On Fri, Mar 15, 2024 at 04:16:33PM +0800, kernel test robot wrote:
>
>
> Hello,
>
> kernel test robot noticed "ltp.readahead01.fail" on:
>
> commit: cb12fd8e0dabb9a1c8aef55a6a41e2c255fcdf4b ("pidfd: add pidfs")
> https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
>
> [test failed on linus/master 65d287c7eb1d14e0f4d56f19cec30d97fc7e8f66]
> [test failed on linux-next/master a1184cae56bcb96b86df3ee0377cec507a3f56e0]
>
> in testcase: ltp
> version: ltp-x86_64-14c1f76-1_20240309
> with following parameters:
>
> disk: 1HDD
> fs: f2fs
> test: syscalls-00/readahead01
>
>
>
> compiler: gcc-12
> test machine: 4 threads 1 sockets Intel(R) Core(TM) i3-3220 CPU @ 3.30GHz (Ivy Bridge) with 8G memory
Yes, this is an expected failure.
Before moving pidfds to pidfs they were based on anonymous inodes.
Anonymous inodes have a strange property: yhey have no file type. IOW,
(stat.st_mode & S_IFMT) == 0.
The readhead code looks at the filetype and if it isn't a regular file
then you'll get EINVAL. This is the case for anonymous inode based
pidfds:
/*
* The readahead() syscall is intended to run only on files
* that can execute readahead. If readahead is not possible
* on this file, then we must return -EINVAL.
*/
ret = -EINVAL;
if (!f.file->f_mapping || !f.file->f_mapping->a_ops ||
(!S_ISREG(file_inode(f.file)->i_mode) &&
!S_ISBLK(file_inode(f.file)->i_mode)))
goto out;
However, pidfs makes them regular files so they're not caught by that
check anymore.
However, pidfs doesn't implement any readahead support. Specifically,
it'll have sb->s_bdi == noop_backing_dev_info. Which will mean the
readahead request is just ignored:
if (IS_DAX(inode) || (bdi == &noop_backing_dev_info)) {
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:
return -EINVAL;
}
return 0;
}
So I'd just remove that test. It's meaningless for pseudo fses.
