[PATCH] fs/fat: replace magic numbers with macros from <uapi/linux/msdos_fs.h>

[PATCH] fs/fat: replace magic numbers with macros from <uapi/linux/msdos_fs.h>

[Alexander Kuleshov]

Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
---
 fs/fat/fatent.c               | 8 ++++----
 include/uapi/linux/msdos_fs.h | 3 +++
 2 files changed, 7 insertions(+), 4 deletions(-)

diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index 260705c..3def7bd 100644
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -129,7 +129,7 @@ static int fat12_ent_get(struct fat_entry *fatent)
 		next = (*ent12_p[1] << 8) | *ent12_p[0];
 	spin_unlock(&fat12_entry_lock);
 
-	next &= 0x0fff;
+	next &= EOF_FAT12;
 	if (next >= BAD_FAT12)
 		next = FAT_ENT_EOF;
 	return next;
@@ -146,7 +146,7 @@ static int fat16_ent_get(struct fat_entry *fatent)
 
 static int fat32_ent_get(struct fat_entry *fatent)
 {
-	int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
+	int next = le32_to_cpu(*fatent->u.ent32_p) & EOF_FAT32;
 	WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
 	if (next >= BAD_FAT32)
 		next = FAT_ENT_EOF;
@@ -186,8 +186,8 @@ static void fat16_ent_put(struct fat_entry *fatent, int new)
 
 static void fat32_ent_put(struct fat_entry *fatent, int new)
 {
-	WARN_ON(new & 0xf0000000);
-	new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
+	WARN_ON(new & FAT_FREE_CLUSTER);
+	new |= le32_to_cpu(*fatent->u.ent32_p) & ~EOF_FAT32;
 	*fatent->u.ent32_p = cpu_to_le32(new);
 	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
 }
diff --git a/include/uapi/linux/msdos_fs.h b/include/uapi/linux/msdos_fs.h
index e956704..6d085bf 100644
--- a/include/uapi/linux/msdos_fs.h
+++ b/include/uapi/linux/msdos_fs.h
@@ -58,6 +58,9 @@
 #define FAT_FIRST_ENT(s, x)	((MSDOS_SB(s)->fat_bits == 32 ? 0x0FFFFF00 : \
 	MSDOS_SB(s)->fat_bits == 16 ? 0xFF00 : 0xF00) | (x))
 
+/* indicates that a cluster is free */
+#define FAT_FREE_CLUSTER	0xf0000000
+
 /* start of data cluster's entry (number of reserved clusters) */
 #define FAT_START_ENT	2
 
-- 
2.3.0.80.g18d0fec

Re: [PATCH] fs/fat: replace magic numbers with macros from <uapi/linux/msdos_fs.h>

[OGAWA Hirofumi]

Alexander Kuleshov <kuleshovmail@gmail.com> writes:

Those are not EOF, those are mask. For example, EOF_FAT12 can be 0xff8
(some old drivers did this really).

And 0xf0000000 means ~0x0fffffff, not free cluster (because FAT32 is
28bits actually).

> Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
> ---
>  fs/fat/fatent.c               | 8 ++++----
>  include/uapi/linux/msdos_fs.h | 3 +++
>  2 files changed, 7 insertions(+), 4 deletions(-)
>
> diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
> index 260705c..3def7bd 100644
> --- a/fs/fat/fatent.c
> +++ b/fs/fat/fatent.c
> @@ -129,7 +129,7 @@ static int fat12_ent_get(struct fat_entry *fatent)
>  		next = (*ent12_p[1] << 8) | *ent12_p[0];
>  	spin_unlock(&fat12_entry_lock);
>  
> -	next &= 0x0fff;
> +	next &= EOF_FAT12;
>  	if (next >= BAD_FAT12)
>  		next = FAT_ENT_EOF;
>  	return next;
> @@ -146,7 +146,7 @@ static int fat16_ent_get(struct fat_entry *fatent)
>  
>  static int fat32_ent_get(struct fat_entry *fatent)
>  {
> -	int next = le32_to_cpu(*fatent->u.ent32_p) & 0x0fffffff;
> +	int next = le32_to_cpu(*fatent->u.ent32_p) & EOF_FAT32;
>  	WARN_ON((unsigned long)fatent->u.ent32_p & (4 - 1));
>  	if (next >= BAD_FAT32)
>  		next = FAT_ENT_EOF;
> @@ -186,8 +186,8 @@ static void fat16_ent_put(struct fat_entry *fatent, int new)
>  
>  static void fat32_ent_put(struct fat_entry *fatent, int new)
>  {
> -	WARN_ON(new & 0xf0000000);
> -	new |= le32_to_cpu(*fatent->u.ent32_p) & ~0x0fffffff;
> +	WARN_ON(new & FAT_FREE_CLUSTER);
> +	new |= le32_to_cpu(*fatent->u.ent32_p) & ~EOF_FAT32;
>  	*fatent->u.ent32_p = cpu_to_le32(new);
>  	mark_buffer_dirty_inode(fatent->bhs[0], fatent->fat_inode);
>  }
> diff --git a/include/uapi/linux/msdos_fs.h b/include/uapi/linux/msdos_fs.h
> index e956704..6d085bf 100644
> --- a/include/uapi/linux/msdos_fs.h
> +++ b/include/uapi/linux/msdos_fs.h
> @@ -58,6 +58,9 @@
>  #define FAT_FIRST_ENT(s, x)	((MSDOS_SB(s)->fat_bits == 32 ? 0x0FFFFF00 : \
>  	MSDOS_SB(s)->fat_bits == 16 ? 0xFF00 : 0xF00) | (x))
>  
> +/* indicates that a cluster is free */
> +#define FAT_FREE_CLUSTER	0xf0000000
> +
>  /* start of data cluster's entry (number of reserved clusters) */
>  #define FAT_START_ENT	2

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