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authorAl Viro <viro@zeniv.linux.org.uk>2018-11-05 17:40:30 +0000
committerAl Viro <viro@zeniv.linux.org.uk>2019-03-20 18:49:06 -0400
commita07b20004793d8926f78d63eb5980559f7813404 (patch)
tree08f7516cbd8ef036fac64b225fd480c2bec3758f /fs/file_table.c
parent9e98c678c2d6ae3a17cb2de55d17f69dddaa231b (diff)
downloadlwn-a07b20004793d8926f78d63eb5980559f7813404.tar.gz
lwn-a07b20004793d8926f78d63eb5980559f7813404.zip
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 <viro@zeniv.linux.org.uk> Signed-off-by: David Howells <dhowells@redhat.com> cc: linux-api@vger.kernel.org Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Diffstat (limited to 'fs/file_table.c')
-rw-r--r--fs/file_table.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/fs/file_table.c b/fs/file_table.c
index 155d7514a094..3f9c1b452c1d 100644
--- a/fs/file_table.c
+++ b/fs/file_table.c
@@ -255,6 +255,7 @@ static void __fput(struct file *file)
struct dentry *dentry = file->f_path.dentry;
struct vfsmount *mnt = file->f_path.mnt;
struct inode *inode = file->f_inode;
+ fmode_t mode = file->f_mode;
if (unlikely(!(file->f_mode & FMODE_OPENED)))
goto out;
@@ -277,18 +278,20 @@ static void __fput(struct file *file)
if (file->f_op->release)
file->f_op->release(inode, file);
if (unlikely(S_ISCHR(inode->i_mode) && inode->i_cdev != NULL &&
- !(file->f_mode & FMODE_PATH))) {
+ !(mode & FMODE_PATH))) {
cdev_put(inode->i_cdev);
}
fops_put(file->f_op);
put_pid(file->f_owner.pid);
- if ((file->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
+ if ((mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ)
i_readcount_dec(inode);
- if (file->f_mode & FMODE_WRITER) {
+ if (mode & FMODE_WRITER) {
put_write_access(inode);
__mnt_drop_write(mnt);
}
dput(dentry);
+ if (unlikely(mode & FMODE_NEED_UNMOUNT))
+ dissolve_on_fput(mnt);
mntput(mnt);
out:
file_free(file);