Re: [RFC PATCH 2/2] jbd: Stabilize pages during writes when in ordered mode
From: Jan Kara <jack@suse.cz>
Date: 2012-11-22 09:19:31
Also in:
linux-fsdevel, lkml
On Wed 21-11-12 18:36:45, Darrick J. Wong wrote:
quoted hunk ↗ jump to hunk
When writing buffers out to disk ahead of committing a transaction, set the Stable bit on the page to prevent others from wandering in and modifying the page. Signed-off-by: Darrick J. Wong <redacted> --- fs/jbd/commit.c | 18 +++++++++++++++++- 1 file changed, 17 insertions(+), 1 deletion(-)diff --git a/fs/jbd/commit.c b/fs/jbd/commit.c index 86b39b1..b1f0eed 100644 --- a/fs/jbd/commit.c +++ b/fs/jbd/commit.c@@ -155,13 +155,29 @@ static int journal_write_commit_record(journal_t *journal, return (ret == -EIO); } +static void end_stable_write_sync(struct buffer_head *bh, int uptodate) +{ + clear_page_stable(bh->b_page); + end_buffer_write_sync(bh, uptodate); +}
This doesn't work when blocksize < pagesize... There can be more buffers in one page under IO so you can clear the stable bit only after the last of them is done. See how PageWriteback bit is handled in end_buffer_async_write().
+
static void journal_do_submit_data(struct buffer_head **wbuf, int bufs,
int write_op)
{
int i;
for (i = 0; i < bufs; i++) {
- wbuf[i]->b_end_io = end_buffer_write_sync;
+ struct page *p = wbuf[i]->b_page;
+ if (TestSetPageStable(p))
+ wbuf[i]->b_end_io = end_buffer_write_sync;
+ else
+ wbuf[i]->b_end_io = end_stable_write_sync;Umm, why is this? It presume it is some attempt to handle blocksize < page size?
+
+ if (trylock_page(p)) {
+ clear_page_dirty_for_io(p);
+ unlock_page(p);
+ }
+And this is wrong again for blocksize < pagesize. There can be other dirty buffers under the page...
/* We use-up our safety reference in submit_bh() */ submit_bh(write_op, wbuf[i]); }
Honza -- Jan Kara [off-list ref] SUSE Labs, CR