2015-02-20 19:04:37

by Alexander Kuleshov

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

Signed-off-by: Alexander Kuleshov <[email protected]>
---
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

2015-02-21 11:42:59

by OGAWA Hirofumi

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

Alexander Kuleshov <[email protected]> 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 <[email protected]>
> ---
> 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 <[email protected]>