diff mbox series

[Concept,02/15] ext4l: Add journal_head detection in bh_cache_clear

Message ID 20251230234134.906477-3-sjg@u-boot.org
State New
Headers
Series ext4l: Infrastructure and fixes for write support (part K) |

Commit Message

Simon Glass Dec. 30, 2025, 11:41 p.m. UTC 
  From: Simon Glass <simon.glass@canonical.com>

When debugging journal-cleanup issues, stale journal_head attachments on
buffer_heads can cause crashes on subsequent mounts.

Add detection logic in bh_cache_clear() to warn when a buffer_head still
has a journal_head attached. This indicates the journal was not properly
destroyed before unmount. Clear the JBD flag and pointer to prevent
issues with subsequent mounts.

Co-developed-by: Claude Opus 4.5 <noreply@anthropic.com>
Signed-off-by: Simon Glass <simon.glass@canonical.com>
---

 fs/ext4l/support.c | 30 ++++++++++++++++++++++++++++--
 1 file changed, 28 insertions(+), 2 deletions(-)
diff mbox series

Patch

diff --git a/fs/ext4l/support.c b/fs/ext4l/support.c
index a046654ca54..127a3920c96 100644
--- a/fs/ext4l/support.c
+++ b/fs/ext4l/support.c
@@ -222,6 +222,29 @@  static void bh_cache_insert(struct buffer_head *bh)
  *
  * Called on unmount to free all cached buffers.
  */
+/**
+ * bh_clear_stale_jbd() - Clear stale journal_head from buffer_head
+ * @bh: buffer_head to check
+ *
+ * Check if the buffer still has journal_head attached. This should not happen
+ * if the journal was properly destroyed, but warn if it does to help debugging.
+ * Clear the JBD flag and b_private to prevent issues with subsequent mounts.
+ */
+static void bh_clear_stale_jbd(struct buffer_head *bh)
+{
+	if (buffer_jbd(bh)) {
+		log_err("bh %p block %llu still has JBD (b_private %p)\n",
+			bh, (unsigned long long)bh->b_blocknr, bh->b_private);
+		/*
+		 * Clear the JBD flag and b_private to prevent issues.
+		 * The journal_head itself will be freed when the
+		 * journal_head cache is destroyed.
+		 */
+		clear_buffer_jbd(bh);
+		bh->b_private = NULL;
+	}
+}
+
 void bh_cache_clear(void)
 {
 	int i;
@@ -231,9 +254,12 @@  void bh_cache_clear(void)
 		for (entry = bh_cache[i]; entry; entry = next) {
 			next = entry->next;
 			if (entry->bh) {
+				struct buffer_head *bh = entry->bh;
+
+				bh_clear_stale_jbd(bh);
 				/* Release the cache's reference */
-				if (atomic_dec_and_test(&entry->bh->b_count))
-					free_buffer_head(entry->bh);
+				if (atomic_dec_and_test(&bh->b_count))
+					free_buffer_head(bh);
 			}
 			free(entry);
 		}