Subject: [PATCH 2/2] On a diff-send, avoid sending PREALLOC extents, if the
parent root has only PREALLOC extents on an appropriate
file range.
This does not fully avoids sending PREALLOC extents, because on full-send or
new inode we need a new send command to do that. But this patch improves
the situation by handling diff-sends.
Signed-off-by: Alex Lyakas <alex.btrfs@xxxxxxxxxxxxxxxxx>
---
fs/btrfs/send.c | 150 +++++++++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 146 insertions(+), 4 deletions(-)
diff --git a/fs/btrfs/send.c b/fs/btrfs/send.c
index 5ab584f..456bc3e 100644
--- a/fs/btrfs/send.c
+++ b/fs/btrfs/send.c
@@ -3763,6 +3763,144 @@ out:
return ret;
}
+static int is_prealloc_extent_unchanged(struct send_ctx *sctx,
+ struct btrfs_path *left_path,
+ struct btrfs_key *ekey)
+{
+ int ret = 0;
+ struct btrfs_key key;
+ struct btrfs_path *path = NULL;
+ struct extent_buffer *eb;
+ int slot;
+ struct btrfs_key found_key;
+ struct btrfs_file_extent_item *ei;
+ u64 left_len;
+ u64 right_len;
+ u8 right_type;
+
+ eb = left_path->nodes[0];
+ slot = left_path->slots[0];
+ ei = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
+ left_len = btrfs_file_extent_num_bytes(eb, ei);
+
+ /*
+ * The logic is similar, but much simpler than in is_extent_unchanged().
+ * We need to check extents on the parent root, and make sure that only
+ * PREALLOC extents are on the same file range as our current extent.
+ *
+ * Following comments will refer to these graphics. L is the left
+ * extents which we are checking at the moment. 1-8 are the right
+ * extents that we iterate.
+ *
+ * |-----L-----|
+ * |-1-|-2a-|-3-|-4-|-5-|-6-|
+ *
+ * |-----L-----|
+ * |--1--|-2b-|...(same as above)
+ *
+ * Alternative situation. Happens on files where extents got split.
+ * |-----L-----|
+ * |-----------7-----------|-6-|
+ *
+ * Alternative situation. Happens on files which got larger.
+ * |-----L-----|
+ * |-8-|
+ * Nothing follows after 8.
+ */
+
+ path = alloc_path_for_send();
+ if (!path)
+ return -ENOMEM;
+
+ key.objectid = ekey->objectid;
+ key.type = BTRFS_EXTENT_DATA_KEY;
+ key.offset = ekey->offset;
+ ret = btrfs_search_slot_for_read(sctx->parent_root, &key, path, 0, 0);
+ if (ret < 0)
+ goto out;
+ if (ret) {
+ ret = 0;
+ goto out;
+ }
+
+ /*
+ * Handle special case where the right side has no extents at all.
+ */
+ eb = path->nodes[0];
+ slot = path->slots[0];
+ btrfs_item_key_to_cpu(eb, &found_key, slot);
+ if (found_key.objectid != key.objectid ||
+ found_key.type != key.type) {
+ /*
+ * We need to send a "prealloc" command, which we don't have yet,
+ * just send this extent fully.
+ */
+ ret = 0;
+ goto out;
+ }
+
+ key = found_key;
+ while (key.offset < ekey->offset + left_len) {
+ ei = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
+ right_type = btrfs_file_extent_type(eb, ei);
+ right_len = btrfs_file_extent_num_bytes(eb, ei);
+
+ if (right_type != BTRFS_FILE_EXTENT_PREALLOC) {
+ ret = 0;
+ goto out;
+ }
+
+ /*
+ * Are we at extent 8? If yes, we know the extent is changed.
+ * This may only happen on the first iteration.
+ */
+ if (found_key.offset + right_len <= ekey->offset) {
+ /*
+ * We need to send a "prealloc" command, which we don't have yet,
+ * just send this extent fully.
+ */
+ ret = 0;
+ goto out;
+ }
+
+ /* The right extent is also PREALLOC, so up to here we are ok,
continue checking */
+
+ ret = btrfs_next_item(sctx->parent_root, path);
+ if (ret < 0)
+ goto out;
+ if (!ret) {
+ eb = path->nodes[0];
+ slot = path->slots[0];
+ btrfs_item_key_to_cpu(eb, &found_key, slot);
+ }
+ if (ret || found_key.objectid != key.objectid ||
+ found_key.type != key.type) {
+ key.offset += right_len;
+ break;
+ } else {
+ if (found_key.offset != key.offset + right_len) {
+ /* Should really not happen */
+ ret = -EIO;
+ goto out;
+ }
+ }
+ key = found_key;
+ }
+
+ /*
+ * We're now behind the left extent (treat as unchanged) or at the end
+ * of the right side (treat as changed).
+ */
+ if (key.offset >= ekey->offset + left_len)
+ ret = 1;
+ else
+ ret = 0;
+
+out:
+ btrfs_free_path(path);
+ return ret;
+}
+
static int is_extent_unchanged(struct send_ctx *sctx,
struct btrfs_path *left_path,
struct btrfs_key *ekey)
@@ -3786,15 +3924,15 @@ static int is_extent_unchanged(struct send_ctx *sctx,
u8 left_type;
u8 right_type;
- path = alloc_path_for_send();
- if (!path)
- return -ENOMEM;
-
eb = left_path->nodes[0];
slot = left_path->slots[0];
ei = btrfs_item_ptr(eb, slot, struct btrfs_file_extent_item);
left_type = btrfs_file_extent_type(eb, ei);
+ if (left_type == BTRFS_FILE_EXTENT_PREALLOC) {
+ ret = is_prealloc_extent_unchanged(sctx, left_path, ekey);
+ goto out;
+ }
if (left_type != BTRFS_FILE_EXTENT_REG) {
ret = 0;
goto out;
@@ -3825,6 +3963,10 @@ static int is_extent_unchanged(struct send_ctx *sctx,
* Nothing follows after 8.
*/
+ path = alloc_path_for_send();
+ if (!path)
+ return -ENOMEM;
+
key.objectid = ekey->objectid;
key.type = BTRFS_EXTENT_DATA_KEY;
key.offset = ekey->offset;
--
1.7.9.5
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