Commit 64078b3d authored by Peter Xu's avatar Peter Xu Committed by Andrew Morton
Browse files

mm: document pXd_leaf() API 

There's one small section already, but since we're going to remove
pXd_huge(), that comment may start to obsolete.

Rewrite that section with more information, hopefully with that the API is
crystal clear on what it implies.

Link: https://lkml.kernel.org/r/20240318200404.448346-15-peterx@redhat.com


Signed-off-by: default avatarPeter Xu <peterx@redhat.com>
Reviewed-by: default avatarJason Gunthorpe <jgg@nvidia.com>
Cc: Alistair Popple <apopple@nvidia.com>
Cc: Andreas Larsson <andreas@gaisler.com>
Cc: "Aneesh Kumar K.V" <aneesh.kumar@kernel.org>
Cc: Arnd Bergmann <arnd@arndb.de>
Cc: Bjorn Andersson <andersson@kernel.org>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Christophe Leroy <christophe.leroy@csgroup.eu>
Cc: Dave Hansen <dave.hansen@linux.intel.com>
Cc: David S. Miller <davem@davemloft.net>
Cc: Fabio Estevam <festevam@denx.de>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Konrad Dybcio <konrad.dybcio@linaro.org>
Cc: Krzysztof Kozlowski <krzysztof.kozlowski@linaro.org>
Cc: Lucas Stach <l.stach@pengutronix.de>
Cc: Mark Salter <msalter@redhat.com>
Cc: "Matthew Wilcox (Oracle)" <willy@infradead.org>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Mike Rapoport (IBM) <rppt@kernel.org>
Cc: Muchun Song <muchun.song@linux.dev>
Cc: Naoya Horiguchi <nao.horiguchi@gmail.com>
Cc: "Naveen N. Rao" <naveen.n.rao@linux.ibm.com>
Cc: Nicholas Piggin <npiggin@gmail.com>
Cc: Russell King <linux@armlinux.org.uk>
Cc: Shawn Guo <shawnguo@kernel.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Will Deacon <will@kernel.org>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent 502016e3

include/linux/pgtable.h

+19 −5
Original line number Diff line number Diff line
@@ -1768,11 +1768,25 @@ typedef unsigned int pgtbl_mod_mask; 
#endif



/*

 * p?d_leaf() - true if this entry is a final mapping to a physical address.

 * This differs from p?d_huge() by the fact that they are always available (if

 * the architecture supports large pages at the appropriate level) even

 * if CONFIG_HUGETLB_PAGE is not defined.

 * Only meaningful when called on a valid entry.

 * pXd_leaf() is the API to check whether a pgtable entry is a huge page

 * mapping.  It should work globally across all archs, without any

 * dependency on CONFIG_* options.  For architectures that do not support

 * huge mappings on specific levels, below fallbacks will be used.

 *

 * A leaf pgtable entry should always imply the following:

 *

 * - It is a "present" entry.  IOW, before using this API, please check it

 *   with pXd_present() first. NOTE: it may not always mean the "present

 *   bit" is set.  For example, PROT_NONE entries are always "present".

 *

 * - It should _never_ be a swap entry of any type.  Above "present" check

 *   should have guarded this, but let's be crystal clear on this.

 *

 * - It should contain a huge PFN, which points to a huge page larger than

 *   PAGE_SIZE of the platform.  The PFN format isn't important here.

 *

 * - It should cover all kinds of huge mappings (e.g., pXd_trans_huge(),

 *   pXd_devmap(), or hugetlb mappings).

 */

#ifndef pgd_leaf

#define pgd_leaf(x)	false