mirror of https://github.com/torvalds/linux.git
38607c62b3
Currently fs dax pages are considered free when the refcount drops to one and their refcounts are not increased when mapped via PTEs or decreased when unmapped. This requires special logic in mm paths to detect that these pages should not be properly refcounted, and to detect when the refcount drops to one instead of zero. On the other hand get_user_pages(), etc. will properly refcount fs dax pages by taking a reference and dropping it when the page is unpinned. Tracking this special behaviour requires extra PTE bits (eg. pte_devmap) and introduces rules that are potentially confusing and specific to FS DAX pages. To fix this, and to possibly allow removal of the special PTE bits in future, convert the fs dax page refcounts to be zero based and instead take a reference on the page each time it is mapped as is currently the case for normal pages. This may also allow a future clean-up to remove the pgmap refcounting that is currently done in mm/gup.c. Link: https://lkml.kernel.org/r/c7d886ad7468a20452ef6e0ddab6cfe220874e7c.1740713401.git-series.apopple@nvidia.com Signed-off-by: Alistair Popple <apopple@nvidia.com> Reviewed-by: Dan Williams <dan.j.williams@intel.com> Tested-by: Alison Schofield <alison.schofield@intel.com> Acked-by: David Hildenbrand <david@redhat.com> Cc: Alexander Gordeev <agordeev@linux.ibm.com> Cc: Asahi Lina <lina@asahilina.net> Cc: Balbir Singh <balbirs@nvidia.com> Cc: Bjorn Helgaas <bhelgaas@google.com> Cc: Catalin Marinas <catalin.marinas@arm.com> Cc: Christian Borntraeger <borntraeger@linux.ibm.com> Cc: Christoph Hellwig <hch@lst.de> Cc: Chunyan Zhang <zhang.lyra@gmail.com> Cc: "Darrick J. Wong" <djwong@kernel.org> Cc: Dave Chinner <david@fromorbit.com> Cc: Dave Hansen <dave.hansen@linux.intel.com> Cc: Dave Jiang <dave.jiang@intel.com> Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com> Cc: Heiko Carstens <hca@linux.ibm.com> Cc: Huacai Chen <chenhuacai@kernel.org> Cc: Ira Weiny <ira.weiny@intel.com> Cc: Jan Kara <jack@suse.cz> Cc: Jason Gunthorpe <jgg@nvidia.com> Cc: Jason Gunthorpe <jgg@ziepe.ca> Cc: John Hubbard <jhubbard@nvidia.com> Cc: linmiaohe <linmiaohe@huawei.com> Cc: Logan Gunthorpe <logang@deltatee.com> Cc: Matthew Wilcow (Oracle) <willy@infradead.org> Cc: Michael "Camp Drill Sergeant" Ellerman <mpe@ellerman.id.au> Cc: Nicholas Piggin <npiggin@gmail.com> Cc: Peter Xu <peterx@redhat.com> Cc: Sven Schnelle <svens@linux.ibm.com> Cc: Ted Ts'o <tytso@mit.edu> Cc: Vasily Gorbik <gor@linux.ibm.com> Cc: Vishal Verma <vishal.l.verma@intel.com> Cc: Vivek Goyal <vgoyal@redhat.com> Cc: WANG Xuerui <kernel@xen0n.name> Cc: Will Deacon <will@kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> |
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