[PATCH] iomap: don't set FIEMAP_EXTENT_MERGED for extent based filesystems

[Christoph Hellwig <hch@xxxxxx>]

Filesystems like XFS that use extents should not set the
FIEMAP_EXTENT_MERGED flag in the fiemap extent structures.  To allow
for both behaviors for the upcoming gfs2 usage split the iomap
type field into type and flags, and only set FIEMAP_EXTENT_MERGED if
the IOMAP_F_MERGED flag is set.  The flags field will also come in
handy for future features such as shared extents on reflink-enabled
file systems.

Reported-by: Andreas Gruenbacher <agruenba@xxxxxxxxxx>
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 fs/iomap.c            | 5 ++++-
 include/linux/iomap.h | 8 +++++++-
 2 files changed, 11 insertions(+), 2 deletions(-)

diff --git a/fs/iomap.c b/fs/iomap.c
index 0342254..706270f 100644
--- a/fs/iomap.c
+++ b/fs/iomap.c
@@ -428,9 +428,12 @@ static int iomap_to_fiemap(struct fiemap_extent_info *fi,
                break;
        }
 
+       if (iomap->flags & IOMAP_F_MERGED)
+               flags |= FIEMAP_EXTENT_MERGED;
+
        return fiemap_fill_next_extent(fi, iomap->offset,
                        iomap->blkno != IOMAP_NULL_BLOCK ? iomap->blkno << 9: 0,
-                       iomap->length, flags | FIEMAP_EXTENT_MERGED);
+                       iomap->length, flags);
 
 }
 
diff --git a/include/linux/iomap.h b/include/linux/iomap.h
index 3267df4..3d70ece 100644
--- a/include/linux/iomap.h
+++ b/include/linux/iomap.h
@@ -19,6 +19,11 @@ struct vm_fault;
 #define IOMAP_UNWRITTEN        0x04    /* blocks allocated @blkno in unwritten 
state */
 
 /*
+ * Flags for iomap mappings:
+ */
+#define IOMAP_F_MERGED 0x01    /* contains multiple blocks/extents */
+
+/*
  * Magic value for blkno:
  */
 #define IOMAP_NULL_BLOCK -1LL  /* blkno is not valid */
@@ -27,7 +32,8 @@ struct iomap {
        sector_t                blkno;  /* 1st sector of mapping, 512b units */
        loff_t                  offset; /* file offset of mapping, bytes */
        u64                     length; /* length of mapping, bytes */
-       int                     type;   /* type of mapping */
+       u16                     type;   /* type of mapping */
+       u16                     flags;  /* flags for mapping */
        struct block_device     *bdev;  /* block device for I/O */
 };
 
-- 
2.1.4