From e9be5a303d271faa42b44b606fbe4d7507a7f026 Mon Sep 17 00:00:00 2001 From: David Sterba Date: Thu, 27 Feb 2020 21:00:47 +0100 Subject: [PATCH] btrfs: simplify tree block checksumming loop Thw whole point of csum_tree_block is to iterate over all extent buffer pages and pass it to checksumming functions. The bytes where checksum is stored must be skipped, thus map_private_extent_buffer. This complicates further offset calculations. As the first page will be always present, checksum the relevant bytes unconditionally and then do a simple iteration over the remaining pages. Reviewed-by: Johannes Thumshirn Reviewed-by: Qu Wenruo Signed-off-by: David Sterba --- fs/btrfs/disk-io.c | 32 ++++++++------------------------ 1 file changed, 8 insertions(+), 24 deletions(-) diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c index 483b540..6f63cc4 100644 --- a/fs/btrfs/disk-io.c +++ b/fs/btrfs/disk-io.c @@ -259,38 +259,22 @@ out: static int csum_tree_block(struct extent_buffer *buf, u8 *result) { struct btrfs_fs_info *fs_info = buf->fs_info; + const int num_pages = fs_info->nodesize >> PAGE_SHIFT; SHASH_DESC_ON_STACK(shash, fs_info->csum_shash); - unsigned long len; - unsigned long cur_len; - unsigned long offset = BTRFS_CSUM_SIZE; char *kaddr; - unsigned long map_start; - unsigned long map_len; - int err; + int i; shash->tfm = fs_info->csum_shash; crypto_shash_init(shash); + kaddr = page_address(buf->pages[0]); + crypto_shash_update(shash, kaddr + BTRFS_CSUM_SIZE, + PAGE_SIZE - BTRFS_CSUM_SIZE); - len = buf->len - offset; - - while (len > 0) { - /* - * Note: we don't need to check for the err == 1 case here, as - * with the given combination of 'start = BTRFS_CSUM_SIZE (32)' - * and 'min_len = 32' and the currently implemented mapping - * algorithm we cannot cross a page boundary. - */ - err = map_private_extent_buffer(buf, offset, 32, - &kaddr, &map_start, &map_len); - if (WARN_ON(err)) - return err; - cur_len = min(len, map_len - (offset - map_start)); - crypto_shash_update(shash, kaddr + offset - map_start, cur_len); - len -= cur_len; - offset += cur_len; + for (i = 1; i < num_pages; i++) { + kaddr = page_address(buf->pages[i]); + crypto_shash_update(shash, kaddr, PAGE_SIZE); } memset(result, 0, BTRFS_CSUM_SIZE); - crypto_shash_final(shash, result); return 0; -- 2.7.4