btrfs: Drop EXTENT_UPTODATE check in hole punching and direct locking
In these instances, we are trying to determine if a page has been accessed
since we began the operation for the sake of retry. This is easily
accomplished by doing a gang lookup in the page mapping radix tree, and it
saves us the dependency on the flag (so that we might eventually delete
it).
btrfs_page_exists_in_range borrows heavily from find_get_page, replacing
the radix tree look up with a gang lookup of 1, so that we can find the
next highest page >= index and see if it falls into our lock range.
Signed-off-by: Chris Mason <clm@fb.com>
Signed-off-by: Alex Gartrell <agartrell@fb.com>
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 0b8ce30..a462da1 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6735,6 +6735,71 @@
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;
+ int found = false;
+ void **pagep = NULL;
+ struct page *page = NULL;
+ int start_idx;
+ int end_idx;
+
+ start_idx = start >> PAGE_CACHE_SHIFT;
+
+ /*
+ * end is the last byte in the last page. end == start is legal
+ */
+ end_idx = end >> PAGE_CACHE_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))
+ continue;
+ /*
+ * Otherwise, shmem/tmpfs must be storing a swap entry
+ * here as an exceptional entry: so return it without
+ * attempting to raise page count.
+ */
+ break; /* TODO: Is this relevant for this use case? */
+ }
+
+ if (!page_cache_get_speculative(page))
+ continue;
+
+ /*
+ * Has the page moved?
+ * This is part of the lockless pagecache protocol. See
+ * include/linux/pagemap.h for details.
+ */
+ if (unlikely(page != *pagep)) {
+ page_cache_release(page);
+ page = NULL;
+ }
+ }
+
+ if (page) {
+ if (page->index <= end_idx)
+ found = true;
+ page_cache_release(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)
{
@@ -6759,10 +6824,9 @@
* invalidate needs to happen so that reads after a write do not
* get stale data.
*/
- if (!ordered && (!writing ||
- !test_range_bit(&BTRFS_I(inode)->io_tree,
- lockstart, lockend, EXTENT_UPTODATE, 0,
- *cached_state)))
+ if (!ordered &&
+ (!writing ||
+ !btrfs_page_exists_in_range(inode, lockstart, lockend)))
break;
unlock_extent_cached(&BTRFS_I(inode)->io_tree, lockstart, lockend,