fat: fix non-atomic NFS i_pos read

fat_encode_fh() can fetch an invalid i_pos value on systems where 64-bit
accesses are not atomic.  Make it use the same accessor as the rest of the
FAT code.

Signed-off-by: Steven J. Magnani <steve@digidescorp.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>

1 files changed, 6 insertions, 7 deletions

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index a3d81ebf6d86..0038b32cb362 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -738,22 +738,21 @@ static int
 fat_encode_fh(struct inode *inode, __u32 *fh, int *lenp, struct inode *parent)
 {
         int len = *lenp;
-        u32 ipos_h, ipos_m, ipos_l;
+        struct msdos_sb_info *sbi = MSDOS_SB(inode->i_sb);
+        loff_t i_pos;
 
         if (len < 5) {
                 *lenp = 5;
                 return 255; /* no room */
         }
 
-        ipos_h = MSDOS_I(inode)->i_pos >> 8;
-        ipos_m = (MSDOS_I(inode)->i_pos & 0xf0) << 24;
-        ipos_l = (MSDOS_I(inode)->i_pos & 0x0f) << 28;
+        i_pos = fat_i_pos_read(sbi, inode);
         *lenp = 5;
         fh[0] = inode->i_ino;
         fh[1] = inode->i_generation;
-        fh[2] = ipos_h;
-        fh[3] = ipos_m | MSDOS_I(inode)->i_logstart;
-        fh[4] = ipos_l;
+        fh[2] = i_pos >> 8;
+        fh[3] = ((i_pos & 0xf0) << 24) | MSDOS_I(inode)->i_logstart;
+        fh[4] = (i_pos & 0x0f) << 28;
         if (parent)
                 fh[4] |= MSDOS_I(parent)->i_logstart;
         return 3;