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Christian Brauner <brauner@kernel.org> says: The f_version member in struct file isn't particularly well-defined. It is mainly used as a cookie to detect concurrent seeks when iterating directories. But it is also abused by some subsystems for completely unrelated things. It is mostly a directory specific thing that doesn't really need to live in struct file and with its wonky semantics it really lacks a specific function. For pipes, f_version is (ab)used to defer poll notifications until a write has happened. And struct pipe_inode_info is used by multiple struct files in their ->private_data so there's no chance of pushing that down into file->private_data without introducing another pointer indirection. But this should be a solvable problem. Only regular files with FMODE_ATOMIC_POS and directories require f_pos_lock. Pipes and other files don't. So this adds a union into struct file encompassing f_pos_lock and a pipe specific f_pipe member that pipes can use. This union of course can be extended to other file types and is similar to what we do in struct inode already. * patches from https://lore.kernel.org/r/20240830-vfs-file-f_version-v1-0-6d3e4816aa7b@kernel.org: fs: remove f_version pipe: use f_pipe fs: add f_pipe ubifs: store cookie in private data ufs: store cookie in private data udf: store cookie in private data proc: store cookie in private data ocfs2: store cookie in private data input: remove f_version abuse ext4: store cookie in private data ext2: store cookie in private data affs: store cookie in private data fs: add generic_llseek_cookie() fs: use must_set_pos() fs: add must_set_pos() fs: add vfs_setpos_cookie() s390: remove unused f_version ceph: remove unused f_version adi: remove unused f_version file: remove pointless comment Link: https://lore.kernel.org/r/20240830-vfs-file-f_version-v1-0-6d3e4816aa7b@kernel.org Signed-off-by: Christian Brauner <brauner@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.