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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>
137 lines
2.9 KiB
C
137 lines
2.9 KiB
C
/*
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* mm/fadvise.c
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*
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* Copyright (C) 2002, Linus Torvalds
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*
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* 11Jan2003 akpm@digeo.com
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* Initial version.
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*/
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#include <linux/kernel.h>
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#include <linux/file.h>
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/pagemap.h>
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#include <linux/backing-dev.h>
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#include <linux/pagevec.h>
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#include <linux/fadvise.h>
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#include <linux/writeback.h>
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#include <linux/syscalls.h>
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#include <asm/unistd.h>
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/*
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* POSIX_FADV_WILLNEED could set PG_Referenced, and POSIX_FADV_NOREUSE could
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* deactivate the pages and clear PG_Referenced.
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*/
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asmlinkage long sys_fadvise64_64(int fd, loff_t offset, loff_t len, int advice)
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{
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struct file *file = fget(fd);
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struct address_space *mapping;
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struct backing_dev_info *bdi;
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loff_t endbyte; /* inclusive */
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pgoff_t start_index;
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pgoff_t end_index;
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unsigned long nrpages;
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int ret = 0;
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if (!file)
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return -EBADF;
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if (S_ISFIFO(file->f_path.dentry->d_inode->i_mode)) {
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ret = -ESPIPE;
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goto out;
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}
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mapping = file->f_mapping;
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if (!mapping || len < 0) {
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ret = -EINVAL;
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goto out;
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}
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if (mapping->a_ops->get_xip_page) {
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switch (advice) {
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case POSIX_FADV_NORMAL:
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case POSIX_FADV_RANDOM:
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case POSIX_FADV_SEQUENTIAL:
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case POSIX_FADV_WILLNEED:
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case POSIX_FADV_NOREUSE:
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case POSIX_FADV_DONTNEED:
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/* no bad return value, but ignore advice */
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break;
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default:
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ret = -EINVAL;
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}
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goto out;
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}
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/* Careful about overflows. Len == 0 means "as much as possible" */
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endbyte = offset + len;
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if (!len || endbyte < len)
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endbyte = -1;
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else
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endbyte--; /* inclusive */
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bdi = mapping->backing_dev_info;
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switch (advice) {
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case POSIX_FADV_NORMAL:
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file->f_ra.ra_pages = bdi->ra_pages;
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break;
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case POSIX_FADV_RANDOM:
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file->f_ra.ra_pages = 0;
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break;
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case POSIX_FADV_SEQUENTIAL:
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file->f_ra.ra_pages = bdi->ra_pages * 2;
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break;
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case POSIX_FADV_WILLNEED:
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if (!mapping->a_ops->readpage) {
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ret = -EINVAL;
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break;
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}
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/* First and last PARTIAL page! */
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start_index = offset >> PAGE_CACHE_SHIFT;
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end_index = endbyte >> PAGE_CACHE_SHIFT;
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/* Careful about overflow on the "+1" */
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nrpages = end_index - start_index + 1;
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if (!nrpages)
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nrpages = ~0UL;
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ret = force_page_cache_readahead(mapping, file,
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start_index,
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max_sane_readahead(nrpages));
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if (ret > 0)
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ret = 0;
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break;
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case POSIX_FADV_NOREUSE:
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break;
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case POSIX_FADV_DONTNEED:
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if (!bdi_write_congested(mapping->backing_dev_info))
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filemap_flush(mapping);
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/* First and last FULL page! */
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start_index = (offset+(PAGE_CACHE_SIZE-1)) >> PAGE_CACHE_SHIFT;
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end_index = (endbyte >> PAGE_CACHE_SHIFT);
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if (end_index >= start_index)
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invalidate_mapping_pages(mapping, start_index,
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end_index);
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break;
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default:
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ret = -EINVAL;
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}
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out:
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fput(file);
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return ret;
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}
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#ifdef __ARCH_WANT_SYS_FADVISE64
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asmlinkage long sys_fadvise64(int fd, loff_t offset, size_t len, int advice)
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{
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return sys_fadvise64_64(fd, offset, len, advice);
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}
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#endif
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