Hi, This patch (against experimental HEAD) attempts to make shrinking more robust, by only updating device size if we've succeeded in creating enough free space without any failures in btrfs_relocate_chunk().
Here's a log with my patch applied. The two things to note are that a near-limit shrink now works, and that a failed shrink (in this case, trying to shrink to less than the used space) no longer updates the device size erroneously: http://dev.laptop.org/~cjb/btrfs/shrink-log Please review carefully -- I'm still new to btrfs. The short version of the patch is: * create a success path, as a break out of the while(1) relocating (rather than going to the "done" label). * move the device size updating code into that path * leave "path->reada = 2;" behind in the entry path, since path is used by the searching operation rather than the later resize. Thanks! Signed-off-by: Chris Ball <c...@laptop.org> diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index 1316139..e2fa072 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -1815,30 +1815,8 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) if (!path) return -ENOMEM; - trans = btrfs_start_transaction(root, 1); - if (!trans) { - ret = -ENOMEM; - goto done; - } - path->reada = 2; - lock_chunks(root); - - 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); - key.objectid = device->devid; key.offset = (u64)-1; key.type = BTRFS_DEV_EXTENT_KEY; @@ -1867,7 +1845,7 @@ 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 +1858,31 @@ int btrfs_shrink_device(struct btrfs_device *device, u64 new_size) goto done; } + /* + * We've succeeded in freeing up enough space and can now update + * the device's size. + */ + trans = btrfs_start_transaction(root, 1); + if (!trans) { + ret = -ENOMEM; + goto done; + } + + lock_chunks(root); + 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); + done: btrfs_free_path(path); return ret; -- Chris Ball <c...@laptop.org> -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
