From: Qu Wenruo <wqu@suse.com>
Date: Tue, 3 Dec 2019 06:42:52 +0000 (+0800)
Subject: btrfs: relocation: Check cancel request after each data page read
X-Git-Url: http://git.hungrycats.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=7ff4a6de7a7a84f353ed39eaf8361fb0d7d37244;p=linux

btrfs: relocation: Check cancel request after each data page read

When relocating a data extents with large large data extents, we spend
most of our time in relocate_file_extent_cluster() at stage "moving data
extents":
 1)               |  btrfs_relocate_block_group [btrfs]() {
 1)               |    relocate_file_extent_cluster [btrfs]() {
 1) $ 6586769 us  |    }
 1) + 18.260 us   |    relocate_file_extent_cluster [btrfs]();
 1) + 15.770 us   |    relocate_file_extent_cluster [btrfs]();
 1) $ 8916340 us  |  }
 1)               |  btrfs_relocate_block_group [btrfs]() {
 1)               |    relocate_file_extent_cluster [btrfs]() {
 1) $ 11611586 us |    }
 1) + 16.930 us   |    relocate_file_extent_cluster [btrfs]();
 1) + 15.870 us   |    relocate_file_extent_cluster [btrfs]();
 1) $ 14986130 us |  }

So to make data relocation cancelling quicker, here add extra balance
cancelling check after each page read in relocate_file_extent_cluster().

Signed-off-by: Qu Wenruo <wqu@suse.com>
(cherry picked from commit 34bb874930d1d6fecec7927101041884fe695aa7)
---

diff --git a/fs/btrfs/relocation.c b/fs/btrfs/relocation.c
index a313fffbb366..d1c7231bd949 100644
--- a/fs/btrfs/relocation.c
+++ b/fs/btrfs/relocation.c
@@ -3352,6 +3352,10 @@ static int relocate_file_extent_cluster(struct inode *inode,
 		btrfs_delalloc_release_extents(BTRFS_I(inode), PAGE_SIZE);
 		balance_dirty_pages_ratelimited(inode->i_mapping);
 		btrfs_throttle(fs_info);
+		if (should_cancel_balance(fs_info)) {
+			ret = -ECANCELED;
+			goto out;
+		}
 	}
 	WARN_ON(nr != cluster->nr);
 out: