linux-kernel - [PATCH AUTOSEL 6.10 23/27] btrfs: reduce nesting for extent processing at btrfs_lookup_extent

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Message-ID: <20240728005329.1723272-23-sashal@kernel.org>
Date: Sat, 27 Jul 2024 20:53:06 -0400
From: Sasha Levin <sashal@...nel.org>
To: linux-kernel@...r.kernel.org,
	stable@...r.kernel.org
Cc: Filipe Manana <fdmanana@...e.com>,
	Qu Wenruo <wqu@...e.com>,
	David Sterba <dsterba@...e.com>,
	Sasha Levin <sashal@...nel.org>,
	clm@...com,
	josef@...icpanda.com,
	linux-btrfs@...r.kernel.org
Subject: [PATCH AUTOSEL 6.10 23/27] btrfs: reduce nesting for extent processing at btrfs_lookup_extent_info()

From: Filipe Manana <fdmanana@...e.com>

[ Upstream commit 5c83b3beaee06aa88d4015408ac2d8bb35380b06 ]

Instead of using an if-else statement when processing the extent item at
btrfs_lookup_extent_info(), use a single if statement for the error case
since it does a goto at the end and leave the success (expected) case
following the if statement, reducing indentation and making the logic a
bit easier to follow. Also make the if statement's condition as unlikely
since it's not expected to ever happen, as it signals some corruption,
making it clear and hint the compiler to generate more efficient code.

Reviewed-by: Qu Wenruo <wqu@...e.com>
Signed-off-by: Filipe Manana <fdmanana@...e.com>
Signed-off-by: David Sterba <dsterba@...e.com>
Signed-off-by: Sasha Levin <sashal@...nel.org>
---
 fs/btrfs/extent-tree.c | 22 +++++++++-------------
 1 file changed, 9 insertions(+), 13 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 41db538e4959e..a7190fd747e07 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -104,10 +104,7 @@ int btrfs_lookup_extent_info(struct btrfs_trans_handle *trans,
 	struct btrfs_delayed_ref_head *head;
 	struct btrfs_delayed_ref_root *delayed_refs;
 	struct btrfs_path *path;
-	struct btrfs_extent_item *ei;
-	struct extent_buffer *leaf;
 	struct btrfs_key key;
-	u32 item_size;
 	u64 num_refs;
 	u64 extent_flags;
 	u64 owner = 0;
@@ -157,16 +154,11 @@ int btrfs_lookup_extent_info(struct btrfs_trans_handle *trans,
 	}
 
 	if (ret == 0) {
-		leaf = path->nodes[0];
-		item_size = btrfs_item_size(leaf, path->slots[0]);
-		if (item_size >= sizeof(*ei)) {
-			ei = btrfs_item_ptr(leaf, path->slots[0],
-					    struct btrfs_extent_item);
-			num_refs = btrfs_extent_refs(leaf, ei);
-			extent_flags = btrfs_extent_flags(leaf, ei);
-			owner = btrfs_get_extent_owner_root(fs_info, leaf,
-							    path->slots[0]);
-		} else {
+		struct extent_buffer *leaf = path->nodes[0];
+		struct btrfs_extent_item *ei;
+		const u32 item_size = btrfs_item_size(leaf, path->slots[0]);
+
+		if (unlikely(item_size < sizeof(*ei))) {
 			ret = -EUCLEAN;
 			btrfs_err(fs_info,
 			"unexpected extent item size, has %u expect >= %zu",
@@ -179,6 +171,10 @@ int btrfs_lookup_extent_info(struct btrfs_trans_handle *trans,
 			goto out_free;
 		}
 
+		ei = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_extent_item);
+		num_refs = btrfs_extent_refs(leaf, ei);
+		extent_flags = btrfs_extent_flags(leaf, ei);
+		owner = btrfs_get_extent_owner_root(fs_info, leaf, path->slots[0]);
 		BUG_ON(num_refs == 0);
 	} else {
 		num_refs = 0;
-- 
2.43.0