fat: Update free_clusters even if it is untrusted

Currently, free_clusters is not updated until it is trusted, because
Windows doesn't update it correctly.

But if user is using FAT driver of Linux, it updates free_clusters
correctly.  Instead, this updates it even if it's untrusted, so if
free_clustes is correct, now keep correct value.

Signed-off-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, 4 insertions, 3 deletions

diff --git a/fs/fat/inode.c b/fs/fat/inode.c
index 886f6095a378..1604a8a5c01f 100644
--- a/fs/fat/inode.c
+++ b/fs/fat/inode.c
@@ -537,7 +537,7 @@ static int fat_statfs(struct dentry *dentry, struct kstatfs *buf)
         struct msdos_sb_info *sbi = MSDOS_SB(dentry->d_sb);
 
         /* If the count of free cluster is still unknown, counts it here. */
-        if (sbi->free_clusters == -1) {
+        if (sbi->free_clusters == -1 || !sbi->free_clus_valid) {
                 int err = fat_count_free_clusters(dentry->d_sb);
                 if (err)
                         return err;
@@ -1274,6 +1274,7 @@ int fat_fill_super(struct super_block *sb, void *data, int silent,
         sbi->fat_length = le16_to_cpu(b->fat_length);
         sbi->root_cluster = 0;
         sbi->free_clusters = -1;        /* Don't know yet */
+        sbi->free_clus_valid = 0;
         sbi->prev_free = FAT_START_ENT;
 
         if (!sbi->fat_length && b->fat32_length) {
@@ -1309,8 +1310,8 @@ int fat_fill_super(struct super_block *sb, void *data, int silent,
                                sbi->fsinfo_sector);
                 } else {
                         if (sbi->options.usefree)
-                                sbi->free_clusters =
-                                        le32_to_cpu(fsinfo->free_clusters);
+                                sbi->free_clus_valid = 1;
+                        sbi->free_clusters = le32_to_cpu(fsinfo->free_clusters);
                         sbi->prev_free = le32_to_cpu(fsinfo->next_cluster);
                 }