fadvise.c

Go to the documentation of this file.

/*
 * mm/fadvise.c
 *
 * Copyright (C) 2002, Linus Torvalds
 *
 * 11Jan2003    Andrew Morton
 *      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.
 */
SYSCALL_DEFINE(fadvise64_64)(int fd, loff_t offset, loff_t len, int advice)
{
    struct fd f = fdget(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 (!f.file)
        return -EBADF;

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

    mapping = f.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:
        f.file->f_ra.ra_pages = bdi->ra_pages;
        spin_lock(&f.file->f_lock);
        f.file->f_mode &= ~FMODE_RANDOM;
        spin_unlock(&f.file->f_lock);
        break;
    case POSIX_FADV_RANDOM:
        spin_lock(&f.file->f_lock);
        f.file->f_mode |= FMODE_RANDOM;
        spin_unlock(&f.file->f_lock);
        break;
    case POSIX_FADV_SEQUENTIAL:
        f.file->f_ra.ra_pages = bdi->ra_pages * 2;
        spin_lock(&f.file->f_lock);
        f.file->f_mode &= ~FMODE_RANDOM;
        spin_unlock(&f.file->f_lock);
        break;
    case POSIX_FADV_WILLNEED:
        /* 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;

        /*
         * Ignore return value because fadvise() shall return
         * success even if filesystem can't retrieve a hint,
         */
        force_page_cache_readahead(mapping, f.file, start_index,
                       nrpages);
        break;
    case POSIX_FADV_NOREUSE:
        break;
    case POSIX_FADV_DONTNEED:
        if (!bdi_write_congested(mapping->backing_dev_info))
            __filemap_fdatawrite_range(mapping, offset, endbyte,
                           WB_SYNC_NONE);

        /* 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:
    fdput(f);
    return ret;
}
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_fadvise64_64(long fd, loff_t offset, loff_t len, long advice)
{
    return SYSC_fadvise64_64((int) fd, offset, len, (int) advice);
}
SYSCALL_ALIAS(sys_fadvise64_64, SyS_fadvise64_64);
#endif

#ifdef __ARCH_WANT_SYS_FADVISE64

SYSCALL_DEFINE(fadvise64)(int fd, loff_t offset, size_t len, int advice)
{
    return sys_fadvise64_64(fd, offset, len, advice);
}
#ifdef CONFIG_HAVE_SYSCALL_WRAPPERS
asmlinkage long SyS_fadvise64(long fd, loff_t offset, long len, long advice)
{
    return SYSC_fadvise64((int) fd, offset, (size_t)len, (int)advice);
}
SYSCALL_ALIAS(sys_fadvise64, SyS_fadvise64);
#endif

#endif