jbd2: improve comments about freeing data buffers whose page mapping …

…is NULL Improve comments in jbd2_journal_commit_transaction() to describe why we don't need to clear the buffer_mapped bit for freeing file mapping buffers whose page mapping is NULL. Link: https://lore.kernel.org/r/[email protected] Fixes: c96dcee ("jbd2: do not clear the BH_Mapped flag when forgetting a metadata buffer") Suggested-by: Jan Kara <[email protected]> Reviewed-by: Jan Kara <[email protected]> Signed-off-by: zhangyi (F) <[email protected]> Signed-off-by: Theodore Ts'o <[email protected]>
numbqq · Mar 6, 2020 · 780f66e · 780f66e
1 parent 6cfb061
commit 780f66e
Showing 1 changed file with 4 additions and 3 deletions.
diff --git a/fs/jbd2/commit.c b/fs/jbd2/commit.c
@@ -997,9 +997,10 @@ void jbd2_journal_commit_transaction(journal_t *journal)
 			 * journalled data) we need to unmap buffer and clear
 			 * more bits. We also need to be careful about the check
 			 * because the data page mapping can get cleared under
-			 * out hands, which alse need not to clear more bits
-			 * because the page and buffers will be freed and can
-			 * never be reused once we are done with them.
+			 * our hands. Note that if mapping == NULL, we don't
+			 * need to make buffer unmapped because the page is
+			 * already detached from the mapping and buffers cannot
+			 * get reused.
 			 */
 			mapping = READ_ONCE(bh->b_page->mapping);
 			if (mapping && !sb_is_blkdev_sb(mapping->host->i_sb)) {