[PATCH] Fix IO error reporting on fsync()

When IO error happens on metadata buffer, buffer is freed from memory and
later fsync() is called, filesystems like ext2 fail to report EIO.  We

solve the problem by introducing a pointer to associated address space into
the buffer_head.  When a buffer is removed from a list of metadata buffers
associated with an address space, IO error is transferred from the buffer to
the address space, so that fsync can later report it.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>