Hi all,

After merging the xarray tree, today's linux-next build (powerpc
ppc64_defconfig) failed like this:

In file included from arch/powerpc/include/asm/bug.h:128:0,
                 from include/linux/bug.h:5,
                 from arch/powerpc/include/asm/cmpxchg.h:9,
                 from arch/powerpc/include/asm/atomic.h:11,
                 from include/linux/atomic.h:5,
                 from fs/dax.c:17:
fs/dax.c: In function 'dax_lock_page':
fs/dax.c:392:21: error: implicit declaration of function 
'radix_tree_exceptional_entry'; did you mean 'radix_tree_exception'? 
[-Werror=implicit-function-declaration]
       WARN_ON_ONCE(!radix_tree_exceptional_entry(entry))) {
                     ^
include/asm-generic/bug.h:69:25: note: in definition of macro 'WARN_ON_ONCE'
  int __ret_warn_on = !!(condition);   \
                         ^~~~~~~~~
fs/dax.c:395:15: error: implicit declaration of function 'slot_locked'; did you 
mean 'iget_locked'? [-Werror=implicit-function-declaration]
   } else if (!slot_locked(mapping, slot)) {
               ^~~~~~~~~~~
               iget_locked
fs/dax.c:396:4: error: implicit declaration of function 'lock_slot'; did you 
mean 'local_set'? [-Werror=implicit-function-declaration]
    lock_slot(mapping, slot);
    ^~~~~~~~~
    local_set
fs/dax.c:402:28: error: passing argument 1 of 'dax_entry_waitqueue' from 
incompatible pointer type [-Werror=incompatible-pointer-types]
   wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
                            ^~~~~~~
fs/dax.c:152:27: note: expected 'struct xa_state *' but argument is of type 
'struct address_space *'
 static wait_queue_head_t *dax_entry_waitqueue(struct xa_state *xas,
                           ^~~~~~~~~~~~~~~~~~~
fs/dax.c:402:37: warning: passing argument 2 of 'dax_entry_waitqueue' makes 
pointer from integer without a cast [-Wint-conversion]
   wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
                                     ^~~~~
fs/dax.c:152:27: note: expected 'void *' but argument is of type 'long unsigned 
int'
 static wait_queue_head_t *dax_entry_waitqueue(struct xa_state *xas,
                           ^~~~~~~~~~~~~~~~~~~
fs/dax.c:402:8: error: too many arguments to function 'dax_entry_waitqueue'
   wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
        ^~~~~~~~~~~~~~~~~~~
fs/dax.c:152:27: note: declared here
 static wait_queue_head_t *dax_entry_waitqueue(struct xa_state *xas,
                           ^~~~~~~~~~~~~~~~~~~
fs/dax.c: In function 'dax_unlock_page':
fs/dax.c:424:2: error: implicit declaration of function 
'dax_unlock_mapping_entry'; did you mean 'dax_delete_mapping_entry'? 
[-Werror=implicit-function-declaration]
  dax_unlock_mapping_entry(mapping, page->index);
  ^~~~~~~~~~~~~~~~~~~~~~~~
  dax_delete_mapping_entry

Caused by commits in the xarray tree interacting with commit

  9b3d53936caa ("filesystem-dax: Introduce dax_lock_page()")

from the nvdimm tree.

Willy thanks for the heads up about this.

I have applied the following merge fix patch (taken from the diff between
the -next tree at this point and the xarray-20180615 branch from the
xarray tree) for today.

From: Stephen Rothwell <[email protected]>
Date: Mon, 18 Jun 2018 13:17:15 +1000
Subject: [PATCH] filesystem-dax: fixups for xaarray changes

Signed-off-by: Stephen Rothwell <[email protected]>
---
 fs/dax.c | 75 +++++++++++++++++++++++++-------------------------------
 1 file changed, 34 insertions(+), 41 deletions(-)

diff --git a/fs/dax.c b/fs/dax.c
index 579088945add..91f7bce6ce64 100644
--- a/fs/dax.c
+++ b/fs/dax.c
@@ -350,78 +350,71 @@ static struct page *dax_busy_page(void *entry)
 
 struct page *dax_lock_page(unsigned long pfn)
 {
-       pgoff_t index;
-       struct inode *inode;
-       wait_queue_head_t *wq;
-       void *entry = NULL, **slot;
+       struct page *page = pfn_to_page(pfn);
+       XA_STATE(xas, NULL, 0);
+       void *entry;
        struct address_space *mapping;
-       struct wait_exceptional_entry_queue ewait;
-       struct page *ret = NULL, *page = pfn_to_page(pfn);
 
-       rcu_read_lock();
        for (;;) {
+               rcu_read_lock();
                mapping = READ_ONCE(page->mapping);
 
-               if (!mapping || !IS_DAX(mapping->host))
+               if (!mapping || !IS_DAX(mapping->host)) {
+                       page = NULL;
                        break;
+               }
 
                /*
                 * In the device-dax case there's no need to lock, a
                 * struct dev_pagemap pin is sufficient to keep the
                 * inode alive.
                 */
-               inode = mapping->host;
-               if (S_ISCHR(inode->i_mode)) {
-                       ret = page;
+               if (S_ISCHR(mapping->host->i_mode))
                        break;
-               }
 
-               xa_lock_irq(&mapping->i_pages);
+               xas.xa = &mapping->i_pages;
+               xas_lock_irq(&xas);
+               rcu_read_unlock();
                if (mapping != page->mapping) {
                        xa_unlock_irq(&mapping->i_pages);
                        continue;
                }
-               index = page->index;
-
-               init_wait(&ewait.wait);
-               ewait.wait.func = wake_exceptional_entry_func;
-
-               entry = __radix_tree_lookup(&mapping->i_pages, index, NULL,
-                               &slot);
-               if (!entry ||
-                   WARN_ON_ONCE(!radix_tree_exceptional_entry(entry))) {
-                       xa_unlock_irq(&mapping->i_pages);
-                       break;
-               } else if (!slot_locked(mapping, slot)) {
-                       lock_slot(mapping, slot);
-                       ret = page;
-                       xa_unlock_irq(&mapping->i_pages);
-                       break;
+               xas_set(&xas, page->index);
+               entry = xas_load(&xas);
+               if (dax_is_locked(entry)) {
+                       entry = get_unlocked_entry(&xas);
+                       /* Did the page move while we slept? */
+                       if (dax_to_pfn(entry) != pfn) {
+                               xas_unlock_irq(&xas);
+                               continue;
+                       }
                }
-
-               wq = dax_entry_waitqueue(mapping, index, entry, &ewait.key);
-               prepare_to_wait_exclusive(wq, &ewait.wait,
-                               TASK_UNINTERRUPTIBLE);
-               xa_unlock_irq(&mapping->i_pages);
-               rcu_read_unlock();
-               schedule();
-               finish_wait(wq, &ewait.wait);
-               rcu_read_lock();
+               dax_lock_entry(&xas, entry);
+               xas_unlock_irq(&xas);
+               goto out;
        }
        rcu_read_unlock();
 
+out:
        return page;
 }
 
 void dax_unlock_page(struct page *page)
 {
        struct address_space *mapping = page->mapping;
-       struct inode *inode = mapping->host;
+       XA_STATE(xas, &mapping->i_pages, page->index);
+       void *entry;
 
-       if (S_ISCHR(inode->i_mode))
+       if (S_ISCHR(mapping->host->i_mode))
                return;
 
-       dax_unlock_mapping_entry(mapping, page->index);
+       xas_lock_irq(&xas);
+       entry = xas_load(&xas);
+       BUG_ON(!dax_is_locked(entry));
+       entry = dax_make_page_entry(page, entry);
+       xas_store(&xas, entry);
+       dax_wake_entry(&xas, entry, false);
+       xas_unlock_irq(&xas);
 }
 
 /*
-- 
2.17.1

-- 
Cheers,
Stephen Rothwell

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