[PATCH 0/2] btrfs: two small and safe fixes for large folios

Qu Wenruo
2025-04-01T06:13:03Z

Two small and simple fixes.

The first one is that with large folios, we can have order 6 folios which
reached our current BITS_PER_LONG limit, triggering a previously
impossible ASSERT(), which is based on the fact that our largest page
size (64K) can not reach BITS_PER_LONG blocks per page.

An easily fix by extending the ASSERT() condition to cover
blocks_per_folio == BITS_PER_LONG cases.

The second one is a little more complex, that with large folios, if we
still go through the single page bio vec iteration, we can not call
page_offset(), as non-head pages of a large folio do not have their
page::index initialized properly.

Fix that by going a helper using page_pgoff() to calculate the file
offset, which handles both head and non-head pages of a large folio.

Qu Wenruo (2):
btrfs: fix the ASSERT() inside GET_SUBPAGE_BITMAP()
btrfs: fix the file offset calculation inside
btrfs_decompress_buf2page()

fs/btrfs/compression.c | 18 +++++++++++++++++-
fs/btrfs/subpage.c | 2 +-
2 files changed, 18 insertions(+), 2 deletions(-)

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2.49.0