kernel.git/fs/fuse/dax.c, branch linux-6.15.y

fs/dax: create a common implementation to break DAX layouts

2025-03-18T05:06:37Z

Prior to freeing a block file systems supporting FS DAX must check that the associated pages are both unmapped from user-space and not undergoing DMA or other access from eg. get_user_pages(). This is achieved by unmapping the file range and scanning the FS DAX page-cache to see if any pages within the mapping have an elevated refcount. This is done using two functions - dax_layout_busy_page_range() which returns a page to wait for the refcount to become idle on. Rather than open-code this introduce a common implementation to both unmap and wait for the page to become idle. Link: https://lkml.kernel.org/r/c4d381e41fc618296cee2820403c166d80599d5c.1740713401.git-series.apopple@nvidia.com Signed-off-by: Alistair Popple Reviewed-by: Dan Williams Tested-by: Alison Schofield Cc: Alexander Gordeev Cc: Asahi Lina Cc: Balbir Singh Cc: Bjorn Helgaas Cc: Catalin Marinas Cc: Christian Borntraeger Cc: Christoph Hellwig Cc: Chunyan Zhang Cc: "Darrick J. Wong" Cc: Dave Chinner Cc: Dave Hansen Cc: Dave Jiang Cc: David Hildenbrand Cc: Gerald Schaefer Cc: Heiko Carstens Cc: Huacai Chen Cc: Ira Weiny Cc: Jan Kara Cc: Jason Gunthorpe Cc: Jason Gunthorpe Cc: John Hubbard Cc: linmiaohe Cc: Logan Gunthorpe Cc: Matthew Wilcow (Oracle) Cc: Michael "Camp Drill Sergeant" Ellerman Cc: Nicholas Piggin Cc: Peter Xu Cc: Sven Schnelle Cc: Ted Ts'o Cc: Vasily Gorbik Cc: Vishal Verma Cc: Vivek Goyal Cc: WANG Xuerui Cc: Will Deacon Signed-off-by: Andrew Morton

fs/dax: refactor wait for dax idle page

2025-03-18T05:06:37Z

A FS DAX page is considered idle when its refcount drops to one. This is currently open-coded in all file systems supporting FS DAX. Move the idle detection to a common function to make future changes easier. Link: https://lkml.kernel.org/r/c2c9d269110b90224eeb1dc661ffbc1d82aa20c9.1740713401.git-series.apopple@nvidia.com Signed-off-by: Alistair Popple Reviewed-by: Jan Kara Reviewed-by: Christoph Hellwig Reviewed-by: Dan Williams Acked-by: Theodore Ts'o Tested-by: Alison Schofield Cc: Alexander Gordeev Cc: Asahi Lina Cc: Balbir Singh Cc: Bjorn Helgaas Cc: Catalin Marinas Cc: Christian Borntraeger Cc: Chunyan Zhang Cc: "Darrick J. Wong" Cc: Dave Chinner Cc: Dave Hansen Cc: Dave Jiang Cc: David Hildenbrand Cc: Gerald Schaefer Cc: Heiko Carstens Cc: Huacai Chen Cc: Ira Weiny Cc: Jason Gunthorpe Cc: Jason Gunthorpe Cc: John Hubbard Cc: linmiaohe Cc: Logan Gunthorpe Cc: Matthew Wilcow (Oracle) Cc: Michael "Camp Drill Sergeant" Ellerman Cc: Nicholas Piggin Cc: Peter Xu Cc: Sven Schnelle Cc: Vasily Gorbik Cc: Vishal Verma Cc: Vivek Goyal Cc: WANG Xuerui Cc: Will Deacon Signed-off-by: Andrew Morton

fuse: fix dax truncate/punch_hole fault path

2025-03-18T05:06:36Z

Patch series "fs/dax: Fix ZONE_DEVICE page reference counts", v9. Device and FS DAX pages have always maintained their own page reference counts without following the normal rules for page reference counting. In particular pages are considered free when the refcount hits one rather than zero and refcounts are not added when mapping the page. Tracking this requires special PTE bits (PTE_DEVMAP) and a secondary mechanism for allowing GUP to hold references on the page (see get_dev_pagemap). However there doesn't seem to be any reason why FS DAX pages need their own reference counting scheme. By treating the refcounts on these pages the same way as normal pages we can remove a lot of special checks. In particular pXd_trans_huge() becomes the same as pXd_leaf(), although I haven't made that change here. It also frees up a valuable SW define PTE bit on architectures that have devmap PTE bits defined. It also almost certainly allows further clean-up of the devmap managed functions, but I have left that as a future improvment. It also enables support for compound ZONE_DEVICE pages which is one of my primary motivators for doing this work. This patch (of 20): FS DAX requires file systems to call into the DAX layout prior to unlinking inodes to ensure there is no ongoing DMA or other remote access to the direct mapped page. The fuse file system implements fuse_dax_break_layouts() to do this which includes a comment indicating that passing dmap_end == 0 leads to unmapping of the whole file. However this is not true - passing dmap_end == 0 will not unmap anything before dmap_start, and further more dax_layout_busy_page_range() will not scan any of the range to see if there maybe ongoing DMA access to the range. Fix this by passing -1 for dmap_end to fuse_dax_break_layouts() which will invalidate the entire file range to dax_layout_busy_page_range(). Link: https://lkml.kernel.org/r/cover.8068ad144a7eea4a813670301f4d2a86a8e68ec4.1740713401.git-series.apopple@nvidia.com Link: https://lkml.kernel.org/r/f09a34b6c40032022e4ddee6fadb7cc676f08867.1740713401.git-series.apopple@nvidia.com Fixes: 6ae330cad6ef ("virtiofs: serialize truncate/punch_hole and dax fault path") Signed-off-by: Alistair Popple Co-developed-by: Dan Williams Signed-off-by: Dan Williams Reviewed-by: Balbir Singh Tested-by: Alison Schofield Cc: Vivek Goyal Cc: Alexander Gordeev Cc: Asahi Lina Cc: Bjorn Helgaas Cc: Catalin Marinas Cc: Christian Borntraeger Cc: Christoph Hellwig Cc: Chunyan Zhang Cc: "Darrick J. Wong" Cc: Dave Chinner Cc: Dave Hansen Cc: Dave Jiang Cc: David Hildenbrand Cc: Gerald Schaefer Cc: Heiko Carstens Cc: Huacai Chen Cc: Ira Weiny Cc: Jan Kara Cc: Jason Gunthorpe Cc: Jason Gunthorpe Cc: John Hubbard Cc: linmiaohe Cc: Logan Gunthorpe Cc: Matthew Wilcow (Oracle) Cc: Michael "Camp Drill Sergeant" Ellerman Cc: Nicholas Piggin Cc: Peter Xu Cc: Sven Schnelle Cc: Ted Ts'o Cc: Vasily Gorbik Cc: Vishal Verma Cc: WANG Xuerui Cc: Will Deacon Signed-off-by: Andrew Morton

fuse: make args->in_args[0] to be always the header

2025-01-24T10:54:02Z

This change sets up FUSE operations to always have headers in args.in_args[0], even for opcodes without an actual header. This step prepares for a clean separation of payload from headers, initially it is used by fuse-over-io-uring. For opcodes without a header, we use a zero-sized struct as a placeholder. This approach: - Keeps things consistent across all FUSE operations - Will help with payload alignment later - Avoids future issues when header sizes change Op codes that already have an op code specific header do not need modification. Op codes that have neither payload nor op code headers are not modified either (FUSE_READLINK and FUSE_DESTROY). FUSE_BATCH_FORGET already has the header in the right place, but is not using fuse_copy_args - as -over-uring is currently not handling forgets it does not matter for now, but header separation will later need special attention for that op code. Correct the struct fuse_args->in_args array max size. Signed-off-by: Bernd Schubert Reviewed-by: Joanne Koong Reviewed-by: Luis Henriques Signed-off-by: Miklos Szeredi

virtiofs: dax: remove ->writepages() callback

2024-11-18T11:24:38Z

When using FUSE DAX with virtiofs, cache coherency is managed by the host. Disk persistence is handled via fsync() and friends, which are passed directly via the FUSE layer to the host. Therefore, there's no need to do dax_writeback_mapping_range(). All that ends up doing is a cache flush operation, which is not caught by KVM and doesn't do much, since the host and guest are already cache-coherent. Since dax_writeback_mapping_range() checks that the inode block size is equal to PAGE_SIZE, this fixes a spurious WARN when virtiofs is used with a mismatched guest PAGE_SIZE and virtiofs backing FS block size (this happens, for example, when it's a tmpfs and the host and guest have a different PAGE_SIZE). FUSE DAX does not require any particular FS block size, since it always performs DAX mappings in aligned 2MiB blocks. See discussion in [1]. [1] https://lore.kernel.org/lkml/20241101-dax-page-size-v1-1-eedbd0c6b08f@asahilina.net/T/#u [SzM: remove the empty callback] Suggested-by: Dan Williams Signed-off-by: Asahi Lina Acked-by: Dan Williams Signed-off-by: Miklos Szeredi

fuse: dax: set fc->dax to NULL in fuse_dax_conn_free()

2023-12-04T09:16:53Z

fuse_dax_conn_free() will be called when fuse_fill_super_common() fails after fuse_dax_conn_alloc(). Then deactivate_locked_super() in virtio_fs_get_tree() will call virtio_kill_sb() to release the discarded superblock. This will call fuse_dax_conn_free() again in fuse_conn_put(), resulting in a possible double free. Fixes: 1dd539577c42 ("virtiofs: add a mount option to enable dax") Signed-off-by: Hangyu Hua Acked-by: Vivek Goyal Reviewed-by: Jingbo Xu Cc: # v5.10 Signed-off-by: Miklos Szeredi

mm: remove enum page_entry_size

2023-08-24T23:20:30Z

Remove the unnecessary encoding of page order into an enum and pass the page order directly. That lets us get rid of pe_order(). The switch constructs have to be changed to if/else constructs to prevent GCC from warning on builds with 3-level page tables where PMD_ORDER and PUD_ORDER have the same value. If you are looking at this commit because your driver stopped compiling, look at the previous commit as well and audit your driver to be sure it doesn't depend on mmap_lock being held in its ->huge_fault method. [willy@infradead.org: use "order %u" to match the (non dev_t) style] Link: https://lkml.kernel.org/r/ZOUYekbtTv+n8hYf@casper.infradead.org Link: https://lkml.kernel.org/r/20230818202335.2739663-4-willy@infradead.org Signed-off-by: Matthew Wilcox (Oracle) Signed-off-by: Andrew Morton

mm: replace vma->vm_flags direct modifications with modifier calls

2023-02-10T00:51:39Z

Replace direct modifications to vma->vm_flags with calls to modifier functions to be able to track flag changes and to keep vma locking correctness. [akpm@linux-foundation.org: fix drivers/misc/open-dice.c, per Hyeonggon Yoo] Link: https://lkml.kernel.org/r/20230126193752.297968-5-surenb@google.com Signed-off-by: Suren Baghdasaryan Acked-by: Michal Hocko Acked-by: Mel Gorman Acked-by: Mike Rapoport (IBM) Acked-by: Sebastian Reichel Reviewed-by: Liam R. Howlett Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com> Cc: Andy Lutomirski Cc: Arjun Roy Cc: Axel Rasmussen Cc: David Hildenbrand Cc: David Howells Cc: Davidlohr Bueso Cc: David Rientjes Cc: Eric Dumazet Cc: Greg Thelen Cc: Hugh Dickins Cc: Ingo Molnar Cc: Jann Horn Cc: Joel Fernandes Cc: Johannes Weiner Cc: Kent Overstreet Cc: Laurent Dufour Cc: Lorenzo Stoakes Cc: Matthew Wilcox Cc: Minchan Kim Cc: Paul E. McKenney Cc: Peter Oskolkov Cc: Peter Xu Cc: Peter Zijlstra Cc: Punit Agrawal Cc: Sebastian Andrzej Siewior Cc: Shakeel Butt Cc: Soheil Hassas Yeganeh Cc: Song Liu Cc: Vlastimil Babka Cc: Will Deacon Signed-off-by: Andrew Morton

fuse: avoid unnecessary spinlock bump

2022-07-21T14:02:45Z

Move dmap free worker kicker inside the critical region, so that extra spinlock lock/unlock could be avoided. Suggested-by: Liu Jiang Signed-off-by: Jeffle Xu Reviewed-by: Stefan Hajnoczi Reviewed-by: Vivek Goyal Signed-off-by: Miklos Szeredi

dax: introduce DAX_RECOVERY_WRITE dax access mode

2022-05-16T20:35:56Z

Up till now, dax_direct_access() is used implicitly for normal access, but for the purpose of recovery write, dax range with poison is requested. To make the interface clear, introduce enum dax_access_mode { DAX_ACCESS, DAX_RECOVERY_WRITE, } where DAX_ACCESS is used for normal dax access, and DAX_RECOVERY_WRITE is used for dax recovery write. Suggested-by: Dan Williams Signed-off-by: Jane Chu Reviewed-by: Christoph Hellwig Cc: Mike Snitzer Reviewed-by: Vivek Goyal Link: https://lore.kernel.org/r/165247982851.52965.11024212198889762949.stgit@dwillia2-desk3.amr.corp.intel.com Signed-off-by: Dan Williams