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[v3,21/49] btrfs: disk-io: make csum_tree_block() handle sectorsize smaller than page size

Message ID 20200930015539.48867-22-wqu@suse.com
State New, archived
Headers show
Series btrfs: add partial rw support for subpage sector size | expand

Commit Message

Qu Wenruo Sept. 30, 2020, 1:55 a.m. UTC
For subpage size support, we only need to handle the first page.

To make the code work for both cases, we modify the following behaviors:

- num_pages calcuation
  Instead of "nodesize >> PAGE_SHIFT", we go
  "DIV_ROUND_UP(nodesize, PAGE_SIZE)", this ensures we get at least one
  page for subpage size support, while still get the same result for
  regular page size.

- The length for the first run
  Instead of PAGE_SIZE - BTRFS_CSUM_SIZE, we go min(PAGE_SIZE, nodesize)
  - BTRFS_CSUM_SIZE.
  This allows us to handle both cases well.

- The start location of the first run
  Instead of always use BTRFS_CSUM_SIZE as csum start position, add
  offset_in_page(eb->start) to get proper offset for both cases.

Signed-off-by: Goldwyn Rodrigues <rgoldwyn@suse.com>
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: Nikolay Borisov <nborisov@suse.com>
---
 fs/btrfs/disk-io.c | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)
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Patch

diff --git a/fs/btrfs/disk-io.c b/fs/btrfs/disk-io.c
index 58928076d08d..55bb4f2def3c 100644
--- a/fs/btrfs/disk-io.c
+++ b/fs/btrfs/disk-io.c
@@ -257,16 +257,16 @@  struct extent_map *btree_get_extent(struct btrfs_inode *inode,
 static void 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;
+	const int num_pages = DIV_ROUND_UP(fs_info->nodesize, PAGE_SIZE);
 	SHASH_DESC_ON_STACK(shash, fs_info->csum_shash);
 	char *kaddr;
 	int i;
 
 	shash->tfm = fs_info->csum_shash;
 	crypto_shash_init(shash);
-	kaddr = page_address(buf->pages[0]);
+	kaddr = page_address(buf->pages[0]) + offset_in_page(buf->start);
 	crypto_shash_update(shash, kaddr + BTRFS_CSUM_SIZE,
-			    PAGE_SIZE - BTRFS_CSUM_SIZE);
+		min_t(u32, PAGE_SIZE, fs_info->nodesize) - BTRFS_CSUM_SIZE);
 
 	for (i = 1; i < num_pages; i++) {
 		kaddr = page_address(buf->pages[i]);