[v2,2/2] btrfs: tree-checker: add one extra file extent item ram_bytes check

Commit Message

Qu Wenruo April 17, 2024, 4:54 a.m. UTC

During my development on extent map cleanups, I hit a case where we can
create a file extent item that has ram_bytes double the size of
num_bytes but it's not compressed.

Later it turns out to be a bug in btrfs_split_ordered_extent(), and
thankfully it doesn't cause any real corruption, just a drift from
on-disk format.

Here we add an extra check on ram_bytes for btrfs_file_extent_item to
catch such problem.

However considering the incorrect ram_bytes are already in the wild, and
no real data corruption, we do not want end users to be bothered as their
data is still consistent.

So this patch would only hide the check behind DEBUG builds for us
developers to catch future problem.

Reviewed-by: Filipe Manana <[e-mail]>
Signed-off-by: Qu Wenruo <[e-mail]>
---
 fs/btrfs/tree-checker.c | 35 +++++++++++++++++++++++++++++------
 1 file changed, 29 insertions(+), 6 deletions(-)

Patch

diff --git a/fs/btrfs/tree-checker.c b/fs/btrfs/tree-checker.c
index c8fbcae4e88e..9f1597fe40e7 100644
--- a/fs/btrfs/tree-checker.c
+++ b/fs/btrfs/tree-checker.c
@@ -212,6 +212,7 @@  static int check_extent_data_item(struct extent_buffer *leaf,
 	u32 sectorsize = fs_info->sectorsize;
 	u32 item_size = btrfs_item_size(leaf, slot);
 	u64 extent_end;
+	u8 compression;
 
 	if (unlikely(!IS_ALIGNED(key->offset, sectorsize))) {
 		file_extent_err(leaf, slot,
@@ -251,16 +252,15 @@  static int check_extent_data_item(struct extent_buffer *leaf,
 		return -EUCLEAN;
 	}
 
+	compression = btrfs_file_extent_compression(leaf, fi);
 	/*
 	 * Support for new compression/encryption must introduce incompat flag,
 	 * and must be caught in open_ctree().
 	 */
-	if (unlikely(btrfs_file_extent_compression(leaf, fi) >=
-		     BTRFS_NR_COMPRESS_TYPES)) {
+	if (unlikely(compression >= BTRFS_NR_COMPRESS_TYPES)) {
 		file_extent_err(leaf, slot,
 	"invalid compression for file extent, have %u expect range [0, %u]",
-			btrfs_file_extent_compression(leaf, fi),
-			BTRFS_NR_COMPRESS_TYPES - 1);
+			compression, BTRFS_NR_COMPRESS_TYPES - 1);
 		return -EUCLEAN;
 	}
 	if (unlikely(btrfs_file_extent_encryption(leaf, fi))) {
@@ -279,8 +279,7 @@  static int check_extent_data_item(struct extent_buffer *leaf,
 		}
 
 		/* Compressed inline extent has no on-disk size, skip it */
-		if (btrfs_file_extent_compression(leaf, fi) !=
-		    BTRFS_COMPRESS_NONE)
+		if (compression != BTRFS_COMPRESS_NONE)
 			return 0;
 
 		/* Uncompressed inline extent size must match item size */
@@ -319,6 +318,30 @@  static int check_extent_data_item(struct extent_buffer *leaf,
 		return -EUCLEAN;
 	}
 
+	/*
+	 * If it's a uncompressed regular extents, its ram size should match
+	 * disk_num_bytes. But for now we have several call sites that doesn't
+	 * properly update @ram_bytes, so at least make sure
+	 * @ram_bytes <= @disk_num_bytes.
+	 *
+	 * However we had a bug related to @ram_bytes update, causing
+	 * all zoned and regular DIO to be affected.
+	 * Thankfully the ram_bytes is not critical for non-compressed file extents.
+	 * So here we hide the check behind DEBUG builds for developers only.
+	 */
+#ifdef CONFIG_BTRFS_DEBUG
+	if (unlikely(compression == BTRFS_COMPRESS_NONE &&
+		     btrfs_file_extent_disk_bytenr(leaf, fi) &&
+		     btrfs_file_extent_ram_bytes(leaf, fi) >
+		     btrfs_file_extent_disk_num_bytes(leaf, fi))) {
+		file_extent_err(leaf, slot,
+				"invalid ram_bytes, have %llu expect <= %llu",
+				btrfs_file_extent_ram_bytes(leaf, fi),
+				btrfs_file_extent_disk_num_bytes(leaf, fi));
+		return -EUCLEAN;
+	}
+#endif
+
 	/*
 	 * Check that no two consecutive file extent items, in the same leaf,
 	 * present ranges that overlap each other.