Fix inline extent handling in btrfs_get_extent
Fix inline extent handling in btrfs_get_extent

1.  Reorder kmap and the test for  'page != NULL'
2.  Zero-fill rest area of a block when inline extent isn't big enough.
3.  Do not insert extent_map into the map tree when page == NULL.
(If insert the extent_map into the map tree,  subsequent read requests
will find it in the map tree directly and the corresponding inline
extent data aren't copied into page by the the get_extent function.
extent_read_full_page can't handle that case)

Signed-off-by: Chris Mason <a169954b4cb1a46cee25f659d3bddfebe02b5fba@oracle.com>

TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,TeamVee-Kanas/android_kernel_samsung_kanas,TeamVee-Kanas/android_kernel_samsung_kanas,KristFoundation/Programs,KristFoundation/Programs,KristFoundation/Programs