Re: [PATCH v2 06/14] jbd2: replace ll_rw_block()

Jan Kara
2022-09-01T15:50:09Z

On Thu 01-09-22 21:34:57, Zhang Yi wrote:
> ll_rw_block() is not safe for the sync read path because it cannot
> guarantee that submitting read IO if the buffer has been locked. We
> could get false positive EIO after wait_on_buffer() if the buffer has
> been locked by others. So stop using ll_rw_block() in
> journal_get_superblock(). We also switch to new bh_readahead_batch()
> for the buffer array readahead path.
>
> Signed-off-by: Zhang Yi <yi.zhang@huawei.com>

Looks good to me. Feel free to add:

Reviewed-by: Jan Kara <jack@suse.cz>

Honza

> ---
> fs/jbd2/journal.c | 15 ++++++---------
> fs/jbd2/recovery.c | 16 ++++++++++------
> 2 files changed, 16 insertions(+), 15 deletions(-)
>
> diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
> index 6350d3857c89..140b070471c0 100644
> --- a/fs/jbd2/journal.c
> +++ b/fs/jbd2/journal.c
> @@ -1893,19 +1893,16 @@ static int journal_get_superblock(journal_t *journal)
> {
> struct buffer_head *bh;
> journal_superblock_t *sb;
> - int err = -EIO;
> + int err;
>
> bh = journal->j_sb_buffer;
>
> J_ASSERT(bh != NULL);
> - if (!buffer_uptodate(bh)) {
> - ll_rw_block(REQ_OP_READ, 1, &bh);
> - wait_on_buffer(bh);
> - if (!buffer_uptodate(bh)) {
> - printk(KERN_ERR
> - "JBD2: IO error reading journal superblock\n");
> - goto out;
> - }
> + err = bh_read(bh, 0);
> + if (err < 0) {
> + printk(KERN_ERR
> + "JBD2: IO error reading journal superblock\n");
> + goto out;
> }
>
> if (buffer_verified(bh))
> diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
> index f548479615c6..1f878c315b03 100644
> --- a/fs/jbd2/recovery.c
> +++ b/fs/jbd2/recovery.c
> @@ -100,7 +100,7 @@ static int do_readahead(journal_t *journal, unsigned int start)
> if (!buffer_uptodate(bh) && !buffer_locked(bh)) {
> bufs[nbufs++] = bh;
> if (nbufs == MAXBUF) {
> - ll_rw_block(REQ_OP_READ, nbufs, bufs);
> + bh_readahead_batch(nbufs, bufs, 0);
> journal_brelse_array(bufs, nbufs);
> nbufs = 0;
> }
> @@ -109,7 +109,7 @@ static int do_readahead(journal_t *journal, unsigned int start)
> }
>
> if (nbufs)
> - ll_rw_block(REQ_OP_READ, nbufs, bufs);
> + bh_readahead_batch(nbufs, bufs, 0);
> err = 0;
>
> failed:
> @@ -152,9 +152,14 @@ static int jread(struct buffer_head **bhp, journal_t *journal,
> return -ENOMEM;
>
> if (!buffer_uptodate(bh)) {
> - /* If this is a brand new buffer, start readahead.
> - Otherwise, we assume we are already reading it. */
> - if (!buffer_req(bh))
> + /*
> + * If this is a brand new buffer, start readahead.
> + * Otherwise, we assume we are already reading it.
> + */
> + bool need_readahead = !buffer_req(bh);
> +
> + bh_read_nowait(bh, 0);
> + if (need_readahead)
> do_readahead(journal, offset);
> wait_on_buffer(bh);
> }
> @@ -687,7 +692,6 @@ static int do_one_pass(journal_t *journal,
> mark_buffer_dirty(nbh);
> BUFFER_TRACE(nbh, "marking uptodate");
> ++info->nr_replays;
> - /* ll_rw_block(WRITE, 1, &nbh); */
> unlock_buffer(nbh);
> brelse(obh);
> brelse(nbh);
> --
> 2.31.1
>
--
Jan Kara <jack@suse.com>
SUSE Labs, CR