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Groups > linux.kernel > #1376415
| From | ebiederm@xmission.com (Eric W. Biederman) |
|---|---|
| Newsgroups | linux.kernel |
| Subject | Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup |
| Date | 2016-04-12 04:30 +0200 |
| Message-ID | <rmWfv-7YP-1@gated-at.bofh.it> (permalink) |
| References | (6 earlier) <rmQD7-3mh-1@gated-at.bofh.it> <rmTKG-5Lf-11@gated-at.bofh.it> <rmU42-6dm-7@gated-at.bofh.it> <rmUno-6qa-1@gated-at.bofh.it> <rmVt7-7gi-1@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Al Viro <viro@ZenIV.linux.org.uk> writes:
> On Mon, Apr 11, 2016 at 07:10:47PM -0500, Eric W. Biederman wrote:
>> Actually for me this is about keeping the semantics simpler, and coming
>> up with a higher performance implementation.
>>
>> A dentry that does an automount is already well defined.
>>
>> Making the rule that accessing /dev/ptmx causes an automount of
>> /dev/pts/ptmx on top of the device node at /dev/ptmx is really simple,
>> with no special games. It also makes it more obvious to userspace what
>> is going on. AKA allows userspace to know which superblock does an open
>> ptmx master tty belongs to (and it happens in a backwards and forwards
>> compatible way).
>
> _What_ dentry? Which filesystem would that be done to? Whatever we have
> on /dev? Or we suddenly get the fucking dentry operations change when
> dentry is attached to magical cdev inode?
Which dentry? Any dentry that corresponds to the /dev/ptmx inode.
No filesystem changes just magic in init_special_inode that I have
not completely figured out yet.
If we can get an automount method in follow_automount from somewhere
cdev specific then a cdev can perform an automount comparitively
cleanly. file_operations is attractive I am have not yet figured out a
clean method for passing the automount method yet.
For my proof of concept I am hardcoding things based on i_rdev. Ugly
but servicable for testing out the idea.
A snip of my proof of concept code that seems to be working:
diff --git a/fs/inode.c b/fs/inode.c
index 69b8b526c194..d3de77b01a84 100644
--- a/fs/inode.c
+++ b/fs/inode.c
@@ -18,6 +18,7 @@
#include <linux/buffer_head.h> /* for inode_has_buffers */
#include <linux/ratelimit.h>
#include <linux/list_lru.h>
+#include <linux/devpts_fs.h>
#include <trace/events/writeback.h>
#include "internal.h"
@@ -1917,6 +1918,11 @@ void init_special_inode(struct inode *inode, umode_t mode, dev_t rdev)
if (S_ISCHR(mode)) {
inode->i_fop = &def_chr_fops;
inode->i_rdev = rdev;
+#if CONFIG_UNIX98_PTYS
+ if (rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)) {
+ inode->i_flags |= S_AUTOMOUNT;
+ }
+#endif
} else if (S_ISBLK(mode)) {
inode->i_fop = &def_blk_fops;
inode->i_rdev = rdev;
diff --git a/fs/namei.c b/fs/namei.c
index afb5137ca199..8894cf5fb43e 100644
--- a/fs/namei.c
+++ b/fs/namei.c
@@ -35,6 +35,8 @@
#include <linux/fs_struct.h>
#include <linux/posix_acl.h>
#include <linux/hash.h>
+#include <linux/devpts_fs.h>
+#include <linux/major.h>
#include <asm/uaccess.h>
#include "internal.h"
@@ -1087,10 +1089,19 @@ EXPORT_SYMBOL(follow_up);
static int follow_automount(struct path *path, struct nameidata *nd,
bool *need_mntput)
{
+ struct vfsmount *(*automount)(struct path *) = NULL;
struct vfsmount *mnt;
int err;
- if (!path->dentry->d_op || !path->dentry->d_op->d_automount)
+ if (path->dentry->d_op)
+ automount = path->dentry->d_op->d_automount;
+#if CONFIG_UNIX98_PTYS
+ if (path->dentry->d_inode &&
+ path->dentry->d_inode->i_rdev == MKDEV(TTYAUX_MAJOR, PTMX_MINOR)) {
+ automount = ptmx_automount;
+ }
+#endif
+ if (!automount)
return -EREMOTE;
/* We don't want to mount if someone's just doing a stat -
@@ -1113,7 +1124,7 @@ static int follow_automount(struct path *path, struct nameidata *nd,
if (nd->total_link_count >= 40)
return -ELOOP;
- mnt = path->dentry->d_op->d_automount(path);
+ mnt = automount(path);
if (IS_ERR(mnt)) {
/*
* The filesystem is allowed to return -EISDIR here to indicate
Back to linux.kernel | Previous | Next — Previous in thread | Next in thread | Find similar | Unroll thread
[PATCH 00/13] devpts: New instances for every mount ebiederm@xmission.com (Eric W. Biederman) - 2016-04-05 02:20 +0200
[PATCH 04/13] devpts: Stop rolling devpts_remount by hand in devpts_mount "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
[PATCH 05/13] devpts: Fail early (if appropriate) on overmount "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
[PATCH 08/13] devpts: Make devpts_kill_sb safe if fsi is NULL "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
[PATCH 03/13] devpts: Cleanup newinstance parsing "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
[PATCH 06/13] devpts: Use the same default mode for both /dev/ptmx and dev/pts/ptmx "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
[PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
[PATCH 09/13] devpts: Move the creation of /dev/pts/ptmx into fill_super "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
[PATCH 02/13] devpts: More obvious check for the system devpts in pty allocation "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
[PATCH 13/13] devpts: Kill the DEVPTS_MULTIPLE_INSTANCE config option "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
[PATCH 07/13] devpts: Move parse_mount_options into fill_super "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 03:50 +0200
[PATCH 12/13] devpts: Always return a distinct instance when mounting "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 04:00 +0200
[PATCH 11/13] vfs: Implement mount_super_once "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 04:00 +0200
[PATCH 10/13] devpts: Simplify devpts_mount by using mount_nodev "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-05 04:00 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Al Viro <viro@ZenIV.linux.org.uk> - 2016-04-05 05:00 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Al Viro <viro@ZenIV.linux.org.uk> - 2016-04-05 05:10 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-08 21:10 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-07 18:10 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-08 21:10 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-08 21:10 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-08 22:20 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Andy Lutomirski <luto@amacapital.net> - 2016-04-08 22:50 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-08 23:50 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Andy Lutomirski <luto@amacapital.net> - 2016-04-09 00:00 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-09 00:00 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-09 01:20 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup One Thousand Gnomes <gnomes@lxorguk.ukuu.org.uk> - 2016-04-09 15:20 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-09 16:20 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-09 17:00 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-10 00:50 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-10 02:10 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-10 02:20 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-10 02:20 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Andy Lutomirski <luto@amacapital.net> - 2016-04-10 02:50 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-11 17:10 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Al Viro <viro@ZenIV.linux.org.uk> - 2016-04-12 03:40 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Andy Lutomirski <luto@amacapital.net> - 2016-04-11 22:20 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-11 22:30 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 01:50 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-12 02:10 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 02:30 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-12 03:20 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-12 03:20 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 03:40 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Al Viro <viro@ZenIV.linux.org.uk> - 2016-04-12 03:50 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Al Viro <viro@ZenIV.linux.org.uk> - 2016-04-12 03:40 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 04:30 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-11 22:30 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Andy Lutomirski <luto@amacapital.net> - 2016-04-12 19:50 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-12 20:20 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup "H. Peter Anvin" <hpa@zytor.com> - 2016-04-12 21:20 +0200
[PATCH 01/16] devpts: Attempting to get it right ebiederm@xmission.com (Eric W. Biederman) - 2016-04-15 17:50 +0200
[PATCH 08/16] devpts: Stop rolling devpts_remount by hand in devpts_mount "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
[PATCH 05/16] vfs: Allow unlink, and rename on expirable file mounts "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
[PATCH 04/16] devpts: Teach /dev/ptmx to automount the appropriate devpts via path lookup "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
[PATCH 09/16] devpts: Fail early (if appropriate) on overmount "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
[PATCH 10/16] devpts: Move parse_mount_options into fill_super "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
[PATCH 06/16] devpts: More obvious check for the system devpts in pty allocation "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
[PATCH 01/16] devpts: Use the same default mode for both /dev/ptmx and dev/pts/ptmx "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 17:50 +0200
[PATCH 12/16] devpts: Move the creation of /dev/pts/ptmx into fill_super "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
[PATCH 11/16] devpts: Make devpts_kill_sb safe if fsi is NULL "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
[PATCH 16/16] devpts: Kill the DEVPTS_MULTIPLE_INSTANCE config option "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
[PATCH 15/16] devpts: Always return a distinct instance when mounting "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
[PATCH 13/16] devpts: Simplify devpts_mount by using mount_nodev "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
[PATCH 14/16] vfs: Implement mount_super_once "Eric W. Biederman" <ebiederm@xmission.com> - 2016-04-15 18:00 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 02:10 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-12 02:10 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-12 02:40 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup Linus Torvalds <torvalds@linux-foundation.org> - 2016-04-12 03:00 +0200
Re: [PATCH 01/13] devpts: Teach /dev/ptmx to find the associated devpts via path lookup ebiederm@xmission.com (Eric W. Biederman) - 2016-04-11 22:20 +0200
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