From: Matthew Wilcox <mawil...@microsoft.com>

The current implementation of btrfs_page_exists_in_range() gives the
wrong answer if the workingset code has stored a shadow entry in the
page cache.  The filemap_range_has_page() function does not have this
problem, and it's shared code, so use it instead.

Signed-off-by: Matthew Wilcox <mawil...@microsoft.com>
---
 fs/btrfs/btrfs_inode.h |  6 ++++-
 fs/btrfs/inode.c       | 70 --------------------------------------------------
 2 files changed, 5 insertions(+), 71 deletions(-)

diff --git a/fs/btrfs/btrfs_inode.h b/fs/btrfs/btrfs_inode.h
index f527e99c9f8d..078a53e01ece 100644
--- a/fs/btrfs/btrfs_inode.h
+++ b/fs/btrfs/btrfs_inode.h
@@ -364,6 +364,10 @@ static inline void btrfs_print_data_csum_error(struct 
btrfs_inode *inode,
                        logical_start, csum, csum_expected, mirror_num);
 }
 
-bool btrfs_page_exists_in_range(struct inode *inode, loff_t start, loff_t end);
+static inline bool btrfs_page_exists_in_range(struct inode *inode,
+                                               loff_t start, loff_t end)
+{
+       return filemap_range_has_page(inode->i_mapping, start, end);
+}
 
 #endif
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 1f5b93ecffca..3340de232944 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -7476,76 +7476,6 @@ noinline int can_nocow_extent(struct inode *inode, u64 
offset, u64 *len,
        return ret;
 }
 
-bool btrfs_page_exists_in_range(struct inode *inode, loff_t start, loff_t end)
-{
-       struct radix_tree_root *root = &inode->i_mapping->page_tree;
-       bool found = false;
-       void **pagep = NULL;
-       struct page *page = NULL;
-       unsigned long start_idx;
-       unsigned long end_idx;
-
-       start_idx = start >> PAGE_SHIFT;
-
-       /*
-        * end is the last byte in the last page.  end == start is legal
-        */
-       end_idx = end >> PAGE_SHIFT;
-
-       rcu_read_lock();
-
-       /* Most of the code in this while loop is lifted from
-        * find_get_page.  It's been modified to begin searching from a
-        * page and return just the first page found in that range.  If the
-        * found idx is less than or equal to the end idx then we know that
-        * a page exists.  If no pages are found or if those pages are
-        * outside of the range then we're fine (yay!) */
-       while (page == NULL &&
-              radix_tree_gang_lookup_slot(root, &pagep, NULL, start_idx, 1)) {
-               page = radix_tree_deref_slot(pagep);
-               if (unlikely(!page))
-                       break;
-
-               if (radix_tree_exception(page)) {
-                       if (radix_tree_deref_retry(page)) {
-                               page = NULL;
-                               continue;
-                       }
-                       /*
-                        * Otherwise, shmem/tmpfs must be storing a swap entry
-                        * here as an exceptional entry: so return it without
-                        * attempting to raise page count.
-                        */
-                       page = NULL;
-                       break; /* TODO: Is this relevant for this use case? */
-               }
-
-               if (!page_cache_get_speculative(page)) {
-                       page = NULL;
-                       continue;
-               }
-
-               /*
-                * Has the page moved?
-                * This is part of the lockless pagecache protocol. See
-                * include/linux/pagemap.h for details.
-                */
-               if (unlikely(page != *pagep)) {
-                       put_page(page);
-                       page = NULL;
-               }
-       }
-
-       if (page) {
-               if (page->index <= end_idx)
-                       found = true;
-               put_page(page);
-       }
-
-       rcu_read_unlock();
-       return found;
-}
-
 static int lock_extent_direct(struct inode *inode, u64 lockstart, u64 lockend,
                              struct extent_state **cached_state, int writing)
 {
-- 
2.16.1

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