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author | Miao Xie <miaox@cn.fujitsu.com> | 2011-01-05 10:07:26 +0000 |
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committer | Chris Mason <chris.mason@oracle.com> | 2011-01-16 11:30:19 -0500 |
commit | 7bfc837df935d850fe996dfe92ef48975cd4170a (patch) | |
tree | 8ca5f83c0c43e505b872368877504fa95c6276ab /fs/btrfs/volumes.c | |
parent | 1974a3b42d8cf7a9c74f1e0310c593023617037a (diff) | |
download | kernel_samsung_smdk4412-7bfc837df935d850fe996dfe92ef48975cd4170a.zip kernel_samsung_smdk4412-7bfc837df935d850fe996dfe92ef48975cd4170a.tar.gz kernel_samsung_smdk4412-7bfc837df935d850fe996dfe92ef48975cd4170a.tar.bz2 |
btrfs: restructure find_free_dev_extent()
- make it return the start position and length of the max free space when it can
not find a suitable free space.
- make it more readability
Signed-off-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Chris Mason <chris.mason@oracle.com>
Diffstat (limited to 'fs/btrfs/volumes.c')
-rw-r--r-- | fs/btrfs/volumes.c | 155 |
1 files changed, 89 insertions, 66 deletions
diff --git a/fs/btrfs/volumes.c b/fs/btrfs/volumes.c index c50a85e..4838bd3 100644 --- a/fs/btrfs/volumes.c +++ b/fs/btrfs/volumes.c @@ -729,58 +729,82 @@ error: } /* + * find_free_dev_extent - find free space in the specified device + * @trans: transaction handler + * @device: the device which we search the free space in + * @num_bytes: the size of the free space that we need + * @start: store the start of the free space. + * @len: the size of the free space. that we find, or the size of the max + * free space if we don't find suitable free space + * * this uses a pretty simple search, the expectation is that it is * called very infrequently and that a given device has a small number * of extents + * + * @start is used to store the start of the free space if we find. But if we + * don't find suitable free space, it will be used to store the start position + * of the max free space. + * + * @len is used to store the size of the free space that we find. + * But if we don't find suitable free space, it is used to store the size of + * the max free space. */ int find_free_dev_extent(struct btrfs_trans_handle *trans, struct btrfs_device *device, u64 num_bytes, - u64 *start, u64 *max_avail) + u64 *start, u64 *len) { struct btrfs_key key; struct btrfs_root *root = device->dev_root; - struct btrfs_dev_extent *dev_extent = NULL; + struct btrfs_dev_extent *dev_extent; struct btrfs_path *path; - u64 hole_size = 0; - u64 last_byte = 0; - u64 search_start = 0; + u64 hole_size; + u64 max_hole_start; + u64 max_hole_size; + u64 extent_end; + u64 search_start; u64 search_end = device->total_bytes; int ret; - int slot = 0; - int start_found; + int slot; struct extent_buffer *l; - path = btrfs_alloc_path(); - if (!path) - return -ENOMEM; - path->reada = 2; - start_found = 0; - /* FIXME use last free of some kind */ /* we don't want to overwrite the superblock on the drive, * so we make sure to start at an offset of at least 1MB */ - search_start = max((u64)1024 * 1024, search_start); + search_start = 1024 * 1024; - if (root->fs_info->alloc_start + num_bytes <= device->total_bytes) + if (root->fs_info->alloc_start + num_bytes <= search_end) search_start = max(root->fs_info->alloc_start, search_start); + max_hole_start = search_start; + max_hole_size = 0; + + if (search_start >= search_end) { + ret = -ENOSPC; + goto error; + } + + path = btrfs_alloc_path(); + if (!path) { + ret = -ENOMEM; + goto error; + } + path->reada = 2; + key.objectid = device->devid; key.offset = search_start; key.type = BTRFS_DEV_EXTENT_KEY; + ret = btrfs_search_slot(trans, root, &key, path, 0, 0); if (ret < 0) - goto error; + goto out; if (ret > 0) { ret = btrfs_previous_item(root, path, key.objectid, key.type); if (ret < 0) - goto error; - if (ret > 0) - start_found = 1; + goto out; } - l = path->nodes[0]; - btrfs_item_key_to_cpu(l, &key, path->slots[0]); + while (1) { l = path->nodes[0]; slot = path->slots[0]; @@ -789,24 +813,9 @@ int find_free_dev_extent(struct btrfs_trans_handle *trans, if (ret == 0) continue; if (ret < 0) - goto error; -no_more_items: - if (!start_found) { - if (search_start >= search_end) { - ret = -ENOSPC; - goto error; - } - *start = search_start; - start_found = 1; - goto check_pending; - } - *start = last_byte > search_start ? - last_byte : search_start; - if (search_end <= *start) { - ret = -ENOSPC; - goto error; - } - goto check_pending; + goto out; + + break; } btrfs_item_key_to_cpu(l, &key, slot); @@ -814,48 +823,62 @@ no_more_items: goto next; if (key.objectid > device->devid) - goto no_more_items; + break; - if (key.offset >= search_start && key.offset > last_byte && - start_found) { - if (last_byte < search_start) - last_byte = search_start; - hole_size = key.offset - last_byte; + if (btrfs_key_type(&key) != BTRFS_DEV_EXTENT_KEY) + goto next; - if (hole_size > *max_avail) - *max_avail = hole_size; + if (key.offset > search_start) { + hole_size = key.offset - search_start; - if (key.offset > last_byte && - hole_size >= num_bytes) { - *start = last_byte; - goto check_pending; + if (hole_size > max_hole_size) { + max_hole_start = search_start; + max_hole_size = hole_size; + } + + /* + * If this free space is greater than which we need, + * it must be the max free space that we have found + * until now, so max_hole_start must point to the start + * of this free space and the length of this free space + * is stored in max_hole_size. Thus, we return + * max_hole_start and max_hole_size and go back to the + * caller. + */ + if (hole_size >= num_bytes) { + ret = 0; + goto out; } } - if (btrfs_key_type(&key) != BTRFS_DEV_EXTENT_KEY) - goto next; - start_found = 1; dev_extent = btrfs_item_ptr(l, slot, struct btrfs_dev_extent); - last_byte = key.offset + btrfs_dev_extent_length(l, dev_extent); + extent_end = key.offset + btrfs_dev_extent_length(l, + dev_extent); + if (extent_end > search_start) + search_start = extent_end; next: path->slots[0]++; cond_resched(); } -check_pending: - /* we have to make sure we didn't find an extent that has already - * been allocated by the map tree or the original allocation - */ - BUG_ON(*start < search_start); - if (*start + num_bytes > search_end) { - ret = -ENOSPC; - goto error; + hole_size = search_end- search_start; + if (hole_size > max_hole_size) { + max_hole_start = search_start; + max_hole_size = hole_size; } - /* check for pending inserts here */ - ret = 0; -error: + /* See above. */ + if (hole_size < num_bytes) + ret = -ENOSPC; + else + ret = 0; + +out: btrfs_free_path(path); +error: + *start = max_hole_start; + if (len && max_hole_size > *len) + *len = max_hole_size; return ret; } |