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From: Al Viro <viro-RmSDqhL/yNMiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
To: Christoph Hellwig <hch-jcswGhMUV9g@public.gmane.org>
Cc: Linus Torvalds
	<torvalds-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>,
	Greg Kroah-Hartman
	<gregkh-hQyY1W1yCW8ekmWlsbkhG0B+6BGkLq7r@public.gmane.org>,
	"Rafael J. Wysocki"
	<rafael-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>,
	linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-raid-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-fsdevel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org,
	linux-api-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
Subject: Re: [PATCH 06/24] md: open code vfs_stat in md_setup_drive
Date: Tue, 21 Jul 2020 17:55:39 +0100	[thread overview]
Message-ID: <20200721165539.GT2786714@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20200721162818.197315-7-hch-jcswGhMUV9g@public.gmane.org>

On Tue, Jul 21, 2020 at 06:28:00PM +0200, Christoph Hellwig wrote:
> Instead of passing a kernel pointer to vfs_stat by relying on the
> implicit set_fs(KERNEL_DS) in md_setup_drive, just open code the
> trivial getattr, and use the opportunity to move a little bit more
> code from the caller into the new helper.

Ugh...

> +static void __init md_lookup_dev(const char *devname, dev_t *dev)
> +{
> +	struct kstat stat;
> +	struct path path;
> +	char filename[64];
> +
> +	if (strncmp(devname, "/dev/", 5) == 0)
> +		devname += 5;
> +	snprintf(filename, 63, "/dev/%s", devname);
> +
> +	if (!kern_path(filename, LOOKUP_FOLLOW, &path) &&
> +	    !vfs_getattr(&path, &stat, STATX_BASIC_STATS, AT_NO_AUTOMOUNT) &&
> +	    S_ISBLK(stat.mode))
> +		*dev = new_decode_dev(stat.rdev);
> +	path_put(&path);
> +}

How about fs/for_init.c and putting the damn helpers there?  With
calling conventions as close to syscalls as possible, and a fat
comment regarding their intended use being _ONLY_ the setup
in should-have-been-done-in-userland parts of init?

I really want to keep the surface as small as possible - we had
fun shite several releases ago when somebody tried that kind of
crap (with open(), IIRC).  Let's not go there again...

WARNING: multiple messages have this Message-ID (diff)
From: Al Viro <viro@zeniv.linux.org.uk>
To: Christoph Hellwig <hch@lst.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
	"Rafael J. Wysocki" <rafael@kernel.org>,
	linux-kernel@vger.kernel.org, linux-raid@vger.kernel.org,
	linux-fsdevel@vger.kernel.org, linux-api@vger.kernel.org
Subject: Re: [PATCH 06/24] md: open code vfs_stat in md_setup_drive
Date: Tue, 21 Jul 2020 17:55:39 +0100	[thread overview]
Message-ID: <20200721165539.GT2786714@ZenIV.linux.org.uk> (raw)
In-Reply-To: <20200721162818.197315-7-hch@lst.de>

On Tue, Jul 21, 2020 at 06:28:00PM +0200, Christoph Hellwig wrote:
> Instead of passing a kernel pointer to vfs_stat by relying on the
> implicit set_fs(KERNEL_DS) in md_setup_drive, just open code the
> trivial getattr, and use the opportunity to move a little bit more
> code from the caller into the new helper.

Ugh...

> +static void __init md_lookup_dev(const char *devname, dev_t *dev)
> +{
> +	struct kstat stat;
> +	struct path path;
> +	char filename[64];
> +
> +	if (strncmp(devname, "/dev/", 5) == 0)
> +		devname += 5;
> +	snprintf(filename, 63, "/dev/%s", devname);
> +
> +	if (!kern_path(filename, LOOKUP_FOLLOW, &path) &&
> +	    !vfs_getattr(&path, &stat, STATX_BASIC_STATS, AT_NO_AUTOMOUNT) &&
> +	    S_ISBLK(stat.mode))
> +		*dev = new_decode_dev(stat.rdev);
> +	path_put(&path);
> +}

How about fs/for_init.c and putting the damn helpers there?  With
calling conventions as close to syscalls as possible, and a fat
comment regarding their intended use being _ONLY_ the setup
in should-have-been-done-in-userland parts of init?

I really want to keep the surface as small as possible - we had
fun shite several releases ago when somebody tried that kind of
crap (with open(), IIRC).  Let's not go there again...

  parent reply	other threads:[~2020-07-21 16:55 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-07-21 16:27 add file system helpers that take kernel pointers for the init code v2 Christoph Hellwig
2020-07-21 16:27 ` [PATCH 01/24] fs: refactor do_mount Christoph Hellwig
2020-07-21 16:27 ` [PATCH 02/24] fs: refactor ksys_umount Christoph Hellwig
2020-07-21 16:27 ` [PATCH 03/24] fs: push the getname from do_rmdir into the callers Christoph Hellwig
2020-07-21 16:27 ` [PATCH 04/24] devtmpfs: open code do_mount Christoph Hellwig
2020-07-21 16:27 ` [PATCH 05/24] devtmpfs: open code ksys_chdir and ksys_chroot Christoph Hellwig
     [not found]   ` <20200721162818.197315-6-hch-jcswGhMUV9g@public.gmane.org>
2020-07-21 16:49     ` Linus Torvalds
2020-07-21 16:49       ` Linus Torvalds
     [not found]       ` <CAHk-=wi0GQqAq6VSY=O2iWnPuuS54TkyRBH5B9Ca0Kg5A9d2aA-JsoAwUIsXosN+BqQ9rBEUg@public.gmane.org>
2020-07-21 17:16         ` Al Viro
2020-07-21 17:16           ` Al Viro
2020-07-21 18:26           ` Christoph Hellwig
2020-07-21 16:28 ` [PATCH 06/24] md: open code vfs_stat in md_setup_drive Christoph Hellwig
     [not found]   ` <20200721162818.197315-7-hch-jcswGhMUV9g@public.gmane.org>
2020-07-21 16:55     ` Al Viro [this message]
2020-07-21 16:55       ` Al Viro
     [not found]       ` <20200721165539.GT2786714-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2020-07-21 18:27         ` Christoph Hellwig
2020-07-21 18:27           ` Christoph Hellwig
     [not found]           ` <20200721182701.GB14450-jcswGhMUV9g@public.gmane.org>
2020-07-22  7:44             ` Al Viro
2020-07-22  7:44               ` Al Viro
     [not found]               ` <20200722074432.GD2786714-3bDd1+5oDREiFSDQTTA3OLVCufUGDwFn@public.gmane.org>
2020-07-22 14:05                 ` Christoph Hellwig
2020-07-22 14:05                   ` Christoph Hellwig
2020-07-21 16:28 ` [PATCH 07/24] init: initialize ramdisk_execute_command at compile time Christoph Hellwig
2020-07-21 16:28 ` [PATCH 08/24] init: move the prepare_namespace prototype to init/do_mounts.h Christoph Hellwig
2020-07-21 16:28 ` [PATCH 09/24] init: mark create_dev as __init Christoph Hellwig
2020-07-21 16:28 ` [PATCH 10/24] init: open code ksys_umount in handle_initrd Christoph Hellwig
2020-07-21 16:28 ` [PATCH 11/24] init: open code do_utimes in do_utime Christoph Hellwig
     [not found] ` <20200721162818.197315-1-hch-jcswGhMUV9g@public.gmane.org>
2020-07-21 16:28   ` [PATCH 12/24] init: add an init_mount helper Christoph Hellwig
2020-07-21 16:28     ` Christoph Hellwig
2020-07-21 16:58     ` Al Viro
2020-07-21 16:28   ` [PATCH 17/24] init: add an init_chown helper Christoph Hellwig
2020-07-21 16:28     ` Christoph Hellwig
2020-07-21 16:28   ` [PATCH 18/24] init: add an init_chmod helper Christoph Hellwig
2020-07-21 16:28     ` Christoph Hellwig
2020-07-21 16:28   ` [PATCH 20/24] init: add an init_link helper Christoph Hellwig
2020-07-21 16:28     ` Christoph Hellwig
2020-07-21 16:28 ` [PATCH 13/24] init: add an init_unlink helper Christoph Hellwig
     [not found]   ` <20200721162818.197315-14-hch-jcswGhMUV9g@public.gmane.org>
2020-07-21 17:12     ` Al Viro
2020-07-21 17:12       ` Al Viro
2020-07-21 16:28 ` [PATCH 14/24] init: add an init_rmdir helper Christoph Hellwig
2020-07-21 16:28 ` [PATCH 15/24] init: add an init_chdir helper Christoph Hellwig
2020-07-21 16:28 ` [PATCH 16/24] init: add an init_chroot helper Christoph Hellwig
2020-07-21 17:10   ` Al Viro
2020-08-01 18:43   ` kernel test robot
2020-07-21 16:28 ` [PATCH 19/24] init: add an init_eaccess helper Christoph Hellwig
2020-07-21 16:28 ` [PATCH 21/24] init: add an init_symlink helper Christoph Hellwig
2020-07-21 17:00   ` Al Viro
2020-07-21 16:28 ` [PATCH 22/24] init: add an init_mkdir helper Christoph Hellwig
2020-07-21 16:28 ` [PATCH 23/24] init: add an init_mknod helper Christoph Hellwig
2020-07-21 17:02   ` Al Viro
2020-07-21 16:28 ` [PATCH 24/24] init: add an init_lstat helper Christoph Hellwig

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