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On filesystems with a block size smaller than PAGE_SIZE, page_mkwrite is called for each memory-mapped page before that page can be written to. When such a memory-mapped file is truncated down to size x which is not a multiple of the page size and then back to a larger size, the page straddling size x can end up with a partial block mapping. In that case, make sure to mark that page read-only so that page_mkwrite will be called before the page can be written to the next time. (There is no point in marking the page straddling size x read-only when truncating down as writing to memory beyond the end of the file will result in SIGBUS instead of growing the file.) Fixes xfstests generic/029, generic/030 on filesystems with a block size smaller than PAGE_SIZE. Signed-off-by: Andreas Gruenbacher <agruenba@redhat.com>
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.