root/mm/fadvise.c

DEFINITIONS

1. sys_fadvise64_64
2. sys_fadvise64

/*
 * mm/fadvise.c
 *
 * Copyright (C) 2002, Linus Torvalds
 *
 * 11Jan2003    akpm@digeo.com
 *              Initial version.
 */

#include <linux/kernel.h>
#include <linux/file.h>
#include <linux/fs.h>
#include <linux/mm.h>
#include <linux/pagemap.h>
#include <linux/backing-dev.h>
#include <linux/pagevec.h>
#include <linux/fadvise.h>
#include <linux/writeback.h>
#include <linux/syscalls.h>

#include <asm/unistd.h>

/*
 * POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
 * deactivate the pages and clear PG_Referenced.
 */
asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
{
        struct file *file = fget(fd);
        struct address_space *mapping;
        struct backing_dev_info *bdi;
        loff_t endbyte;                 /* inclusive */
        pgoff_t start_index;
        pgoff_t end_index;
        unsigned long nrpages;
        int ret = 0;

        if (!file)
                return -EBADF;

        if (S_ISFIFO(file->f_path.dentry->d_inode->i_mode)) {
                ret = -ESPIPE;
                goto out;
        }

        mapping = file->f_mapping;
        if (!mapping || len < 0) {
                ret = -EINVAL;
                goto out;
        }

        if (mapping->a_ops->get_xip_mem) {
                switch (advice) {
                case POSIX_FADV_NORMAL:
                case POSIX_FADV_RANDOM:
                case POSIX_FADV_SEQUENTIAL:
                case POSIX_FADV_WILLNEED:
                case POSIX_FADV_NOREUSE:
                case POSIX_FADV_DONTNEED:
                        /* no bad return value, but ignore advice */
                        break;
                default:
                        ret = -EINVAL;
                }
                goto out;
        }

        /* Careful about overflows. Len == 0 means "as much as possible" */
        endbyte = offset + len;
        if (!len || endbyte < len)
                endbyte = -1;
        else
                endbyte--;              /* inclusive */

        bdi = mapping->backing_dev_info;

        switch (advice) {
        case POSIX_FADV_NORMAL:
                file->f_ra.ra_pages = bdi->ra_pages;
                break;
        case POSIX_FADV_RANDOM:
                file->f_ra.ra_pages = 0;
                break;
        case POSIX_FADV_SEQUENTIAL:
                file->f_ra.ra_pages = bdi->ra_pages * 2;
                break;
        case POSIX_FADV_WILLNEED:
                if (!mapping->a_ops->readpage) {
                        ret = -EINVAL;
                        break;
                }

                /* First and last PARTIAL page! */
                start_index = offset >> PAGE_CACHE_SHIFT;
                end_index = endbyte >> PAGE_CACHE_SHIFT;

                /* Careful about overflow on the "+1" */
                nrpages = end_index - start_index + 1;
                if (!nrpages)
                        nrpages = ~0UL;
                
                ret = force_page_cache_readahead(mapping, file,
                                start_index,
                                max_sane_readahead(nrpages));
                if (ret > 0)
                        ret = 0;
                break;
        case POSIX_FADV_NOREUSE:
                break;
        case POSIX_FADV_DONTNEED:
                if (!bdi_write_congested(mapping->backing_dev_info))
                        filemap_flush(mapping);

                /* First and last FULL page! */
                start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
                end_index = (endbyte >> PAGE_CACHE_SHIFT);

                if (end_index >= start_index)
                        invalidate_mapping_pages(mapping, start_index,
                                                end_index);
                break;
        default:
                ret = -EINVAL;
        }
out:
        fput(file);
        return ret;
}

#ifdef __ARCH_WANT_SYS_FADVISE64

asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
{
        return sys_fadvise64_64(fd, offset, len, advice);
}

#endif