[PATCH] fs/fat: remove fat12_ent_blocknr and use fat_ent_blocknr instead

[PATCH] fs/fat: remove fat12_ent_blocknr and use fat_ent_blocknr instead

[Alexander Kuleshov]

There is only one difference between fat12_ent_blocknr and fat_ent_blocknr
functions in bytes calculation. Let's add bits checking to fat_ent_blocknr
instead code duplication.

Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
---
 fs/fat/fatent.c | 19 +++++++------------
 1 file changed, 7 insertions(+), 12 deletions(-)

diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index 260705c..314ab50 100644
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -21,21 +21,16 @@ struct fatent_operations {
 
 static DEFINE_SPINLOCK(fat12_entry_lock);
 
-static void fat12_ent_blocknr(struct super_block *sb, int entry,
-			      int *offset, sector_t *blocknr)
-{
-	struct msdos_sb_info *sbi = MSDOS_SB(sb);
-	int bytes = entry + (entry >> 1);
-	WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
-	*offset = bytes & (sb->s_blocksize - 1);
-	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
-}
-
 static void fat_ent_blocknr(struct super_block *sb, int entry,
 			    int *offset, sector_t *blocknr)
 {
 	struct msdos_sb_info *sbi = MSDOS_SB(sb);
-	int bytes = (entry << sbi->fatent_shift);
+	int bytes;
+
+	if (sbi->fat_bits == 12)
+		bytes = entry + (entry >> 1);
+	else
+		bytes = (entry << sbi->fatent_shift);
 	WARN_ON(entry < FAT_START_ENT || sbi->max_cluster <= entry);
 	*offset = bytes & (sb->s_blocksize - 1);
 	*blocknr = sbi->fat_start + (bytes >> sb->s_blocksize_bits);
@@ -250,7 +245,7 @@ static int fat32_ent_next(struct fat_entry *fatent)
 }
 
 static struct fatent_operations fat12_ops = {
-	.ent_blocknr	= fat12_ent_blocknr,
+	.ent_blocknr	= fat_ent_blocknr,
 	.ent_set_ptr	= fat12_ent_set_ptr,
 	.ent_bread	= fat12_ent_bread,
 	.ent_get	= fat12_ent_get,
-- 
2.3.0.80.g18d0fec

Re: [PATCH] fs/fat: remove fat12_ent_blocknr and use fat_ent_blocknr instead

[OGAWA Hirofumi]

Alexander Kuleshov <kuleshovmail@gmail.com> writes:

> There is only one difference between fat12_ent_blocknr and fat_ent_blocknr
> functions in bytes calculation. Let's add bits checking to fat_ent_blocknr
> instead code duplication.

I guess, fat12 (very small volume size) is uncommon to be used now, and
there is no way to switch fat12 <= fat16/fat32 at runtime. It is why has
special handler, i.e. avoid overhead to fat16/fat32 by fat12 code.

Thanks.
-- 
OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>

Re: [PATCH] fs/fat: remove fat12_ent_blocknr and use fat_ent_blocknr instead

[Alexander Kuleshov]

> I guess, fat12 (very small volume size) is uncommon to be used now, and
> there is no way to switch fat12 <= fat16/fat32 at runtime. It is why has
> special handler, i.e. avoid overhead to fat16/fat32 by fat12 code.

Understand. Thank you for explanation.