REQ_OP_FLUSH is only for internal use in the blk-mq and request based drivers. File systems and other block layer consumers must use REQ_OP_WRITE | REQ_PREFLUSH as documented in Documentation/block/writeback_cache_control.rst.
While REQ_OP_FLUSH appears to work for blk-mq drivers it does not get the proper flush state machine handling, and completely fails for any bio based drivers, including all the stacking drivers. The block layer will also get a check in 6.8 to reject this use case entirely. [Note: completely untested, but as this never got fixed since the original bug report in November: https://bugzilla.kernel.org/show_bug.cgi?id=218184 and the the discussion in December: https://lore.kernel.org/all/[email protected]/T/ this seems to be best way to force it] Signed-off-by: Christoph Hellwig <[email protected]> --- fs/bcachefs/fs-io.c | 2 +- fs/bcachefs/journal_io.c | 3 ++- 2 files changed, 3 insertions(+), 2 deletions(-) diff --git a/fs/bcachefs/fs-io.c b/fs/bcachefs/fs-io.c index b0e8144ec5500c..a8500af6c7438f 100644 --- a/fs/bcachefs/fs-io.c +++ b/fs/bcachefs/fs-io.c @@ -79,7 +79,7 @@ void bch2_inode_flush_nocow_writes_async(struct bch_fs *c, continue; bio = container_of(bio_alloc_bioset(ca->disk_sb.bdev, 0, - REQ_OP_FLUSH, + REQ_OP_WRITE | REQ_PREFLUSH, GFP_KERNEL, &c->nocow_flush_bioset), struct nocow_flush, bio); diff --git a/fs/bcachefs/journal_io.c b/fs/bcachefs/journal_io.c index 3eb6c3f62a811b..43c76c9ad9a316 100644 --- a/fs/bcachefs/journal_io.c +++ b/fs/bcachefs/journal_io.c @@ -1948,7 +1948,8 @@ CLOSURE_CALLBACK(bch2_journal_write) percpu_ref_get(&ca->io_ref); bio = ca->journal.bio; - bio_reset(bio, ca->disk_sb.bdev, REQ_OP_FLUSH); + bio_reset(bio, ca->disk_sb.bdev, + REQ_OP_WRITE | REQ_PREFLUSH), bio->bi_end_io = journal_write_endio; bio->bi_private = ca; closure_bio_submit(bio, cl); -- 2.39.2
