From 61d0d0d2cbb7e52d3defe8089d5f360cf6d836ef Mon Sep 17 00:00:00 2001 From: Nikolay Borisov Date: Mon, 25 Mar 2019 14:31:23 +0200 Subject: [PATCH] btrfs: Handle pending/pinned chunks before blockgroup relocation during device shrink During device shrink pinned/pending chunks (i.e. those which have been deleted/created respectively, in the current transaction and haven't touched disk) need to be accounted when doing device shrink. Presently this happens after the main relocation loop in btrfs_shrink_device, which could lead to making another go in the body of the function. Since there is no hard requirement to perform pinned/pending chunks handling after the relocation loop, move the code before it. This leads to simplifying the code flow around - i.e. no need to use 'goto again'. A notable side effect of this change is that modification of the device's size requires a transaction to be started and committed before the relocation loop starts. This is necessary to ensure that relocation process sees the shrunk device size. Signed-off-by: Nikolay Borisov Reviewed-by: David Sterba Signed-off-by: David Sterba --- fs/btrfs/volumes.c | 55 +++++++++++++++++++++++------------------------------- 1 file changed, 23 insertions(+), 32 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 72e069c..a64b76d 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -4720,15 +4720,16 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) int slot; int failed = 0; bool retried = false; - bool checked_pending_chunks = false; struct extent_buffer *l; struct btrfs_key key; struct btrfs_super_block *super_copy = fs_info->super_copy; u64 old_total = btrfs_super_total_bytes(super_copy); u64 old_size = btrfs_device_get_total_bytes(device); u64 diff; + u64 start; new_size = round_down(new_size, fs_info->sectorsize); + start = new_size; diff = round_down(old_size - new_size, fs_info->sectorsize); if (test_bit(BTRFS_DEV_STATE_REPLACE_TGT, &device->dev_state)) @@ -4740,6 +4741,12 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) path->reada = READA_BACK; + trans = btrfs_start_transaction(root, 0); + if (IS_ERR(trans)) { + btrfs_free_path(path); + return PTR_ERR(trans); + } + mutex_lock(&fs_info->chunk_mutex); btrfs_device_set_total_bytes(device, new_size); @@ -4747,7 +4754,21 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) device->fs_devices->total_rw_bytes -= diff; atomic64_sub(diff, &fs_info->free_chunk_space); } - mutex_unlock(&fs_info->chunk_mutex); + + /* + * Once the device's size has been set to the new size, ensure all + * in-memory chunks are synced to disk so that the loop below sees them + * and relocates them accordingly. + */ + if (contains_pending_extent(trans->transaction, device, &start, diff)) { + mutex_unlock(&fs_info->chunk_mutex); + ret = btrfs_commit_transaction(trans); + if (ret) + goto done; + } else { + mutex_unlock(&fs_info->chunk_mutex); + btrfs_end_transaction(trans); + } again: key.objectid = device->devid; @@ -4838,36 +4859,6 @@ again: } mutex_lock(&fs_info->chunk_mutex); - - /* - * We checked in the above loop all device extents that were already in - * the device tree. However before we have updated the device's - * total_bytes to the new size, we might have had chunk allocations that - * have not complete yet (new block groups attached to transaction - * handles), and therefore their device extents were not yet in the - * device tree and we missed them in the loop above. So if we have any - * pending chunk using a device extent that overlaps the device range - * that we can not use anymore, commit the current transaction and - * repeat the search on the device tree - this way we guarantee we will - * not have chunks using device extents that end beyond 'new_size'. - */ - if (!checked_pending_chunks) { - u64 start = new_size; - u64 len = old_size - new_size; - - if (contains_pending_extent(trans->transaction, device, - &start, len)) { - mutex_unlock(&fs_info->chunk_mutex); - checked_pending_chunks = true; - failed = 0; - retried = false; - ret = btrfs_commit_transaction(trans); - if (ret) - goto done; - goto again; - } - } - btrfs_device_set_disk_total_bytes(device, new_size); if (list_empty(&device->post_commit_list)) list_add_tail(&device->post_commit_list, -- 2.7.4