The writepage_io is not mandatory, e.g. my port of xfs to the extent_map
code does not have one for now.  So handle a NULL pointer gracefully
here.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

generic_bmap is completely trivial, while the extent to bh mapping in
btrfs is rather complex.  So provide a extent_bmap instead that takes
a get_extent callback and can be used by filesystem using the extent_map
code.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

The bio completion handlers can be run in any context, e.g. when using
the old ide driver they run in hardirq context with irqs disabled so
lockdep rightfully warns about using write_lock_irq useage in these
handlers.

This patch switches clear_extent_bit and set_extent_bit to
write_lock_irqsave to fix this problem.
Signed-off-by: NChristoph Hellwig <hch@lst.de>
Signed-off-by: NChris Mason <chris.mason@oracle.com>

Yan Zheng noticed that set_extent_bit was exiting too early when there
was a hole in the map.  The fix is to reorder the tests to check for the
hole first.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

defrag.
Signed-off-by: NChris Mason <chris.mason@oracle.com>

Signed-off-by: NChris Mason <chris.mason@oracle.com>

Signed-off-by: NChris Mason <chris.mason@oracle.com>

Signed-off-by: NChris Mason <chris.mason@oracle.com>

instead of buffer heads.
Signed-off-by: NChris Mason <chris.mason@oracle.com>