From 1a1a8b732c7e958e6eba0680439e814efde2362d Mon Sep 17 00:00:00 2001 From: Filipe Manana Date: Sat, 14 May 2016 19:44:40 +0100 Subject: [PATCH] Btrfs: fix race setting block group back to RW mode during device replace After it finishes processing a device extent, the device replace code sets back the block group to RW mode and then after that it sets the left cursor to match the logical end address of the block group, so that future writes into extents belonging to the block group go both the source (old) and target (new) devices. However from the moment we turn the block group back to RW mode we have a short time window, that lasts until we update the left cursor's value, where extents can be allocated from the block group and written to, in which case they will not be copied/written to the target (new) device. Fix this by updating the left cursor's value before turning the block group back to RW mode. Signed-off-by: Filipe Manana Reviewed-by: Josef Bacik --- fs/btrfs/scrub.c | 10 +++++----- 1 file changed, 5 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/scrub.c b/fs/btrfs/scrub.c index 19a1eda70361..70427ef66b04 100644 --- a/fs/btrfs/scrub.c +++ b/fs/btrfs/scrub.c @@ -3682,6 +3682,11 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx, scrub_pause_off(fs_info); + btrfs_dev_replace_lock(&fs_info->dev_replace, 1); + dev_replace->cursor_left = dev_replace->cursor_right; + dev_replace->item_needs_writeback = 1; + btrfs_dev_replace_unlock(&fs_info->dev_replace, 1); + if (ro_set) btrfs_dec_block_group_ro(root, cache); @@ -3719,11 +3724,6 @@ int scrub_enumerate_chunks(struct scrub_ctx *sctx, ret = -ENOMEM; break; } - - btrfs_dev_replace_lock(&fs_info->dev_replace, 1); - dev_replace->cursor_left = dev_replace->cursor_right; - dev_replace->item_needs_writeback = 1; - btrfs_dev_replace_unlock(&fs_info->dev_replace, 1); skip: key.offset = found_key.offset + length; btrfs_release_path(path);