There is a bug report about discard mount option not trimming some range properly, and causing unexpected space usage for thin device. It turns out to be that, if there are pinned extents across block group boundary, we will only trim to the end of current block group, skipping the remaining. This patchset will fix it by ensuring btrfs_discard_extent() will iterate the full range before exiting. The first patch is just a tiny readability improvement found during the fix. The second patch is the main body of the fix. Meanwhile I'm still looking into how to craft such test case for btrfs, so the test case may be late for several days. Changelog: v2: - Fold the __btrfs_map_block_for_discard() @length change into the main patch Since the @length parameter change itself doesn't make much sense, folding it into the fix looks more reasonable. - Split the tiny readability improvement patch into its own patch v3: - Reset @num_bytes for btrfs_map_block() to limit the trim range inside the original range. Or we can trim into existing extent to corrupt data. Qu Wenruo (2): btrfs: volumes: Use more straightforward way to calculate map length btrfs: extent-tree: Ensure we trim ranges across block group boundary fs/btrfs/extent-tree.c | 41 +++++++++++++++++++++++++++++++---------- fs/btrfs/volumes.c | 8 +++++--- 2 files changed, 36 insertions(+), 13 deletions(-) -- 2.23.0
