[PATCH 31/67] xfs: read leaf blocks when computing keys for bulkloading into node blocks

[cem@kernel.org]

From: "Darrick J. Wong" <djwong@kernel.org>

Source kernel commit: 26de64629d8b439a03bce243f14a46f7440729f3

When constructing a new btree, xfs_btree_bload_node needs to read the
btree blocks for level N to compute the keyptrs for the blocks that will
be loaded into level N+1.  The level N blocks must be formatted at that
point.

A subsequent patch will change the btree bulkloader to write new btree
blocks in 256K chunks to moderate memory consumption if the new btree is
very large.  As a consequence of that, it's possible that the buffers
for lower level blocks might have been reclaimed by the time the node
builder comes back to the block.

Therefore, change xfs_btree_bload_node to read the lower level blocks
to handle the reclaimed buffer case.  As a side effect, the read will
increase the LRU refs, which will bias towards keeping new btree buffers
in memory after the new btree commits.

Signed-off-by: Darrick J. Wong <djwong@kernel.org>
Reviewed-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Carlos Maiolino <cem@kernel.org>
---
 libxfs/xfs_btree.c         | 2 +-
 libxfs/xfs_btree.h         | 3 +++
 libxfs/xfs_btree_staging.c | 7 ++++++-
 3 files changed, 10 insertions(+), 2 deletions(-)

diff --git a/libxfs/xfs_btree.c b/libxfs/xfs_btree.c
index 85f8bef06..97962fc16 100644
--- a/libxfs/xfs_btree.c
+++ b/libxfs/xfs_btree.c
@@ -1327,7 +1327,7 @@ xfs_btree_get_buf_block(
  * Read in the buffer at the given ptr and return the buffer and
  * the block pointer within the buffer.
  */
-STATIC int
+int
 xfs_btree_read_buf_block(
 	struct xfs_btree_cur		*cur,
 	const union xfs_btree_ptr	*ptr,
diff --git a/libxfs/xfs_btree.h b/libxfs/xfs_btree.h
index 4d68a58be..e0875cec4 100644
--- a/libxfs/xfs_btree.h
+++ b/libxfs/xfs_btree.h
@@ -700,6 +700,9 @@ void xfs_btree_set_ptr_null(struct xfs_btree_cur *cur,
 int xfs_btree_get_buf_block(struct xfs_btree_cur *cur,
 		const union xfs_btree_ptr *ptr, struct xfs_btree_block **block,
 		struct xfs_buf **bpp);
+int xfs_btree_read_buf_block(struct xfs_btree_cur *cur,
+		const union xfs_btree_ptr *ptr, int flags,
+		struct xfs_btree_block **block, struct xfs_buf **bpp);
 void xfs_btree_set_sibling(struct xfs_btree_cur *cur,
 		struct xfs_btree_block *block, const union xfs_btree_ptr *ptr,
 		int lr);
diff --git a/libxfs/xfs_btree_staging.c b/libxfs/xfs_btree_staging.c
index ae2d9c63f..be0b43e45 100644
--- a/libxfs/xfs_btree_staging.c
+++ b/libxfs/xfs_btree_staging.c
@@ -489,7 +489,12 @@ xfs_btree_bload_node(
 
 		ASSERT(!xfs_btree_ptr_is_null(cur, child_ptr));
 
-		ret = xfs_btree_get_buf_block(cur, child_ptr, &child_block,
+		/*
+		 * Read the lower-level block in case the buffer for it has
+		 * been reclaimed.  LRU refs will be set on the block, which is
+		 * desirable if the new btree commits.
+		 */
+		ret = xfs_btree_read_buf_block(cur, child_ptr, 0, &child_block,
 				&child_bp);
 		if (ret)
 			return ret;
-- 
2.44.0