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Date: Tue, 31 Oct 2017 16:22:51 -0700
From: Dan Williams <dan.j.williams@...el.com>
To: linux-nvdimm@...ts.01.org
Cc: Jan Kara <jack@...e.cz>, Matthew Wilcox <mawilcox@...rosoft.com>,
linux-kernel@...r.kernel.org, linux-xfs@...r.kernel.org,
linux-mm@...ck.org, Jeff Moyer <jmoyer@...hat.com>,
Ross Zwisler <ross.zwisler@...ux.intel.com>,
linux-fsdevel@...r.kernel.org, akpm@...ux-foundation.org,
hch@....de
Subject: [PATCH 14/15] dax: associate mappings with inodes,
and warn if dma collides with truncate
Catch cases where truncate encounters pages that are still under active
dma. This warning is a canary for potential data corruption as truncated
blocks could be allocated to a new file while the device is still
perform i/o.
Cc: Jan Kara <jack@...e.cz>
Cc: Jeff Moyer <jmoyer@...hat.com>
Cc: Christoph Hellwig <hch@....de>
Cc: Matthew Wilcox <mawilcox@...rosoft.com>
Cc: Ross Zwisler <ross.zwisler@...ux.intel.com>
Signed-off-by: Dan Williams <dan.j.williams@...el.com>
---
fs/dax.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++
include/linux/mm_types.h | 20 ++++++++++++----
kernel/memremap.c | 10 ++++----
3 files changed, 76 insertions(+), 10 deletions(-)
diff --git a/fs/dax.c b/fs/dax.c
index ac6497dcfebd..fd5d385988d1 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -297,6 +297,55 @@ static void put_unlocked_mapping_entry(struct address_space *mapping,
dax_wake_mapping_entry_waiter(mapping, index, entry, false);
}
+static unsigned long dax_entry_size(void *entry)
+{
+ if (dax_is_zero_entry(entry))
+ return 0;
+ else if (dax_is_empty_entry(entry))
+ return 0;
+ else if (dax_is_pmd_entry(entry))
+ return HPAGE_SIZE;
+ else
+ return PAGE_SIZE;
+}
+
+#define for_each_entry_pfn(entry, pfn, end_pfn) \
+ for (pfn = dax_radix_pfn(entry), \
+ end_pfn = pfn + dax_entry_size(entry) / PAGE_SIZE; \
+ pfn < end_pfn; \
+ pfn++)
+
+static void dax_associate_entry(void *entry, struct inode *inode)
+{
+ unsigned long pfn, end_pfn;
+
+ if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
+ return;
+
+ for_each_entry_pfn(entry, pfn, end_pfn) {
+ struct page *page = pfn_to_page(pfn);
+
+ WARN_ON_ONCE(page->inode);
+ page->inode = inode;
+ }
+}
+
+static void dax_disassociate_entry(void *entry, struct inode *inode, bool trunc)
+{
+ unsigned long pfn, end_pfn;
+
+ if (IS_ENABLED(CONFIG_FS_DAX_LIMITED))
+ return;
+
+ for_each_entry_pfn(entry, pfn, end_pfn) {
+ struct page *page = pfn_to_page(pfn);
+
+ WARN_ON_ONCE(trunc && page_ref_count(page) > 1);
+ WARN_ON_ONCE(page->inode && page->inode != inode);
+ page->inode = NULL;
+ }
+}
+
/*
* Find radix tree entry at given index. If it points to an exceptional entry,
* return it with the radix tree entry locked. If the radix tree doesn't
@@ -403,6 +452,7 @@ static void *grab_mapping_entry(struct address_space *mapping, pgoff_t index,
}
if (pmd_downgrade) {
+ dax_disassociate_entry(entry, mapping->host, false);
radix_tree_delete(&mapping->page_tree, index);
mapping->nrexceptional--;
dax_wake_mapping_entry_waiter(mapping, index, entry,
@@ -452,6 +502,7 @@ static int __dax_invalidate_mapping_entry(struct address_space *mapping,
(radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_DIRTY) ||
radix_tree_tag_get(page_tree, index, PAGECACHE_TAG_TOWRITE)))
goto out;
+ dax_disassociate_entry(entry, mapping->host, trunc);
radix_tree_delete(page_tree, index);
mapping->nrexceptional--;
ret = 1;
@@ -529,6 +580,7 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
{
struct radix_tree_root *page_tree = &mapping->page_tree;
unsigned long pfn = pfn_t_to_pfn(pfn_t);
+ struct inode *inode = mapping->host;
pgoff_t index = vmf->pgoff;
void *new_entry;
@@ -548,6 +600,10 @@ static void *dax_insert_mapping_entry(struct address_space *mapping,
spin_lock_irq(&mapping->tree_lock);
new_entry = dax_radix_locked_entry(pfn, flags);
+ if (dax_entry_size(entry) != dax_entry_size(new_entry)) {
+ dax_disassociate_entry(entry, inode, false);
+ dax_associate_entry(new_entry, inode);
+ }
if (dax_is_zero_entry(entry) || dax_is_empty_entry(entry)) {
/*
diff --git a/include/linux/mm_types.h b/include/linux/mm_types.h
index 46f4ecf5479a..dd976851e8d8 100644
--- a/include/linux/mm_types.h
+++ b/include/linux/mm_types.h
@@ -118,11 +118,21 @@ struct page {
* Can be used as a generic list
* by the page owner.
*/
- struct dev_pagemap *pgmap; /* ZONE_DEVICE pages are never on an
- * lru or handled by a slab
- * allocator, this points to the
- * hosting device page map.
- */
+ struct {
+ /*
+ * ZONE_DEVICE pages are never on an lru or handled by
+ * a slab allocator, this points to the hosting device
+ * page map.
+ */
+ struct dev_pagemap *pgmap;
+ /*
+ * inode association for MEMORY_DEVICE_FS_DAX page-idle
+ * callbacks. Note that we don't use ->mapping since
+ * that has hard coded page-cache assumptions in
+ * several paths.
+ */
+ struct inode *inode;
+ };
struct { /* slub per cpu partial pages */
struct page *next; /* Next partial slab */
#ifdef CONFIG_64BIT
diff --git a/kernel/memremap.c b/kernel/memremap.c
index 8a4ebfe9db4e..f9a2929fc310 100644
--- a/kernel/memremap.c
+++ b/kernel/memremap.c
@@ -441,13 +441,13 @@ void *devm_memremap_pages(struct device *dev, struct resource *res,
struct page *page = pfn_to_page(pfn);
/*
- * ZONE_DEVICE pages union ->lru with a ->pgmap back
- * pointer. It is a bug if a ZONE_DEVICE page is ever
- * freed or placed on a driver-private list. Seed the
- * storage with LIST_POISON* values.
+ * ZONE_DEVICE pages union ->lru with a ->pgmap back pointer
+ * and ->inode (for the MEMORY_DEVICE_FS_DAX case) association.
+ * It is a bug if a ZONE_DEVICE page is ever freed or placed on
+ * a driver-private list.
*/
- list_del(&page->lru);
page->pgmap = pgmap;
+ page->inode = NULL;
percpu_ref_get(ref);
if (!(++i % 1024))
cond_resched();
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