[PATCH v2] Btrfs: set leave_spinning in btrfs_get_extent

[Liu Bo <bo.liu@linux.alibaba.com>]

Unless it's going to read inline extents from btree leaf to page,
btrfs_get_extent won't sleep during the period of holding path lock.

This sets leave_spinning at first and sets path to blocking mode right
before reading inline extent if that's the case.  The benefit is that a
path in spinning mode typically has less impact (faster) on waiters
rather than that in blocking mode.

Also fixes the misalignment of the prototype, which is too trivial for
a single patch.

Signed-off-by: Liu Bo <bo.liu@linux.alibaba.com>
---
v2: send out the correct patch.

 fs/btrfs/ctree.h |  4 ++--
 fs/btrfs/inode.c | 14 +++++++++++---
 2 files changed, 13 insertions(+), 5 deletions(-)

diff --git a/fs/btrfs/ctree.h b/fs/btrfs/ctree.h
index 1aeed3c0e949..00e506de70ba 100644
--- a/fs/btrfs/ctree.h
+++ b/fs/btrfs/ctree.h
@@ -3177,8 +3177,8 @@ int btrfs_merge_bio_hook(struct page *page, unsigned long offset,
 struct inode *btrfs_iget(struct super_block *s, struct btrfs_key *location,
 			 struct btrfs_root *root, int *was_new);
 struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
-		struct page *page, size_t pg_offset,
-		u64 start, u64 end, int create);
+				    struct page *page, size_t pg_offset,
+				    u64 start, u64 end, int create);
 int btrfs_update_inode(struct btrfs_trans_handle *trans,
 			      struct btrfs_root *root,
 			      struct inode *inode);
diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 10e86f7b5398..31d43355f052 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -6787,9 +6787,9 @@ static noinline int uncompress_inline(struct btrfs_path *path,
  * This also copies inline extents directly into the page.
  */
 struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
-		struct page *page,
-	    size_t pg_offset, u64 start, u64 len,
-		int create)
+				    struct page *page,
+				    size_t pg_offset, u64 start, u64 len,
+				    int create)
 {
 	struct btrfs_fs_info *fs_info = inode->root->fs_info;
 	int ret;
@@ -6843,6 +6843,12 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 	 */
 	path->reada = READA_FORWARD;
 
+	/*
+	 * Unless we're going to uncompress inline extent, no sleep would
+	 * happen.
+	 */
+	path->leave_spinning = 1;
+
 	ret = btrfs_lookup_file_extent(NULL, root, path, objectid, start, 0);
 	if (ret < 0) {
 		err = ret;
@@ -6945,6 +6951,8 @@ struct extent_map *btrfs_get_extent(struct btrfs_inode *inode,
 		em->orig_block_len = em->len;
 		em->orig_start = em->start;
 		ptr = btrfs_file_extent_inline_start(item) + extent_offset;
+
+		btrfs_set_path_blocking(path);
 		if (!PageUptodate(page)) {
 			if (btrfs_file_extent_compression(leaf, item) !=
 			    BTRFS_COMPRESS_NONE) {
-- 
1.8.3.1