btrfs: don't generate any code from ASSERT() in release builds

The current definition of ASSERT(cond) as (void)(cond) is redundant,
since these checks have no side effects and don't affect code logic.

However, some checks contain READ_ONCE() or other compiler-unfriendly
constructs. For example, ASSERT(list_empty) in btrfs_add_dealloc_inode()
was compiled to a redundant mov instruction due to this issue.

Define ASSERT as BUILD_BUG_ON_INVALID for !CONFIG_BTRFS_ASSERT builds
which uses sizeof(cond) trick.  Also mark full_page_sectors_uptodate()
as __maybe_unused to suppress "unneeded declaration" warning (it's
needed in compile time)

Signed-off-by: Gladyshev Ilya <foxido@foxido.dev>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/messages.h b/fs/btrfs/messages.h
index 4416c165644fa40521ef67cd13d03ea5664f44a7..d8c0bd17dcdaf018ac4f444618b50fd53068cf86 100644 (file)
--- a/fs/btrfs/messages.h
+++ b/fs/btrfs/messages.h
@@ -168,7 +168,8 @@ do {                                                                                \
 #endif
 
 #else
-#define ASSERT(cond, args...)                  (void)(cond)
+/* Compile check the @cond expression but don't generate any code. */
+#define ASSERT(cond, args...)                  BUILD_BUG_ON_INVALID(cond)
 #endif
 
 #ifdef CONFIG_BTRFS_DEBUG

diff --git a/fs/btrfs/raid56.c b/fs/btrfs/raid56.c
index 0135dceb7baaa0908b3c238dc7c787e93371213a..302f20d8c33518dc6367fe82bb719000de1cdd99 100644 (file)
--- a/fs/btrfs/raid56.c
+++ b/fs/btrfs/raid56.c
@@ -299,8 +299,8 @@ static int rbio_bucket(struct btrfs_raid_bio *rbio)
        return hash_64(num >> 16, BTRFS_STRIPE_HASH_TABLE_BITS);
 }
 
-static bool full_page_sectors_uptodate(struct btrfs_raid_bio *rbio,
-                                      unsigned int page_nr)
+static __maybe_unused bool full_page_sectors_uptodate(struct btrfs_raid_bio *rbio,
+                                                     unsigned int page_nr)
 {
        const u32 sectorsize = rbio->bioc->fs_info->sectorsize;
        const u32 sectors_per_page = PAGE_SIZE / sectorsize;