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authorMatthew Wilcox <willy@infradead.org>2018-11-30 11:05:06 -0500
committerDan Williams <dan.j.williams@intel.com>2018-12-04 21:32:00 -0800
commit27359fd6e5f3c5db8fe544b63238b6170e8806d8 (patch)
tree1f6bd40a9fdc8f43c76b97fe4eb0fa309d9f61d7
parent55e56f06ed71d9441f3abd5b1d3c1a870812b3fe (diff)
dax: Fix unlock mismatch with updated API
Internal to dax_unlock_mapping_entry(), dax_unlock_entry() is used to store a replacement entry in the Xarray at the given xas-index with the DAX_LOCKED bit clear. When called, dax_unlock_entry() expects the unlocked value of the entry relative to the current Xarray state to be specified. In most contexts dax_unlock_entry() is operating in the same scope as the matched dax_lock_entry(). However, in the dax_unlock_mapping_entry() case the implementation needs to recall the original entry. In the case where the original entry is a 'pmd' entry it is possible that the pfn performed to do the lookup is misaligned to the value retrieved in the Xarray. Change the api to return the unlock cookie from dax_lock_page() and pass it to dax_unlock_page(). This fixes a bug where dax_unlock_page() was assuming that the page was PMD-aligned if the entry was a PMD entry with signatures like: WARNING: CPU: 38 PID: 1396 at fs/dax.c:340 dax_insert_entry+0x2b2/0x2d0 RIP: 0010:dax_insert_entry+0x2b2/0x2d0 [..] Call Trace: dax_iomap_pte_fault.isra.41+0x791/0xde0 ext4_dax_huge_fault+0x16f/0x1f0 ? up_read+0x1c/0xa0 __do_fault+0x1f/0x160 __handle_mm_fault+0x1033/0x1490 handle_mm_fault+0x18b/0x3d0 Link: https://lkml.kernel.org/r/20181130154902.GL10377@bombadil.infradead.org Fixes: 9f32d221301c ("dax: Convert dax_lock_mapping_entry to XArray") Reported-by: Dan Williams <dan.j.williams@intel.com> Signed-off-by: Matthew Wilcox <willy@infradead.org> Tested-by: Dan Williams <dan.j.williams@intel.com> Reviewed-by: Jan Kara <jack@suse.cz> Signed-off-by: Dan Williams <dan.j.williams@intel.com>
-rw-r--r--fs/dax.c21
-rw-r--r--include/linux/dax.h14
-rw-r--r--mm/memory-failure.c6
3 files changed, 20 insertions, 21 deletions
diff --git a/fs/dax.c b/fs/dax.c
index 3f592dc18d67..48132eca3761 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -379,20 +379,20 @@ static struct page *dax_busy_page(void *entry)
* @page: The page whose entry we want to lock
*
* Context: Process context.
- * Return: %true if the entry was locked or does not need to be locked.
+ * Return: A cookie to pass to dax_unlock_page() or 0 if the entry could
+ * not be locked.
*/
-bool dax_lock_mapping_entry(struct page *page)
+dax_entry_t dax_lock_page(struct page *page)
{
XA_STATE(xas, NULL, 0);
void *entry;
- bool locked;
/* Ensure page->mapping isn't freed while we look at it */
rcu_read_lock();
for (;;) {
struct address_space *mapping = READ_ONCE(page->mapping);
- locked = false;
+ entry = NULL;
if (!mapping || !dax_mapping(mapping))
break;
@@ -403,7 +403,7 @@ bool dax_lock_mapping_entry(struct page *page)
* otherwise we would not have a valid pfn_to_page()
* translation.
*/
- locked = true;
+ entry = (void *)~0UL;
if (S_ISCHR(mapping->host->i_mode))
break;
@@ -426,23 +426,18 @@ bool dax_lock_mapping_entry(struct page *page)
break;
}
rcu_read_unlock();
- return locked;
+ return (dax_entry_t)entry;
}
-void dax_unlock_mapping_entry(struct page *page)
+void dax_unlock_page(struct page *page, dax_entry_t cookie)
{
struct address_space *mapping = page->mapping;
XA_STATE(xas, &mapping->i_pages, page->index);
- void *entry;
if (S_ISCHR(mapping->host->i_mode))
return;
- rcu_read_lock();
- entry = xas_load(&xas);
- rcu_read_unlock();
- entry = dax_make_entry(page_to_pfn_t(page), dax_is_pmd_entry(entry));
- dax_unlock_entry(&xas, entry);
+ dax_unlock_entry(&xas, (void *)cookie);
}
/*
diff --git a/include/linux/dax.h b/include/linux/dax.h
index 450b28db9533..0dd316a74a29 100644
--- a/include/linux/dax.h
+++ b/include/linux/dax.h
@@ -7,6 +7,8 @@
#include <linux/radix-tree.h>
#include <asm/pgtable.h>
+typedef unsigned long dax_entry_t;
+
struct iomap_ops;
struct dax_device;
struct dax_operations {
@@ -88,8 +90,8 @@ int dax_writeback_mapping_range(struct address_space *mapping,
struct block_device *bdev, struct writeback_control *wbc);
struct page *dax_layout_busy_page(struct address_space *mapping);
-bool dax_lock_mapping_entry(struct page *page);
-void dax_unlock_mapping_entry(struct page *page);
+dax_entry_t dax_lock_page(struct page *page);
+void dax_unlock_page(struct page *page, dax_entry_t cookie);
#else
static inline bool bdev_dax_supported(struct block_device *bdev,
int blocksize)
@@ -122,14 +124,14 @@ static inline int dax_writeback_mapping_range(struct address_space *mapping,
return -EOPNOTSUPP;
}
-static inline bool dax_lock_mapping_entry(struct page *page)
+static inline dax_entry_t dax_lock_page(struct page *page)
{
if (IS_DAX(page->mapping->host))
- return true;
- return false;
+ return ~0UL;
+ return 0;
}
-static inline void dax_unlock_mapping_entry(struct page *page)
+static inline void dax_unlock_page(struct page *page, dax_entry_t cookie)
{
}
#endif
diff --git a/mm/memory-failure.c b/mm/memory-failure.c
index 0cd3de3550f0..7c72f2a95785 100644
--- a/mm/memory-failure.c
+++ b/mm/memory-failure.c
@@ -1161,6 +1161,7 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
LIST_HEAD(tokill);
int rc = -EBUSY;
loff_t start;
+ dax_entry_t cookie;
/*
* Prevent the inode from being freed while we are interrogating
@@ -1169,7 +1170,8 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
* also prevents changes to the mapping of this pfn until
* poison signaling is complete.
*/
- if (!dax_lock_mapping_entry(page))
+ cookie = dax_lock_page(page);
+ if (!cookie)
goto out;
if (hwpoison_filter(page)) {
@@ -1220,7 +1222,7 @@ static int memory_failure_dev_pagemap(unsigned long pfn, int flags,
kill_procs(&tokill, flags & MF_MUST_KILL, !unmap_success, pfn, flags);
rc = 0;
unlock:
- dax_unlock_mapping_entry(page);
+ dax_unlock_page(page, cookie);
out:
/* drop pgmap ref acquired in caller */
put_dev_pagemap(pgmap);