[PATCH 15/15] btrfs: Switch btrfs_trim_free_extents to find_first_clear_extent_bit

Nikolay Borisov
2019-01-30T14:51:13Z

Instead of always calling the allocator to search for a free extent,
that satisfies the input criteria, switch btrfs_trim_free_extents to
using find_first_clear_extent_bit. With this change it's no longer
necessary to read the device tree in order to figure out holes in
the devices.

Now the code always searches in-memory data structure to figure out the
space range which contains the requested which should result in speed
oups.

Signed-off-by: Nikolay Borisov <nborisov@suse.com>
---
fs/btrfs/extent-tree.c | 87 ++++++++++++------------------------------
1 file changed, 24 insertions(+), 63 deletions(-)

diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index f5005ef39f98..7a2b144bdb76 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -11127,54 +11127,6 @@ int btrfs_error_unpin_extent_range(struct btrfs_fs_info *fs_info,
return unpin_extent_range(fs_info, start, end, false);
}

-static bool should_skip_trim(struct btrfs_device *device, u64 *start, u64 *len)
-{
- u64 trimmed_start = 0, trimmed_end = 0;
- u64 end = *start + *len - 1;
-
- if (!find_first_extent_bit(&device->alloc_state, *start, &trimmed_start,
- &trimmed_end, CHUNK_TRIMMED, NULL)) {
- u64 trimmed_len = trimmed_end - trimmed_start + 1;
-
- if (*start < trimmed_start) {
- if (in_range(end, trimmed_start, trimmed_len) ||
- end > trimmed_end) {
- /*
- * start|------|end
- * ts|--|trimmed_len
- * OR
- * start|-----|end
- * ts|-----|trimmed_len
- */
- *len = trimmed_start - *start;
- return false;
- } else if (end < trimmed_start) {
- /*
- * start|------|end
- * ts|--|trimmed_len
- */
- return false;
- }
- } else if (in_range(*start, trimmed_start, trimmed_len)) {
- if (in_range(end, trimmed_start, trimmed_len)) {
- /*
- * start|------|end
- * ts|----------|trimmed_len
- */
- return true;
- } else {
- /*
- * start|-----------|end
- * ts|----------|trimmed_len
- */
- *start = trimmed_end + 1;
- *len = end - *start + 1;
- return false;
- }
- }
- }
- return false;
-}
/*
* It used to be that old block groups would be left around forever.
* Iterating over them would be enough to trim unused space. Since we
@@ -11198,7 +11150,7 @@ static bool should_skip_trim(struct btrfs_device *device, u64 *start, u64 *len)
static int btrfs_trim_free_extents(struct btrfs_device *device,
struct fstrim_range *range, u64 *trimmed)
{
- u64 start = range->start, len = 0;
+ u64 start = range->start, len = 0, end = 0;
int ret;

*trimmed = 0;
@@ -11225,34 +11177,43 @@ static int btrfs_trim_free_extents(struct btrfs_device *device,
if (ret)
break;

- ret = find_free_dev_extent_start(device, range->minlen, start,
- &start, &len);
-
+ ret = find_first_clear_extent_bit(&device->alloc_state, start,
+ &start, &end,
+ CHUNK_TRIMMED | CHUNK_ALLOCATED);
if (ret) {
mutex_unlock(&fs_info->chunk_mutex);
- if (ret == -ENOSPC)
- ret = 0;
+ ret = 0;
break;
}
+ /* If find_first_clear_extent_bit find a range that spans the
+ * end of the device it will set end to -1, in this case it's up
+ * to the caller to trim the value to the size of the device.
+ */
+ end = min(end, device->total_bytes);
+ len = end - start + 1;
+
+ /* Keep going until we satisfy minlen or reach end of space */
+ if (len < range->minlen) {
+ mutex_unlock(&fs_info->chunk_mutex);
+ start += len;
+ continue;
+ }

/* If we are out of the passed range break */
if (start > range->start + range->len - 1) {
mutex_unlock(&fs_info->chunk_mutex);
- ret = 0;
break;
}

start = max(range->start, start);
len = min(range->len, len);

- if (!should_skip_trim(device, &start, &len)) {
- ret = btrfs_issue_discard(device->bdev, start, len,
- &bytes);
- if (!ret)
- set_extent_bits(&device->alloc_state, start,
- start + bytes - 1,
- CHUNK_TRIMMED);
- }
+ ret = btrfs_issue_discard(device->bdev, start, len,
+ &bytes);
+ if (!ret)
+ set_extent_bits(&device->alloc_state, start,
+ start + bytes - 1,
+ CHUNK_TRIMMED);
mutex_unlock(&fs_info->chunk_mutex);

if (ret)
--
2.17.1