_BUF_SIZE);
        if (nbytes < 0)
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not read file \"%s\": %m", fromfile)));
        if (nbytes == 0)
            break;
        errno = 0;
        if ((int) write(dstfd, buffer, nbytes) != nbytes)
        {
            /* if write didn't set errno, assume problem is no disk space */
            if (errno == 0)
                errno = ENOSPC;
            ereport(ERROR,
                    (errcode_for_file_access(),
                     errmsg("could not write to file \"%s\": %m", tofile)));
        }

        /*
         * We fsync the files later but first flush them to avoid spamming the
         * cache and hopefully get the kernel to start writing them out before
         * the fsync comes.  Ignore any error, since it's only a hint.
         */
        (void) pg_flush_data(dstfd, offset, nbytes);
    }

    if (CloseTransientFile(dstfd))
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not close file \"%s\": %m", tofile)));

    CloseTransientFile(srcfd);

    pfree(buffer);
}


/*
 * fsync a file
 *
 * Try to fsync directories but ignore errors that indicate the OS
 * just doesn't allow/require fsyncing directories.
 */
static void
fsync_fname(char *fname, bool isdir)
{
    int         fd;
    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
     */
    if (!isdir)
        fd = OpenTransientFile(fname,
                               O_RDWR | PG_BINARY,
                               S_IRUSR | S_IWUSR);
    else
        fd = OpenTransientFile(fname,
                               O_RDONLY | PG_BINARY,
                               S_IRUSR | S_IWUSR);

    /*
     * Some OSs don't allow us to open directories at all (Windows returns
     * EACCES)
     */
    if (fd < 0 && isdir && (errno == EISDIR || errno == EACCES))
        return;

    else if (fd < 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not open file \"%s\": %m", fname)));

    returncode = pg_fsync(fd);

    /* Some OSs don't allow us to fsync directories at all */
    if (returncode != 0 && isdir && errno == EBADF)
    {
        CloseTransientFile(fd);
        return;
    }

    if (returncode != 0)
        ereport(ERROR,
                (errcode_for_file_access(),
                 errmsg("could not fsync file \"%s\": %m", fname)));

    CloseTransientFile(fd);
}