From: Filipe Manana Date: Fri, 19 Sep 2025 08:16:20 +0000 (+0100) Subject: btrfs: make the rule checking more readable for should_cow_block() X-Git-Url: https://www.infradead.org/git/?a=commitdiff_plain;h=f07575bab632af8d665c8cc95be0e83ca5d3bd80;p=users%2Fhch%2Fmisc.git 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: Johannes Thumshirn Reviewed-by: Qu Wenruo Signed-off-by: Filipe Manana Reviewed-by: David Sterba Signed-off-by: David Sterba --- diff --git a/fs/btrfs/ctree.c b/fs/btrfs/ctree.c index dc185322362b..13dc44e90762 100644 --- a/fs/btrfs/ctree.c +++ b/fs/btrfs/ctree.c @@ -613,15 +613,12 @@ error_unlock_cow: return ret; } -static inline int should_cow_block(const struct btrfs_trans_handle *trans, - const struct btrfs_root *root, - const struct extent_buffer *buf) +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; } /*