Ryan Roberts
2ad2067e9f
commit ec056cef76 upstream.
The THP machinery does not support order-1 folios because it requires meta
data spanning the first 3 `struct page`s. So order-2 is the smallest
large folio that we can safely create.
There was a theoretical bug whereby if ra->size was 2 or 3 pages (due to
the device-specific bdi->ra_pages being set that way), we could end up
with order = 1. Fix this by unconditionally checking if the preferred
order is 1 and if so, set it to 0. Previously this was done in a few
specific places, but with this refactoring it is done just once,
unconditionally, at the end of the calculation.
This is a theoretical bug found during review of the code; I have no
evidence to suggest this manifests in the real world (I expect all
device-specific ra_pages values are much bigger than 3).
Link: https://lkml.kernel.org/r/20231201161045.3962614-1-ryan.roberts@arm.com
Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
Reviewed-by: Matthew Wilcox (Oracle) <willy@infradead.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Hugh Dickins <hughd@google.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.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 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.