Btrfs: Don't drop extent_map cache during releasepage on the btree inode

The btree inode should only have a single extent_map in the cache,
it doesn't make sense to ever drop it.

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

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 76ee7a4ae00c7f420274c8de52e073421e0b97e7..2de2b00afebc933f91603190f117e1d46cc71771 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -76,13 +76,12 @@ struct extent_map *btree_get_extent(struct inode *inode, struct page *page,
        struct extent_map *em;
        int ret;
 
-again:
        spin_lock(&em_tree->lock);
        em = lookup_extent_mapping(em_tree, start, len);
        spin_unlock(&em_tree->lock);
-       if (em) {
+       if (em)
                goto out;
-       }
+
        em = alloc_extent_map(GFP_NOFS);
        if (!em) {
                em = ERR_PTR(-ENOMEM);
@@ -95,15 +94,21 @@ again:
 
        spin_lock(&em_tree->lock);
        ret = add_extent_mapping(em_tree, em);
-       spin_unlock(&em_tree->lock);
-
        if (ret == -EEXIST) {
                free_extent_map(em);
-               em = NULL;
-               goto again;
+               em = lookup_extent_mapping(em_tree, start, len);
+               if (em)
+                       ret = 0;
+               else
+                       ret = -EIO;
        } else if (ret) {
-               em = ERR_PTR(ret);
+               free_extent_map(em);
+               em = NULL;
        }
+       spin_unlock(&em_tree->lock);
+
+       if (ret)
+               em = ERR_PTR(ret);
 out:
        return em;
 }
@@ -496,7 +501,7 @@ static int btree_releasepage(struct page *page, gfp_t gfp_flags)
        }
        tree = &BTRFS_I(page->mapping->host)->io_tree;
        map = &BTRFS_I(page->mapping->host)->extent_tree;
-       ret = try_release_extent_mapping(map, tree, page, gfp_flags);
+       ret = try_release_extent_state(map, tree, page, gfp_flags);
        if (ret == 1) {
                invalidate_extent_lru(tree, page_offset(page), PAGE_CACHE_SIZE);
                ClearPagePrivate(page);

diff --git a/fs/btrfs/extent_io.c b/fs/btrfs/extent_io.c
index a984a7bc119739e96843387cd5e75482bd760298..81f8b4fd069b1d843a1e502dd06c5f0261ef3069 100644 (file)
--- a/fs/btrfs/extent_io.c
+++ b/fs/btrfs/extent_io.c
@@ -2463,6 +2463,31 @@ err:
 }
 EXPORT_SYMBOL(extent_prepare_write);
 
+/*
+ * a helper for releasepage, this tests for areas of the page that
+ * are locked or under IO and drops the related state bits if it is safe
+ * to drop the page.
+ */
+int try_release_extent_state(struct extent_map_tree *map,
+                            struct extent_io_tree *tree, struct page *page,
+                            gfp_t mask)
+{
+       u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
+       u64 end = start + PAGE_CACHE_SIZE - 1;
+       int ret = 1;
+
+       if (test_range_bit(tree, start, end, EXTENT_IOBITS, 0))
+               ret = 0;
+       else {
+               if ((mask & GFP_NOFS) == GFP_NOFS)
+                       mask = GFP_NOFS;
+               clear_extent_bit(tree, start, end, EXTENT_UPTODATE,
+                                1, 1, mask);
+       }
+       return ret;
+}
+EXPORT_SYMBOL(try_release_extent_state);
+
 /*
  * a helper for releasepage.  As long as there are no locked extents
  * in the range corresponding to the page, both state records and extent
@@ -2475,8 +2500,7 @@ int try_release_extent_mapping(struct extent_map_tree *map,
        struct extent_map *em;
        u64 start = (u64)page->index << PAGE_CACHE_SHIFT;
        u64 end = start + PAGE_CACHE_SIZE - 1;
-       u64 orig_start = start;
-       int ret = 1;
+
        if ((mask & __GFP_WAIT) &&
            page->mapping->host->i_size > 16 * 1024 * 1024) {
                u64 len;
@@ -2507,15 +2531,7 @@ int try_release_extent_mapping(struct extent_map_tree *map,
                        free_extent_map(em);
                }
        }
-       if (test_range_bit(tree, orig_start, end, EXTENT_IOBITS, 0))
-               ret = 0;
-       else {
-               if ((mask & GFP_NOFS) == GFP_NOFS)
-                       mask = GFP_NOFS;
-               clear_extent_bit(tree, orig_start, end, EXTENT_UPTODATE,
-                                1, 1, mask);
-       }
-       return ret;
+       return try_release_extent_state(map, tree, page, mask);
 }
 EXPORT_SYMBOL(try_release_extent_mapping);
 

diff --git a/fs/btrfs/extent_io.h b/fs/btrfs/extent_io.h
index 232300d13be2d70ef9c4285841cb2b87458a7d9d..e483461475144c4603e8076881982603c473c9d5 100644 (file)
--- a/fs/btrfs/extent_io.h
+++ b/fs/btrfs/extent_io.h
@@ -110,6 +110,9 @@ void extent_io_tree_empty_lru(struct extent_io_tree *tree);
 int try_release_extent_mapping(struct extent_map_tree *map,
                               struct extent_io_tree *tree, struct page *page,
                               gfp_t mask);
+int try_release_extent_state(struct extent_map_tree *map,
+                            struct extent_io_tree *tree, struct page *page,
+                            gfp_t mask);
 int lock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask);
 int unlock_extent(struct extent_io_tree *tree, u64 start, u64 end, gfp_t mask);
 int extent_read_full_page(struct extent_io_tree *tree, struct page *page,