With 32-bit block numbers, we don't allocate the array for journal
buffer heads large enough for corresponding descriptor tags to fill the
descriptor block. Thus we end up writing out half-full descriptor blocks
to the journal unnecessarily growing the transaction. Fix the logic to
allocate the array large enough.
Signed-off-by: Jan Kara <jack@xxxxxxx>
---
fs/jbd2/journal.c | 13 ++++++++++++-
1 file changed, 12 insertions(+), 1 deletion(-)
diff --git a/fs/jbd2/journal.c b/fs/jbd2/journal.c
index 1c58859aa592..cc11097f1176 100644
--- a/fs/jbd2/journal.c
+++ b/fs/jbd2/journal.c
@@ -1098,6 +1098,16 @@ static void jbd2_stats_proc_exit(journal_t *journal)
remove_proc_entry(journal->j_devname, proc_jbd2_stats);
}
+/* Minimum size of descriptor tag */
+static int jbd2_min_tag_size(void)
+{
+ /*
+ * Tag with 32-bit block numbers does not use last four bytes of the
+ * structure
+ */
+ return sizeof(journal_block_tag_t) - 4;
+}
+
/*
* Management for journal control blocks: functions to create and
* destroy journal_t structures, and to initialise and read existing
@@ -1156,7 +1166,8 @@ static journal_t *journal_init_common(struct block_device *bdev,
journal->j_fs_dev = fs_dev;
journal->j_blk_offset = start;
journal->j_maxlen = len;
- n = journal->j_blocksize / sizeof(journal_block_tag_t);
+ /* We need enough buffers to write out full descriptor block. */
+ n = journal->j_blocksize / jbd2_min_tag_size();
journal->j_wbufsize = n;
journal->j_wbuf = kmalloc_array(n, sizeof(struct buffer_head *),
GFP_KERNEL);
--
2.16.4
