[PATCH v4 15/18] xfs: filter out sparse regions from individual inode allocation

[Brian Foster <bfoster@redhat.com>]

Inode allocation from an existing record with free inodes traditionally
selects the first inode available according to the ir_free mask. With
sparse inode chunks, the ir_free mask could refer to an unallocated
region. We must mask the unallocated regions out of ir_free before using
it to select a free inode in the chunk.

Update the xfs_inobt_first_free_inode() helper to find the first free
inode available of the allocated regions of the inode chunk.

Signed-off-by: Brian Foster <bfoster@redhat.com>
---
 fs/xfs/libxfs/xfs_ialloc.c | 15 +++++++++++++--
 1 file changed, 13 insertions(+), 2 deletions(-)

diff --git a/fs/xfs/libxfs/xfs_ialloc.c b/fs/xfs/libxfs/xfs_ialloc.c
index d96c5e1..62fc075 100644
--- a/fs/xfs/libxfs/xfs_ialloc.c
+++ b/fs/xfs/libxfs/xfs_ialloc.c
@@ -1077,13 +1077,24 @@ xfs_ialloc_get_rec(
 }
 
 /*
- * Return the offset of the first free inode in the record.
+ * Return the offset of the first free inode in the record. If the inode chunk
+ * is sparsely allocated, we convert the record holemask to inode granularity
+ * and mask off the unallocated regions from the inode free mask.
  */
 STATIC int
 xfs_inobt_first_free_inode(
 	struct xfs_inobt_rec_incore	*rec)
 {
-	return xfs_lowbit64(rec->ir_free);
+	xfs_inofree_t			realfree;
+
+	/* if there are no holes, return the first available offset */
+	if (!xfs_inobt_issparse(rec->ir_holemask))
+		return xfs_lowbit64(rec->ir_free);
+
+	realfree = xfs_inobt_irec_to_allocmask(rec);
+	realfree &= rec->ir_free;
+
+	return xfs_lowbit64(realfree);
 }
 
 /*
-- 
1.8.3.1

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