fat: mmu_private race fix

[linux-2.6-omap-h63xx.git] / fs / fat / cache.c

diff --git a/fs/fat/cache.c b/fs/fat/cache.c
index 589edde9053cb4e970ba897ea24cbe67e30a35d7..b4260229808790859871d7cf0e013cdf2601116c 100644 (file)
--- a/fs/fat/cache.c
+++ b/fs/fat/cache.c
@@ -293,10 +293,12 @@ static int fat_bmap_cluster(struct inode *inode, int cluster)
 }
 
 int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
-            unsigned long *mapped_blocks)
+            unsigned long *mapped_blocks, int create)
 {
        struct super_block *sb = inode->i_sb;
        struct msdos_sb_info *sbi = MSDOS_SB(sb);
+       const unsigned long blocksize = sb->s_blocksize;
+       const unsigned char blocksize_bits = sb->s_blocksize_bits;
        sector_t last_block;
        int cluster, offset;
 
@@ -309,10 +311,21 @@ int fat_bmap(struct inode *inode, sector_t sector, sector_t *phys,
                }
                return 0;
        }
-       last_block = (MSDOS_I(inode)->mmu_private + (sb->s_blocksize - 1))
-               >> sb->s_blocksize_bits;
-       if (sector >= last_block)
-               return 0;
+
+       last_block = (i_size_read(inode) + (blocksize - 1)) >> blocksize_bits;
+       if (sector >= last_block) {
+               if (!create)
+                       return 0;
+
+               /*
+                * ->mmu_private can access on only allocation path.
+                * (caller must hold ->i_mutex)
+                */
+               last_block = (MSDOS_I(inode)->mmu_private + (blocksize - 1))
+                       >> blocksize_bits;
+               if (sector >= last_block)
+                       return 0;
+       }
 
        cluster = sector >> (sbi->cluster_bits - sb->s_blocksize_bits);
        offset  = sector & (sbi->sec_per_clus - 1);