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authorDan Williams <dan.j.williams@intel.com>2018-05-16 11:46:08 -0700
committerDan Williams <dan.j.williams@intel.com>2018-05-22 06:59:39 -0700
commite7638488434415aa478e78435cac8f0365737638 (patch)
tree7ce50f0ed69889aa44cb0124451cf7a56b34eba6 /kernel/memremap.c
parent5981690ddb8f72f9546a2d017a914cf56095fc1f (diff)
downloadlinux-e7638488434415aa478e78435cac8f0365737638.tar.bz2
mm: introduce MEMORY_DEVICE_FS_DAX and CONFIG_DEV_PAGEMAP_OPS
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>
Diffstat (limited to 'kernel/memremap.c')
-rw-r--r--kernel/memremap.c32
1 files changed, 28 insertions, 4 deletions
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 37a9604133f6..5857267a4af5 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -9,6 +9,7 @@
#include <linux/memory_hotplug.h>
#include <linux/swap.h>
#include <linux/swapops.h>
+#include <linux/wait_bit.h>
static DEFINE_MUTEX(pgmap_lock);
static RADIX_TREE(pgmap_radix, GFP_KERNEL);
@@ -300,9 +301,32 @@ struct dev_pagemap *get_dev_pagemap(unsigned long pfn,
return pgmap;
}
+EXPORT_SYMBOL_GPL(get_dev_pagemap);
-#if IS_ENABLED(CONFIG_DEVICE_PRIVATE) || IS_ENABLED(CONFIG_DEVICE_PUBLIC)
-void put_zone_device_private_or_public_page(struct page *page)
+#ifdef CONFIG_DEV_PAGEMAP_OPS
+DEFINE_STATIC_KEY_FALSE(devmap_managed_key);
+EXPORT_SYMBOL_GPL(devmap_managed_key);
+static atomic_t devmap_enable;
+
+/*
+ * Toggle the static key for ->page_free() callbacks when dev_pagemap
+ * pages go idle.
+ */
+void dev_pagemap_get_ops(void)
+{
+ if (atomic_inc_return(&devmap_enable) == 1)
+ static_branch_enable(&devmap_managed_key);
+}
+EXPORT_SYMBOL_GPL(dev_pagemap_get_ops);
+
+void dev_pagemap_put_ops(void)
+{
+ if (atomic_dec_and_test(&devmap_enable))
+ static_branch_disable(&devmap_managed_key);
+}
+EXPORT_SYMBOL_GPL(dev_pagemap_put_ops);
+
+void __put_devmap_managed_page(struct page *page)
{
int count = page_ref_dec_return(page);
@@ -322,5 +346,5 @@ void put_zone_device_private_or_public_page(struct page *page)
} else if (!count)
__put_page(page);
}
-EXPORT_SYMBOL(put_zone_device_private_or_public_page);
-#endif /* CONFIG_DEVICE_PRIVATE || CONFIG_DEVICE_PUBLIC */
+EXPORT_SYMBOL_GPL(__put_devmap_managed_page);
+#endif /* CONFIG_DEV_PAGEMAP_OPS */