From fc38ae7f4826f0cb0c668c1e044cab1fe624fe0b Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@suse.com>
Date: Mon, 9 Nov 2020 13:39:51 +0800
Subject: [PATCH] btrfs-progs: check: detect and warn about tree blocks
 crossing 64K page boundary

For the incoming subpage support, there is a new requirement for tree
blocks.  Tree blocks should not cross 64K page boundary.

For current btrfs-progs and kernel, there shouldn't be any causes to
create such tree blocks.  But still, we want to detect such tree blocks
in the wild before subpage support fully lands in upstream.

This patch will add such check for both lowmem and original mode.
Currently it's just a warning, since there aren't many users using 64K
page size yet.

Signed-off-by: Qu Wenruo <wqu@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
 check/main.c        |  2 ++
 check/mode-common.h | 18 ++++++++++++++++++
 check/mode-lowmem.c |  2 ++
 3 files changed, 22 insertions(+)

diff --git a/check/main.c b/check/main.c
index c7c5408b..0c4eb3ca 100644
--- a/check/main.c
+++ b/check/main.c
@@ -5400,6 +5400,8 @@ static int process_extent_item(struct btrfs_root *root,
 		      num_bytes, gfs_info->sectorsize);
 		return -EIO;
 	}
+	if (metadata)
+		btrfs_check_subpage_eb_alignment(key.objectid, num_bytes);
 
 	memset(&tmpl, 0, sizeof(tmpl));
 	tmpl.start = key.objectid;
diff --git a/check/mode-common.h b/check/mode-common.h
index 604dc3e8..8fdeb7f6 100644
--- a/check/mode-common.h
+++ b/check/mode-common.h
@@ -174,4 +174,22 @@ static inline u32 btrfs_type_to_imode(u8 type)
 
 int get_extent_item_generation(u64 bytenr, u64 *gen_ret);
 
+/*
+ * Check tree block alignement for future subpage support on 64K page system.
+ *
+ * Subpage support on 64K page size require one eb to be completely contained
+ * by a page. Not allowing a tree block to cross 64K page boudanry.
+ *
+ * Since subpage support is still under development, this check only provides
+ * warning.
+ */
+static inline void btrfs_check_subpage_eb_alignment(u64 start, u32 len)
+{
+	if (start / BTRFS_MAX_METADATA_BLOCKSIZE !=
+	    (start + len) / BTRFS_MAX_METADATA_BLOCKSIZE)
+		warning(
+"tree block [%llu, %llu) crosses 64K page boudnary, may cause problem for 64K page system",
+			start, start + len);
+}
+
 #endif
diff --git a/check/mode-lowmem.c b/check/mode-lowmem.c
index 8c80e5f0..2531fde8 100644
--- a/check/mode-lowmem.c
+++ b/check/mode-lowmem.c
@@ -4264,6 +4264,8 @@ static int check_extent_item(struct btrfs_path *path)
 		      key.objectid, key.objectid + nodesize);
 		err |= CROSSING_STRIPE_BOUNDARY;
 	}
+	if (metadata)
+		btrfs_check_subpage_eb_alignment(key.objectid, nodesize);
 
 	ptr = (unsigned long)(ei + 1);