btrfs: switch to on-stack csum buffer in csum_tree_block

The maximum size of a checksum buffer is known, BTRFS_CSUM_SIZE, and we
don't have to allocate it dynamically. This code path is not used at all
as we have only the crc32c and use an on-stack buffer already.

Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index cbf37df..5f94300 100644 (file)
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -285,7 +285,7 @@ static int csum_tree_block(struct btrfs_fs_info *fs_info,
                           int verify)
 {
        u16 csum_size = btrfs_super_csum_size(fs_info->super_copy);
-       char *result = NULL;
+       char result[BTRFS_CSUM_SIZE];
        unsigned long len;
        unsigned long cur_len;
        unsigned long offset = BTRFS_CSUM_SIZE;
@@ -294,7 +294,6 @@ static int csum_tree_block(struct btrfs_fs_info *fs_info,
        unsigned long map_len;
        int err;
        u32 crc = ~(u32)0;
-       unsigned long inline_result;
 
        len = buf->len - offset;
        while (len > 0) {
@@ -308,13 +307,7 @@ static int csum_tree_block(struct btrfs_fs_info *fs_info,
                len -= cur_len;
                offset += cur_len;
        }
-       if (csum_size > sizeof(inline_result)) {
-               result = kzalloc(csum_size, GFP_NOFS);
-               if (!result)
-                       return -ENOMEM;
-       } else {
-               result = (char *)&inline_result;
-       }
+       memset(result, 0, BTRFS_CSUM_SIZE);
 
        btrfs_csum_final(crc, result);
 
@@ -329,15 +322,12 @@ static int csum_tree_block(struct btrfs_fs_info *fs_info,
                                "%s checksum verify failed on %llu wanted %X found %X level %d",
                                fs_info->sb->s_id, buf->start,
                                val, found, btrfs_header_level(buf));
-                       if (result != (char *)&inline_result)
-                               kfree(result);
                        return -EUCLEAN;
                }
        } else {
                write_extent_buffer(buf, result, 0, csum_size);
        }
-       if (result != (char *)&inline_result)
-               kfree(result);
+
        return 0;
 }