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commit2bb6d28370upstream. Patch series "introduce get_user_pages_longterm()", v2. Here is a new get_user_pages api for cases where a driver intends to keep an elevated page count indefinitely. This is distinct from usages like iov_iter_get_pages where the elevated page counts are transient. The iov_iter_get_pages cases immediately turn around and submit the pages to a device driver which will put_page when the i/o operation completes (under kernel control). In the longterm case userspace is responsible for dropping the page reference at some undefined point in the future. This is untenable for filesystem-dax case where the filesystem is in control of the lifetime of the block / page and needs reasonable limits on how long it can wait for pages in a mapping to become idle. Fixing filesystems to actually wait for dax pages to be idle before blocks from a truncate/hole-punch operation are repurposed is saved for a later patch series. Also, allowing longterm registration of dax mappings is a future patch series that introduces a "map with lease" semantic where the kernel can revoke a lease and force userspace to drop its page references. I have also tagged these for -stable to purposely break cases that might assume that longterm memory registrations for filesystem-dax mappings were supported by the kernel. The behavior regression this policy change implies is one of the reasons we maintain the "dax enabled. Warning: EXPERIMENTAL, use at your own risk" notification when mounting a filesystem in dax mode. It is worth noting the device-dax interface does not suffer the same constraints since it does not support file space management operations like hole-punch. This patch (of 4): Until there is a solution to the dma-to-dax vs truncate problem it is not safe to allow long standing memory registrations against filesytem-dax vmas. Device-dax vmas do not have this problem and are explicitly allowed. This is temporary until a "memory registration with layout-lease" mechanism can be implemented for the affected sub-systems (RDMA and V4L2). [akpm@linux-foundation.org: use kcalloc()] Link: http://lkml.kernel.org/r/151068939435.7446.13560129395419350737.stgit@dwillia2-desk3.amr.corp.intel.com Fixes:3565fce3a6("mm, x86: get_user_pages() for dax mappings") Signed-off-by: Dan Williams <dan.j.williams@intel.com> Suggested-by: Christoph Hellwig <hch@lst.de> Cc: Doug Ledford <dledford@redhat.com> Cc: Hal Rosenstock <hal.rosenstock@gmail.com> Cc: Inki Dae <inki.dae@samsung.com> Cc: Jan Kara <jack@suse.cz> Cc: Jason Gunthorpe <jgg@mellanox.com> Cc: Jeff Moyer <jmoyer@redhat.com> Cc: Joonyoung Shim <jy0922.shim@samsung.com> Cc: Kyungmin Park <kyungmin.park@samsung.com> Cc: Mauro Carvalho Chehab <mchehab@kernel.org> Cc: Mel Gorman <mgorman@suse.de> Cc: Ross Zwisler <ross.zwisler@linux.intel.com> Cc: Sean Hefty <sean.hefty@intel.com> Cc: Seung-Woo Kim <sw0312.kim@samsung.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: <stable@vger.kernel.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
73 lines
2.4 KiB
C
73 lines
2.4 KiB
C
#ifndef _LINUX_DAX_H
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#define _LINUX_DAX_H
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#include <linux/fs.h>
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#include <linux/mm.h>
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#include <linux/radix-tree.h>
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#include <asm/pgtable.h>
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struct iomap_ops;
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/* We use lowest available exceptional entry bit for locking */
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#define RADIX_DAX_ENTRY_LOCK (1 << RADIX_TREE_EXCEPTIONAL_SHIFT)
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ssize_t iomap_dax_rw(struct kiocb *iocb, struct iov_iter *iter,
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struct iomap_ops *ops);
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ssize_t dax_do_io(struct kiocb *, struct inode *, struct iov_iter *,
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get_block_t, dio_iodone_t, int flags);
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int dax_zero_page_range(struct inode *, loff_t from, unsigned len, get_block_t);
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int dax_truncate_page(struct inode *, loff_t from, get_block_t);
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int iomap_dax_fault(struct vm_area_struct *vma, struct vm_fault *vmf,
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struct iomap_ops *ops);
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int dax_fault(struct vm_area_struct *, struct vm_fault *, get_block_t);
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int dax_delete_mapping_entry(struct address_space *mapping, pgoff_t index);
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void dax_wake_mapping_entry_waiter(struct address_space *mapping,
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pgoff_t index, bool wake_all);
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#ifdef CONFIG_FS_DAX
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struct page *read_dax_sector(struct block_device *bdev, sector_t n);
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void dax_unlock_mapping_entry(struct address_space *mapping, pgoff_t index);
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int __dax_zero_page_range(struct block_device *bdev, sector_t sector,
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unsigned int offset, unsigned int length);
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#else
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static inline struct page *read_dax_sector(struct block_device *bdev,
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sector_t n)
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{
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return ERR_PTR(-ENXIO);
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}
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/* Shouldn't ever be called when dax is disabled. */
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static inline void dax_unlock_mapping_entry(struct address_space *mapping,
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pgoff_t index)
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{
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BUG();
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}
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static inline int __dax_zero_page_range(struct block_device *bdev,
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sector_t sector, unsigned int offset, unsigned int length)
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{
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return -ENXIO;
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}
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#endif
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#if defined(CONFIG_TRANSPARENT_HUGEPAGE)
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int dax_pmd_fault(struct vm_area_struct *, unsigned long addr, pmd_t *,
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unsigned int flags, get_block_t);
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#else
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static inline int dax_pmd_fault(struct vm_area_struct *vma, unsigned long addr,
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pmd_t *pmd, unsigned int flags, get_block_t gb)
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{
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return VM_FAULT_FALLBACK;
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}
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#endif
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int dax_pfn_mkwrite(struct vm_area_struct *, struct vm_fault *);
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#define dax_mkwrite(vma, vmf, gb) dax_fault(vma, vmf, gb)
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static inline bool dax_mapping(struct address_space *mapping)
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{
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return mapping->host && IS_DAX(mapping->host);
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}
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struct writeback_control;
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int dax_writeback_mapping_range(struct address_space *mapping,
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struct block_device *bdev, struct writeback_control *wbc);
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#endif
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