src/lib/file-set-size.c

	file-set-size.c revision 3ed2d0f6b5e67e2663d44489d9da3176823789a8
/* Copyright (c) 2002-2010 Dovecot authors, see the included COPYING file */

#ifdef HAVE_CONFIG_H
#  include "config.h"
#endif

#ifdef HAVE_POSIX_FALLOCATE
#  define _XOPEN_SOURCE 600 /* Required by glibc, breaks Solaris 9 */
#endif
#include "lib.h"
#include "file-set-size.h"

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

int file_set_size(int fd, off_t size)
{
#ifdef HAVE_POSIX_FALLOCATE
    static bool posix_fallocate_supported = TRUE;
#endif
    char block[IO_BLOCK_SIZE];
    off_t offset;
    ssize_t ret;
    struct stat st;

    i_assert(size >= 0);

    if (fstat(fd, &st) < 0) {
        i_error("fstat() failed: %m");
        return -1;
    }

    if (size < st.st_size) {
        if (ftruncate(fd, size) < 0) {
            i_error("ftruncate() failed: %m");
            return -1;
        }
        return 0;
    }
    if (size == st.st_size)
        return 0;

#ifdef HAVE_POSIX_FALLOCATE
    if (posix_fallocate_supported) {
        int err;

        err = posix_fallocate(fd, st.st_size, size - st.st_size);
        if (err == 0)
            return 0;

        if (err != EINVAL /* Solaris */ &&
            err != EOPNOTSUPP /* AOX */) {
            if (!ENOSPACE(err))
                i_error("posix_fallocate() failed: %m");
            return -1;
        }
        /* Not supported by kernel, fallback to writing. */
        posix_fallocate_supported = FALSE;
    }
#endif
    /* start growing the file */
    offset = st.st_size;
    memset(block, 0, I_MIN((ssize_t)sizeof(block), size - offset));

    while (offset < size) {
        ret = pwrite(fd, block,
                 I_MIN((ssize_t)sizeof(block), size - offset),
                 offset);
        if (ret < 0) {
            if (!ENOSPACE(errno))
                i_error("pwrite() failed: %m");
            return -1;
        }
        offset += ret;
    }
    return 0;
}