[PATCH V15 03/15] Btrfs: subpage-blocksize: Make sure delalloc range intersects with the locked page's range

[Chandan Rajendra <chandan@linux.vnet.ibm.com>]

find_delalloc_range indirectly depends on EXTENT_UPTODDATE to make sure that
the delalloc range returned intersects with the file range mapped by the
page. Since we now track "uptodate" state in a per-page
bitmap (i.e. in btrfs_page_private->bstate), this commit makes an explicit
check to make sure that the delalloc range starts from within the file range
mapped by the page.

Signed-off-by: Chandan Rajendra <chandan@linux.vnet.ibm.com>
---
 fs/btrfs/extent_io.c | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 3228446..da54e49 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -1570,6 +1570,7 @@ out:
  * 1 is returned if we find something, 0 if nothing was in the tree
  */
 static noinline u64 find_delalloc_range(struct extent_io_tree *tree,
+					struct page *locked_page,
 					u64 *start, u64 *end, u64 max_bytes,
 					struct extent_state **cached_state)
 {
@@ -1578,6 +1579,9 @@ static noinline u64 find_delalloc_range(struct extent_io_tree *tree,
 	u64 cur_start = *start;
 	u64 found = 0;
 	u64 total_bytes = 0;
+	u64 page_end;
+
+	page_end = page_offset(locked_page) + PAGE_CACHE_SIZE - 1;
 
 	spin_lock(&tree->lock);
 
@@ -1598,7 +1602,8 @@ static noinline u64 find_delalloc_range(struct extent_io_tree *tree,
 			      (state->state & EXTENT_BOUNDARY))) {
 			goto out;
 		}
-		if (!(state->state & EXTENT_DELALLOC)) {
+		if (!(state->state & EXTENT_DELALLOC)
+			|| (page_end < state->start)) {
 			if (!found)
 				*end = state->end;
 			goto out;
@@ -1736,8 +1741,9 @@ again:
 	/* step one, find a bunch of delalloc bytes starting at start */
 	delalloc_start = *start;
 	delalloc_end = 0;
-	found = find_delalloc_range(tree, &delalloc_start, &delalloc_end,
-				    max_bytes, &cached_state);
+	found = find_delalloc_range(tree, locked_page,
+				&delalloc_start, &delalloc_end,
+				max_bytes, &cached_state);
 	if (!found || delalloc_end <= *start) {
 		*start = delalloc_start;
 		*end = delalloc_end;
-- 
2.1.0