modules/vfs_readahead.c

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/*
 * Copyright (c) Jeremy Allison 2007.
 *
 * 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"

#if !defined(HAVE_LINUX_READAHEAD) && !defined(HAVE_POSIX_FADVISE)
static BOOL didmsg;
#endif

struct readahead_data {
        SMB_OFF_T off_bound;
        SMB_OFF_T len;
        BOOL didmsg;
};

/* 
 * This module copes with Vista AIO read requests on Linux
 * by detecting the initial 0x80000 boundary reads and causing
 * the buffer cache to be filled in advance.
 */

/*******************************************************************
 sendfile wrapper that does readahead/posix_fadvise.
*******************************************************************/

static ssize_t readahead_sendfile(struct vfs_handle_struct *handle,
                                        int tofd,
                                        files_struct *fsp,
                                        int fromfd,
                                        const DATA_BLOB *header,
                                        SMB_OFF_T offset,
                                        size_t count)
{
        struct readahead_data *rhd = (struct readahead_data *)handle->data;

        if ( offset % rhd->off_bound == 0) {
#if defined(HAVE_LINUX_READAHEAD)
                int err = readahead(fromfd, offset, (size_t)rhd->len);
                DEBUG(10,("readahead_sendfile: readahead on fd %u, offset %llu, len %u returned %d\n",
                        (unsigned int)fromfd,
                        (unsigned long long)offset,
                        (unsigned int)rhd->len,
                        err ));
#elif defined(HAVE_POSIX_FADVISE)
                int err = posix_fadvise(fromfd, offset, (off_t)rhd->len, POSIX_FADV_WILLNEED);
                DEBUG(10,("readahead_sendfile: posix_fadvise on fd %u, offset %llu, len %u returned %d\n",
                        (unsigned int)fromfd,
                        (unsigned long long)offset,
                        (unsigned int)rhd->len,
                        err ));
#else
                if (!rhd->didmsg) {
                        DEBUG(0,("readahead_sendfile: no readahead on this platform\n"));
                        rhd->didmsg = True;
                }
#endif
        }
        return SMB_VFS_NEXT_SENDFILE(handle,
                                        tofd,
                                        fsp,
                                        fromfd,
                                        header,
                                        offset,
                                        count);
}

/*******************************************************************
 pread wrapper that does readahead/posix_fadvise.
*******************************************************************/

static ssize_t readahead_pread(vfs_handle_struct *handle,
                                files_struct *fsp,
                                int fd,
                                void *data,
                                size_t count,
                                SMB_OFF_T offset)
{
        struct readahead_data *rhd = (struct readahead_data *)handle->data;

        if ( offset % rhd->off_bound == 0) {
#if defined(HAVE_LINUX_READAHEAD)
                int err = readahead(fd, offset, (size_t)rhd->len);
                DEBUG(10,("readahead_pread: readahead on fd %u, offset %llu, len %u returned %d\n",
                        (unsigned int)fd,
                        (unsigned long long)offset,
                        (unsigned int)rhd->len,
                        err ));
#elif defined(HAVE_POSIX_FADVISE)
                int err = posix_fadvise(fd, offset, (off_t)rhd->len, POSIX_FADV_WILLNEED);
                DEBUG(10,("readahead_pread: posix_fadvise on fd %u, offset %llu, len %u returned %d\n",
                        (unsigned int)fd,
                        (unsigned long long)offset,
                        (unsigned int)rhd->len,
                        err ));
#else
                if (!rhd->didmsg) {
                        DEBUG(0,("readahead_pread: no readahead on this platform\n"));
                        rhd->didmsg = True;
                }
#endif
        }
        return SMB_VFS_NEXT_PREAD(handle, fsp, fd, data, count, offset);
}

/*******************************************************************
 Directly called from main smbd when freeing handle.
*******************************************************************/

static void free_readahead_data(void **pptr)
{
        SAFE_FREE(*pptr);
}

/*******************************************************************
 Allocate the handle specific data so we don't call the expensive
 conv_str_size function for each sendfile/pread.
*******************************************************************/

static int readahead_connect(struct vfs_handle_struct *handle,
                                const char *service,
                                const char *user)
{
        struct readahead_data *rhd = SMB_MALLOC_P(struct readahead_data);
        if (!rhd) {
                DEBUG(0,("readahead_connect: out of memory\n"));
                return -1;
        }
        ZERO_STRUCTP(rhd);

        rhd->didmsg = False;
        rhd->off_bound = conv_str_size(lp_parm_const_string(SNUM(handle->conn),
                                                "readahead",
                                                "offset",
                                                NULL));
        if (rhd->off_bound == 0) {
                rhd->off_bound = 0x80000;
        }
        rhd->len = conv_str_size(lp_parm_const_string(SNUM(handle->conn),
                                                "readahead",
                                                "length",
                                                NULL));
        if (rhd->len == 0) {
                rhd->len = rhd->off_bound;
        }

        handle->data = (void *)rhd;
        handle->free_data = free_readahead_data;
        return SMB_VFS_NEXT_CONNECT(handle, service, user);
}

/*******************************************************************
 Functions we're replacing.
 We don't replace read as it isn't used from smbd to read file
 data.
*******************************************************************/

static vfs_op_tuple readahead_ops [] =
{
        {SMB_VFS_OP(readahead_sendfile), SMB_VFS_OP_SENDFILE, SMB_VFS_LAYER_TRANSPARENT},
        {SMB_VFS_OP(readahead_pread), SMB_VFS_OP_PREAD, SMB_VFS_LAYER_TRANSPARENT},
        {SMB_VFS_OP(readahead_connect), SMB_VFS_OP_CONNECT,  SMB_VFS_LAYER_TRANSPARENT},
        {SMB_VFS_OP(NULL), SMB_VFS_OP_NOOP, SMB_VFS_LAYER_NOOP}
};

/*******************************************************************
 Module initialization boilerplate.
*******************************************************************/

NTSTATUS vfs_readahead_init(void);
NTSTATUS vfs_readahead_init(void)
{
        return smb_register_vfs(SMB_VFS_INTERFACE_VERSION, "readahead", readahead_ops);
}

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