[RFC PATCH v1 10/57] fs/ext4: Remove PAGE_SIZE compile-time constant assumption

Ryan Roberts
2024-10-14T11:37:53Z

To prepare for supporting boot-time page size selection, refactor code
to remove assumptions about PAGE_SIZE being compile-time constant. Code
intended to be equivalent when compile-time page size is active.

Convert CPP PAGE_SIZE conditionals to C if/else. For compile-time page
size, the compiler will strip the dead part, and for boot-time page
size, the condition will be evaluated at run time.

Signed-off-by: Ryan Roberts <ryan.roberts@arm.com>
---

***NOTE***
Any confused maintainers may want to read the cover note here for context:
https://lore.kernel.org/all/20241014105514.3206191-1-ryan.roberts@arm.com/

fs/ext4/ext4.h | 36 ++++++++++++++++++------------------
1 file changed, 18 insertions(+), 18 deletions(-)

diff --git a/fs/ext4/ext4.h b/fs/ext4/ext4.h
index 08acd152261ed..1a6dbd925024a 100644
--- a/fs/ext4/ext4.h
+++ b/fs/ext4/ext4.h
@@ -2415,31 +2415,31 @@ ext4_rec_len_from_disk(__le16 dlen, unsigned blocksize)
{
unsigned len = le16_to_cpu(dlen);

-#if (PAGE_SIZE >= 65536)
- if (len == EXT4_MAX_REC_LEN || len == 0)
- return blocksize;
- return (len & 65532) | ((len & 3) << 16);
-#else
- return len;
-#endif
+ if (PAGE_SIZE >= 65536) {
+ if (len == EXT4_MAX_REC_LEN || len == 0)
+ return blocksize;
+ return (len & 65532) | ((len & 3) << 16);
+ } else {
+ return len;
+ }
}

static inline __le16 ext4_rec_len_to_disk(unsigned len, unsigned blocksize)
{
BUG_ON((len > blocksize) || (blocksize > (1 << 18)) || (len & 3));
-#if (PAGE_SIZE >= 65536)
- if (len < 65536)
+ if (PAGE_SIZE >= 65536) {
+ if (len < 65536)
+ return cpu_to_le16(len);
+ if (len == blocksize) {
+ if (blocksize == 65536)
+ return cpu_to_le16(EXT4_MAX_REC_LEN);
+ else
+ return cpu_to_le16(0);
+ }
+ return cpu_to_le16((len & 65532) | ((len >> 16) & 3));
+ } else {
return cpu_to_le16(len);
- if (len == blocksize) {
- if (blocksize == 65536)
- return cpu_to_le16(EXT4_MAX_REC_LEN);
- else
- return cpu_to_le16(0);
}
- return cpu_to_le16((len & 65532) | ((len >> 16) & 3));
-#else
- return cpu_to_le16(len);
-#endif
}

/*
--
2.43.0