fat: introduce a helper fat_get_blknr_offset()

Introduce helper function to get the block number and offset for a given
i_pos value.  Use it in __fat_write_inode() now and later on in nfs.c

Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Ravishankar N <ravi.n1@samsung.com>
Signed-off-by: Amit Sahrawat <a.sahrawat@samsung.com>
Acked-by: OGAWA Hirofumi <hirofumi@mail.parknet.co.jp>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

2 files changed, 12 insertions, 4 deletions

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index f16948ed5bf8..980c0346c168 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -218,6 +218,13 @@ static inline sector_t fat_clus_to_blknr(struct msdos_sb_info *sbi, int clus)
                 + sbi->data_start;
 }
 
+static inline void fat_get_blknr_offset(struct msdos_sb_info *sbi,
+                                loff_t i_pos, sector_t *blknr, int *offset)
+{
+        *blknr = i_pos >> sbi->dir_per_block_bits;
+        *offset = i_pos & (sbi->dir_per_block - 1);
+}
+
 static inline loff_t fat_i_pos_read(struct msdos_sb_info *sbi,
                                         struct inode *inode)
 {
diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 78e363c844cb..68cb5a6eb539 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -662,7 +662,8 @@ static int __fat_write_inode(struct inode *inode, int wait)
         struct buffer_head *bh;
         struct msdos_dir_entry *raw_entry;
         loff_t i_pos;
-        int err;
+        sector_t blocknr;
+        int err, offset;
 
         if (inode->i_ino == MSDOS_ROOT_INO)
                 return 0;
@@ -672,7 +673,8 @@ retry:
         if (!i_pos)
                 return 0;
 
-        bh = sb_bread(sb, i_pos >> sbi->dir_per_block_bits);
+        fat_get_blknr_offset(sbi, i_pos, &blocknr, &offset);
+        bh = sb_bread(sb, blocknr);
         if (!bh) {
                 fat_msg(sb, KERN_ERR, "unable to read inode block "
                        "for updating (i_pos %lld)", i_pos);
@@ -685,8 +687,7 @@ retry:
                 goto retry;
         }
 
-        raw_entry = &((struct msdos_dir_entry *) (bh->b_data))
-            [i_pos & (sbi->dir_per_block - 1)];
+        raw_entry = &((struct msdos_dir_entry *) (bh->b_data))[offset];
         if (S_ISDIR(inode->i_mode))
                 raw_entry->size = 0;
         else