mirror of
https://github.com/torvalds/linux.git
synced 2026-07-29 02:31:27 +02:00
Linux kernel source tree
cedae19487
Patch series "expose mapping wrprotect, fix fb_defio use", v3. Right now the only means by which we can write-protect a range using the reverse mapping is via folio_mkclean(). However this is not always the appropriate means of doing so, specifically in the case of the framebuffer deferred I/O logic (fb_defio enabled by CONFIG_FB_DEFERRED_IO). There, kernel pages are mapped read-only and write-protect faults used to batch up I/O operations. Each time the deferred work is done, folio_mkclean() is used to mark the framebuffer page as having had I/O performed on it. However doing so requires the kernel page (perhaps allocated via vmalloc()) to have its page->mapping, index fields set so the rmap can find everything that maps it in order to write-protect. This is problematic as firstly, these fields should not be set for kernel-allocated memory, and secondly these are not folios (it's not user memory) and page->index, mapping fields are now deprecated and soon to be removed. The removal of these fields is imminent, rendering this series more urgent than it might first appear. The implementers cannot be blamed for having used this however, as there is simply no other way of performing this operation correctly. This series fixes this - we provide the mapping_wrprotect_range() function to allow the reverse mapping to be used to look up mappings from the page cache object (i.e. its address_space pointer) at a specific offset. The fb_defio logic already stores this offset, and can simply be expanded to keep track of the page cache object, so the change then becomes straight-forward. This series should have no functional change. This patch (of 3): In order to permit the traversal of the reverse mapping at a specified mapping and offset rather than those specified by an input folio, we need to separate out the portion of the rmap file logic which deals with this traversal from those parts of the logic which interact with the folio. This patch achieves this by adding a new static __rmap_walk_file() function which rmap_walk_file() invokes. This function permits the ability to pass NULL folio, on the assumption that the caller has provided for this correctly in the callbacks specified in the rmap_walk_control object. Though it provides for this, and adds debug asserts to ensure that, should a folio be specified, these are equal to the mapping and offset specified in the folio, there should be no functional change as a result of this patch. The reason for adding this is to enable for future changes to permit users to be able to traverse mappings of userland-mapped kernel memory, write-protecting those mappings to enable page_mkwrite() or pfn_mkwrite() fault handlers to be retriggered on subsequent dirty. Link: https://lkml.kernel.org/r/cover.1739029358.git.lorenzo.stoakes@oracle.com Link: https://lkml.kernel.org/r/0d1acec0cba1e5a12f9b53efcabc397541c90517.1739029358.git.lorenzo.stoakes@oracle.com Signed-off-by: Lorenzo Stoakes <lorenzo.stoakes@oracle.com> Cc: David Hildenbrand <david@redhat.com> Cc: Helge Deller <deller@gmx.de> Cc: Jaya Kumar <jayakumar.lkml@gmail.com> Cc: Kajtar Zsolt <soci@c64.rulez.org> Cc: Maíra Canal <mcanal@igalia.com> Cc: Matthew Wilcox <willy@infradead.org> [English fixes] Cc: Simona Vetter <simona.vetter@ffwll.ch> Cc: Thomas Zimemrmann <tzimmermann@suse.de> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
||
|---|---|---|
| arch | ||
| block | ||
| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
| net | ||
| rust | ||
| samples | ||
| scripts | ||
| security | ||
| sound | ||
| tools | ||
| usr | ||
| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
| .gitattributes | ||
| .gitignore | ||
| .mailmap | ||
| .rustfmt.toml | ||
| COPYING | ||
| CREDITS | ||
| Kbuild | ||
| Kconfig | ||
| MAINTAINERS | ||
| Makefile | ||
| 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 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.