From a07b20004793d8926f78d63eb5980559f7813404 Mon Sep 17 00:00:00 2001 From: Al Viro Date: Mon, 5 Nov 2018 17:40:30 +0000 Subject: vfs: syscall: Add open_tree(2) to reference or clone a mount open_tree(dfd, pathname, flags) Returns an O_PATH-opened file descriptor or an error. dfd and pathname specify the location to open, in usual fashion (see e.g. fstatat(2)). flags should be an OR of some of the following: * AT_PATH_EMPTY, AT_NO_AUTOMOUNT, AT_SYMLINK_NOFOLLOW - same meanings as usual * OPEN_TREE_CLOEXEC - make the resulting descriptor close-on-exec * OPEN_TREE_CLONE or OPEN_TREE_CLONE | AT_RECURSIVE - instead of opening the location in question, create a detached mount tree matching the subtree rooted at location specified by dfd/pathname. With AT_RECURSIVE the entire subtree is cloned, without it - only the part within in the mount containing the location in question. In other words, the same as mount --rbind or mount --bind would've taken. The detached tree will be dissolved on the final close of obtained file. Creation of such detached trees requires the same capabilities as doing mount --bind. Signed-off-by: Al Viro Signed-off-by: David Howells cc: linux-api@vger.kernel.org Signed-off-by: Al Viro --- include/linux/fs.h | 7 +++++-- include/linux/syscalls.h | 1 + 2 files changed, 6 insertions(+), 2 deletions(-) (limited to 'include/linux') diff --git a/include/linux/fs.h b/include/linux/fs.h index 8b42df09b04c..09b05ec5d059 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -162,10 +162,13 @@ typedef int (dio_iodone_t)(struct kiocb *iocb, loff_t offset, #define FMODE_NONOTIFY ((__force fmode_t)0x4000000) /* File is capable of returning -EAGAIN if I/O will block */ -#define FMODE_NOWAIT ((__force fmode_t)0x8000000) +#define FMODE_NOWAIT ((__force fmode_t)0x8000000) + +/* File represents mount that needs unmounting */ +#define FMODE_NEED_UNMOUNT ((__force fmode_t)0x10000000) /* File does not contribute to nr_files count */ -#define FMODE_NOACCOUNT ((__force fmode_t)0x20000000) +#define FMODE_NOACCOUNT ((__force fmode_t)0x20000000) /* * Flag for rw_copy_check_uvector and compat_rw_copy_check_uvector diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h index e446806a561f..6c29d586e66b 100644 --- a/include/linux/syscalls.h +++ b/include/linux/syscalls.h @@ -985,6 +985,7 @@ asmlinkage long sys_statx(int dfd, const char __user *path, unsigned flags, unsigned mask, struct statx __user *buffer); asmlinkage long sys_rseq(struct rseq __user *rseq, uint32_t rseq_len, int flags, uint32_t sig); +asmlinkage long sys_open_tree(int dfd, const char __user *path, unsigned flags); asmlinkage long sys_pidfd_send_signal(int pidfd, int sig, siginfo_t __user *info, unsigned int flags); -- cgit v1.2.3-71-gd317