From eb793cf857828dbb1f21bfe405e5e493fdceae6c Mon Sep 17 00:00:00 2001
From: Qu Wenruo <wqu@suse.com>
Date: Fri, 6 Aug 2021 16:12:36 +0800
Subject: [PATCH] btrfs: defrag: introduce helper to collect target file
extents
Introduce a helper, defrag_collect_targets(), to collect all possible
targets to be defragged.
This function will not consider things like max_sectors_to_defrag, thus
caller should be responsible to ensure we don't exceed the limit.
This function will be the first stage of later defrag rework.
Signed-off-by: Qu Wenruo <wqu@suse.com>
Reviewed-by: David Sterba <dsterba@suse.com>
Signed-off-by: David Sterba <dsterba@suse.com>
---
fs/btrfs/ioctl.c | 120 +++++++++++++++++++++++++++++++++++++++++++++++
1 file changed, 120 insertions(+)
diff --git a/fs/btrfs/ioctl.c b/fs/btrfs/ioctl.c
index 30456253ee597..07a70520819f0 100644
--- a/fs/btrfs/ioctl.c
+++ b/fs/btrfs/ioctl.c
@@ -1431,6 +1431,126 @@ out:
}
+struct defrag_target_range {
+ struct list_head list;
+ u64 start;
+ u64 len;
+};
+
+/*
+ * Collect all valid target extents.
+ *
+ * @start: file offset to lookup
+ * @len: length to lookup
+ * @extent_thresh: file extent size threshold, any extent size >= this value
+ * will be ignored
+ * @newer_than: only defrag extents newer than this value
+ * @do_compress: whether the defrag is doing compression
+ * if true, @extent_thresh will be ignored and all regular
+ * file extents meeting @newer_than will be targets.
+ * @target_list: list of targets file extents
+ */
+static int defrag_collect_targets(struct btrfs_inode *inode,
+ u64 start, u64 len, u32 extent_thresh,
+ u64 newer_than, bool do_compress,
+ struct list_head *target_list)
+{
+ u64 cur = start;
+ int ret = 0;
+
+ while (cur < start + len) {
+ struct extent_map *em;
+ struct defrag_target_range *new;
+ bool next_mergeable = true;
+ u64 range_len;
+
+ em = defrag_lookup_extent(&inode->vfs_inode, cur);
+ if (!em)
+ break;
+
+ /* Skip hole/inline/preallocated extents */
+ if (em->block_start >= EXTENT_MAP_LAST_BYTE ||
+ test_bit(EXTENT_FLAG_PREALLOC, &em->flags))
+ goto next;
+
+ /* Skip older extent */
+ if (em->generation < newer_than)
+ goto next;
+
+ /*
+ * For do_compress case, we want to compress all valid file
+ * extents, thus no @extent_thresh or mergeable check.
+ */
+ if (do_compress)
+ goto add;
+
+ /* Skip too large extent */
+ if (em->len >= extent_thresh)
+ goto next;
+
+ next_mergeable = defrag_check_next_extent(&inode->vfs_inode, em);
+ if (!next_mergeable) {
+ struct defrag_target_range *last;
+
+ /* Empty target list, no way to merge with last entry */
+ if (list_empty(target_list))
+ goto next;
+ last = list_entry(target_list->prev,
+ struct defrag_target_range, list);
+ /* Not mergeable with last entry */
+ if (last->start + last->len != cur)
+ goto next;
+
+ /* Mergeable, fall through to add it to @target_list. */
+ }
+
+add:
+ range_len = min(extent_map_end(em), start + len) - cur;
+ /*
+ * This one is a good target, check if it can be merged into
+ * last range of the target list.
+ */
+ if (!list_empty(target_list)) {
+ struct defrag_target_range *last;
+
+ last = list_entry(target_list->prev,
+ struct defrag_target_range, list);
+ ASSERT(last->start + last->len <= cur);
+ if (last->start + last->len == cur) {
+ /* Mergeable, enlarge the last entry */
+ last->len += range_len;
+ goto next;
+ }
+ /* Fall through to allocate a new entry */
+ }
+
+ /* Allocate new defrag_target_range */
+ new = kmalloc(sizeof(*new), GFP_NOFS);
+ if (!new) {
+ free_extent_map(em);
+ ret = -ENOMEM;
+ break;
+ }
+ new->start = cur;
+ new->len = range_len;
+ list_add_tail(&new->list, target_list);
+
+next:
+ cur = extent_map_end(em);
+ free_extent_map(em);
+ }
+ if (ret < 0) {
+ struct defrag_target_range *entry;
+ struct defrag_target_range *tmp;
+
+ list_for_each_entry_safe(entry, tmp, target_list, list) {
+ list_del_init(&entry->list);
+ kfree(entry);
+ }
+ }
+ return ret;
+}
+
/*
* Entry point to file defragmentation.
*
--
2.30.2