btrfs-progs: convert: Introduce new function to remove reserved ranges

Introduce functions to remove reserved ranges for later btrfs-convert
rework.

The reserved ranges includes:
1. [0,1M)
2. [btrfs_sb_offset(1), +BTRFS_STRIPE_LEN)
3. [btrfs_sb_offset(2), +BTRFS_STRIPE_LEN)

Signed-off-by: Qu Wenruo <quwenruo@cn.fujitsu.com>
Signed-off-by: David Sterba <dsterba@suse.com>

diff --git a/btrfs-convert.c b/btrfs-convert.c
index 28ac84d..9776c67 100644 (file)
--- a/btrfs-convert.c
+++ b/btrfs-convert.c
@@ -2548,6 +2548,123 @@ static int convert_open_fs(const char *devname,
 }
 
 /*
+ * Remove one reserve range from given cache tree
+ * if min_stripe_size is non-zero, it will ensure for split case,
+ * all its split cache extent is no smaller than @min_strip_size / 2.
+ */
+static int wipe_one_reserved_range(struct cache_tree *tree,
+                                  u64 start, u64 len, u64 min_stripe_size,
+                                  int ensure_size)
+{
+       struct cache_extent *cache;
+       int ret;
+
+       BUG_ON(ensure_size && min_stripe_size == 0);
+       /*
+        * The logical here is simplified to handle special cases only
+        * So we don't need to consider merge case for ensure_size
+        */
+       BUG_ON(min_stripe_size && (min_stripe_size < len * 2 ||
+              min_stripe_size / 2 < BTRFS_STRIPE_LEN));
+
+       /* Also, wipe range should already be aligned */
+       BUG_ON(start != round_down(start, BTRFS_STRIPE_LEN) ||
+              start + len != round_up(start + len, BTRFS_STRIPE_LEN));
+
+       min_stripe_size /= 2;
+
+       cache = lookup_cache_extent(tree, start, len);
+       if (!cache)
+               return 0;
+
+       if (start <= cache->start) {
+               /*
+                *      |--------cache---------|
+                * |-wipe-|
+                */
+               BUG_ON(start + len <= cache->start);
+
+               /*
+                * The wipe size is smaller than min_stripe_size / 2,
+                * so the result length should still meet min_stripe_size
+                * And no need to do alignment
+                */
+               cache->size -= (start + len - cache->start);
+               if (cache->size == 0) {
+                       remove_cache_extent(tree, cache);
+                       free(cache);
+                       return 0;
+               }
+
+               BUG_ON(ensure_size && cache->size < min_stripe_size);
+
+               cache->start = start + len;
+               return 0;
+       } else if (start > cache->start && start + len < cache->start +
+                  cache->size) {
+               /*
+                * |-------cache-----|
+                *      |-wipe-|
+                */
+               u64 old_len = cache->size;
+               u64 insert_start = start + len;
+               u64 insert_len;
+
+               cache->size = start - cache->start;
+               if (ensure_size)
+                       cache->size = max(cache->size, min_stripe_size);
+               cache->start = start - cache->size;
+
+               /* And insert the new one */
+               insert_len = old_len - start - len;
+               if (ensure_size)
+                       insert_len = max(insert_len, min_stripe_size);
+
+               ret = add_merge_cache_extent(tree, insert_start, insert_len);
+               return ret;
+       }
+       /*
+        * |----cache-----|
+        *              |--wipe-|
+        * Wipe len should be small enough and no need to expand the
+        * remaining extent
+        */
+       cache->size = start - cache->start;
+       BUG_ON(ensure_size && cache->size < min_stripe_size);
+       return 0;
+}
+
+/*
+ * Remove reserved ranges from given cache_tree
+ *
+ * It will remove the following ranges
+ * 1) 0~1M
+ * 2) 2nd superblock, +64K (make sure chunks are 64K aligned)
+ * 3) 3rd superblock, +64K
+ *
+ * @min_stripe must be given for safety check
+ * and if @ensure_size is given, it will ensure affected cache_extent will be
+ * larger than min_stripe_size
+ */
+static int wipe_reserved_ranges(struct cache_tree *tree, u64 min_stripe_size,
+                               int ensure_size)
+{
+       int ret;
+
+       ret = wipe_one_reserved_range(tree, 0, 1024 * 1024, min_stripe_size,
+                                     ensure_size);
+       if (ret < 0)
+               return ret;
+       ret = wipe_one_reserved_range(tree, btrfs_sb_offset(1),
+                       BTRFS_STRIPE_LEN, min_stripe_size, ensure_size);
+       if (ret < 0)
+               return ret;
+       ret = wipe_one_reserved_range(tree, btrfs_sb_offset(2),
+                       BTRFS_STRIPE_LEN, min_stripe_size, ensure_size);
+       return ret;
+}
+
+/*
  * Read used space
  */
 static int convert_read_used_space(struct btrfs_convert_context *cctx)