Patch Amiga AFFS Partition Race Condition

diff --git a/fs/affs/affs.h b/fs/affs/affs.h
index 45a0ce4..fc1d4ca 100644
--- a/fs/affs/affs.h
+++ b/fs/affs/affs.h
@@ -66,6 +66,8 @@ struct affs_inode_info {
    u32  i_protect;         /* unused attribute bits */
    u32  i_lastalloc;           /* last allocated block */
    int  i_pa_cnt;          /* number of preallocated blocks */
+   spinlock_t i_alloc;             /* Protects last 2 fields. */
+
    struct inode vfs_inode;
};

diff --git a/fs/affs/bitmap.c b/fs/affs/bitmap.c
index 3e26271..3341bde 100644
--- a/fs/affs/bitmap.c
+++ b/fs/affs/bitmap.c
@@ -151,12 +151,18 @@ affs_alloc_block(struct inode *inode, u32 goal)

    pr_debug("AFFS: balloc(inode=%lu,goal=%u): ", inode->i_ino, goal);

+   spin_lock(&AFFS_I(inode)->i_alloc);
+
    if (AFFS_I(inode)->i_pa_cnt) {
-       pr_debug("%d\n", AFFS_I(inode)->i_lastalloc+1);
+       u32 ret;
        AFFS_I(inode)->i_pa_cnt--;
-       return ++AFFS_I(inode)->i_lastalloc;
+       ret = ++AFFS_I(inode)->i_lastalloc;
+       spin_unlock(&AFFS_I(inode)->i_alloc);
+       return ret;
    }

+   spin_unlock(&AFFS_I(inode)->i_alloc);
+
    if (!goal || goal > sbi->s_partition_size) {
        if (goal)
            affs_warning(sb, "affs_balloc", "invalid goal %d", goal);
@@ -230,16 +236,22 @@ find_bit:
    bit = ffs(tmp & mask) - 1;
    blk += bit + sbi->s_reserved;
    mask2 = mask = 1 << (bit & 31);
-   AFFS_I(inode)->i_lastalloc = blk;
-
-   /* prealloc as much as possible within this word */
-   while ((mask2 <<= 1)) {
-       if (!(tmp & mask2))
-           break;
-       AFFS_I(inode)->i_pa_cnt++;
-       mask |= mask2;
+
+   spin_lock(&AFFS_I(inode)->i_alloc);
+   if (!AFFS_I(inode)->i_pa_cnt) {
+       AFFS_I(inode)->i_lastalloc = blk;
+
+       /* prealloc as much as possible within this word */
+       while ((mask2 <<= 1)) {
+           if (!(tmp & mask2))
+               break;
+           AFFS_I(inode)->i_pa_cnt++;
+           mask |= mask2;
+       }
+       bm->bm_free -= AFFS_I(inode)->i_pa_cnt + 1;
    }
-   bm->bm_free -= AFFS_I(inode)->i_pa_cnt + 1;
+
+   spin_unlock(&AFFS_I(inode)->i_alloc);

    *data = cpu_to_be32(tmp & ~mask);

diff --git a/fs/affs/file.c b/fs/affs/file.c
index 2f4c935..829e976 100644
--- a/fs/affs/file.c
+++ b/fs/affs/file.c
@@ -795,12 +795,21 @@ void
affs_free_prealloc(struct inode *inode)
{
    struct super_block *sb = inode->i_sb;
+   u32 first, cnt;

    pr_debug("AFFS: free_prealloc(ino=%lu)\n", inode->i_ino);

-   while (AFFS_I(inode)->i_pa_cnt) {
-       AFFS_I(inode)->i_pa_cnt--;
-       affs_free_block(sb, ++AFFS_I(inode)->i_lastalloc);
+   spin_lock(&AFFS_I(inode)->i_alloc);
+   first = AFFS_I(inode)->i_lastalloc;
+   cnt = AFFS_I(inode)->i_pa_cnt;
+   AFFS_I(inode)->i_lastalloc += cnt;
+   AFFS_I(inode)->i_pa_cnt = 0;
+
+   spin_unlock(&AFFS_I(inode)->i_alloc);
+
+   while (cnt) {
+       cnt--;
+       affs_free_block(sb, ++first);
    }
}

diff --git a/fs/affs/super.c b/fs/affs/super.c
index 0782653..1df3c95 100644
--- a/fs/affs/super.c
+++ b/fs/affs/super.c
@@ -91,6 +91,7 @@ static struct inode *affs_alloc_inode(struct super_block *sb)
    i->i_lc = NULL;
    i->i_ext_bh = NULL;
    i->i_pa_cnt = 0;
+   spin_lock_init(&i->i_alloc);

    return &i->vfs_inode;
}