1 files changed, 46 insertions, 11 deletions

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index 0d40d082f0c7..daf180dafe39 100644
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2720,6 +2720,33 @@ void set_page_extent_mapped(struct page *page)
         }
 }
 
+static struct extent_map *
+__get_extent_map(struct inode *inode, struct page *page, size_t pg_offset,
+                 u64 start, u64 len, get_extent_t *get_extent,
+                 struct extent_map **em_cached)
+{
+        struct extent_map *em;
+
+        if (em_cached && *em_cached) {
+                em = *em_cached;
+                if (em->in_tree && start >= em->start &&
+                    start < extent_map_end(em)) {
+                        atomic_inc(&em->refs);
+                        return em;
+                }
+
+                free_extent_map(em);
+                *em_cached = NULL;
+        }
+
+        em = get_extent(inode, page, pg_offset, start, len, 0);
+        if (em_cached && !IS_ERR_OR_NULL(em)) {
+                BUG_ON(*em_cached);
+                atomic_inc(&em->refs);
+                *em_cached = em;
+        }
+        return em;
+}
 /*
  * basic readpage implementation.  Locked extent state structs are inserted
  * into the tree that are removed when the IO is done (by the end_io
@@ -2729,6 +2756,7 @@ void set_page_extent_mapped(struct page *page)
 static int __do_readpage(struct extent_io_tree *tree,
                          struct page *page,
                          get_extent_t *get_extent,
+                         struct extent_map **em_cached,
                          struct bio **bio, int mirror_num,
                          unsigned long *bio_flags, int rw)
 {
@@ -2793,8 +2821,8 @@ static int __do_readpage(struct extent_io_tree *tree,
                                              &cached, GFP_NOFS);
                         break;
                 }
-                em = get_extent(inode, page, pg_offset, cur,
-                                end - cur + 1, 0);
+                em = __get_extent_map(inode, page, pg_offset, cur,
+                                      end - cur + 1, get_extent, em_cached);
                 if (IS_ERR_OR_NULL(em)) {
                         SetPageError(page);
                         unlock_extent(tree, cur, end);
@@ -2895,6 +2923,7 @@ static inline void __do_contiguous_readpages(struct extent_io_tree *tree,
                                              struct page *pages[], int nr_pages,
                                              u64 start, u64 end,
                                              get_extent_t *get_extent,
+                                             struct extent_map **em_cached,
                                              struct bio **bio, int mirror_num,
                                              unsigned long *bio_flags, int rw)
 {
@@ -2915,8 +2944,8 @@ static inline void __do_contiguous_readpages(struct extent_io_tree *tree,
         }
 
         for (index = 0; index < nr_pages; index++) {
-                __do_readpage(tree, pages[index], get_extent, bio, mirror_num,
-                              bio_flags, rw);
+                __do_readpage(tree, pages[index], get_extent, em_cached, bio,
+                              mirror_num, bio_flags, rw);
                 page_cache_release(pages[index]);
         }
 }
@@ -2924,6 +2953,7 @@ static inline void __do_contiguous_readpages(struct extent_io_tree *tree,
 static void __extent_readpages(struct extent_io_tree *tree,
                                struct page *pages[],
                                int nr_pages, get_extent_t *get_extent,
+                               struct extent_map **em_cached,
                                struct bio **bio, int mirror_num,
                                unsigned long *bio_flags, int rw)
 {
@@ -2944,8 +2974,9 @@ static void __extent_readpages(struct extent_io_tree *tree,
                 } else {
                         __do_contiguous_readpages(tree, &pages[first_index],
                                                   index - first_index, start,
-                                                  end, get_extent, bio,
-                                                  mirror_num, bio_flags, rw);
+                                                  end, get_extent, em_cached,
+                                                  bio, mirror_num, bio_flags,
+                                                  rw);
                         start = page_start;
                         end = start + PAGE_CACHE_SIZE - 1;
                         first_index = index;
@@ -2955,7 +2986,7 @@ static void __extent_readpages(struct extent_io_tree *tree,
         if (end)
                 __do_contiguous_readpages(tree, &pages[first_index],
                                           index - first_index, start,
-                                          end, get_extent, bio,
+                                          end, get_extent, em_cached, bio,
                                           mirror_num, bio_flags, rw);
 }
 
@@ -2981,8 +3012,8 @@ static int __extent_read_full_page(struct extent_io_tree *tree,
                 btrfs_put_ordered_extent(ordered);
         }
 
-        ret = __do_readpage(tree, page, get_extent, bio, mirror_num, bio_flags,
-                            rw);
+        ret = __do_readpage(tree, page, get_extent, NULL, bio, mirror_num,
+                            bio_flags, rw);
         return ret;
 }
 
@@ -3836,6 +3867,7 @@ int extent_readpages(struct extent_io_tree *tree,
         unsigned long bio_flags = 0;
         struct page *pagepool[16];
         struct page *page;
+        struct extent_map *em_cached = NULL;
         int nr = 0;
 
         for (page_idx = 0; page_idx < nr_pages; page_idx++) {
@@ -3852,14 +3884,17 @@ int extent_readpages(struct extent_io_tree *tree,
                 pagepool[nr++] = page;
                 if (nr < ARRAY_SIZE(pagepool))
                         continue;
-                __extent_readpages(tree, pagepool, nr, get_extent,
+                __extent_readpages(tree, pagepool, nr, get_extent, &em_cached,
                                    &bio, 0, &bio_flags, READ);
                 nr = 0;
         }
         if (nr)
-                __extent_readpages(tree, pagepool, nr, get_extent,
+                __extent_readpages(tree, pagepool, nr, get_extent, &em_cached,
                                    &bio, 0, &bio_flags, READ);
 
+        if (em_cached)
+                free_extent_map(em_cached);
+
         BUG_ON(!list_empty(pages));
         if (bio)
                 return submit_one_bio(READ, bio, 0, bio_flags);