1 files changed, 18 insertions, 32 deletions

diff --git a/fs/btrfs/file-item.c b/fs/btrfs/file-item.c
index 90d4ee52cd4..a1cb7821bec 100644
--- a/fs/btrfs/file-item.c
+++ b/fs/btrfs/file-item.c
@@ -177,6 +177,17 @@ static int __btrfs_lookup_bio_sums(struct btrfs_root *root,
 
         WARN_ON(bio->bi_vcnt <= 0);
 
+        /*
+         * the free space stuff is only read when it hasn't been
+         * updated in the current transaction.  So, we can safely
+         * read from the commit root and sidestep a nasty deadlock
+         * between reading the free space cache and updating the csum tree.
+         */
+        if (btrfs_is_free_space_inode(root, inode)) {
+                path->search_commit_root = 1;
+                path->skip_locking = 1;
+        }
+
         disk_bytenr = (u64)bio->bi_sector << 9;
         if (dio)
                 offset = logical_offset;
@@ -282,7 +293,8 @@ int btrfs_lookup_csums_range(struct btrfs_root *root, u64 start, u64 end,
         u16 csum_size = btrfs_super_csum_size(&root->fs_info->super_copy);
 
         path = btrfs_alloc_path();
-        BUG_ON(!path);
+        if (!path)
+                return -ENOMEM;
 
         if (search_commit) {
                 path->skip_locking = 1;
@@ -664,15 +676,13 @@ int btrfs_csum_file_blocks(struct btrfs_trans_handle *trans,
         struct btrfs_sector_sum *sector_sum;
         u32 nritems;
         u32 ins_size;
-        char *eb_map;
-        char *eb_token;
-        unsigned long map_len;
-        unsigned long map_start;
         u16 csum_size =
                 btrfs_super_csum_size(&root->fs_info->super_copy);
 
         path = btrfs_alloc_path();
-        BUG_ON(!path);
+        if (!path)
+                return -ENOMEM;
+
         sector_sum = sums->sums;
 again:
         next_offset = (u64)-1;
@@ -814,30 +824,9 @@ found:
         item_end = btrfs_item_ptr(leaf, path->slots[0], struct btrfs_csum_item);
         item_end = (struct btrfs_csum_item *)((unsigned char *)item_end +
                                       btrfs_item_size_nr(leaf, path->slots[0]));
-        eb_token = NULL;
 next_sector:
 
-        if (!eb_token ||
-           (unsigned long)item + csum_size >= map_start + map_len) {
-                int err;
-
-                if (eb_token)
-                        unmap_extent_buffer(leaf, eb_token, KM_USER1);
-                eb_token = NULL;
-                err = map_private_extent_buffer(leaf, (unsigned long)item,
-                                                csum_size,
-                                                &eb_token, &eb_map,
-                                                &map_start, &map_len, KM_USER1);
-                if (err)
-                        eb_token = NULL;
-        }
-        if (eb_token) {
-                memcpy(eb_token + ((unsigned long)item & (PAGE_CACHE_SIZE - 1)),
-                       &sector_sum->sum, csum_size);
-        } else {
-                write_extent_buffer(leaf, &sector_sum->sum,
-                                    (unsigned long)item, csum_size);
-        }
+        write_extent_buffer(leaf, &sector_sum->sum, (unsigned long)item, csum_size);
 
         total_bytes += root->sectorsize;
         sector_sum++;
@@ -850,10 +839,7 @@ next_sector:
                         goto next_sector;
                 }
         }
-        if (eb_token) {
-                unmap_extent_buffer(leaf, eb_token, KM_USER1);
-                eb_token = NULL;
-        }
+
         btrfs_mark_buffer_dirty(path->nodes[0]);
         if (total_bytes < sums->len) {
                 btrfs_release_path(path);