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 <chris.mason@oracle.com>

1 files changed, 18 insertions, 16 deletions

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index c88f13a88555..0ba1cdbdf112 100644
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1596,8 +1596,7 @@ again:
 
                 size = btrfs_file_extent_inline_len(leaf, btrfs_item_nr(leaf,
                                                     path->slots[0]));
-
-                extent_end = (extent_start + size) |
+                extent_end = (extent_start + size - 1) |
                         ((u64)root->sectorsize - 1);
                 if (start < extent_start || start >= extent_end) {
                         em->start = start;
@@ -1610,29 +1609,32 @@ again:
                         }
                         goto not_found_em;
                 }
+                em->block_start = EXTENT_MAP_INLINE;
+                em->block_end = EXTENT_MAP_INLINE;
+
+                if (!page) {
+                        em->start = extent_start;
+                        em->end = extent_start + size - 1;
+                        goto out;
+                }
 
                 extent_offset = (page->index << PAGE_CACHE_SHIFT) -
-                        extent_start;
-                ptr = btrfs_file_extent_inline_start(item) + extent_offset;
-                map = kmap(page);
+                        extent_start + page_offset;
                 copy_size = min_t(u64, PAGE_CACHE_SIZE - page_offset,
                                 size - extent_offset);
-
-                em->block_start = EXTENT_MAP_INLINE;
-                em->block_end = EXTENT_MAP_INLINE;
                 em->start = extent_start + extent_offset;
                 em->end = (em->start + copy_size -1) |
                         ((u64)root->sectorsize -1);
-
-                if (!page) {
-                        goto insert;
+                map = kmap(page);
+                ptr = btrfs_file_extent_inline_start(item) + extent_offset;
+                read_extent_buffer(leaf, map + page_offset, ptr, copy_size);
+                
+                if (em->start + copy_size <= em->end) {
+                        size = min_t(u64, em->end + 1 - em->start,
+                                PAGE_CACHE_SIZE - page_offset) - copy_size;
+                        memset(map + page_offset + copy_size, 0, size);
                 }
 
-                read_extent_buffer(leaf, map + page_offset, ptr, copy_size);
-                /*
-                memset(map + page_offset + copy_size, 0,
-                       PAGE_CACHE_SIZE - copy_size - page_offset);
-                       */
                 flush_dcache_page(page);
                 kunmap(page);
                 set_extent_uptodate(em_tree, em->start, em->end, GFP_NOFS);