[PATCH v4 1/2] btrfs: factor our read/write stage off csum_tree_block() into its callers

[PATCH v4 1/2] btrfs: factor our read/write stage off csum_tree_block() into its callers

[Johannes Thumshirn]

Currently csum_tree_block() does two things, first it as it's name
suggests it calculates the checksum for a tree-block. But it also writes
this checksum to disk or reads an extent_buffer from disk and compares the
checksum with the calculated checksum, depending on the verify argument.

Furthermore one of the two callers passes in '1' for the verify argument,
the other one passes in '0'.

For clarity and less layering violations, factor out the second stage in
csum_tree_block()'s callers.

Suggested-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>

---

Changes to v3:
- Move WARN_ON() from csum_dirty_buffer() into csum_tree_buffer()

Changes to v2:
- Directly return -EINVAL instead of EUCLEAN

Changes to v1:
- return error from csum_tree_buffer() in csum_dirty_buffer() instead of
  EUCLEAN (Nikolay)
---
 fs/btrfs/disk-io.c | 51 +++++++++++++++++++++++++++------------------------
 1 file changed, 27 insertions(+), 24 deletions(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 5216e7b3f9ad..8090e8f4ccc2 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -263,12 +263,9 @@ void btrfs_csum_final(u32 crc, u8 *result)
  * compute the csum for a btree block, and either verify it or write it
  * into the csum field of the block.
  */
-static int csum_tree_block(struct btrfs_fs_info *fs_info,
-			   struct extent_buffer *buf,
-			   int verify)
+static int csum_tree_block(struct extent_buffer *buf,
+			   u8 *result)
 {
-	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
-	char result[BTRFS_CSUM_SIZE];
 	unsigned long len;
 	unsigned long cur_len;
 	unsigned long offset = BTRFS_CSUM_SIZE;
@@ -300,23 +297,6 @@ static int csum_tree_block(struct btrfs_fs_info *fs_info,
 
 	btrfs_csum_final(crc, result);
 
-	if (verify) {
-		if (memcmp_extent_buffer(buf, result, 0, csum_size)) {
-			u32 val;
-			u32 found = 0;
-			memcpy(&found, result, csum_size);
-
-			read_extent_buffer(buf, &val, 0, csum_size);
-			btrfs_warn_rl(fs_info,
-				"%s checksum verify failed on %llu wanted %X found %X level %d",
-				fs_info->sb->s_id, buf->start,
-				val, found, btrfs_header_level(buf));
-			return -EUCLEAN;
-		}
-	} else {
-		write_extent_buffer(buf, result, 0, csum_size);
-	}
-
 	return 0;
 }
 
@@ -533,6 +513,8 @@ static int csum_dirty_buffer(struct btrfs_fs_info *fs_info, struct page *page)
 {
 	u64 start = page_offset(page);
 	u64 found_start;
+	u8 result[BTRFS_CSUM_SIZE];
+	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
 	struct extent_buffer *eb;
 
 	eb = (struct extent_buffer *)page->private;
@@ -552,7 +534,11 @@ static int csum_dirty_buffer(struct btrfs_fs_info *fs_info, struct page *page)
 	ASSERT(memcmp_extent_buffer(eb, fs_info->fs_devices->metadata_uuid,
 			btrfs_header_fsid(), BTRFS_FSID_SIZE) == 0);
 
-	return csum_tree_block(fs_info, eb, 0);
+	if (csum_tree_block(eb, result))
+		return -EINVAL;
+
+	write_extent_buffer(eb, result, 0, csum_size);
+	return 0;
 }
 
 static int check_tree_block_fsid(struct btrfs_fs_info *fs_info,
@@ -595,7 +581,9 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
 	struct extent_buffer *eb;
 	struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
 	struct btrfs_fs_info *fs_info = root->fs_info;
+	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
 	int ret = 0;
+	char result[BTRFS_CSUM_SIZE];
 	int reads_done;
 
 	if (!page->private)
@@ -642,10 +630,25 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
 	btrfs_set_buffer_lockdep_class(btrfs_header_owner(eb),
 				       eb, found_level);
 
-	ret = csum_tree_block(fs_info, eb, 1);
+	ret = csum_tree_block(eb, result);
 	if (ret)
 		goto err;
 
+	if (memcmp_extent_buffer(eb, result, 0, csum_size)) {
+		u32 val;
+		u32 found = 0;
+
+		memcpy(&found, result, csum_size);
+
+		read_extent_buffer(eb, &val, 0, csum_size);
+		btrfs_warn_rl(fs_info,
+			      "%s checksum verify failed on %llu wanted %x found %x level %d",
+			      fs_info->sb->s_id, eb->start,
+			      val, found, btrfs_header_level(eb));
+		ret = -EUCLEAN;
+		goto err;
+	}
+
 	/*
 	 * If this is a leaf block and it is corrupt, set the corrupt bit so
 	 * that we don't try and read the other copies of this block, just
-- 
2.16.4

[PATCH 2/2] btrfs: warn if extent buffer mapping crosses a page boundary in csum_tree_block

[Johannes Thumshirn]

Since commit d2e174d5d3ee ("btrfs: document extent mapping assumptions in
checksum") we have a comment in place why map_private_extent_buffer() 
can't return 1 in the csum_tree_block() case.

Make this a bit more explicit and WARN_ON() in case this this assumption
breaks.

Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
---
 fs/btrfs/disk-io.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 8090e8f4ccc2..21407252eb44 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -285,7 +285,7 @@ static int csum_tree_block(struct extent_buffer *buf,
 		 */
 		err = map_private_extent_buffer(buf, offset, 32,
 					&kaddr, &map_start, &map_len);
-		if (err)
+		if (WARN_ON(err))
 			return err;
 		cur_len = min(len, map_len - (offset - map_start));
 		crc = btrfs_csum_data(kaddr + offset - map_start,
-- 
2.16.4

Re: [PATCH v4 1/2] btrfs: factor our read/write stage off csum_tree_block() into its callers

[David Sterba]

On Mon, Feb 25, 2019 at 02:24:15PM +0100, Johannes Thumshirn wrote:
> Currently csum_tree_block() does two things, first it as it's name
> suggests it calculates the checksum for a tree-block. But it also writes
> this checksum to disk or reads an extent_buffer from disk and compares the
> checksum with the calculated checksum, depending on the verify argument.
> 
> Furthermore one of the two callers passes in '1' for the verify argument,
> the other one passes in '0'.
> 
> For clarity and less layering violations, factor out the second stage in
> csum_tree_block()'s callers.
> 
> Suggested-by: Nikolay Borisov <nborisov@suse.com>
> Reviewed-by: Qu Wenruo <wqu@suse.com>
> Reviewed-by: Nikolay Borisov <nborisov@suse.com>
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>
> 
> ---
> 
> Changes to v3:
> - Move WARN_ON() from csum_dirty_buffer() into csum_tree_buffer()
> 
> Changes to v2:
> - Directly return -EINVAL instead of EUCLEAN
> 
> Changes to v1:
> - return error from csum_tree_buffer() in csum_dirty_buffer() instead of
>   EUCLEAN (Nikolay)
> ---
>  fs/btrfs/disk-io.c | 51 +++++++++++++++++++++++++++------------------------
>  1 file changed, 27 insertions(+), 24 deletions(-)
> 
> diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
> index 5216e7b3f9ad..8090e8f4ccc2 100644
> --- a/fs/btrfs/disk-io.c
> +++ b/fs/btrfs/disk-io.c
> @@ -263,12 +263,9 @@ void btrfs_csum_final(u32 crc, u8 *result)
>   * compute the csum for a btree block, and either verify it or write it
>   * into the csum field of the block.

The comment does not match the function anymore

>   */
> -static int csum_tree_block(struct btrfs_fs_info *fs_info,
> -			   struct extent_buffer *buf,
> -			   int verify)
> +static int csum_tree_block(struct extent_buffer *buf,
> +			   u8 *result)

Formatting

>  {
> -	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
> -	char result[BTRFS_CSUM_SIZE];
>  	unsigned long len;
>  	unsigned long cur_len;
>  	unsigned long offset = BTRFS_CSUM_SIZE;
> @@ -300,23 +297,6 @@ static int csum_tree_block(struct btrfs_fs_info *fs_info,
>  
>  	btrfs_csum_final(crc, result);
>  
> -	if (verify) {
> -		if (memcmp_extent_buffer(buf, result, 0, csum_size)) {
> -			u32 val;
> -			u32 found = 0;
> -			memcpy(&found, result, csum_size);
> -
> -			read_extent_buffer(buf, &val, 0, csum_size);
> -			btrfs_warn_rl(fs_info,
> -				"%s checksum verify failed on %llu wanted %X found %X level %d",
> -				fs_info->sb->s_id, buf->start,
> -				val, found, btrfs_header_level(buf));
> -			return -EUCLEAN;
> -		}
> -	} else {
> -		write_extent_buffer(buf, result, 0, csum_size);
> -	}
> -
>  	return 0;
>  }
>  
> @@ -533,6 +513,8 @@ static int csum_dirty_buffer(struct btrfs_fs_info *fs_info, struct page *page)
>  {
>  	u64 start = page_offset(page);
>  	u64 found_start;
> +	u8 result[BTRFS_CSUM_SIZE];
> +	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
>  	struct extent_buffer *eb;
>  
>  	eb = (struct extent_buffer *)page->private;
> @@ -552,7 +534,11 @@ static int csum_dirty_buffer(struct btrfs_fs_info *fs_info, struct page *page)
>  	ASSERT(memcmp_extent_buffer(eb, fs_info->fs_devices->metadata_uuid,
>  			btrfs_header_fsid(), BTRFS_FSID_SIZE) == 0);
>  
> -	return csum_tree_block(fs_info, eb, 0);
> +	if (csum_tree_block(eb, result))
> +		return -EINVAL;
> +
> +	write_extent_buffer(eb, result, 0, csum_size);
> +	return 0;
>  }
>  
>  static int check_tree_block_fsid(struct btrfs_fs_info *fs_info,
> @@ -595,7 +581,9 @@ static int btree_readpage_end_io_hook(struct btrfs_io_bio *io_bio,
>  	struct extent_buffer *eb;
>  	struct btrfs_root *root = BTRFS_I(page->mapping->host)->root;
>  	struct btrfs_fs_info *fs_info = root->fs_info;
> +	u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
>  	int ret = 0;
> +	char result[BTRFS_CSUM_SIZE];

This should be 'u8'

All of the above fixed and added to 5.2 queue, thanks.

Re: [PATCH 2/2] btrfs: warn if extent buffer mapping crosses a page boundary in csum_tree_block

[David Sterba]

On Mon, Feb 25, 2019 at 02:24:16PM +0100, Johannes Thumshirn wrote:
> Since commit d2e174d5d3ee ("btrfs: document extent mapping assumptions in
> checksum") we have a comment in place why map_private_extent_buffer() 
> can't return 1 in the csum_tree_block() case.
> 
> Make this a bit more explicit and WARN_ON() in case this this assumption
> breaks.
> 
> Signed-off-by: Johannes Thumshirn <jthumshirn@suse.de>

Reviewed-by: David Sterba <dsterba@suse.com>