diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 212157473ad8..ffebd420829e 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1012,8 +1012,155 @@ out:
return ret;
}
+/*
+ * Defrag specific helper to get an extent map.
+ *
+ * Differences between this and btrfs_get_extent() are:
+ *
+ * - No extent_map will be added to inode->extent_tree
+ * To reduce memory usage in the long run.
+ *
+ * - Extra optimization to skip file extents older than @newer_than
+ * By using btrfs_search_forward() we can skip entire file ranges that
+ * have extents created in past transactions, because btrfs_search_forward()
+ * will not visit leaves and nodes with a generation smaller than given
+ * minimal generation threshold (@newer_than).
+ *
+ * Return valid em if we find a file extent matching the requirement.
+ * Return NULL if we can not find a file extent matching the requirement.
+ *
+ * Return ERR_PTR() for error.
+ */
+static struct extent_map *defrag_get_extent(struct btrfs_inode *inode,
+ u64 start, u64 newer_than)
+{
+ struct btrfs_root *root = inode->root;
+ struct btrfs_file_extent_item *fi;
+ struct btrfs_path path = { 0 };
+ struct extent_map *em;
+ struct btrfs_key key;
+ u64 ino = btrfs_ino(inode);
+ int ret;
+
+ em = alloc_extent_map();
+ if (!em) {
+ ret = -ENOMEM;
+ goto err;
+ }
+
+ key.objectid = ino;
+ key.type = BTRFS_EXTENT_DATA_KEY;
+ key.offset = start;
+
+ if (newer_than) {
+ ret = btrfs_search_forward(root, &key, &path, newer_than);
+ if (ret < 0)
+ goto err;
+ /* Can't find anything newer */
+ if (ret > 0)
+ goto not_found;
+ } else {
+ ret = btrfs_search_slot(NULL, root, &key, &path, 0, 0);
+ if (ret < 0)
+ goto err;
+ }
+ if (path.slots[0] >= btrfs_header_nritems(path.nodes[0])) {
+ /*
+ * If btrfs_search_slot() makes path to point beyond nritems,
+ * we should not have an empty leaf, as this inode must at
+ * least have its INODE_ITEM.
+ */
+ ASSERT(btrfs_header_nritems(path.nodes[0]));
+ path.slots[0] = btrfs_header_nritems(path.nodes[0]) - 1;
+ }
+ btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+ /* Perfect match, no need to go one slot back */
+ if (key.objectid == ino && key.type == BTRFS_EXTENT_DATA_KEY &&
+ key.offset == start)
+ goto iterate;
+
+ /* We didn't find a perfect match, needs to go one slot back */
+ if (path.slots[0] > 0) {
+ btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+ if (key.objectid == ino && key.type == BTRFS_EXTENT_DATA_KEY)
+ path.slots[0]--;
+ }
+
+iterate:
+ /* Iterate through the path to find a file extent covering @start */
+ while (true) {
+ u64 extent_end;
+
+ if (path.slots[0] >= btrfs_header_nritems(path.nodes[0]))
+ goto next;
+
+ btrfs_item_key_to_cpu(path.nodes[0], &key, path.slots[0]);
+
+ /*
+ * We may go one slot back to INODE_REF/XATTR item, then
+ * need to go forward until we reach an EXTENT_DATA.
+ * But we should still has the correct ino as key.objectid.
+ */
+ if (WARN_ON(key.objectid < ino) || key.type < BTRFS_EXTENT_DATA_KEY)
+ goto next;
+
+ /* It's beyond our target range, definitely not extent found */
+ if (key.objectid > ino || key.type > BTRFS_EXTENT_DATA_KEY)
+ goto not_found;
+
+ /*
+ * | |<- File extent ->|
+ * \- start
+ *
+ * This means there is a hole between start and key.offset.
+ */
+ if (key.offset > start) {
+ em->start = start;
+ em->orig_start = start;
+ em->block_start = EXTENT_MAP_HOLE;
+ em->len = key.offset - start;
+ break;
+ }
+
+ fi = btrfs_item_ptr(path.nodes[0], path.slots[0],
+ struct btrfs_file_extent_item);
+ extent_end = btrfs_file_extent_end(&path);
+
+ /*
+ * |<- file extent ->| |
+ * \- start
+ *
+ * We haven't reached start, search next slot.
+ */
+ if (extent_end <= start)
+ goto next;
+
+ /* Now this extent covers @start, convert it to em */
+ btrfs_extent_item_to_extent_map(inode, &path, fi, false, em);
+ break;
+next:
+ ret = btrfs_next_item(root, &path);
+ if (ret < 0)
+ goto err;
+ if (ret > 0)
+ goto not_found;
+ }
+ btrfs_release_path(&path);
+ return em;
+
+not_found:
+ btrfs_release_path(&path);
+ free_extent_map(em);
+ return NULL;
+
+err:
+ btrfs_release_path(&path);
+ free_extent_map(em);
+ return ERR_PTR(ret);
+}
+
static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start,
- bool locked)
+ u64 newer_than, bool locked)
{
struct extent_map_tree *em_tree = &BTRFS_I(inode)->extent_tree;
struct extent_io_tree *io_tree = &BTRFS_I(inode)->io_tree;
@@ -1035,7 +1182,7 @@ static struct extent_map *defrag_lookup_extent(struct inode *inode, u64 start,
/* get the big lock and read metadata off disk */
if (!locked)
lock_extent_bits(io_tree, start, end, &cached);
- em = btrfs_get_extent(BTRFS_I(inode), NULL, 0, start, sectorsize);
+ em = defrag_get_extent(BTRFS_I(inode), start, newer_than);
if (!locked)
unlock_extent_cached(io_tree, start, end, &cached);
@@ -1063,7 +1210,12 @@ static bool defrag_check_next_extent(struct inode *inode, struct extent_map *em,
if (em->start + em->len >= i_size_read(inode))
return false;
- next = defrag_lookup_extent(inode, em->start + em->len, locked);
+ /*
+ * We want to check if the next extent can be merged with the current
+ * one, which can be an extent created in a past generation, so we pass
+ * a minimum generation of 0 to defrag_lookup_extent().
+ */
+ next = defrag_lookup_extent(inode, em->start + em->len, 0, locked);
/* No more em or hole */
if (!next || next->block_start >= EXTENT_MAP_LAST_BYTE)
goto out;
@@ -1214,7 +1366,8 @@ static int defrag_collect_targets(struct btrfs_inode *inode,
u64 range_len;
last_is_target = false;
- em = defrag_lookup_extent(&inode->vfs_inode, cur, locked);
+ em = defrag_lookup_extent(&inode->vfs_inode, cur,
+ newer_than, locked);
if (!em)
break;