btrfs: refactor variable scope in run_delalloc_nocow

Of the 22 (!!!) local variables declared in this function only 9 have
function-wide context. Of the remaining 13, 12 are needed in the main
while loop of the function and 1 is needed in a tiny if branch, only in
case we have prealloc extent. This commit reduces the lifespan of every
variable to its bare minimum. It also renames the 'nolock' boolean to
freespace_inode to clearly indicate its purpose.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/inode.c b/fs/btrfs/inode.c
index 31eacbf51d4e43222925971c25a687785fe74261..fdc20d81af82aed1f6730dee80782295ebce1f54 100644 (file)
--- a/fs/btrfs/inode.c
+++ b/fs/btrfs/inode.c
@@ -1301,30 +1301,18 @@ static noinline int csum_exist_in_range(struct btrfs_fs_info *fs_info,
  */
 static noinline int run_delalloc_nocow(struct inode *inode,
                                       struct page *locked_page,
-                             u64 start, u64 end, int *page_started, int force,
-                             unsigned long *nr_written)
+                                      const u64 start, const u64 end,
+                                      int *page_started, int force,
+                                      unsigned long *nr_written)
 {
        struct btrfs_fs_info *fs_info = btrfs_sb(inode->i_sb);
        struct btrfs_root *root = BTRFS_I(inode)->root;
-       struct extent_buffer *leaf;
        struct btrfs_path *path;
-       struct btrfs_file_extent_item *fi;
-       struct btrfs_key found_key;
-       struct extent_map *em;
-       u64 cow_start;
-       u64 cur_offset;
-       u64 extent_end;
-       u64 extent_offset;
-       u64 disk_bytenr;
-       u64 num_bytes;
-       u64 disk_num_bytes;
-       u64 ram_bytes;
-       int extent_type;
+       u64 cow_start = (u64)-1;
+       u64 cur_offset = start;
        int ret;
-       int type;
-       int nocow;
-       int check_prev = 1;
-       bool nolock;
+       bool check_prev = true;
+       const bool freespace_inode = btrfs_is_free_space_inode(BTRFS_I(inode));
        u64 ino = btrfs_ino(BTRFS_I(inode));
 
        path = btrfs_alloc_path();
@@ -1339,11 +1327,20 @@ static noinline int run_delalloc_nocow(struct inode *inode,
                return -ENOMEM;
        }
 
-       nolock = btrfs_is_free_space_inode(BTRFS_I(inode));
-
-       cow_start = (u64)-1;
-       cur_offset = start;
        while (1) {
+               struct btrfs_key found_key;
+               struct btrfs_file_extent_item *fi;
+               struct extent_buffer *leaf;
+               u64 extent_end;
+               u64 extent_offset;
+               u64 disk_bytenr = 0;
+               u64 num_bytes = 0;
+               u64 disk_num_bytes;
+               int type;
+               u64 ram_bytes;
+               int extent_type;
+               bool nocow = false;
+
                ret = btrfs_lookup_file_extent(NULL, root, path, ino,
                                               cur_offset, 0);
                if (ret < 0)
@@ -1356,7 +1353,7 @@ static noinline int run_delalloc_nocow(struct inode *inode,
                            found_key.type == BTRFS_EXTENT_DATA_KEY)
                                path->slots[0]--;
                }
-               check_prev = 0;
+               check_prev = false;
 next_slot:
                leaf = path->nodes[0];
                if (path->slots[0] >= btrfs_header_nritems(leaf)) {
@@ -1371,9 +1368,6 @@ next_slot:
                        leaf = path->nodes[0];
                }
 
-               nocow = 0;
-               disk_bytenr = 0;
-               num_bytes = 0;
                btrfs_item_key_to_cpu(leaf, &found_key, path->slots[0]);
 
                if (found_key.objectid > ino)
@@ -1420,7 +1414,7 @@ next_slot:
                         * Do the same check as in btrfs_cross_ref_exist but
                         * without the unnecessary search.
                         */
-                       if (!nolock &&
+                       if (!freespace_inode &&
                            btrfs_file_extent_generation(leaf, fi) <=
                            btrfs_root_last_snapshot(&root->root_item))
                                goto out_check;
@@ -1442,7 +1436,7 @@ next_slot:
                                        goto error;
                                }
 
-                               WARN_ON_ONCE(nolock);
+                               WARN_ON_ONCE(freespace_inode);
                                goto out_check;
                        }
                        disk_bytenr += extent_offset;
@@ -1452,7 +1446,7 @@ next_slot:
                         * if there are pending snapshots for this root,
                         * we fall into common COW way.
                         */
-                       if (!nolock && atomic_read(&root->snapshot_force_cow))
+                       if (!freespace_inode && atomic_read(&root->snapshot_force_cow))
                                goto out_check;
                        /*
                         * force cow if csum exists in the range.
@@ -1471,12 +1465,12 @@ next_slot:
                                                cur_offset = cow_start;
                                        goto error;
                                }
-                               WARN_ON_ONCE(nolock);
+                               WARN_ON_ONCE(freespace_inode);
                                goto out_check;
                        }
                        if (!btrfs_inc_nocow_writers(fs_info, disk_bytenr))
                                goto out_check;
-                       nocow = 1;
+                       nocow = true;
                } else if (extent_type == BTRFS_FILE_EXTENT_INLINE) {
                        extent_end = found_key.offset +
                                btrfs_file_extent_ram_bytes(leaf, fi);
@@ -1518,6 +1512,7 @@ out_check:
 
                if (extent_type == BTRFS_FILE_EXTENT_PREALLOC) {
                        u64 orig_start = found_key.offset - extent_offset;
+                       struct extent_map *em;
 
                        em = create_io_em(inode, cur_offset, num_bytes,
                                          orig_start,
@@ -1543,7 +1538,7 @@ out_check:
                }
 
                ret = btrfs_add_ordered_extent(inode, cur_offset, disk_bytenr,
-                                              num_bytes, num_bytes, type);
+                                              num_bytes, num_bytes,type);
                if (nocow)
                        btrfs_dec_nocow_writers(fs_info, disk_bytenr);
                BUG_ON(ret); /* -ENOMEM */