fs: get mnt_writers count for an open backing file's real path

[thirdparty/kernel/linux.git] / fs / open.c

diff --git a/fs/open.c b/fs/open.c
index e6ead0f19964957afd601cb4f7ad1ab88a9a510c..fe63e236da2225e1ac4579d8b5b41dea06cd51a3 100644 (file)
--- a/fs/open.c
+++ b/fs/open.c
@@ -671,11 +671,20 @@ SYSCALL_DEFINE2(fchmod, unsigned int, fd, umode_t, mode)
        return err;
 }
 
-static int do_fchmodat(int dfd, const char __user *filename, umode_t mode)
+static int do_fchmodat(int dfd, const char __user *filename, umode_t mode,
+                      unsigned int flags)
 {
        struct path path;
        int error;
-       unsigned int lookup_flags = LOOKUP_FOLLOW;
+       unsigned int lookup_flags;
+
+       if (unlikely(flags & ~(AT_SYMLINK_NOFOLLOW | AT_EMPTY_PATH)))
+               return -EINVAL;
+
+       lookup_flags = (flags & AT_SYMLINK_NOFOLLOW) ? 0 : LOOKUP_FOLLOW;
+       if (flags & AT_EMPTY_PATH)
+               lookup_flags |= LOOKUP_EMPTY;
+
 retry:
        error = user_path_at(dfd, filename, lookup_flags, &path);
        if (!error) {
@@ -689,15 +698,21 @@ retry:
        return error;
 }
 
+SYSCALL_DEFINE4(fchmodat2, int, dfd, const char __user *, filename,
+               umode_t, mode, unsigned int, flags)
+{
+       return do_fchmodat(dfd, filename, mode, flags);
+}
+
 SYSCALL_DEFINE3(fchmodat, int, dfd, const char __user *, filename,
                umode_t, mode)
 {
-       return do_fchmodat(dfd, filename, mode);
+       return do_fchmodat(dfd, filename, mode, 0);
 }
 
 SYSCALL_DEFINE2(chmod, const char __user *, filename, umode_t, mode)
 {
-       return do_fchmodat(AT_FDCWD, filename, mode);
+       return do_fchmodat(AT_FDCWD, filename, mode, 0);
 }
 
 /*
@@ -855,6 +870,30 @@ SYSCALL_DEFINE3(fchown, unsigned int, fd, uid_t, user, gid_t, group)
        return ksys_fchown(fd, user, group);
 }
 
+static inline int file_get_write_access(struct file *f)
+{
+       int error;
+
+       error = get_write_access(f->f_inode);
+       if (unlikely(error))
+               return error;
+       error = mnt_get_write_access(f->f_path.mnt);
+       if (unlikely(error))
+               goto cleanup_inode;
+       if (unlikely(f->f_mode & FMODE_BACKING)) {
+               error = mnt_get_write_access(backing_file_real_path(f)->mnt);
+               if (unlikely(error))
+                       goto cleanup_mnt;
+       }
+       return 0;
+
+cleanup_mnt:
+       mnt_put_write_access(f->f_path.mnt);
+cleanup_inode:
+       put_write_access(f->f_inode);
+       return error;
+}
+
 static int do_dentry_open(struct file *f,
                          struct inode *inode,
                          int (*open)(struct inode *, struct file *))
@@ -877,14 +916,9 @@ static int do_dentry_open(struct file *f,
        if ((f->f_mode & (FMODE_READ | FMODE_WRITE)) == FMODE_READ) {
                i_readcount_inc(inode);
        } else if (f->f_mode & FMODE_WRITE && !special_file(inode->i_mode)) {
-               error = get_write_access(inode);
+               error = file_get_write_access(f);
                if (unlikely(error))
                        goto cleanup_file;
-               error = __mnt_want_write(f->f_path.mnt);
-               if (unlikely(error)) {
-                       put_write_access(inode);
-                       goto cleanup_file;
-               }
                f->f_mode |= FMODE_WRITER;
        }
 
@@ -1150,7 +1184,7 @@ EXPORT_SYMBOL_GPL(kernel_file_open);
  * backing_file_open - open a backing file for kernel internal use
  * @path:      path of the file to open
  * @flags:     open flags
- * @path:      path of the backing file
+ * @real_path: path of the backing file
  * @cred:      credentials for open
  *
  * Open a backing file for a stackable filesystem (e.g., overlayfs).
@@ -1503,7 +1537,7 @@ SYSCALL_DEFINE2(creat, const char __user *, pathname, umode_t, mode)
  * "id" is the POSIX thread ID. We use the
  * files pointer for this..
  */
-int filp_close(struct file *filp, fl_owner_t id)
+static int filp_flush(struct file *filp, fl_owner_t id)
 {
        int retval = 0;
 
@@ -1520,10 +1554,18 @@ int filp_close(struct file *filp, fl_owner_t id)
                dnotify_flush(filp, id);
                locks_remove_posix(filp, id);
        }
-       fput(filp);
        return retval;
 }
 
+int filp_close(struct file *filp, fl_owner_t id)
+{
+       int retval;
+
+       retval = filp_flush(filp, id);
+       fput(filp);
+
+       return retval;
+}
 EXPORT_SYMBOL(filp_close);
 
 /*
@@ -1533,7 +1575,20 @@ EXPORT_SYMBOL(filp_close);
  */
 SYSCALL_DEFINE1(close, unsigned int, fd)
 {
-       int retval = close_fd(fd);
+       int retval;
+       struct file *file;
+
+       file = close_fd_get_file(fd);
+       if (!file)
+               return -EBADF;
+
+       retval = filp_flush(file, current->files);
+
+       /*
+        * We're returning to user space. Don't bother
+        * with any delayed fput() cases.
+        */
+       __fput_sync(file);
 
        /* can't restart close syscall because file table entry was cleared */
        if (unlikely(retval == -ERESTARTSYS ||
@@ -1546,7 +1601,7 @@ SYSCALL_DEFINE1(close, unsigned int, fd)
 }
 
 /**
- * close_range() - Close all file descriptors in a given range.
+ * sys_close_range() - Close all file descriptors in a given range.
  *
  * @fd:     starting file descriptor to close
  * @max_fd: last file descriptor to close