The ext4_mb_normalize_request() function contains a large if-else
ladder for predicting file size and uses a macro NRL_CHECK_SIZE.
Factor these out into proper helper functions to improve code
readability and maintainability.

This patch introduces:
- ext4_mb_check_size(): static inline function replacing NRL_CHECK_SIZE macro
- ext4_mb_predict_file_size(): extracts size prediction logic

No functional change.

Signed-off-by: Yu Kuai <yukuai@fnnas.com>
---
 fs/ext4/mballoc.c | 101 +++++++++++++++++++++++++++-------------------
 1 file changed, 60 insertions(+), 41 deletions(-)

diff --git a/fs/ext4/mballoc.c b/fs/ext4/mballoc.c
index 9087183602e4..eb46a4f5fb4f 100644
--- a/fs/ext4/mballoc.c
+++ b/fs/ext4/mballoc.c
@@ -4489,6 +4489,63 @@ ext4_mb_pa_adjust_overlap(struct ext4_allocation_context *ac,
 	*end = new_end;
 }
 
+/*
+ * Check if request size allows for chunk-based allocation
+ */
+static inline bool ext4_mb_check_size(loff_t req, loff_t size,
+				      int max, int chunk_size)
+{
+	return (req <= size) || (max <= chunk_size);
+}
+
+/*
+ * Predict file size for preallocation. Returns the predicted size
+ * in bytes and sets start_off if alignment is needed for large files.
+ */
+static loff_t ext4_mb_predict_file_size(struct ext4_sb_info *sbi,
+					struct ext4_allocation_context *ac,
+					loff_t size, loff_t *start_off)
+{
+	int bsbits = ac->ac_sb->s_blocksize_bits;
+	int max = 2 << bsbits;
+
+	*start_off = 0;
+
+	if (size <= 16 * 1024) {
+		size = 16 * 1024;
+	} else if (size <= 32 * 1024) {
+		size = 32 * 1024;
+	} else if (size <= 64 * 1024) {
+		size = 64 * 1024;
+	} else if (size <= 128 * 1024) {
+		size = 128 * 1024;
+	} else if (size <= 256 * 1024) {
+		size = 256 * 1024;
+	} else if (size <= 512 * 1024) {
+		size = 512 * 1024;
+	} else if (size <= 1024 * 1024) {
+		size = 1024 * 1024;
+	} else if (ext4_mb_check_size(size, 4 * 1024 * 1024, max, 2 * 1024)) {
+		*start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
+						(21 - bsbits)) << 21;
+		size = 2 * 1024 * 1024;
+	} else if (ext4_mb_check_size(size, 8 * 1024 * 1024, max, 4 * 1024)) {
+		*start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
+							(22 - bsbits)) << 22;
+		size = 4 * 1024 * 1024;
+	} else if (ext4_mb_check_size(EXT4_C2B(sbi, ac->ac_o_ex.fe_len),
+					(8<<20)>>bsbits, max, 8 * 1024)) {
+		*start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
+							(23 - bsbits)) << 23;
+		size = 8 * 1024 * 1024;
+	} else {
+		*start_off = (loff_t)ac->ac_o_ex.fe_logical << bsbits;
+		size = (loff_t)EXT4_C2B(sbi, ac->ac_o_ex.fe_len) << bsbits;
+	}
+
+	return size;
+}
+
 /*
  * Normalization means making request better in terms of
  * size and alignment
@@ -4500,7 +4557,7 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
 	struct ext4_sb_info *sbi = EXT4_SB(ac->ac_sb);
 	struct ext4_super_block *es = sbi->s_es;
 	int bsbits, max;
-	loff_t size, start_off, end;
+	loff_t size, start_off = 0, end;
 	loff_t orig_size __maybe_unused;
 	ext4_lblk_t start;
 
@@ -4533,47 +4590,9 @@ ext4_mb_normalize_request(struct ext4_allocation_context *ac,
 		size = i_size_read(ac->ac_inode);
 	orig_size = size;
 
-	/* max size of free chunks */
-	max = 2 << bsbits;
+	/* Predict file size for preallocation */
+	size = ext4_mb_predict_file_size(sbi, ac, size, &start_off);
 
-#define NRL_CHECK_SIZE(req, size, max, chunk_size)	\
-		(req <= (size) || max <= (chunk_size))
-
-	/* first, try to predict filesize */
-	/* XXX: should this table be tunable? */
-	start_off = 0;
-	if (size <= 16 * 1024) {
-		size = 16 * 1024;
-	} else if (size <= 32 * 1024) {
-		size = 32 * 1024;
-	} else if (size <= 64 * 1024) {
-		size = 64 * 1024;
-	} else if (size <= 128 * 1024) {
-		size = 128 * 1024;
-	} else if (size <= 256 * 1024) {
-		size = 256 * 1024;
-	} else if (size <= 512 * 1024) {
-		size = 512 * 1024;
-	} else if (size <= 1024 * 1024) {
-		size = 1024 * 1024;
-	} else if (NRL_CHECK_SIZE(size, 4 * 1024 * 1024, max, 2 * 1024)) {
-		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
-						(21 - bsbits)) << 21;
-		size = 2 * 1024 * 1024;
-	} else if (NRL_CHECK_SIZE(size, 8 * 1024 * 1024, max, 4 * 1024)) {
-		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
-							(22 - bsbits)) << 22;
-		size = 4 * 1024 * 1024;
-	} else if (NRL_CHECK_SIZE(EXT4_C2B(sbi, ac->ac_o_ex.fe_len),
-					(8<<20)>>bsbits, max, 8 * 1024)) {
-		start_off = ((loff_t)ac->ac_o_ex.fe_logical >>
-							(23 - bsbits)) << 23;
-		size = 8 * 1024 * 1024;
-	} else {
-		start_off = (loff_t) ac->ac_o_ex.fe_logical << bsbits;
-		size	  = (loff_t) EXT4_C2B(sbi,
-					      ac->ac_o_ex.fe_len) << bsbits;
-	}
 	size = size >> bsbits;
 	start = start_off >> bsbits;
 
-- 
2.51.0