Lorenzo Stoakes 311150343e mm/gup: add missing gup_must_unshare() check to gup_huge_pgd()
All other instances of gup_huge_pXd() perform the unshare check, so update
the PGD-specific function to do so as well.

While checking pgd_write() might seem unusual, this function already
performs such a check via pgd_access_permitted() so this is in line with
the existing implementation.

David said:

: This change makes unshare handling across all GUP-fast variants
: consistent, which is desirable as GUP-fast is complicated enough
: already even when consistent.
: 
: This function was the only one I seemed to have missed (or left out and
: forgot why -- maybe because it's really dead code for now).  The COW
: selftest would identify the problem, so far there was no report. 
: Either the selftest wasn't run on corresponding architectures with that
: hugetlb size, or that code is still dead code and unused by
: architectures.
: 
: the original commit(s) that added unsharing explain why we care about
: these checks:
: 
: a7f2266041 ("mm/gup: trigger FAULT_FLAG_UNSHARE when R/O-pinning a possibly shared anonymous page")
: 84209e87c6 ("mm/gup: reliable R/O long-term pinning in COW mappings")

Link: https://lkml.kernel.org/r/cb971ac8dd315df97058ea69442ecc007b9a364a.1683381545.git.lstoakes@gmail.com
Signed-off-by: Lorenzo Stoakes <lstoakes@gmail.com>
Suggested-by: David Hildenbrand <david@redhat.com>
Acked-by: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
2023-06-09 16:25:17 -07:00
2023-05-19 13:56:26 -04:00
2022-09-28 09:02:20 +02:00
2023-05-28 07:49:00 -04:00

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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