1b151e2435
The special casing was originally added in pre-git history; reproducing
the commit log here:
> commit a318a92567d77
> Author: Andrew Morton <akpm@osdl.org>
> Date: Sun Sep 21 01:42:22 2003 -0700
>
> [PATCH] Speed up direct-io hugetlbpage handling
>
> This patch short-circuits all the direct-io page dirtying logic for
> higher-order pages. Without this, we pointlessly bounce BIOs up to
> keventd all the time.
In the last twenty years, compound pages have become used for more than
just hugetlb. Rewrite these functions to operate on folios instead
of pages and remove the special case for hugetlbfs; I don't think
it's needed any more (and if it is, we can put it back in as a call
to folio_test_hugetlb()).
This was found by inspection; as far as I can tell, this bug can lead
to pages used as the destination of a direct I/O read not being marked
as dirty. If those pages are then reclaimed by the MM without being
dirtied for some other reason, they won't be written out. Then when
they're faulted back in, they will not contain the data they should.
It'll take a pretty unusual setup to produce this problem with several
races all going the wrong way.
This problem predates the folio work; it could for example have been
triggered by mmaping a THP in tmpfs and using that as the target of an
O_DIRECT read.
Fixes:
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|---|---|---|
| Documentation | ||
| LICENSES | ||
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .cocciconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| README | ||
README
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.