Commit f07575ba authored by Filipe Manana's avatar Filipe Manana Committed by David Sterba
Browse files

btrfs: make the rule checking more readable for should_cow_block() 



It's quite hard and unreadable the way the rule checks are organized in
should_cow_block(). We have a single if statement that returns 0 (false)
and it checks several conditions, with one them being a negated compound
condition which is particularly hard to reason immediately.

Improve on this by using multiple if statements, each checking a single
condition and returning immediately. Also change the return type from an
integer to a boolean, since all we need is to return true or false.

At least on x86_64 with Debian's gcc 14.2.0-19, this also reduces the
object code size by 64 bytes.

Before this change:

   $ size fs/btrfs/btrfs.ko
      text	   data	    bss	    dec	    hex	filename
   1913327	 161567	  15592	2090486	 1fe5f6	fs/btrfs/btrfs.ko

After this change:

   $ size fs/btrfs/btrfs.ko
      text	   data	    bss	    dec	    hex	filename
   1913263	 161567	  15592	2090422	 1fe5b6	fs/btrfs/btrfs.ko

Reviewed-by: default avatarJohannes Thumshirn <johannes.thumshirn@wdc.com>
Reviewed-by: default avatarQu Wenruo <wqu@suse.com>
Signed-off-by: default avatarFilipe Manana <fdmanana@suse.com>
Reviewed-by: default avatarDavid Sterba <dsterba@suse.com>
Signed-off-by: default avatarDavid Sterba <dsterba@suse.com>
parent b7ff7b0d

fs/btrfs/ctree.c

+23 −14
Original line number Diff line number Diff line
@@ -613,15 +613,12 @@ int btrfs_force_cow_block(struct btrfs_trans_handle *trans, 
	return ret;

}



static inline int should_cow_block(const struct btrfs_trans_handle *trans,

static inline bool should_cow_block(const struct btrfs_trans_handle *trans,

				    const struct btrfs_root *root,

				    const struct extent_buffer *buf)

{

	if (btrfs_is_testing(root->fs_info))

		return 0;



	/* Ensure we can see the FORCE_COW bit */

	smp_mb__before_atomic();

		return false;



	/*

	 * We do not need to cow a block if
@@ -634,13 +631,25 @@ static inline int should_cow_block(const struct btrfs_trans_handle *trans, 
	 *    after we've finished copying src root, we must COW the shared

	 *    block to ensure the metadata consistency.

	 */

	if (btrfs_header_generation(buf) == trans->transid &&

	    !btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN) &&

	    !(btrfs_root_id(root) != BTRFS_TREE_RELOC_OBJECTID &&

	      btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC)) &&

	    !test_bit(BTRFS_ROOT_FORCE_COW, &root->state))

		return 0;

	return 1;



	if (btrfs_header_generation(buf) != trans->transid)

		return true;



	if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_WRITTEN))

		return true;



	/* Ensure we can see the FORCE_COW bit. */

	smp_mb__before_atomic();

	if (test_bit(BTRFS_ROOT_FORCE_COW, &root->state))

		return true;



	if (btrfs_root_id(root) == BTRFS_TREE_RELOC_OBJECTID)

		return false;



	if (btrfs_header_flag(buf, BTRFS_HEADER_FLAG_RELOC))

		return true;



	return false;

}



/*