fat: Fix the race of read/write the FAT12 entry

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

diff --git a/fs/fat/fatent.c b/fs/fat/fatent.c
index ab171ea8e869b2cc9da6369abad3a83c970d2a96..2c1b73fb82ae29f5a135342c75c2d73fe0d5d931 100644 (file)
--- a/fs/fat/fatent.c
+++ b/fs/fat/fatent.c
@@ -17,6 +17,8 @@ struct fatent_operations {
        int (*ent_next)(struct fat_entry *);
 };
 
+static DEFINE_SPINLOCK(fat12_entry_lock);
+
 static void fat12_ent_blocknr(struct super_block *sb, int entry,
                              int *offset, sector_t *blocknr)
 {
@@ -116,10 +118,13 @@ static int fat12_ent_get(struct fat_entry *fatent)
        u8 **ent12_p = fatent->u.ent12_p;
        int next;
 
+       spin_lock(&fat12_entry_lock);
        if (fatent->entry & 1)
                next = (*ent12_p[0] >> 4) | (*ent12_p[1] << 4);
        else
                next = (*ent12_p[1] << 8) | *ent12_p[0];
+       spin_unlock(&fat12_entry_lock);
+
        next &= 0x0fff;
        if (next >= BAD_FAT12)
                next = FAT_ENT_EOF;
@@ -151,6 +156,7 @@ static void fat12_ent_put(struct fat_entry *fatent, int new)
        if (new == FAT_ENT_EOF)
                new = EOF_FAT12;
 
+       spin_lock(&fat12_entry_lock);
        if (fatent->entry & 1) {
                *ent12_p[0] = (new << 4) | (*ent12_p[0] & 0x0f);
                *ent12_p[1] = new >> 4;
@@ -158,6 +164,7 @@ static void fat12_ent_put(struct fat_entry *fatent, int new)
                *ent12_p[0] = new & 0xff;
                *ent12_p[1] = (*ent12_p[1] & 0xf0) | (new >> 8);
        }
+       spin_unlock(&fat12_entry_lock);
 
        mark_buffer_dirty(fatent->bhs[0]);
        if (fatent->nr_bhs == 2)