From: "Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>
To: Dan Williams <dan.j.williams@intel.com>, linux-mm@kvack.org
Cc: Matthew Wilcox <willy@infradead.org>, Jan Kara <jack@suse.cz>,
"Darrick J. Wong" <djwong@kernel.org>,
Jason Gunthorpe <jgg@nvidia.com>, Christoph Hellwig <hch@lst.de>,
John Hubbard <jhubbard@nvidia.com>,
david@fromorbit.com, nvdimm@lists.linux.dev,
akpm@linux-foundation.org, linux-fsdevel@vger.kernel.org
Subject: Re: [PATCH v3 04/25] fsdax: Introduce dax_zap_mappings()
Date: Wed, 02 Nov 2022 18:34:17 +0530 [thread overview]
Message-ID: <87tu3h1p9q.fsf@linux.ibm.com> (raw)
In-Reply-To: <166579183976.2236710.17370760087488536715.stgit@dwillia2-xfh.jf.intel.com>
Dan Williams <dan.j.williams@intel.com> writes:
> Typical pages take a reference at pte insertion and drop it at
> zap_pte_range() time. That reference management is missing for DAX
> leading to a situation where DAX pages are mapped in user page tables,
> but are not referenced.
>
> Once fsdax decides it wants to unmap the page it can drop its reference,
> but unlike typical pages it needs to maintain the association of the
> page to the inode that arbitrated the access in the first instance. It
> maintains that association until explicit truncate(), or the implicit
> truncate() that occurs at inode death, truncate_inode_pages_final().
>
> The zapped state tracks whether the fsdax has dropped its interest in a
> page, but still allows the associated i_pages entry to live until
> truncate. This facilitates inode lookup while awaiting any page pin
> users to drop their pins. For example, if memory_failure() is triggered
> on the page after it has been unmapped, but before it has been truncated
> from the inode, memory_failure() can still associate the event with the
> inode.
>
> Once truncate begins fsdax unmaps the page to prevent any new references
> from being taken without calling back into fsdax core to reestablish
> the mapping.
The gup path should now check dax_is_zap()? Where do we
prevent new referenced from being taken?
-aneesh
next prev parent reply other threads:[~2022-11-02 13:04 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-10-14 23:56 [PATCH v3 00/25] Fix the DAX-gup mistake Dan Williams
2022-10-14 23:57 ` [PATCH v3 01/25] fsdax: Wait on @page not @page->_refcount Dan Williams
2022-10-14 23:57 ` [PATCH v3 02/25] fsdax: Use dax_page_idle() to document DAX busy page checking Dan Williams
2022-10-14 23:57 ` [PATCH v3 03/25] fsdax: Include unmapped inodes for page-idle detection Dan Williams
2022-10-14 23:57 ` [PATCH v3 04/25] fsdax: Introduce dax_zap_mappings() Dan Williams
2022-11-02 13:04 ` Aneesh Kumar K.V [this message]
2022-10-14 23:57 ` [PATCH v3 05/25] fsdax: Wait for pinned pages during truncate_inode_pages_final() Dan Williams
2022-10-14 23:57 ` [PATCH v3 06/25] fsdax: Validate DAX layouts broken before truncate Dan Williams
2022-10-14 23:57 ` [PATCH v3 07/25] fsdax: Hold dax lock over mapping insertion Dan Williams
2022-10-17 19:31 ` Jason Gunthorpe
2022-10-17 20:17 ` Dan Williams
2022-10-18 5:26 ` Christoph Hellwig
2022-10-18 17:30 ` Dan Williams
2022-10-14 23:57 ` [PATCH v3 08/25] fsdax: Update dax_insert_entry() calling convention to return an error Dan Williams
2022-10-14 23:57 ` [PATCH v3 09/25] fsdax: Rework for_each_mapped_pfn() to dax_for_each_folio() Dan Williams
2022-10-14 23:57 ` [PATCH v3 10/25] fsdax: Introduce pgmap_request_folios() Dan Williams
2022-10-17 6:31 ` Alistair Popple
2022-10-17 20:06 ` Dan Williams
2022-10-17 20:11 ` Jason Gunthorpe
2022-10-17 20:51 ` Dan Williams
2022-10-17 23:57 ` Jason Gunthorpe
2022-10-18 0:19 ` Dan Williams
2022-10-17 19:41 ` Jason Gunthorpe
2022-10-14 23:58 ` [PATCH v3 11/25] fsdax: Rework dax_insert_entry() calling convention Dan Williams
2022-10-14 23:58 ` [PATCH v3 12/25] fsdax: Cleanup dax_associate_entry() Dan Williams
2022-10-14 23:58 ` [PATCH v3 13/25] devdax: Minor warning fixups Dan Williams
2022-10-14 23:58 ` [PATCH v3 14/25] devdax: Fix sparse lock imbalance warning Dan Williams
2022-10-14 23:58 ` [PATCH v3 15/25] libnvdimm/pmem: Support pmem block devices without dax Dan Williams
2022-10-14 23:58 ` [PATCH v3 16/25] devdax: Move address_space helpers to the DAX core Dan Williams
2022-10-14 23:58 ` [PATCH v3 17/25] devdax: Sparse fixes for xarray locking Dan Williams
2022-10-14 23:58 ` [PATCH v3 18/25] devdax: Sparse fixes for vmfault_t / dax-entry conversions Dan Williams
2022-10-14 23:58 ` [PATCH v3 19/25] devdax: Sparse fixes for vm_fault_t in tracepoints Dan Williams
2022-10-14 23:58 ` [PATCH v3 20/25] devdax: add PUD support to the DAX mapping infrastructure Dan Williams
2022-10-14 23:59 ` [PATCH v3 21/25] devdax: Use dax_insert_entry() + dax_delete_mapping_entry() Dan Williams
2022-10-14 23:59 ` [PATCH v3 22/25] mm/memremap_pages: Replace zone_device_page_init() with pgmap_request_folios() Dan Williams
2022-10-17 19:17 ` Lyude Paul
2022-10-14 23:59 ` [PATCH v3 23/25] mm/memremap_pages: Initialize all ZONE_DEVICE pages to start at refcount 0 Dan Williams
2022-10-17 7:04 ` Alistair Popple
2022-10-17 19:48 ` Jason Gunthorpe
2022-10-14 23:59 ` [PATCH v3 24/25] mm/meremap_pages: Delete put_devmap_managed_page_refs() Dan Williams
2022-10-17 7:08 ` Alistair Popple
2022-10-14 23:59 ` [PATCH v3 25/25] mm/gup: Drop DAX pgmap accounting Dan Williams
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