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![Dan Williams](/assets/img/avatar_default.png)
In preparation for fixing dax-dma-vs-unmap issues, filesystems need to be able to rely on the fact that they will get wakeups on dev_pagemap page-idle events. Introduce MEMORY_DEVICE_FS_DAX and generic_dax_page_free() as common indicator / infrastructure for dax filesytems to require. With this change there are no users of the MEMORY_DEVICE_HOST designation, so remove it. The HMM sub-system extended dev_pagemap to arrange a callback when a dev_pagemap managed page is freed. Since a dev_pagemap page is free / idle when its reference count is 1 it requires an additional branch to check the page-type at put_page() time. Given put_page() is a hot-path we do not want to incur that check if HMM is not in use, so a static branch is used to avoid that overhead when not necessary. Now, the FS_DAX implementation wants to reuse this mechanism for receiving dev_pagemap ->page_free() callbacks. Rework the HMM-specific static-key into a generic mechanism that either HMM or FS_DAX code paths can enable. For ARCH=um builds, and any other arch that lacks ZONE_DEVICE support, care must be taken to compile out the DEV_PAGEMAP_OPS infrastructure. However, we still need to support FS_DAX in the FS_DAX_LIMITED case implemented by the s390/dcssblk driver. Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com> Cc: Michal Hocko <mhocko@suse.com> Reported-by: kbuild test robot <lkp@intel.com> Reported-by: Thomas Meyer <thomas@m3y3r.de> Reported-by: Dave Jiang <dave.jiang@intel.com> Cc: "Jérôme Glisse" <jglisse@redhat.com> Reviewed-by: Jan Kara <jack@suse.cz> Reviewed-by: Christoph Hellwig <hch@lst.de> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
350 lines
9.7 KiB
C
350 lines
9.7 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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/* Copyright(c) 2015 Intel Corporation. All rights reserved. */
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#include <linux/radix-tree.h>
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#include <linux/device.h>
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#include <linux/types.h>
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#include <linux/pfn_t.h>
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#include <linux/io.h>
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#include <linux/mm.h>
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#include <linux/memory_hotplug.h>
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#include <linux/swap.h>
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#include <linux/swapops.h>
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#include <linux/wait_bit.h>
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static DEFINE_MUTEX(pgmap_lock);
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static RADIX_TREE(pgmap_radix, GFP_KERNEL);
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#define SECTION_MASK ~((1UL << PA_SECTION_SHIFT) - 1)
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#define SECTION_SIZE (1UL << PA_SECTION_SHIFT)
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static unsigned long order_at(struct resource *res, unsigned long pgoff)
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{
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unsigned long phys_pgoff = PHYS_PFN(res->start) + pgoff;
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unsigned long nr_pages, mask;
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nr_pages = PHYS_PFN(resource_size(res));
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if (nr_pages == pgoff)
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return ULONG_MAX;
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/*
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* What is the largest aligned power-of-2 range available from
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* this resource pgoff to the end of the resource range,
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* considering the alignment of the current pgoff?
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*/
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mask = phys_pgoff | rounddown_pow_of_two(nr_pages - pgoff);
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if (!mask)
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return ULONG_MAX;
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return find_first_bit(&mask, BITS_PER_LONG);
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}
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#define foreach_order_pgoff(res, order, pgoff) \
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for (pgoff = 0, order = order_at((res), pgoff); order < ULONG_MAX; \
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pgoff += 1UL << order, order = order_at((res), pgoff))
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#if IS_ENABLED(CONFIG_DEVICE_PRIVATE)
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int device_private_entry_fault(struct vm_area_struct *vma,
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unsigned long addr,
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swp_entry_t entry,
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unsigned int flags,
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pmd_t *pmdp)
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{
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struct page *page = device_private_entry_to_page(entry);
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/*
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* The page_fault() callback must migrate page back to system memory
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* so that CPU can access it. This might fail for various reasons
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* (device issue, device was unsafely unplugged, ...). When such
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* error conditions happen, the callback must return VM_FAULT_SIGBUS.
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*
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* Note that because memory cgroup charges are accounted to the device
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* memory, this should never fail because of memory restrictions (but
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* allocation of regular system page might still fail because we are
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* out of memory).
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*
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* There is a more in-depth description of what that callback can and
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* cannot do, in include/linux/memremap.h
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*/
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return page->pgmap->page_fault(vma, addr, page, flags, pmdp);
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}
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EXPORT_SYMBOL(device_private_entry_fault);
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#endif /* CONFIG_DEVICE_PRIVATE */
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static void pgmap_radix_release(struct resource *res, unsigned long end_pgoff)
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{
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unsigned long pgoff, order;
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mutex_lock(&pgmap_lock);
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foreach_order_pgoff(res, order, pgoff) {
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if (pgoff >= end_pgoff)
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break;
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radix_tree_delete(&pgmap_radix, PHYS_PFN(res->start) + pgoff);
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}
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mutex_unlock(&pgmap_lock);
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synchronize_rcu();
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}
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static unsigned long pfn_first(struct dev_pagemap *pgmap)
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{
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const struct resource *res = &pgmap->res;
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struct vmem_altmap *altmap = &pgmap->altmap;
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unsigned long pfn;
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pfn = res->start >> PAGE_SHIFT;
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if (pgmap->altmap_valid)
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pfn += vmem_altmap_offset(altmap);
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return pfn;
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}
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static unsigned long pfn_end(struct dev_pagemap *pgmap)
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{
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const struct resource *res = &pgmap->res;
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return (res->start + resource_size(res)) >> PAGE_SHIFT;
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}
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static unsigned long pfn_next(unsigned long pfn)
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{
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if (pfn % 1024 == 0)
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cond_resched();
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return pfn + 1;
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}
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#define for_each_device_pfn(pfn, map) \
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for (pfn = pfn_first(map); pfn < pfn_end(map); pfn = pfn_next(pfn))
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static void devm_memremap_pages_release(void *data)
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{
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struct dev_pagemap *pgmap = data;
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struct device *dev = pgmap->dev;
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struct resource *res = &pgmap->res;
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resource_size_t align_start, align_size;
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unsigned long pfn;
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for_each_device_pfn(pfn, pgmap)
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put_page(pfn_to_page(pfn));
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if (percpu_ref_tryget_live(pgmap->ref)) {
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dev_WARN(dev, "%s: page mapping is still live!\n", __func__);
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percpu_ref_put(pgmap->ref);
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}
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/* pages are dead and unused, undo the arch mapping */
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align_start = res->start & ~(SECTION_SIZE - 1);
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align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
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- align_start;
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mem_hotplug_begin();
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arch_remove_memory(align_start, align_size, pgmap->altmap_valid ?
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&pgmap->altmap : NULL);
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mem_hotplug_done();
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untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
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pgmap_radix_release(res, -1);
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dev_WARN_ONCE(dev, pgmap->altmap.alloc,
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"%s: failed to free all reserved pages\n", __func__);
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}
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/**
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* devm_memremap_pages - remap and provide memmap backing for the given resource
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* @dev: hosting device for @res
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* @pgmap: pointer to a struct dev_pgmap
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*
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* Notes:
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* 1/ At a minimum the res, ref and type members of @pgmap must be initialized
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* by the caller before passing it to this function
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*
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* 2/ The altmap field may optionally be initialized, in which case altmap_valid
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* must be set to true
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*
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* 3/ pgmap.ref must be 'live' on entry and 'dead' before devm_memunmap_pages()
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* time (or devm release event). The expected order of events is that ref has
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* been through percpu_ref_kill() before devm_memremap_pages_release(). The
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* wait for the completion of all references being dropped and
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* percpu_ref_exit() must occur after devm_memremap_pages_release().
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*
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* 4/ res is expected to be a host memory range that could feasibly be
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* treated as a "System RAM" range, i.e. not a device mmio range, but
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* this is not enforced.
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*/
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void *devm_memremap_pages(struct device *dev, struct dev_pagemap *pgmap)
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{
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resource_size_t align_start, align_size, align_end;
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struct vmem_altmap *altmap = pgmap->altmap_valid ?
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&pgmap->altmap : NULL;
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struct resource *res = &pgmap->res;
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unsigned long pfn, pgoff, order;
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pgprot_t pgprot = PAGE_KERNEL;
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int error, nid, is_ram;
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align_start = res->start & ~(SECTION_SIZE - 1);
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align_size = ALIGN(res->start + resource_size(res), SECTION_SIZE)
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- align_start;
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is_ram = region_intersects(align_start, align_size,
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IORESOURCE_SYSTEM_RAM, IORES_DESC_NONE);
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if (is_ram == REGION_MIXED) {
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WARN_ONCE(1, "%s attempted on mixed region %pr\n",
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__func__, res);
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return ERR_PTR(-ENXIO);
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}
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if (is_ram == REGION_INTERSECTS)
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return __va(res->start);
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if (!pgmap->ref)
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return ERR_PTR(-EINVAL);
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pgmap->dev = dev;
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mutex_lock(&pgmap_lock);
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error = 0;
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align_end = align_start + align_size - 1;
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foreach_order_pgoff(res, order, pgoff) {
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error = __radix_tree_insert(&pgmap_radix,
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PHYS_PFN(res->start) + pgoff, order, pgmap);
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if (error) {
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dev_err(dev, "%s: failed: %d\n", __func__, error);
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break;
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}
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}
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mutex_unlock(&pgmap_lock);
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if (error)
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goto err_radix;
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nid = dev_to_node(dev);
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if (nid < 0)
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nid = numa_mem_id();
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error = track_pfn_remap(NULL, &pgprot, PHYS_PFN(align_start), 0,
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align_size);
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if (error)
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goto err_pfn_remap;
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mem_hotplug_begin();
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error = arch_add_memory(nid, align_start, align_size, altmap, false);
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if (!error)
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move_pfn_range_to_zone(&NODE_DATA(nid)->node_zones[ZONE_DEVICE],
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align_start >> PAGE_SHIFT,
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align_size >> PAGE_SHIFT, altmap);
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mem_hotplug_done();
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if (error)
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goto err_add_memory;
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for_each_device_pfn(pfn, pgmap) {
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struct page *page = pfn_to_page(pfn);
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/*
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* ZONE_DEVICE pages union ->lru with a ->pgmap back
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* pointer. It is a bug if a ZONE_DEVICE page is ever
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* freed or placed on a driver-private list. Seed the
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* storage with LIST_POISON* values.
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*/
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list_del(&page->lru);
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page->pgmap = pgmap;
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percpu_ref_get(pgmap->ref);
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}
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devm_add_action(dev, devm_memremap_pages_release, pgmap);
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return __va(res->start);
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err_add_memory:
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untrack_pfn(NULL, PHYS_PFN(align_start), align_size);
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err_pfn_remap:
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err_radix:
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pgmap_radix_release(res, pgoff);
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return ERR_PTR(error);
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}
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EXPORT_SYMBOL(devm_memremap_pages);
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unsigned long vmem_altmap_offset(struct vmem_altmap *altmap)
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{
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/* number of pfns from base where pfn_to_page() is valid */
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return altmap->reserve + altmap->free;
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}
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void vmem_altmap_free(struct vmem_altmap *altmap, unsigned long nr_pfns)
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{
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altmap->alloc -= nr_pfns;
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}
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/**
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* get_dev_pagemap() - take a new live reference on the dev_pagemap for @pfn
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* @pfn: page frame number to lookup page_map
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* @pgmap: optional known pgmap that already has a reference
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*
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* If @pgmap is non-NULL and covers @pfn it will be returned as-is. If @pgmap
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* is non-NULL but does not cover @pfn the reference to it will be released.
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*/
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struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
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struct dev_pagemap *pgmap)
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{
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resource_size_t phys = PFN_PHYS(pfn);
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/*
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* In the cached case we're already holding a live reference.
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*/
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if (pgmap) {
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if (phys >= pgmap->res.start && phys <= pgmap->res.end)
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return pgmap;
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put_dev_pagemap(pgmap);
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}
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/* fall back to slow path lookup */
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rcu_read_lock();
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pgmap = radix_tree_lookup(&pgmap_radix, PHYS_PFN(phys));
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if (pgmap && !percpu_ref_tryget_live(pgmap->ref))
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pgmap = NULL;
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rcu_read_unlock();
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return pgmap;
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}
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EXPORT_SYMBOL_GPL(get_dev_pagemap);
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#ifdef CONFIG_DEV_PAGEMAP_OPS
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DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
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EXPORT_SYMBOL_GPL(devmap_managed_key);
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static atomic_t devmap_enable;
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/*
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* Toggle the static key for ->page_free() callbacks when dev_pagemap
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* pages go idle.
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*/
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void dev_pagemap_get_ops(void)
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{
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if (atomic_inc_return(&devmap_enable) == 1)
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static_branch_enable(&devmap_managed_key);
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}
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EXPORT_SYMBOL_GPL(dev_pagemap_get_ops);
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void dev_pagemap_put_ops(void)
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{
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if (atomic_dec_and_test(&devmap_enable))
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static_branch_disable(&devmap_managed_key);
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}
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EXPORT_SYMBOL_GPL(dev_pagemap_put_ops);
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void __put_devmap_managed_page(struct page *page)
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{
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int count = page_ref_dec_return(page);
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/*
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* If refcount is 1 then page is freed and refcount is stable as nobody
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* holds a reference on the page.
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*/
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if (count == 1) {
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/* Clear Active bit in case of parallel mark_page_accessed */
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__ClearPageActive(page);
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__ClearPageWaiters(page);
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page->mapping = NULL;
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mem_cgroup_uncharge(page);
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page->pgmap->page_free(page, page->pgmap->data);
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} else if (!count)
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__put_page(page);
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}
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EXPORT_SYMBOL_GPL(__put_devmap_managed_page);
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#endif /* CONFIG_DEV_PAGEMAP_OPS */
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