This is a note to let you know that I've just added the patch titled
bcachefs: fix incorrect usage of REQ_OP_FLUSH
to the 6.7-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
bcachefs-fix-incorrect-usage-of-req_op_flush.patch
and it can be found in the queue-6.7 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From 3e44f325f6f75078cdcd44cd337f517ba3650d05 Mon Sep 17 00:00:00 2001
From: Christoph Hellwig <hch@xxxxxx>
Date: Thu, 11 Jan 2024 08:36:55 +0100
Subject: bcachefs: fix incorrect usage of REQ_OP_FLUSH
From: Christoph Hellwig <hch@xxxxxx>
commit 3e44f325f6f75078cdcd44cd337f517ba3650d05 upstream.
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/20231221053016.72cqcfg46vxwohcj@xxxxxxxxxxxxxx/T/
this seems to be best way to force it]
Signed-off-by: Christoph Hellwig <hch@xxxxxx>
Signed-off-by: Kent Overstreet <kent.overstreet@xxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
fs/bcachefs/fs-io.c | 2 +-
fs/bcachefs/journal_io.c | 3 ++-
2 files changed, 3 insertions(+), 2 deletions(-)
--- a/fs/bcachefs/fs-io.c
+++ b/fs/bcachefs/fs-io.c
@@ -79,7 +79,7 @@ void bch2_inode_flush_nocow_writes_async
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);
--- 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);
Patches currently in stable-queue which might be from hch@xxxxxx are
queue-6.7/bcachefs-fix-incorrect-usage-of-req_op_flush.patch
