source: trunk-3.0/source/modules/vfs_prealloc.c@ 101

/*
 * XFS preallocation support module.
 *
 * Copyright (c) James Peach 2006
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 */

#include "includes.h"

/* Extent preallocation module.
 *
 * The purpose of this module is to preallocate space on the filesystem when
 * we have a good idea of how large files are supposed to be. This lets writes
 * proceed without having to allocate new extents and results in better file
 * layouts on disk.
 *
 * Currently only implemented for XFS. This module is based on an original idea
 * and implementation by Sebastian Brings.
 *
 * Tunables.
 *
 *      prealloc: <ext>     Number of bytes to preallocate for a file with
 *                          the matching extension.
 *      prealloc:debug      Debug level at which to emit messages.
 *
 * Example.
 *
 *      prealloc:mpeg = 500M  # Preallocate *.mpeg to 500 MiB.
 */

#ifdef HAVE_XFS_LIBXFS_H
#include <xfs/libxfs.h>
#define lock_type xfs_flock64_t
#else
#define lock_type struct flock64
#endif

#define MODULE "prealloc"
static int module_debug;

static int preallocate_space(int fd, SMB_OFF_T size)
{
        lock_type fl = {0};
        int err;

        if (size <= 0) {
                return 0;
        }

        fl.l_whence = SEEK_SET;
        fl.l_start = 0;
        fl.l_len = size;

        /* IMPORTANT: We use RESVSP because we want the extents to be
         * allocated, but we don't want the allocation to show up in
         * st_size or persist after the close(2).
         */

#if defined(XFS_IOC_RESVSP64)
        /* On Linux this comes in via libxfs.h. */
        err = xfsctl(NULL, fd, XFS_IOC_RESVSP64, &fl);
#elif defined(F_RESVSP64)
        /* On IRIX, this comes from fcntl.h. */
        err = fcntl(fd, F_RESVSP64, &fl);
#else
        err = -1;
        errno = ENOSYS;
#endif

        if (err) {
                DEBUG(module_debug,
                        ("%s: preallocate failed on fd=%d size=%lld: %s\n",
                        MODULE, fd, (long long)size, strerror(errno)));
        }

        return err;
}

static int prealloc_connect(
                struct vfs_handle_struct *  handle,
                const char *                service,
                const char *                user)
{
            module_debug = lp_parm_int(SNUM(handle->conn),
                                        MODULE, "debug", 100);

            return SMB_VFS_NEXT_CONNECT(handle, service, user);
}

static int prealloc_open(vfs_handle_struct* handle,
                        const char *        fname,
                        files_struct *      fsp,
                        int                 flags,
                        mode_t              mode)
{
        int fd;
        off64_t size = 0;

        const char * dot;
        char fext[10];

        if (!(flags & (O_CREAT|O_TRUNC))) {
                /* Caller is not intending to rewrite the file. Let's not mess
                 * with the allocation in this case.
                 */
                goto normal_open;
        }

        *fext = '\0';
        dot = strrchr(fname, '.');
        if (dot && *++dot) {
                if (strlen(dot) < sizeof(fext)) {
                        strncpy(fext, dot, sizeof(fext));
                        strnorm(fext, CASE_LOWER);
                }
        }

        if (*fext == '\0') {
                goto normal_open;
        }

        /* Syntax for specifying preallocation size is:
         *      MODULE: <extension> = <size>
         * where
         *      <extension> is the file extension in lower case
         *      <size> is a size like 10, 10K, 10M
         */
        size = conv_str_size(lp_parm_const_string(SNUM(handle->conn), MODULE,
                                                    fext, NULL));
        if (size <= 0) {
                /* No need to preallocate this file. */
                goto normal_open;
        }

        fd = SMB_VFS_NEXT_OPEN(handle, fname, fsp, flags, mode);
        if (fd < 0) {
                return fd;
        }

        /* Prellocate only if the file is being created or replaced. Note that
         * Samba won't ever pass down O_TRUNC, which is why we have to handle
         * truncate calls specially.
         */
        if ((flags & O_CREAT) || (flags & O_TRUNC)) {
                SMB_OFF_T * psize;

                psize = VFS_ADD_FSP_EXTENSION(handle, fsp, SMB_OFF_T);
                if (psize == NULL || *psize == -1) {
                        return fd;
                }

                DEBUG(module_debug,
                        ("%s: preallocating %s (fd=%d) to %lld bytes\n",
                        MODULE, fname, fd, (long long)size));

                *psize = size;
                if (preallocate_space(fd, *psize) < 0) {
                        VFS_REMOVE_FSP_EXTENSION(handle, fsp);
                }
        }

        return fd;

normal_open:
        /* We are not creating or replacing a file. Skip the
         * preallocation.
         */
        DEBUG(module_debug, ("%s: skipping preallocation for %s\n",
                    MODULE, fname));
        return SMB_VFS_NEXT_OPEN(handle, fname, fsp, flags, mode);
}

static int prealloc_ftruncate(vfs_handle_struct * handle,
                        files_struct *  fsp,
                        int             fd,
                        SMB_OFF_T       offset)
{
        SMB_OFF_T *psize;
        int ret = SMB_VFS_NEXT_FTRUNCATE(handle, fsp, fd, offset);

        /* Maintain the allocated space even in the face of truncates. */
        if ((psize = VFS_FETCH_FSP_EXTENSION(handle, fsp))) {
                preallocate_space(fd, *psize);
        }

        return ret;
}

static vfs_op_tuple prealloc_op_tuples[] = {
        {SMB_VFS_OP(prealloc_open), SMB_VFS_OP_OPEN, SMB_VFS_LAYER_TRANSPARENT},
        {SMB_VFS_OP(prealloc_ftruncate), SMB_VFS_OP_FTRUNCATE, SMB_VFS_LAYER_TRANSPARENT},
        {SMB_VFS_OP(prealloc_connect), SMB_VFS_OP_CONNECT, SMB_VFS_LAYER_TRANSPARENT},
        {NULL,  SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
};

NTSTATUS vfs_prealloc_init(void);
NTSTATUS vfs_prealloc_init(void)
{
        return smb_register_vfs(SMB_VFS_INTERFACE_VERSION,
                MODULE, prealloc_op_tuples);
}