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Subject[PATCH 10/22] ext4: Verify and calculate checksums for extent tree blocks
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Calculate and verify the checksum for each extent tree block.  The checksum is
located in the space immediately after the last possible ext4_extent in the
block. The space is is typically the last 4-8 bytes in the block.

Signed-off-by: Darrick J. Wong <djwong@us.ibm.com>
---
fs/ext4/ext4_extents.h | 25 +++++++++++++++++++++++-
fs/ext4/extents.c | 50 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 74 insertions(+), 1 deletions(-)

diff --git a/fs/ext4/ext4_extents.h b/fs/ext4/ext4_extents.h
index a52db3a..56e891a 100644
--- a/fs/ext4/ext4_extents.h
+++ b/fs/ext4/ext4_extents.h
@@ -62,10 +62,22 @@
/*
* ext4_inode has i_block array (60 bytes total).
* The first 12 bytes store ext4_extent_header;
- * the remainder stores an array of ext4_extent.
+ * the remainder stores an array of ext4_extent,
+ * followed by ext4_extent_tail.
*/

/*
+ * This is the extent tail on-disk structure.
+ * All other extent structures are 12 bytes long. It turns out that
+ * block_size % 12 >= 4 for all valid block sizes (1k, 2k, 4k).
+ * Therefore, this tail structure can be crammed into the end of the block
+ * without having to rebalance the tree.
+ */
+struct ext4_extent_tail {
+ __le32 et_checksum; /* crc32c(uuid+inum+extent_block) */
+};
+
+/*
* This is the extent on-disk structure.
* It's used at the bottom of the tree.
*/
@@ -101,6 +113,17 @@ struct ext4_extent_header {

#define EXT4_EXT_MAGIC cpu_to_le16(0xf30a)

+#define EXT4_EXTENT_TAIL_OFFSET(hdr) \
+ (sizeof(struct ext4_extent_header) + \
+ (sizeof(struct ext4_extent) * le16_to_cpu((hdr)->eh_max)))
+
+static inline struct ext4_extent_tail *
+find_ext4_extent_tail(struct ext4_extent_header *eh)
+{
+ return (struct ext4_extent_tail *)(((void *)eh) +
+ EXT4_EXTENT_TAIL_OFFSET(eh));
+}
+
/*
* Array of ext4_ext_path contains path to some extent.
* Creation/lookup routines use it for traversal/splitting/etc.
diff --git a/fs/ext4/extents.c b/fs/ext4/extents.c
index 00f97f4..5db751e 100644
--- a/fs/ext4/extents.c
+++ b/fs/ext4/extents.c
@@ -45,6 +45,46 @@

#include <trace/events/ext4.h>

+static __le32 ext4_extent_block_csum(struct inode *inode,
+ struct ext4_extent_header *eh)
+{
+ struct ext4_inode_info *ei = EXT4_I(inode);
+ struct ext4_sb_info *sbi = EXT4_SB(inode->i_sb);
+ __u32 csum;
+
+ csum = ext4_chksum(sbi, ei->i_uuid_inum_csum, (__u8 *)eh,
+ EXT4_EXTENT_TAIL_OFFSET(eh));
+ return cpu_to_le32(csum);
+}
+
+static int ext4_extent_block_csum_verify(struct inode *inode,
+ struct ext4_extent_header *eh)
+{
+ struct ext4_extent_tail *et;
+
+ if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+ EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+ return 1;
+
+ et = find_ext4_extent_tail(eh);
+ if (et->et_checksum != ext4_extent_block_csum(inode, eh))
+ return 0;
+ return 1;
+}
+
+static void ext4_extent_block_csum_set(struct inode *inode,
+ struct ext4_extent_header *eh)
+{
+ struct ext4_extent_tail *et;
+
+ if (!EXT4_HAS_RO_COMPAT_FEATURE(inode->i_sb,
+ EXT4_FEATURE_RO_COMPAT_METADATA_CSUM))
+ return;
+
+ et = find_ext4_extent_tail(eh);
+ et->et_checksum = ext4_extent_block_csum(inode, eh);
+}
+
static int ext4_split_extent(handle_t *handle,
struct inode *inode,
struct ext4_ext_path *path,
@@ -103,6 +143,7 @@ static int __ext4_ext_dirty(const char *where, unsigned int line,
{
int err;
if (path->p_bh) {
+ ext4_extent_block_csum_set(inode, ext_block_hdr(path->p_bh));
/* path points to block */
err = __ext4_handle_dirty_metadata(where, line, handle,
inode, path->p_bh);
@@ -375,6 +416,12 @@ static int __ext4_ext_check(const char *function, unsigned int line,
error_msg = "invalid extent entries";
goto corrupted;
}
+ /* Verify checksum on non-root extent tree nodes */
+ if (ext_depth(inode) != depth &&
+ !ext4_extent_block_csum_verify(inode, eh)) {
+ error_msg = "extent tree corrupted";
+ goto corrupted;
+ }
return 0;

corrupted:
@@ -914,6 +961,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,
le16_add_cpu(&neh->eh_entries, m);
}

+ ext4_extent_block_csum_set(inode, neh);
set_buffer_uptodate(bh);
unlock_buffer(bh);

@@ -992,6 +1040,7 @@ static int ext4_ext_split(handle_t *handle, struct inode *inode,
sizeof(struct ext4_extent_idx) * m);
le16_add_cpu(&neh->eh_entries, m);
}
+ ext4_extent_block_csum_set(inode, neh);
set_buffer_uptodate(bh);
unlock_buffer(bh);

@@ -1089,6 +1138,7 @@ static int ext4_ext_grow_indepth(handle_t *handle, struct inode *inode,
else
neh->eh_max = cpu_to_le16(ext4_ext_space_block(inode, 0));
neh->eh_magic = EXT4_EXT_MAGIC;
+ ext4_extent_block_csum_set(inode, neh);
set_buffer_uptodate(bh);
unlock_buffer(bh);



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