[BUG]
fstrim on some btrfs only trims the unallocated space, not trimming any
space in existing block groups.
[CAUSE]
fstrim_range passed in by default fstrim will be:
range->start = 0
range->len = fs_size (which equals with super->total_bytes)
range->min_len = 512
However btrfs_trim_fs() following above parameter to search block groups
to trim.
While it's quite possible that all chunks start beyond
super->total_bytes if the fs is balanced several times.
In that case, btrfs will skip trimming block groups and only trim the
unallocated space of each device.
[FIX]
For common full fs trimming range passed in, extent its len to (u64)-1
so we will iterate all block groups.
And for custom fs trimming range, due to the fact that the range will
always be truncated by range [0, super->total_bytes), making custom fs
trimming range useless.
Just return -ENOTTY for custom fs trimming range.
Reported-by: Chris Murphy <lists@xxxxxxxxxxxxxxxxx>
Signed-off-by: Qu Wenruo <wqu@xxxxxxxx>
---
fs/btrfs/extent-tree.c | 29 ++++++++++++++++++++++++-----
1 file changed, 24 insertions(+), 5 deletions(-)
diff --git a/fs/btrfs/extent-tree.c b/fs/btrfs/extent-tree.c
index 3a252d7af158..22bbcc8c4f6c 100644
--- a/fs/btrfs/extent-tree.c
+++ b/fs/btrfs/extent-tree.c
@@ -11024,12 +11024,31 @@ int btrfs_trim_fs(struct btrfs_fs_info *fs_info, struct fstrim_range *range)
int ret = 0;
/*
- * try to trim all FS space, our block group may start from non-zero.
+ * NOTE: Btrfs uses its own logical address space, where its first
+ * chunk can start anywhere if it wants.
+ * If we follow common start = 0 and len = fs_size from @range, we
+ * can end up without trimming any block groups, since it's highly
+ * possible all chunks start beyond that range.
+ *
+ * So if we want to trim the whole fs, extent the len to (u64)-1 to trim
+ * all block groups.
+ *
+ * Also, since @range will always be truncated to fs size, manually
+ * passing range to trim specified range doesn't make much sense.
+ * (No mean to trim any block group whose bytenr starts beyond
+ * @total_bytes)
+ * So in that case, return -ENOTTY directly to prevent any custom trim
+ * request.
*/
- if (range->len == total_bytes)
- cache = btrfs_lookup_first_block_group(fs_info, range->start);
- else
- cache = btrfs_lookup_block_group(fs_info, range->start);
+ if (range->start == 0 && range->len == total_bytes) {
+ range->len = (u64)-1;
+ } else {
+ btrfs_info(fs_info,
+ "trimming custom range is not supported due to the limitation of fstrim_range");
+ return -ENOTTY;
+ }
+
+ cache = btrfs_lookup_first_block_group(fs_info, range->start);
for (; cache; cache = next_block_group(fs_info, cache)) {
if (cache->key.objectid >= (range->start + range->len)) {
--
2.15.0
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