[PATCH 6/8] btrfs: Wait for extent bits to release page

[Goldwyn Rodrigues <rgoldwyn@xxxxxxx>]

From: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>

While trying to release a page, the extent containing the page may be locked
which would stop the page from being released. Wait for the
extent lock to be cleared, if blocking is allowed and then clear
the bits.

While we are at it, clean the code of try_release_extent_state() to make
it simpler.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@xxxxxxxx>
Reviewed-by: Johannes Thumshirn <jthumshirn@xxxxxxx>
Reviewed-by: Nikolay Borisov <nborisov@xxxxxxxx>
---
 fs/btrfs/extent_io.c | 37 ++++++++++++++++---------------------
 fs/btrfs/extent_io.h |  2 +-
 fs/btrfs/inode.c     |  4 ++--
 3 files changed, 19 insertions(+), 24 deletions(-)

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index cceaf05aada2..153f78be973f 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -4362,33 +4362,28 @@ int extent_invalidatepage(struct extent_io_tree *tree,
  * are locked or under IO and drops the related state bits if it is safe
  * to drop the page.
  */
-static int try_release_extent_state(struct extent_io_tree *tree,
+static bool try_release_extent_state(struct extent_io_tree *tree,
 				    struct page *page, gfp_t mask)
 {
 	u64 start = page_offset(page);
 	u64 end = start + PAGE_SIZE - 1;
-	int ret = 1;
 
 	if (test_range_bit(tree, start, end, EXTENT_LOCKED, 0, NULL)) {
-		ret = 0;
-	} else {
-		/*
-		 * at this point we can safely clear everything except the
-		 * locked bit and the nodatasum bit
-		 */
-		ret = __clear_extent_bit(tree, start, end,
-				 ~(EXTENT_LOCKED | EXTENT_NODATASUM),
-				 0, 0, NULL, mask, NULL);
-
-		/* if clear_extent_bit failed for enomem reasons,
-		 * we can't allow the release to continue.
-		 */
-		if (ret < 0)
-			ret = 0;
-		else
-			ret = 1;
+		if (!gfpflags_allow_blocking(mask))
+			return false;
+		wait_extent_bit(tree, start, end, EXTENT_LOCKED);
 	}
-	return ret;
+	/*
+	 * At this point we can safely clear everything except the locked and
+	 * nodatasum bits. If clear_extent_bit failed due to -ENOMEM,
+	 * don't allow release.
+	 */
+	if (__clear_extent_bit(tree, start, end,
+				~(EXTENT_LOCKED | EXTENT_NODATASUM), 0, 0,
+				NULL, mask, NULL) < 0)
+		return false;
+
+	return true;
 }
 
 /*
@@ -4396,7 +4391,7 @@ static int try_release_extent_state(struct extent_io_tree *tree,
  * in the range corresponding to the page, both state records and extent
  * map records are removed
  */
-int try_release_extent_mapping(struct page *page, gfp_t mask)
+bool try_release_extent_mapping(struct page *page, gfp_t mask)
 {
 	struct extent_map *em;
 	u64 start = page_offset(page);
diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index cf3424d58fec..0735cadb5e55 100644
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -263,7 +263,7 @@ void extent_io_tree_init(struct btrfs_fs_info *fs_info,
 			 struct extent_io_tree *tree, unsigned int owner,
 			 void *private_data);
 void extent_io_tree_release(struct extent_io_tree *tree);
-int try_release_extent_mapping(struct page *page, gfp_t mask);
+bool try_release_extent_mapping(struct page *page, gfp_t mask);
 int try_release_extent_buffer(struct page *page);
 int lock_extent_bits(struct extent_io_tree *tree, u64 start, u64 end,
 		     struct extent_state **cached);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index b4a297407672..f619b5f6a095 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -8787,8 +8787,8 @@ btrfs_readpages(struct file *file, struct address_space *mapping,
 
 static int __btrfs_releasepage(struct page *page, gfp_t gfp_flags)
 {
-	int ret = try_release_extent_mapping(page, gfp_flags);
-	if (ret == 1) {
+	bool ret = try_release_extent_mapping(page, gfp_flags);
+	if (ret) {
 		ClearPagePrivate(page);
 		set_page_private(page, 0);
 		put_page(page);
-- 
2.16.4