- 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>
---
fs/btrfs/extent-tree.c | 4 +-
fs/btrfs/volumes.c | 155 +++++++++++++++++++++++++++--------------------
2 files changed, 91 insertions(+), 68 deletions(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 4bcd875..7c1a053 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -8098,7 +8098,7 @@ int btrfs_can_relocate(struct btrfs_root *root, u64
bytenr)
mutex_lock(&root->fs_info->chunk_mutex);
list_for_each_entry(device, &fs_devices->alloc_list, dev_alloc_list) {
u64 min_free = btrfs_block_group_used(&block_group->item);
- u64 dev_offset, max_avail;
+ u64 dev_offset;
/*
* check to make sure we can actually find a chunk with enough
@@ -8106,7 +8106,7 @@ int btrfs_can_relocate(struct btrfs_root *root, u64
bytenr)
*/
if (device->total_bytes > device->bytes_used + min_free) {
ret = find_free_dev_extent(NULL, device, min_free,
- &dev_offset, &max_avail);
+ &dev_offset, NULL);
if (!ret)
break;
ret = -1;
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;
}
--
1.7.0.1
--
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