Btrfs: add pinned extents to on-disk free space cache correctly

I got this while running xfstests:

[24256.836098] block group 317849600 has an wrong amount of free space
[24256.836100] btrfs: failed to load free space cache for block group 317849600

We should clamp the extent returned by find_first_extent_bit(),
so the start of the extent won't smaller than the start of the
block group.

Signed-off-by: Li Zefan <lizf@cn.fujitsu.com>

diff --git a/fs/btrfs/free-space-cache.c b/fs/btrfs/free-space-cache.c
index ec23d43d0c357870a14bf6e79a0ce5baeb93a43d..01840ef95a32b7a56ecf3c17f2ab0deebf7bc85b 100644 (file)
--- a/fs/btrfs/free-space-cache.c
+++ b/fs/btrfs/free-space-cache.c
@@ -838,7 +838,7 @@ int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
        struct io_ctl io_ctl;
        struct list_head bitmap_list;
        struct btrfs_key key;
-       u64 start, end, len;
+       u64 start, extent_start, extent_end, len;
        int entries = 0;
        int bitmaps = 0;
        int ret;
@@ -857,25 +857,12 @@ int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
                                     struct btrfs_free_cluster,
                                     block_group_list);
 
-       /*
-        * We shouldn't have switched the pinned extents yet so this is the
-        * right one
-        */
-       unpin = root->fs_info->pinned_extents;
-
        /* Lock all pages first so we can lock the extent safely. */
        io_ctl_prepare_pages(&io_ctl, inode, 0);
 
        lock_extent_bits(&BTRFS_I(inode)->io_tree, 0, i_size_read(inode) - 1,
                         0, &cached_state, GFP_NOFS);
 
-       /*
-        * When searching for pinned extents, we need to start at our start
-        * offset.
-        */
-       if (block_group)
-               start = block_group->key.objectid;
-
        node = rb_first(&ctl->free_space_offset);
        if (!node && cluster) {
                node = rb_first(&cluster->root);
@@ -918,9 +905,20 @@ int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
         * We want to add any pinned extents to our free space cache
         * so we don't leak the space
         */
+
+       /*
+        * We shouldn't have switched the pinned extents yet so this is the
+        * right one
+        */
+       unpin = root->fs_info->pinned_extents;
+
+       if (block_group)
+               start = block_group->key.objectid;
+
        while (block_group && (start < block_group->key.objectid +
                               block_group->key.offset)) {
-               ret = find_first_extent_bit(unpin, start, &start, &end,
+               ret = find_first_extent_bit(unpin, start,
+                                           &extent_start, &extent_end,
                                            EXTENT_DIRTY);
                if (ret) {
                        ret = 0;
@@ -928,20 +926,21 @@ int __btrfs_write_out_cache(struct btrfs_root *root, struct inode *inode,
                }
 
                /* This pinned extent is out of our range */
-               if (start >= block_group->key.objectid +
+               if (extent_start >= block_group->key.objectid +
                    block_group->key.offset)
                        break;
 
-               len = block_group->key.objectid +
-                       block_group->key.offset - start;
-               len = min(len, end + 1 - start);
+               extent_start = max(extent_start, start);
+               extent_end = min(block_group->key.objectid +
+                                block_group->key.offset, extent_end + 1);
+               len = extent_end - extent_start;
 
                entries++;
-               ret = io_ctl_add_entry(&io_ctl, start, len, NULL);
+               ret = io_ctl_add_entry(&io_ctl, extent_start, len, NULL);
                if (ret)
                        goto out_nospc;
 
-               start = end + 1;
+               start = extent_end;
        }
 
        /* Write out the bitmaps */