ll_rw_block() will skip locked buffer before submitting IO, it assumes
that locked buffer means it is under IO. This assumption is not always
true because we cannot guarantee every buffer lock path would submit
IO. After commit 88dbcbb3a484 ("blkdev: avoid migration stalls for
blkdev pages"), buffer_migrate_folio_norefs() becomes one exceptional
case, and there may be others. So ll_rw_block() is not safe on the sync
read path, we could get false positive EIO return value when filesystem
reading metadata. It seems that it could be only used on the readahead
path.
Unfortunately, many filesystem misuse the ll_rw_block() on the sync read
path. This patch set just remove ll_rw_block() and add new friendly
helpers, which could prevent false positive EIO on the read metadata
path. Thanks for the suggestion from Jan, the original discussion is at
[1].
patch 1: remove unused helpers in fs/buffer.c
patch 2: add new bh_read_[*] helpers
patch 3-11: remove all ll_rw_block() calls in filesystems
patch 12-14: do some leftover cleanups.
Thanks,
Yi.
[1]. https://lore.kernel.org/linux-mm/20220825080146.2021641-1-chengzhihao1@xxxxxxxxxx/
Zhang Yi (14):
fs/buffer: remove __breadahead_gfp()
fs/buffer: add some new buffer read helpers
fs/buffer: replace ll_rw_block()
gfs2: replace ll_rw_block()
isofs: replace ll_rw_block()
jbd2: replace ll_rw_block()
ntfs3: replace ll_rw_block()
ocfs2: replace ll_rw_block()
reiserfs: replace ll_rw_block()
udf: replace ll_rw_block()
ufs: replace ll_rw_block()
fs/buffer: remove ll_rw_block() helper
ext2: replace bh_submit_read() helper with bh_read_locked()
fs/buffer: remove bh_submit_read() helper
fs/buffer.c | 150 +++++++++++++++---------------------
fs/ext2/balloc.c | 2 +-
fs/gfs2/meta_io.c | 6 +-
fs/gfs2/quota.c | 4 +-
fs/isofs/compress.c | 2 +-
fs/jbd2/journal.c | 7 +-
fs/jbd2/recovery.c | 16 ++--
fs/ntfs3/inode.c | 7 +-
fs/ocfs2/aops.c | 2 +-
fs/ocfs2/super.c | 5 +-
fs/reiserfs/journal.c | 11 +--
fs/reiserfs/stree.c | 4 +-
fs/reiserfs/super.c | 4 +-
fs/udf/dir.c | 2 +-
fs/udf/directory.c | 2 +-
fs/udf/inode.c | 5 +-
fs/ufs/balloc.c | 4 +-
include/linux/buffer_head.h | 47 ++++++++---
18 files changed, 135 insertions(+), 145 deletions(-)
--
2.31.1
