Eric Biggers 14e43bf435 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 <ebiggers@google.com>
Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
2021-01-04 14:02:08 -05:00
2020-12-22 08:43:06 -07:00
2020-12-22 12:55:07 -08:00
…
2020-12-27 15:30:22 -08:00
…

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 Restructured Text 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.
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