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, 5 insertions, 2 deletions

diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index 5fb366992b73..c7c8ab2209e1 100644
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -450,7 +450,8 @@ int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
         BUG_ON(nr_cluster > (MAX_BUF_PER_PAGE / 2));    /* fixed limit */
 
         lock_fat(sbi);
-        if (sbi->free_clusters != -1 && sbi->free_clusters < nr_cluster) {
+        if (sbi->free_clusters != -1 && sbi->free_clus_valid &&
+            sbi->free_clusters < nr_cluster) {
                 unlock_fat(sbi);
                 return -ENOSPC;
         }
@@ -504,6 +505,7 @@ int fat_alloc_clusters(struct inode *inode, int *cluster, int nr_cluster)
 
         /* Couldn't allocate the free entries */
         sbi->free_clusters = 0;
+        sbi->free_clus_valid = 1;
         sb->s_dirt = 1;
         err = -ENOSPC;
 
@@ -615,7 +617,7 @@ int fat_count_free_clusters(struct super_block *sb)
         int err = 0, free;
 
         lock_fat(sbi);
-        if (sbi->free_clusters != -1)
+        if (sbi->free_clusters != -1 && sbi->free_clus_valid)
                 goto out;
 
         reada_blocks = FAT_READA_SIZE >> sb->s_blocksize_bits;
@@ -643,6 +645,7 @@ int fat_count_free_clusters(struct super_block *sb)
                 } while (fat_ent_next(sbi, &fatent));
         }
         sbi->free_clusters = free;
+        sbi->free_clus_valid = 1;
         sb->s_dirt = 1;
         fatent_brelse(&fatent);
 out: