xfs: helper to convert holemask to inode alloc. bitmap

[cascardo/linux.git] / fs / xfs / libxfs / xfs_ialloc_btree.c

diff --git a/fs/xfs/libxfs/xfs_ialloc_btree.c b/fs/xfs/libxfs/xfs_ialloc_btree.c
index b95aac5..aa13b46 100644 (file)
--- a/fs/xfs/libxfs/xfs_ialloc_btree.c
+++ b/fs/xfs/libxfs/xfs_ialloc_btree.c
@@ -427,3 +427,54 @@ xfs_inobt_maxrecs(
                return blocklen / sizeof(xfs_inobt_rec_t);
        return blocklen / (sizeof(xfs_inobt_key_t) + sizeof(xfs_inobt_ptr_t));
 }
+
+/*
+ * Convert the inode record holemask to an inode allocation bitmap. The inode
+ * allocation bitmap is inode granularity and specifies whether an inode is
+ * physically allocated on disk (not whether the inode is considered allocated
+ * or free by the fs).
+ *
+ * A bit value of 1 means the inode is allocated, a value of 0 means it is free.
+ */
+uint64_t
+xfs_inobt_irec_to_allocmask(
+       struct xfs_inobt_rec_incore     *rec)
+{
+       uint64_t                        bitmap = 0;
+       uint64_t                        inodespbit;
+       int                             nextbit;
+       uint                            allocbitmap;
+
+       /*
+        * The holemask has 16-bits for a 64 inode record. Therefore each
+        * holemask bit represents multiple inodes. Create a mask of bits to set
+        * in the allocmask for each holemask bit.
+        */
+       inodespbit = (1 << XFS_INODES_PER_HOLEMASK_BIT) - 1;
+
+       /*
+        * Allocated inodes are represented by 0 bits in holemask. Invert the 0
+        * bits to 1 and convert to a uint so we can use xfs_next_bit(). Mask
+        * anything beyond the 16 holemask bits since this casts to a larger
+        * type.
+        */
+       allocbitmap = ~rec->ir_holemask & ((1 << XFS_INOBT_HOLEMASK_BITS) - 1);
+
+       /*
+        * allocbitmap is the inverted holemask so every set bit represents
+        * allocated inodes. To expand from 16-bit holemask granularity to
+        * 64-bit (e.g., bit-per-inode), set inodespbit bits in the target
+        * bitmap for every holemask bit.
+        */
+       nextbit = xfs_next_bit(&allocbitmap, 1, 0);
+       while (nextbit != -1) {
+               ASSERT(nextbit < (sizeof(rec->ir_holemask) * NBBY));
+
+               bitmap |= (inodespbit <<
+                          (nextbit * XFS_INODES_PER_HOLEMASK_BIT));
+
+               nextbit = xfs_next_bit(&allocbitmap, 1, nextbit + 1);
+       }
+
+       return bitmap;
+}