Commit fa82dcbf authored by Linus Torvalds's avatar Linus Torvalds
Browse files

Merge tag 'dax-fixes-4.20-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm 

Pull dax fixes from Dan Williams:
 "The last of the known regression fixes and fallout from the Xarray
  conversion of the filesystem-dax implementation.

  On the path to debugging why the dax memory-failure injection test
  started failing after the Xarray conversion a couple more fixes for
  the dax_lock_mapping_entry(), now called dax_lock_page(), surfaced.
  Those plus the bug that started the hunt are now addressed. These
  patches have appeared in a -next release with no issues reported.

  Note the touches to mm/memory-failure.c are just the conversion to the
  new function signature for dax_lock_page().

  Summary:

   - Fix the Xarray conversion of fsdax to properly handle
     dax_lock_mapping_entry() in the presense of pmd entries

   - Fix inode destruction racing a new lock request"

* tag 'dax-fixes-4.20-rc6' of git://git.kernel.org/pub/scm/linux/kernel/git/nvdimm/nvdimm:
  dax: Fix unlock mismatch with updated API
  dax: Don't access a freed inode
  dax: Check page->mapping isn't NULL
parents bd799eb6 27359fd6

fs/dax.c

+38 −17
Original line number Diff line number Diff line
@@ -232,6 +232,34 @@ static void *get_unlocked_entry(struct xa_state *xas) 
	}

}



/*

 * The only thing keeping the address space around is the i_pages lock

 * (it's cycled in clear_inode() after removing the entries from i_pages)

 * After we call xas_unlock_irq(), we cannot touch xas->xa.

 */

static void wait_entry_unlocked(struct xa_state *xas, void *entry)

{

	struct wait_exceptional_entry_queue ewait;

	wait_queue_head_t *wq;



	init_wait(&ewait.wait);

	ewait.wait.func = wake_exceptional_entry_func;



	wq = dax_entry_waitqueue(xas, entry, &ewait.key);

	prepare_to_wait_exclusive(wq, &ewait.wait, TASK_UNINTERRUPTIBLE);

	xas_unlock_irq(xas);

	schedule();

	finish_wait(wq, &ewait.wait);



	/*

	 * Entry lock waits are exclusive. Wake up the next waiter since

	 * we aren't sure we will acquire the entry lock and thus wake

	 * the next waiter up on unlock.

	 */

	if (waitqueue_active(wq))

		__wake_up(wq, TASK_NORMAL, 1, &ewait.key);

}



static void put_unlocked_entry(struct xa_state *xas, void *entry)

{

	/* If we were the only waiter woken, wake the next one */
@@ -351,21 +379,21 @@ 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;

		if (!dax_mapping(mapping))

		entry = NULL;

		if (!mapping || !dax_mapping(mapping))

			break;



		/*
@@ -375,7 +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;
@@ -389,9 +417,7 @@ bool dax_lock_mapping_entry(struct page *page) 
		entry = xas_load(&xas);

		if (dax_is_locked(entry)) {

			rcu_read_unlock();

			entry = get_unlocked_entry(&xas);

			xas_unlock_irq(&xas);

			put_unlocked_entry(&xas, entry);

			wait_entry_unlocked(&xas, entry);

			rcu_read_lock();

			continue;

		}
@@ -400,23 +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);

}



/*

include/linux/dax.h

+8 −6
Original line number Diff line number Diff line
@@ -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

mm/memory-failure.c

+4 −2
Original line number Diff line number Diff line
@@ -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);

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