From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chris Ball Subject: Re: [review] Btrfs: Allow shrinking close to used space Date: Sun, 01 Mar 2009 21:29:37 -0500 Message-ID: References: <20090225200229.GB10849@unused.rdu.redhat.com> <3d0408630902251831x4fad55d3t2375135067bdd3ce@mail.gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: Josef Bacik , linux-btrfs@vger.kernel.org To: Yan Zheng Return-path: In-Reply-To: <3d0408630902251831x4fad55d3t2375135067bdd3ce@mail.gmail.com> (Yan Zheng's message of "Thu, 26 Feb 2009 10:31:09 +0800") List-ID: Hi, Here's a new patch that incorporates these comments. We now update device->fs_devices->total_rw_bytes before the shrink, as Josef suggests, and create a new field in btrfs_device to store an on-disk size that is only updated on a successful shrink operation, as requested by Yan. (Thanks, Yan and Josef, for the patient explanations.) == From: Chris Ball Btrfs: When shrinking, only update disk size on success Previously, we updated a device's size prior to attempting a shrink operation. This patch moves the device resizing logic to only happen if the shrink completes successfully. In the process, it introduces a new field to btrfs_device -- disk_total_bytes -- to track the on-disk size. Signed-off-by: Chris Ball --- fs/btrfs/volumes.c | 35 ++++++++++++++++++++++++----------- fs/btrfs/volumes.h | 3 +++ 2 files changed, 27 insertions(+), 11 deletions(-) diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 1316139..303b7d6 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1433,7 +1433,7 @@ static noinline int btrfs_update_device(struct btrfs_trans_handle *trans, btrfs_set_device_io_align(leaf, dev_item, device->io_align); btrfs_set_device_io_width(leaf, dev_item, device->io_width); btrfs_set_device_sector_size(leaf, dev_item, device->sector_size); - btrfs_set_device_total_bytes(leaf, dev_item, device->total_bytes); + btrfs_set_device_total_bytes(leaf, dev_item, device->disk_total_bytes); btrfs_set_device_bytes_used(leaf, dev_item, device->bytes_used); btrfs_mark_buffer_dirty(leaf); @@ -1828,14 +1828,6 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) device->total_bytes = new_size; if (device->writeable) device->fs_devices->total_rw_bytes -= diff; - ret = btrfs_update_device(trans, device); - if (ret) { - unlock_chunks(root); - btrfs_end_transaction(trans, root); - goto done; - } - WARN_ON(diff > old_total); - btrfs_set_super_total_bytes(super_copy, old_total - diff); unlock_chunks(root); btrfs_end_transaction(trans, root); @@ -1867,7 +1859,7 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) length = btrfs_dev_extent_length(l, dev_extent); if (key.offset + length <= new_size) - goto done; + break; chunk_tree = btrfs_dev_extent_chunk_tree(l, dev_extent); chunk_objectid = btrfs_dev_extent_chunk_objectid(l, dev_extent); @@ -1880,6 +1872,26 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) goto done; } + /* Shrinking succeeded, else we would be at "done". */ + trans = btrfs_start_transaction(root, 1); + if (!trans) { + ret = -ENOMEM; + goto done; + } + lock_chunks(root); + + device->disk_total_bytes = new_size; + /* Now btrfs_update_device() will change the on-disk size. */ + ret = btrfs_update_device(trans, device); + if (ret) { + unlock_chunks(root); + btrfs_end_transaction(trans, root); + goto done; + } + WARN_ON(diff > old_total); + btrfs_set_super_total_bytes(super_copy, old_total - diff); + unlock_chunks(root); + btrfs_end_transaction(trans, root); done: btrfs_free_path(path); return ret; @@ -2959,7 +2971,8 @@ static int fill_device_from_item(struct extent_buffer *leaf, unsigned long ptr; device->devid = btrfs_device_id(leaf, dev_item); - device->total_bytes = btrfs_device_total_bytes(leaf, dev_item); + device->disk_total_bytes = btrfs_device_total_bytes(leaf, dev_item); + device->total_bytes = device->disk_total_bytes; device->bytes_used = btrfs_device_bytes_used(leaf, dev_item); device->type = btrfs_device_type(leaf, dev_item); device->io_align = btrfs_device_io_align(leaf, dev_item); diff --git a/fs/btrfs/volumes.h b/fs/btrfs/volumes.h index 86c44e9..bf1ba75 100644 --- a/fs/btrfs/volumes.h +++ b/fs/btrfs/volumes.h @@ -52,6 +52,9 @@ struct btrfs_device { /* size of the device */ u64 total_bytes; + /* size of the disk */ + u64 disk_total_bytes; + /* bytes used */ u64 bytes_used; -- 1.6.1.3 - Chris. -- Chris Ball