btrfs: fix deadlock when cloning inline extent and low on free metadata space

[platform/kernel/linux-rpi.git] / fs / btrfs / reflink.c

diff --git a/fs/btrfs/reflink.c b/fs/btrfs/reflink.c
index ab80896..b03e789 100644 (file)
--- a/fs/btrfs/reflink.c
+++ b/fs/btrfs/reflink.c
@@ -89,6 +89,19 @@ static int copy_inline_to_page(struct btrfs_inode *inode,
        if (ret)
                goto out_unlock;
 
+       /*
+        * After dirtying the page our caller will need to start a transaction,
+        * and if we are low on metadata free space, that can cause flushing of
+        * delalloc for all inodes in order to get metadata space released.
+        * However we are holding the range locked for the whole duration of
+        * the clone/dedupe operation, so we may deadlock if that happens and no
+        * other task releases enough space. So mark this inode as not being
+        * possible to flush to avoid such deadlock. We will clear that flag
+        * when we finish cloning all extents, since a transaction is started
+        * after finding each extent to clone.
+        */
+       set_bit(BTRFS_INODE_NO_DELALLOC_FLUSH, &inode->runtime_flags);
+
        if (comp_type == BTRFS_COMPRESS_NONE) {
                char *map;
 
@@ -549,6 +562,8 @@ process_slot:
 out:
        btrfs_free_path(path);
        kvfree(buf);
+       clear_bit(BTRFS_INODE_NO_DELALLOC_FLUSH, &BTRFS_I(inode)->runtime_flags);
+
        return ret;
 }