@@ -7320,11 +7320,49 @@ static struct extent_map *create_io_em(struct btrfs_inode *inode, u64 start,
struct extent_map *em;
int ret;
+ /*
+ * Note the missing of NOCOW type.
+ *
+ * For pure NOCOW writes, we should not create an io extent map,
+ * but just reusing the existing one.
+ * Only PREALLOC writes (NOCOW write into preallocated range) can
+ * create io extent map.
+ */
ASSERT(type == BTRFS_ORDERED_PREALLOC ||
type == BTRFS_ORDERED_COMPRESSED ||
- type == BTRFS_ORDERED_NOCOW ||
type == BTRFS_ORDERED_REGULAR);
+ switch (type) {
+ case BTRFS_ORDERED_PREALLOC:
+ /* Uncompressed extents. */
+ ASSERT(block_len == len);
+
+ /* We're only referring part of a larger preallocated extent. */
+ ASSERT(block_len <= ram_bytes);
+ break;
+ case BTRFS_ORDERED_REGULAR:
+ /* Uncompressed extents. */
+ ASSERT(block_len == len);
+
+ /* COW results a new extent matching our file extent size. */
+ ASSERT(orig_block_len == len);
+ ASSERT(ram_bytes == len);
+
+ /* Since it's a new extent, we should not have any offset. */
+ ASSERT(orig_start == start);
+ break;
+ case BTRFS_ORDERED_COMPRESSED:
+ /* Must be compressed. */
+ ASSERT(compress_type != BTRFS_COMPRESS_NONE);
+
+ /*
+ * Encoded write can make us to refer to part of the
+ * uncompressed extent.
+ */
+ ASSERT(len <= ram_bytes);
+ break;
+ }
+
em = alloc_extent_map();
if (!em)
return ERR_PTR(-ENOMEM);
The function create_io_em() is called before we submit an IO, to update the in-memory extent map for the involved range. This patch changes the following aspects: - Does not allow BTRFS_ORDERED_NOCOW type For real NOCOW (excluding NOCOW writes into preallocated ranges) writes, we never call create_io_em(), as we does not need to update the extent map at all. So remove the sanity check allowing BTRFS_ORDERED_NOCOW type. - Add extra sanity checks * PREALLOC - @block_len == len For uncompressed writes. * REGULAR - @block_len == @orig_block_len == @ram_bytes == @len We're creating a new uncompressed extent, and referring all of it. - @orig_start == @start We haven no offset inside the extent. * COMPRESSED - valid @compress_type - @len <= @ram_bytes This is to co-operate with encoded writes, which can cause a new file extent referring only part of a uncompressed extent. Reviewed-by: Filipe Manana <fdmanana@suse.com> Signed-off-by: Qu Wenruo <wqu@suse.com> --- fs/btrfs/inode.c | 40 +++++++++++++++++++++++++++++++++++++++- 1 file changed, 39 insertions(+), 1 deletion(-)