linux-kernel - [PATCH 06/14] jbd2: replace ll_rw

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Date:   Wed, 31 Aug 2022 15:21:03 +0800
From:   Zhang Yi <yi.zhang@...wei.com>
To:     <linux-ext4@...r.kernel.org>, <linux-fsdevel@...r.kernel.org>,
        <linux-kernel@...r.kernel.org>, <cluster-devel@...hat.com>,
        <ntfs3@...ts.linux.dev>, <ocfs2-devel@....oracle.com>,
        <reiserfs-devel@...r.kernel.org>
CC:     <jack@...e.cz>, <tytso@....edu>, <akpm@...ux-foundation.org>,
        <axboe@...nel.dk>, <viro@...iv.linux.org.uk>,
        <rpeterso@...hat.com>, <agruenba@...hat.com>,
        <almaz.alexandrovich@...agon-software.com>, <mark@...heh.com>,
        <dushistov@...l.ru>, <hch@...radead.org>, <yi.zhang@...wei.com>,
        <chengzhihao1@...wei.com>, <yukuai3@...wei.com>
Subject: [PATCH 06/14] jbd2: replace ll_rw_block()

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@...wei.com>
---
 fs/jbd2/journal.c  |  7 +++----
 fs/jbd2/recovery.c | 16 ++++++++++------
 2 files changed, 13 insertions(+), 10 deletions(-)

diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 6350d3857c89..5a903aae6aad 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1893,15 +1893,14 @@ 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)) {
+		err = bh_read(bh, 0);
+		if (err) {
 			printk(KERN_ERR
 				"JBD2: IO error reading journal superblock\n");
 			goto out;
diff --git a/fs/jbd2/recovery.c b/fs/jbd2/recovery.c
index f548479615c6..ee56a30b71cf 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(bufs, nbufs, 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(bufs, nbufs, 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