android_kernel_xiaomi_sm8350/mm/fadvise.c
Masatake YAMATO b5beb1caff check ADVICE of fadvise64_64 even if get_xip_page is given
I've written some test programs in ltp project.  During writing I met an
problem which I cannot solve in user land.  So I wrote a patch for linux
kernel.  Please, include this patch if acceptable.

The test program tests the 4th parameter of fadvise64_64:

    long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice);

My test case calls fadvise64_64 with invalid advice value and checks errno is
set to EINVAL.  About the advice parameter man page says:

    ...
    Permissible values for advice include:

	   POSIX_FADV_NORMAL
                  ...
	   POSIX_FADV_SEQUENTIAL
                  ...
	   POSIX_FADV_RANDOM
		  ...
	   POSIX_FADV_NOREUSE
                  ...
	   POSIX_FADV_WILLNEED
                  ...
	   POSIX_FADV_DONTNEED
		  ...
    ERRORS
           ...
	   EINVAL An invalid value was specified for advice.

However, I got a bug report that the system call invocations
in my test case returned 0 unexpectedly.

I've inspected the kernel code:

    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_page)
		    /* no bad return value, but ignore advice */
		    goto out;
    ...
    out:
	    fput(file);
	    return ret;
    }

I found the advice parameter is just ignored in the case
mapping->a_ops->get_xip_page is given. This behavior is different from
what is written on the man page. Is this o.k.?

get_xip_page is given if CONFIG_EXT2_FS_XIP is true.
Anyway I cannot find the easy way to detect get_xip_page
field is given or CONFIG_EXT2_FS_XIP is true from the
user space.

I propose the following patch which checks the advice parameter
even if get_xip_page is given.

Signed-off-by: Masatake YAMATO <yamato@redhat.com>
Acked-by: Carsten Otte <cotte@de.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2008-02-05 09:44:19 -08:00

138 lines
2.9 KiB
C

/*
* 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_page) {
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