[PATCH v4 2/4] ext4: use jbd2 jinode dirty range accessor

[Li Chen <me@linux.beauty>]

ext4 journal commit callbacks access jbd2_inode dirty range fields without
holding journal->j_list_lock.
Use jbd2_jinode_get_dirty_range() to get the range in bytes, and read
i_transaction with READ_ONCE() in the redirty check.

Suggested-by: Jan Kara <jack@suse.cz>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Li Chen <me@linux.beauty>
---
Changes since v3:
- No changes.

Changes since v2:
- Use jbd2_jinode_get_dirty_range() instead of direct i_dirty_* reads.
- Drop per-caller page->byte conversion (now handled by the accessor).

Changes since v1:
- Convert the jinode dirty range from PAGE_SIZE units (pgoff_t) back to byte
  offsets before passing it to writeback.

 fs/ext4/inode.c | 10 ++++++++--
 fs/ext4/super.c | 16 +++++++++++-----
 2 files changed, 19 insertions(+), 7 deletions(-)

diff --git a/fs/ext4/inode.c b/fs/ext4/inode.c
index da96db5f23450..f87d35bda9276 100644
--- a/fs/ext4/inode.c
+++ b/fs/ext4/inode.c
@@ -3031,17 +3031,23 @@ static int ext4_writepages(struct address_space *mapping,
 
 int ext4_normal_submit_inode_data_buffers(struct jbd2_inode *jinode)
 {
+	loff_t range_start, range_end;
 	struct writeback_control wbc = {
 		.sync_mode = WB_SYNC_ALL,
 		.nr_to_write = LONG_MAX,
-		.range_start = jinode->i_dirty_start,
-		.range_end = jinode->i_dirty_end,
 	};
 	struct mpage_da_data mpd = {
 		.inode = jinode->i_vfs_inode,
 		.wbc = &wbc,
 		.can_map = 0,
 	};
+
+	if (!jbd2_jinode_get_dirty_range(jinode, &range_start, &range_end))
+		return 0;
+
+	wbc.range_start = range_start;
+	wbc.range_end = range_end;
+
 	return ext4_do_writepages(&mpd);
 }
 
diff --git a/fs/ext4/super.c b/fs/ext4/super.c
index 69eb63dde9839..685951cd58394 100644
--- a/fs/ext4/super.c
+++ b/fs/ext4/super.c
@@ -521,6 +521,7 @@ static bool ext4_journalled_writepage_needs_redirty(struct jbd2_inode *jinode,
 {
 	struct buffer_head *bh, *head;
 	struct journal_head *jh;
+	transaction_t *trans = READ_ONCE(jinode->i_transaction);
 
 	bh = head = folio_buffers(folio);
 	do {
@@ -539,7 +540,7 @@ static bool ext4_journalled_writepage_needs_redirty(struct jbd2_inode *jinode,
 		 */
 		jh = bh2jh(bh);
 		if (buffer_dirty(bh) ||
-		    (jh && (jh->b_transaction != jinode->i_transaction ||
+		    (jh && (jh->b_transaction != trans ||
 			    jh->b_next_transaction)))
 			return true;
 	} while ((bh = bh->b_this_page) != head);
@@ -550,15 +551,20 @@ static bool ext4_journalled_writepage_needs_redirty(struct jbd2_inode *jinode,
 static int ext4_journalled_submit_inode_data_buffers(struct jbd2_inode *jinode)
 {
 	struct address_space *mapping = jinode->i_vfs_inode->i_mapping;
+	loff_t range_start, range_end;
 	struct writeback_control wbc = {
-		.sync_mode =  WB_SYNC_ALL,
+		.sync_mode = WB_SYNC_ALL,
 		.nr_to_write = LONG_MAX,
-		.range_start = jinode->i_dirty_start,
-		.range_end = jinode->i_dirty_end,
-        };
+	};
 	struct folio *folio = NULL;
 	int error;
 
+	if (!jbd2_jinode_get_dirty_range(jinode, &range_start, &range_end))
+		return 0;
+
+	wbc.range_start = range_start;
+	wbc.range_end = range_end;
+
 	/*
 	 * writeback_iter() already checks for dirty pages and calls
 	 * folio_clear_dirty_for_io(), which we want to write protect the
-- 
2.53.0