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devpts: comment devpts_mntget()

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Signed-off-by: Christian Brauner <christian.brauner@ubuntu.com>
Acked-by: "Eric W. Biederman" <ebiederm@xmission.com>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
This commit is contained in:
Christian Brauner 2018-03-13 17:55:26 +01:00 committed by Greg Kroah-Hartman
parent a319b01d90
commit 4e15f760a4
1 changed files with 18 additions and 0 deletions
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18
fs/devpts/inode.c
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@ -152,6 +152,24 @@ static int devpts_ptmx_path(struct path *path)
return 0;
}
/*
* Try to find a suitable devpts filesystem. We support the following
* scenarios:
* - The ptmx device node is located in the same directory as the devpts
* mount where the pts device nodes are located.
* This is e.g. the case when calling open on the /dev/pts/ptmx device
* node when the devpts filesystem is mounted at /dev/pts.
* - The ptmx device node is located outside the devpts filesystem mount
* where the pts device nodes are located. For example, the ptmx device
* is a symlink, separate device node, or bind-mount.
* A supported scenario is bind-mounting /dev/pts/ptmx to /dev/ptmx and
* then calling open on /dev/ptmx. In this case a suitable pts
* subdirectory can be found in the common parent directory /dev of the
* devpts mount and the ptmx bind-mount, after resolving the /dev/ptmx
* bind-mount.
* If no suitable pts subdirectory can be found this function will fail.
* This is e.g. the case when bind-mounting /dev/pts/ptmx to /ptmx.
*/
struct vfsmount *devpts_mntget(struct file *filp, struct pts_fs_info *fsi)
{
struct path path;