@@ -262,22 +262,23 @@ static noinline int lock_delalloc_folios(struct inode *inode,
for (i = 0; i < found_folios; i++) {
struct folio *folio = fbatch.folios[i];
- u32 len = end + 1 - start;
+ u64 range_start;
+ u32 range_len;
if (folio == locked_folio)
continue;
- if (btrfs_folio_start_writer_lock(fs_info, folio, start,
- len))
- goto out;
-
+ folio_lock(folio);
if (!folio_test_dirty(folio) || folio->mapping != mapping) {
- btrfs_folio_end_writer_lock(fs_info, folio, start,
- len);
+ folio_unlock(folio);
goto out;
}
+ range_start = max_t(u64, folio_pos(folio), start);
+ range_len = min_t(u64, folio_pos(folio) + folio_size(folio),
+ end + 1) - range_start;
+ btrfs_folio_set_writer_lock(fs_info, folio, range_start, range_len);
- processed_end = folio_pos(folio) + folio_size(folio) - 1;
+ processed_end = range_start + range_len - 1;
}
folio_batch_release(&fbatch);
cond_resched();
Inside lock_delalloc_folios(), there are several problems related to sector size < page size handling: - Set the writer locks without checking if the folio is still valid We call btrfs_folio_start_writer_lock() just like it's folio_lock(). But since the folio may not even be the folio of the current mapping, we can easily screw up the folio->private. - The range is not clamped inside the page This means we can over write other bitmaps if the start/len is not properly handled, and trigger the btrfs_subpage_assert(). - @processed_end is always rounded up to page end If the delalloc range is not page aligned, and we need to retry (returning -EAGAIN), then we will unlock to the page end. Thankfully this is not a huge problem, as now btrfs_folio_end_writer_lock() can handle range larger than the locked range, and only unlock what is already locked. Fix all these problems by: - Lock and check the folio first, then call btrfs_folio_set_writer_lock() So that if we got a folio not belonging to the inode, we won't touch folio->private. - Properly truncate the range inside the page - Update @processed_end to the locked range end Fixes: 1e1de38792e0 ("btrfs: make process_one_page() to handle subpage locking") Signed-off-by: Qu Wenruo <wqu@suse.com> Signed-off-by: Qu Wenruo <wqu@suse.com> --- fs/btrfs/extent_io.c | 17 +++++++++-------- 1 file changed, 9 insertions(+), 8 deletions(-)