From 14e43bf435612639cab01541fce7cc41bf7e370b Mon Sep 17 00:00:00 2001 From: Eric Biggers Date: Tue, 22 Sep 2020 09:44:18 -0700 Subject: vfs: don't unnecessarily clone write access for writable fds There's no need for mnt_want_write_file() to increment mnt_writers when the file is already open for writing, provided that mnt_drop_write_file() is changed to conditionally decrement it. We seem to have ended up in the current situation because mnt_want_write_file() used to be paired with mnt_drop_write(), due to mnt_drop_write_file() not having been added yet. So originally mnt_want_write_file() had to always increment mnt_writers. But later mnt_drop_write_file() was added, and all callers of mnt_want_write_file() were paired with it. This makes the compatibility between mnt_want_write_file() and mnt_drop_write() no longer necessary. Therefore, make __mnt_want_write_file() and __mnt_drop_write_file() skip incrementing mnt_writers on files already open for writing. This removes the only caller of mnt_clone_write(), so remove that too. Signed-off-by: Eric Biggers Signed-off-by: Al Viro --- Documentation/filesystems/porting.rst | 7 +++++++ 1 file changed, 7 insertions(+) (limited to 'Documentation/filesystems/porting.rst') diff --git a/Documentation/filesystems/porting.rst b/Documentation/filesystems/porting.rst index 867036aa90b8..6a6d3e673b48 100644 --- a/Documentation/filesystems/porting.rst +++ b/Documentation/filesystems/porting.rst @@ -865,3 +865,10 @@ no matter what. Everything is handled by the caller. clone_private_mount() returns a longterm mount now, so the proper destructor of its result is kern_unmount() or kern_unmount_array(). + +--- + +**mandatory** + +mnt_want_write_file() can now only be paired with mnt_drop_write_file(), +whereas previously it could be paired with mnt_drop_write() as well. -- cgit v1.2.3