fat: mmu_private race fix

mmu_private is 64bits value, hence it's not atomic to update.

So, the access rule for mmu_private is we must hold ->i_mutex.  But,
fat_get_block() path doesn't follow the rule on non-allocation path.

This fixes by using i_size instead if non-allocation path.

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, 2 deletions

diff --git a/fs/fat/fat.h b/fs/fat/fat.h
index a69f7f9757c0..4efc5038ed29 100644
--- a/fs/fat/fat.h
+++ b/fs/fat/fat.h
@@ -91,7 +91,9 @@ struct msdos_inode_info {
         /* for avoiding the race between fat_free() and fat_get_cluster() */
         unsigned int cache_valid_id;
 
-        loff_t mmu_private;
+        /* NOTE: mmu_private is 64bits, so must hold ->i_mutex to access */
+        loff_t mmu_private;     /* physically allocated size */
+
         int i_start;            /* first cluster or 0 */
         int i_logstart;         /* logical first cluster */
         int i_attrs;            /* unused attribute bits */
@@ -222,7 +224,7 @@ extern void fat_cache_inval_inode(struct inode *inode);
 extern int fat_get_cluster(struct inode *inode, int cluster,
                            int *fclus, int *dclus);
 extern int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
-                    unsigned long *mapped_blocks);
+                    unsigned long *mapped_blocks, int create);
 
 /* fat/dir.c */
 extern const struct file_operations fat_dir_operations;